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你知道 Linux 内核是如何构建的吗？
================================================================================
###介绍
我不会告诉你怎么在自己的电脑上去构建、安装一个定制化的 Linux 内核，这样的[资料](https://encrypted.google.com/search?q=building+linux+kernel#q=building+linux+kernel+from+source+code)太多了，它们会对你有帮助。本文会告诉你当你在内核源码路径里敲下`make` 时会发生什么。
当我刚刚开始学习内核代码时，[Makefile](https://github.com/torvalds/linux/blob/master/Makefile) 是我打开的第一个文件，这个文件看起来真令人害怕 :)。那时候这个 [Makefile](https://en.wikipedia.org/wiki/Make_%28software%29) 还只包含了`1591` 行代码，当我开始写本文时，内核已经是[4.2.0的第三个候选版本](https://github.com/torvalds/linux/commit/52721d9d3334c1cb1f76219a161084094ec634dc) 了。
这个 makefile 是 Linux 内核代码的根 makefile ，内核构建就始于此处。是的，它的内容很多，但是如果你已经读过内核源代码，你就会发现每个包含代码的目录都有一个自己的 makefile。当然了，我们不会去描述每个代码文件是怎么编译链接的，所以我们将只会挑选一些通用的例子来说明问题。而你不会在这里找到构建内核的文档、如何整洁内核代码、[tags](https://en.wikipedia.org/wiki/Ctags) 的生成和[交叉编译](https://en.wikipedia.org/wiki/Cross_compiler) 相关的说明，等等。我们将从`make` 开始，使用标准的内核配置文件，到生成了内核镜像 [bzImage](https://en.wikipedia.org/wiki/Vmlinux#bzImage) 结束。
如果你已经很了解 [make](https://en.wikipedia.org/wiki/Make_%28software%29) 工具那是最好，但是我也会描述本文出现的相关代码。
让我们开始吧！
###编译内核前的准备
在开始编译前要进行很多准备工作。最主要的就是找到并配置好配置文件，`make` 命令要使用到的参数都需要从这些配置文件获取。现在就让我们深入内核的根 `makefile` 吧
内核的根 `Makefile` 负责构建两个主要的文件：[vmlinux](https://en.wikipedia.org/wiki/Vmlinux) （内核镜像可执行文件）和模块文件。内核的 [Makefile](https://github.com/torvalds/linux/blob/master/Makefile) 从定义如下变量开始：
```Makefile
VERSION = 4
PATCHLEVEL = 2
SUBLEVEL = 0
EXTRAVERSION = -rc3
NAME = Hurr durr I'ma sheep
```
这些变量决定了当前内核的版本，并且被使用在很多不同的地方，比如同一个 `Makefile` 中的 `KERNELVERSION` ：
```Makefile
KERNELVERSION = $(VERSION)$(if $(PATCHLEVEL),.$(PATCHLEVEL)$(if $(SUBLEVEL),.$(SUBLEVEL)))$(EXTRAVERSION)
```
接下来我们会看到很多`ifeq` 条件判断语句，它们负责检查传递给 `make` 的参数。内核的 `Makefile` 提供了一个特殊的编译选项 `make help` ，这个选项可以生成所有的可用目标和一些能传给 `make` 的有效的命令行参数。举个例子，`make V=1` 会在构建过程中输出详细的编译信息，第一个 `ifeq` 就是检查传递给 make 的 `V=n` 选项。
```Makefile
ifeq ("$(origin V)", "command line")
KBUILD_VERBOSE = $(V)
endif
ifndef KBUILD_VERBOSE
KBUILD_VERBOSE = 0
endif
ifeq ($(KBUILD_VERBOSE),1)
quiet =
Q =
else
quiet=quiet_
Q = @
endif
export quiet Q KBUILD_VERBOSE
```
如果 `V=n` 这个选项传给了 `make` ，系统就会给变量 `KBUILD_VERBOSE` 选项附上 `V` 的值，否则的话`KBUILD_VERBOSE` 就会为 `0`。然后系统会检查 `KBUILD_VERBOSE` 的值，以此来决定 `quiet` 和`Q` 的值。符号 `@` 控制命令的输出，如果它被放在一个命令之前，这条命令的输出将会是 `CC scripts/mod/empty.o`，而不是`Compiling .... scripts/mod/empty.o`（LCTT 译注：CC 在 makefile 中一般都是编译命令）。在这段最后，系统导出了所有的变量。
下一个 `ifeq` 语句检查的是传递给 `make` 的选项 `O=/dir`，这个选项允许在指定的目录 `dir` 输出所有的结果文件：
```Makefile
ifeq ($(KBUILD_SRC),)
ifeq ("$(origin O)", "command line")
KBUILD_OUTPUT := $(O)
endif
ifneq ($(KBUILD_OUTPUT),)
saved-output := $(KBUILD_OUTPUT)
KBUILD_OUTPUT := $(shell mkdir -p $(KBUILD_OUTPUT) && cd $(KBUILD_OUTPUT) \
&& /bin/pwd)
$(if $(KBUILD_OUTPUT),, \
$(error failed to create output directory "$(saved-output)"))
sub-make: FORCE
$(Q)$(MAKE) -C $(KBUILD_OUTPUT) KBUILD_SRC=$(CURDIR) \
-f $(CURDIR)/Makefile $(filter-out _all sub-make,$(MAKECMDGOALS))
skip-makefile := 1
endif # ifneq ($(KBUILD_OUTPUT),)
endif # ifeq ($(KBUILD_SRC),)
```
系统会检查变量 `KBUILD_SRC`，它代表内核代码的顶层目录，如果它是空的（第一次执行 makefile 时总是空的），我们会设置变量 `KBUILD_OUTPUT` 为传递给选项 `O` 的值（如果这个选项被传进来了）。下一步会检查变量 `KBUILD_OUTPUT` ，如果已经设置好，那么接下来会做以下几件事：
* 将变量 `KBUILD_OUTPUT` 的值保存到临时变量 `saved-output`；
* 尝试创建给定的输出目录；
* 检查创建的输出目录，如果失败了就打印错误；
* 如果成功创建了输出目录，那么就在新目录重新执行 `make` 命令（参见选项`-C`）。
下一个 `ifeq` 语句会检查传递给 make 的选项 `C` 和 `M`：
```Makefile
ifeq ("$(origin C)", "command line")
KBUILD_CHECKSRC = $(C)
endif
ifndef KBUILD_CHECKSRC
KBUILD_CHECKSRC = 0
endif
ifeq ("$(origin M)", "command line")
KBUILD_EXTMOD := $(M)
endif
```
第一个选项 `C` 会告诉 `makefile` 需要使用环境变量 `$CHECK` 提供的工具来检查全部 `c` 代码，默认情况下会使用[sparse](https://en.wikipedia.org/wiki/Sparse)。第二个选项 `M` 会用来编译外部模块（本文不做讨论）。
系统还会检查变量 `KBUILD_SRC`，如果 `KBUILD_SRC` 没有被设置，系统会设置变量 `srctree` 为`.`：
```Makefile
ifeq ($(KBUILD_SRC),)
srctree := .
endif
objtree := .
src := $(srctree)
obj := $(objtree)
export srctree objtree VPATH
```
这将会告诉 `Makefile` 内核的源码树就在执行 `make` 命令的目录，然后要设置 `objtree` 和其他变量为这个目录，并且将这些变量导出。接着就是要获取 `SUBARCH` 的值，这个变量代表了当前的系统架构（LCTT 译注：一般都指CPU 架构）：
```Makefile
SUBARCH := $(shell uname -m | sed -e s/i.86/x86/ -e s/x86_64/x86/ \
-e s/sun4u/sparc64/ \
-e s/arm.*/arm/ -e s/sa110/arm/ \
-e s/s390x/s390/ -e s/parisc64/parisc/ \
-e s/ppc.*/powerpc/ -e s/mips.*/mips/ \
-e s/sh[234].*/sh/ -e s/aarch64.*/arm64/ )
```
如你所见，系统执行 [uname](https://en.wikipedia.org/wiki/Uname) 得到机器、操作系统和架构的信息。因为我们得到的是 `uname` 的输出，所以我们需要做一些处理再赋给变量 `SUBARCH` 。获得 `SUBARCH` 之后就要设置`SRCARCH` 和 `hfr-arch`，`SRCARCH` 提供了硬件架构相关代码的目录，`hfr-arch` 提供了相关头文件的目录：
```Makefile
ifeq ($(ARCH),i386)
SRCARCH := x86
endif
ifeq ($(ARCH),x86_64)
SRCARCH := x86
endif
hdr-arch := $(SRCARCH)
```
注意：`ARCH` 是 `SUBARCH` 的别名。如果没有设置过代表内核配置文件路径的变量 `KCONFIG_CONFIG`，下一步系统会设置它，默认情况下就是 `.config` ：
```Makefile
KCONFIG_CONFIG ?= .config
export KCONFIG_CONFIG
```
以及编译内核过程中要用到的 [shell](https://en.wikipedia.org/wiki/Shell_%28computing%29)
```Makefile
CONFIG_SHELL := $(shell if [ -x "$$BASH" ]; then echo $$BASH; \
else if [ -x /bin/bash ]; then echo /bin/bash; \
else echo sh; fi ; fi)
```
接下来就要设置一组和编译内核的编译器相关的变量。我们会设置主机的 `C` 和 `C++` 的编译器及相关配置项：
```Makefile
HOSTCC = gcc
HOSTCXX = g++
HOSTCFLAGS = -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 -fomit-frame-pointer -std=gnu89
HOSTCXXFLAGS = -O2
```
接下来会去适配代表编译器的变量 `CC`，那为什么还要 `HOST*` 这些变量呢？这是因为 `CC` 是编译内核过程中要使用的目标架构的编译器，但是 `HOSTCC` 是要被用来编译一组 `host` 程序的（下面我们就会看到）。
然后我们就看到变量 `KBUILD_MODULES` 和 `KBUILD_BUILTIN` 的定义，这两个变量决定了我们要编译什么东西（内核、模块或者两者）：
```Makefile
KBUILD_MODULES :=
KBUILD_BUILTIN := 1
ifeq ($(MAKECMDGOALS),modules)
KBUILD_BUILTIN := $(if $(CONFIG_MODVERSIONS),1)
endif
```
在这我们可以看到这些变量的定义，并且，如果们仅仅传递了 `modules` 给 `make`，变量 `KBUILD_BUILTIN` 会依赖于内核配置选项 `CONFIG_MODVERSIONS`。
下一步操作是引入下面的文件：
```Makefile
include scripts/Kbuild.include
```
文件 [Kbuild](https://github.com/torvalds/linux/blob/master/Documentation/kbuild/kbuild.txt) 或者又叫做 `Kernel Build System` 是一个用来管理构建内核及其模块的特殊框架。`kbuild` 文件的语法与 makefile 一样。文件[scripts/Kbuild.include](https://github.com/torvalds/linux/blob/master/scripts/Kbuild.include) 为 `kbuild` 系统提供了一些常规的定义。因为我们包含了这个 `kbuild` 文件，我们可以看到和不同工具关联的这些变量的定义，这些工具会在内核和模块编译过程中被使用（比如链接器、编译器、来自 [binutils](http://www.gnu.org/software/binutils/) 的二进制工具包 ，等等）：
```Makefile
AS = $(CROSS_COMPILE)as
LD = $(CROSS_COMPILE)ld
CC = $(CROSS_COMPILE)gcc
CPP = $(CC) -E
AR = $(CROSS_COMPILE)ar
NM = $(CROSS_COMPILE)nm
STRIP = $(CROSS_COMPILE)strip
OBJCOPY = $(CROSS_COMPILE)objcopy
OBJDUMP = $(CROSS_COMPILE)objdump
AWK = awk
...
...
...
```
在这些定义好的变量后面，我们又定义了两个变量：`USERINCLUDE` 和 `LINUXINCLUDE`。他们包含了头文件的路径（第一个是给用户用的，第二个是给内核用的）：
```Makefile
USERINCLUDE := \
-I$(srctree)/arch/$(hdr-arch)/include/uapi \
-Iarch/$(hdr-arch)/include/generated/uapi \
-I$(srctree)/include/uapi \
-Iinclude/generated/uapi \
-include $(srctree)/include/linux/kconfig.h
LINUXINCLUDE := \
-I$(srctree)/arch/$(hdr-arch)/include \
...
```
以及给 C 编译器的标准标志：
```Makefile
KBUILD_CFLAGS := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
-fno-strict-aliasing -fno-common \
-Werror-implicit-function-declaration \
-Wno-format-security \
-std=gnu89
```
这并不是最终确定的编译器标志，它们还可以在其他 makefile 里面更新（比如 `arch/` 里面的 kbuild）。变量定义完之后，全部会被导出供其他 makefile 使用。
下面的两个变量 `RCS_FIND_IGNORE` 和 `RCS_TAR_IGNORE` 包含了被版本控制系统忽略的文件：
```Makefile
export RCS_FIND_IGNORE := \( -name SCCS -o -name BitKeeper -o -name .svn -o \
-name CVS -o -name .pc -o -name .hg -o -name .git \) \
-prune -o
export RCS_TAR_IGNORE := --exclude SCCS --exclude BitKeeper --exclude .svn \
--exclude CVS --exclude .pc --exclude .hg --exclude .git
```
这就是全部了，我们已经完成了所有的准备工作，下一个点就是如果构建`vmlinux`。
###直面内核构建
现在我们已经完成了所有的准备工作，根 makefile（注：内核根目录下的 makefile）的下一步工作就是和编译内核相关的了。在这之前，我们不会在终端看到 `make` 命令输出的任何东西。但是现在编译的第一步开始了，这里我们需要从内核根 makefile 的 [598](https://github.com/torvalds/linux/blob/master/Makefile#L598) 行开始，这里可以看到目标`vmlinux`：
```Makefile
all: vmlinux
include arch/$(SRCARCH)/Makefile
```
不要操心我们略过的从 `export RCS_FIND_IGNORE.....` 到 `all: vmlinux.....` 这一部分 makefile 代码，他们只是负责根据各种配置文件（`make *.config`）生成不同目标内核的，因为之前我就说了这一部分我们只讨论构建内核的通用途径。
目标 `all:` 是在命令行如果不指定具体目标时默认使用的目标。你可以看到这里包含了架构相关的 makefile（在这里就指的是 [arch/x86/Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/Makefile)）。从这一时刻起，我们会从这个 makefile 继续进行下去。如我们所见，目标 `all` 依赖于根 makefile 后面声明的 `vmlinux`：
```Makefile
vmlinux: scripts/link-vmlinux.sh $(vmlinux-deps) FORCE
```
`vmlinux` 是 linux 内核的静态链接可执行文件格式。脚本 [scripts/link-vmlinux.sh](https://github.com/torvalds/linux/blob/master/scripts/link-vmlinux.sh) 把不同的编译好的子模块链接到一起形成了 vmlinux。
第二个目标是 `vmlinux-deps`，它的定义如下：
```Makefile
vmlinux-deps := $(KBUILD_LDS) $(KBUILD_VMLINUX_INIT) $(KBUILD_VMLINUX_MAIN)
```
它是由内核代码下的每个顶级目录的 `built-in.o` 组成的。之后我们还会检查内核所有的目录，`kbuild` 会编译各个目录下所有的对应 `$(obj-y)` 的源文件。接着调用 `$(LD) -r` 把这些文件合并到一个 `build-in.o` 文件里。此时我们还没有`vmlinux-deps`，所以目标 `vmlinux` 现在还不会被构建。对我而言 `vmlinux-deps` 包含下面的文件：
```
arch/x86/kernel/vmlinux.lds arch/x86/kernel/head_64.o
arch/x86/kernel/head64.o arch/x86/kernel/head.o
init/built-in.o usr/built-in.o
arch/x86/built-in.o kernel/built-in.o
mm/built-in.o fs/built-in.o
ipc/built-in.o security/built-in.o
crypto/built-in.o block/built-in.o
lib/lib.a arch/x86/lib/lib.a
lib/built-in.o arch/x86/lib/built-in.o
drivers/built-in.o sound/built-in.o
firmware/built-in.o arch/x86/pci/built-in.o
arch/x86/power/built-in.o arch/x86/video/built-in.o
net/built-in.o
```
下一个可以被执行的目标如下：
```Makefile
$(sort $(vmlinux-deps)): $(vmlinux-dirs) ;
$(vmlinux-dirs): prepare scripts
$(Q)$(MAKE) $(build)=$@
```
就像我们看到的，`vmlinux-dir` 依赖于两部分：`prepare` 和 `scripts`。第一个 `prepare` 定义在内核的根 `makefile` 中，准备工作分成三个阶段：
```Makefile
prepare: prepare0
prepare0: archprepare FORCE
$(Q)$(MAKE) $(build)=.
archprepare: archheaders archscripts prepare1 scripts_basic
prepare1: prepare2 $(version_h) include/generated/utsrelease.h \
include/config/auto.conf
$(cmd_crmodverdir)
prepare2: prepare3 outputmakefile asm-generic
```
第一个 `prepare0` 展开到 `archprepare` ，后者又展开到 `archheader` 和 `archscripts`，这两个变量定义在 `x86_64` 相关的 [Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/Makefile)。让我们看看这个文件。`x86_64` 特定的 makefile 从变量定义开始，这些变量都是和特定架构的配置文件 ([defconfig](https://github.com/torvalds/linux/tree/master/arch/x86/configs)，等等)有关联。在定义了编译 [16-bit](https://en.wikipedia.org/wiki/Real_mode) 代码的编译选项之后，根据变量 `BITS` 的值，如果是 `32`， 汇编代码、链接器、以及其它很多东西（全部的定义都可以在[arch/x86/Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/Makefile)找到）对应的参数就是 `i386`，而 `64` 就对应的是 `x86_84`。
第一个目标是 makefile 生成的系统调用列表（syscall table）中的 `archheaders` ：
```Makefile
archheaders:
$(Q)$(MAKE) $(build)=arch/x86/entry/syscalls all
```
第二个目标是 makefile 里的 `archscripts`：
```Makefile
archscripts: scripts_basic
$(Q)$(MAKE) $(build)=arch/x86/tools relocs
```
我们可以看到 `archscripts` 是依赖于根 [Makefile](https://github.com/torvalds/linux/blob/master/Makefile)里的`scripts_basic` 。首先我们可以看出 `scripts_basic` 是按照 [scripts/basic](https://github.com/torvalds/linux/blob/master/scripts/basic/Makefile) 的 makefile 执行 make 的：
```Maklefile
scripts_basic:
$(Q)$(MAKE) $(build)=scripts/basic
```
`scripts/basic/Makefile` 包含了编译两个主机程序 `fixdep` 和 `bin2` 的目标：
```Makefile
hostprogs-y := fixdep
hostprogs-$(CONFIG_BUILD_BIN2C) += bin2c
always := $(hostprogs-y)
$(addprefix $(obj)/,$(filter-out fixdep,$(always))): $(obj)/fixdep
```
第一个工具是 `fixdep`：用来优化 [gcc](https://gcc.gnu.org/) 生成的依赖列表，然后在重新编译源文件的时候告诉make。第二个工具是 `bin2c`，它依赖于内核配置选项 `CONFIG_BUILD_BIN2C`，并且它是一个用来将标准输入接口（LCTT 译注：即 stdin）收到的二进制流通过标准输出接口（即：stdout）转换成 C 头文件的非常小的 C 程序。你可能注意到这里有些奇怪的标志，如 `hostprogs-y` 等。这个标志用于所有的 `kbuild` 文件，更多的信息你可以从[documentation](https://github.com/torvalds/linux/blob/master/Documentation/kbuild/makefiles.txt) 获得。在我们这里， `hostprogs-y` 告诉 `kbuild` 这里有个名为 `fixed` 的程序，这个程序会通过和 `Makefile` 相同目录的 `fixdep.c` 编译而来。
执行 make 之后，终端的第一个输出就是 `kbuild` 的结果：
```
$ make
HOSTCC scripts/basic/fixdep
```
当目标 `script_basic` 被执行，目标 `archscripts` 就会 make [arch/x86/tools](https://github.com/torvalds/linux/blob/master/arch/x86/tools/Makefile) 下的 makefile 和目标 `relocs`:
```Makefile
$(Q)$(MAKE) $(build)=arch/x86/tools relocs
```
包含了[重定位](https://en.wikipedia.org/wiki/Relocation_%28computing%29) 的信息的代码 `relocs_32.c` 和 `relocs_64.c` 将会被编译，这可以在`make` 的输出中看到：
```Makefile
HOSTCC arch/x86/tools/relocs_32.o
HOSTCC arch/x86/tools/relocs_64.o
HOSTCC arch/x86/tools/relocs_common.o
HOSTLD arch/x86/tools/relocs
```
在编译完 `relocs.c` 之后会检查 `version.h`:
```Makefile
$(version_h): $(srctree)/Makefile FORCE
$(call filechk,version.h)
$(Q)rm -f $(old_version_h)
```
我们可以在输出看到它：
```
CHK include/config/kernel.release
```
以及在内核的根 Makefiel 使用 `arch/x86/include/generated/asm` 的目标 `asm-generic` 来构建 `generic` 汇编头文件。在目标 `asm-generic` 之后，`archprepare` 就完成了，所以目标 `prepare0` 会接着被执行，如我上面所写：
```Makefile
prepare0: archprepare FORCE
$(Q)$(MAKE) $(build)=.
```
注意 `build`，它是定义在文件 [scripts/Kbuild.include](https://github.com/torvalds/linux/blob/master/scripts/Kbuild.include)，内容是这样的：
```Makefile
build := -f $(srctree)/scripts/Makefile.build obj
```
或者在我们的例子中，它就是当前源码目录路径：`.`：
```Makefile
$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.build obj=.
```
脚本 [scripts/Makefile.build](https://github.com/torvalds/linux/blob/master/scripts/Makefile.build) 通过参数 `obj` 给定的目录找到 `Kbuild` 文件，然后引入 `kbuild` 文件：
```Makefile
include $(kbuild-file)
```
并根据这个构建目标。我们这里 `.` 包含了生成 `kernel/bounds.s` 和 `arch/x86/kernel/asm-offsets.s` 的 [Kbuild](https://github.com/torvalds/linux/blob/master/Kbuild) 文件。在此之后，目标 `prepare` 就完成了它的工作。 `vmlinux-dirs` 也依赖于第二个目标 `scripts` ，它会编译接下来的几个程序：`filealias`，`mk_elfconfig`，`modpost` 等等。之后，`scripts/host-programs` 就可以开始编译我们的目标 `vmlinux-dirs` 了。
首先，我们先来理解一下 `vmlinux-dirs` 都包含了那些东西。在我们的例子中它包含了下列内核目录的路径：
```
init usr arch/x86 kernel mm fs ipc security crypto block
drivers sound firmware arch/x86/pci arch/x86/power
arch/x86/video net lib arch/x86/lib
```
我们可以在内核的根 [Makefile](https://github.com/torvalds/linux/blob/master/Makefile) 里找到 `vmlinux-dirs` 的定义：
```Makefile
vmlinux-dirs := $(patsubst %/,%,$(filter %/, $(init-y) $(init-m) \
$(core-y) $(core-m) $(drivers-y) $(drivers-m) \
$(net-y) $(net-m) $(libs-y) $(libs-m)))
init-y := init/
drivers-y := drivers/ sound/ firmware/
net-y := net/
libs-y := lib/
...
...
...
```
这里我们借助函数 `patsubst` 和 `filter`去掉了每个目录路径里的符号 `/`，并且把结果放到 `vmlinux-dirs` 里。所以我们就有了 `vmlinux-dirs` 里的目录列表，以及下面的代码：
```Makefile
$(vmlinux-dirs): prepare scripts
$(Q)$(MAKE) $(build)=$@
```
符号 `$@` 在这里代表了 `vmlinux-dirs`，这就表明程序会递归遍历从 `vmlinux-dirs` 以及它内部的全部目录（依赖于配置），并且在对应的目录下执行 `make` 命令。我们可以在输出看到结果：
```
CC init/main.o
CHK include/generated/compile.h
CC init/version.o
CC init/do_mounts.o
...
CC arch/x86/crypto/glue_helper.o
AS arch/x86/crypto/aes-x86_64-asm_64.o
CC arch/x86/crypto/aes_glue.o
...
AS arch/x86/entry/entry_64.o
AS arch/x86/entry/thunk_64.o
CC arch/x86/entry/syscall_64.o
```
每个目录下的源代码将会被编译并且链接到 `built-io.o` 里：
```
$ find . -name built-in.o
./arch/x86/crypto/built-in.o
./arch/x86/crypto/sha-mb/built-in.o
./arch/x86/net/built-in.o
./init/built-in.o
./usr/built-in.o
...
...
```
好了，所有的 `built-in.o` 都构建完了，现在我们回到目标 `vmlinux` 上。你应该还记得，目标 `vmlinux` 是在内核的根makefile 里。在链接 `vmlinux` 之前，系统会构建 [samples](https://github.com/torvalds/linux/tree/master/samples), [Documentation](https://github.com/torvalds/linux/tree/master/Documentation) 等等，但是如上文所述，我不会在本文描述这些。
```Makefile
vmlinux: scripts/link-vmlinux.sh $(vmlinux-deps) FORCE
...
...
+$(call if_changed,link-vmlinux)
```
你可以看到，调用脚本 [scripts/link-vmlinux.sh](https://github.com/torvalds/linux/blob/master/scripts/link-vmlinux.sh) 的主要目的是把所有的 `built-in.o` 链接成一个静态可执行文件，和生成 [System.map](https://en.wikipedia.org/wiki/System.map)。 最后我们来看看下面的输出：
```
LINK vmlinux
LD vmlinux.o
MODPOST vmlinux.o
GEN .version
CHK include/generated/compile.h
UPD include/generated/compile.h
CC init/version.o
LD init/built-in.o
KSYM .tmp_kallsyms1.o
KSYM .tmp_kallsyms2.o
LD vmlinux
SORTEX vmlinux
SYSMAP System.map
```
`vmlinux` 和`System.map` 生成在内核源码树根目录下。
```
$ ls vmlinux System.map
System.map vmlinux
```
这就是全部了，`vmlinux` 构建好了，下一步就是创建 [bzImage](https://en.wikipedia.org/wiki/Vmlinux#bzImage).
###制作bzImage
`bzImage` 就是压缩了的 linux 内核镜像。我们可以在构建了 `vmlinux` 之后通过执行 `make bzImage` 获得`bzImage`。同时我们可以仅仅执行 `make` 而不带任何参数也可以生成 `bzImage` ，因为它是在 [arch/x86/kernel/Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/Makefile) 里预定义的、默认生成的镜像：
```Makefile
all: bzImage
```
让我们看看这个目标，它能帮助我们理解这个镜像是怎么构建的。我已经说过了 `bzImage` 是被定义在 [arch/x86/kernel/Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/Makefile)，定义如下：
```Makefile
bzImage: vmlinux
$(Q)$(MAKE) $(build)=$(boot) $(KBUILD_IMAGE)
$(Q)mkdir -p $(objtree)/arch/$(UTS_MACHINE)/boot
$(Q)ln -fsn ../../x86/boot/bzImage $(objtree)/arch/$(UTS_MACHINE)/boot/$@
```
在这里我们可以看到第一次为 boot 目录执行 `make`，在我们的例子里是这样的：
```Makefile
boot := arch/x86/boot
```
现在的主要目标是编译目录 `arch/x86/boot` 和 `arch/x86/boot/compressed` 的代码，构建 `setup.bin` 和 `vmlinux.bin`，最后用这两个文件生成 `bzImage`。第一个目标是定义在 [arch/x86/boot/Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/boot/Makefile) 的 `$(obj)/setup.elf`:
```Makefile
$(obj)/setup.elf: $(src)/setup.ld $(SETUP_OBJS) FORCE
$(call if_changed,ld)
```
我们已经在目录 `arch/x86/boot` 有了链接脚本 `setup.ld`，和扩展到 `boot` 目录下全部源代码的变量 `SETUP_OBJS` 。我们可以看看第一个输出：
```Makefile
AS arch/x86/boot/bioscall.o
CC arch/x86/boot/cmdline.o
AS arch/x86/boot/copy.o
HOSTCC arch/x86/boot/mkcpustr
CPUSTR arch/x86/boot/cpustr.h
CC arch/x86/boot/cpu.o
CC arch/x86/boot/cpuflags.o
CC arch/x86/boot/cpucheck.o
CC arch/x86/boot/early_serial_console.o
CC arch/x86/boot/edd.o
```
下一个源码文件是 [arch/x86/boot/header.S](https://github.com/torvalds/linux/blob/master/arch/x86/boot/header.S)，但是我们不能现在就编译它，因为这个目标依赖于下面两个头文件：
```Makefile
$(obj)/header.o: $(obj)/voffset.h $(obj)/zoffset.h
```
第一个头文件 `voffset.h` 是使用 `sed` 脚本生成的，包含用 `nm` 工具从 `vmlinux` 获取的两个地址：
```C
#define VO__end 0xffffffff82ab0000
#define VO__text 0xffffffff81000000
```
这两个地址是内核的起始和结束地址。第二个头文件 `zoffset.h` 在 [arch/x86/boot/compressed/Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/boot/compressed/Makefile) 可以看出是依赖于目标 `vmlinux`的：
```Makefile
$(obj)/zoffset.h: $(obj)/compressed/vmlinux FORCE
$(call if_changed,zoffset)
```
目标 `$(obj)/compressed/vmlinux` 依赖于 `vmlinux-objs-y` —— 说明需要编译目录 [arch/x86/boot/compressed](https://github.com/torvalds/linux/tree/master/arch/x86/boot/compressed) 下的源代码，然后生成 `vmlinux.bin`、`vmlinux.bin.bz2`，和编译工具 `mkpiggy`。我们可以在下面的输出看出来：
```Makefile
LDS arch/x86/boot/compressed/vmlinux.lds
AS arch/x86/boot/compressed/head_64.o
CC arch/x86/boot/compressed/misc.o
CC arch/x86/boot/compressed/string.o
CC arch/x86/boot/compressed/cmdline.o
OBJCOPY arch/x86/boot/compressed/vmlinux.bin
BZIP2 arch/x86/boot/compressed/vmlinux.bin.bz2
HOSTCC arch/x86/boot/compressed/mkpiggy
```
`vmlinux.bin` 是去掉了调试信息和注释的 `vmlinux` 二进制文件，加上了占用了 `u32` （LCTT 译注：即4-Byte）的长度信息的 `vmlinux.bin.all` 压缩后就是 `vmlinux.bin.bz2`。其中 `vmlinux.bin.all` 包含了 `vmlinux.bin` 和`vmlinux.relocs`（LCTT 译注：vmlinux 的重定位信息），其中 `vmlinux.relocs` 是 `vmlinux` 经过程序 `relocs` 处理之后的 `vmlinux` 镜像（见上文所述）。我们现在已经获取到了这些文件，汇编文件 `piggy.S` 将会被 `mkpiggy` 生成、然后编译：
```Makefile
MKPIGGY arch/x86/boot/compressed/piggy.S
AS arch/x86/boot/compressed/piggy.o
```
这个汇编文件会包含经过计算得来的、压缩内核的偏移信息。处理完这个汇编文件，我们就可以看到 `zoffset` 生成了：
```Makefile
ZOFFSET arch/x86/boot/zoffset.h
```
现在 `zoffset.h` 和 `voffset.h` 已经生成了，[arch/x86/boot](https://github.com/torvalds/linux/tree/master/arch/x86/boot/) 里的源文件可以继续编译：
```Makefile
AS arch/x86/boot/header.o
CC arch/x86/boot/main.o
CC arch/x86/boot/mca.o
CC arch/x86/boot/memory.o
CC arch/x86/boot/pm.o
AS arch/x86/boot/pmjump.o
CC arch/x86/boot/printf.o
CC arch/x86/boot/regs.o
CC arch/x86/boot/string.o
CC arch/x86/boot/tty.o
CC arch/x86/boot/video.o
CC arch/x86/boot/video-mode.o
CC arch/x86/boot/video-vga.o
CC arch/x86/boot/video-vesa.o
CC arch/x86/boot/video-bios.o
```
所有的源代码会被编译，他们最终会被链接到 `setup.elf` ：
```Makefile
LD arch/x86/boot/setup.elf
```
或者：
```
ld -m elf_x86_64 -T arch/x86/boot/setup.ld arch/x86/boot/a20.o arch/x86/boot/bioscall.o arch/x86/boot/cmdline.o arch/x86/boot/copy.o arch/x86/boot/cpu.o arch/x86/boot/cpuflags.o arch/x86/boot/cpucheck.o arch/x86/boot/early_serial_console.o arch/x86/boot/edd.o arch/x86/boot/header.o arch/x86/boot/main.o arch/x86/boot/mca.o arch/x86/boot/memory.o arch/x86/boot/pm.o arch/x86/boot/pmjump.o arch/x86/boot/printf.o arch/x86/boot/regs.o arch/x86/boot/string.o arch/x86/boot/tty.o arch/x86/boot/video.o arch/x86/boot/video-mode.o arch/x86/boot/version.o arch/x86/boot/video-vga.o arch/x86/boot/video-vesa.o arch/x86/boot/video-bios.o -o arch/x86/boot/setup.elf
```
最后的两件事是创建包含目录 `arch/x86/boot/*` 下的编译过的代码的 `setup.bin`：
```
objcopy -O binary arch/x86/boot/setup.elf arch/x86/boot/setup.bin
```
以及从 `vmlinux` 生成 `vmlinux.bin` :
```
objcopy -O binary -R .note -R .comment -S arch/x86/boot/compressed/vmlinux arch/x86/boot/vmlinux.bin
```
最最后，我们编译主机程序 [arch/x86/boot/tools/build.c](https://github.com/torvalds/linux/blob/master/arch/x86/boot/tools/build.c)，它将会用来把 `setup.bin` 和 `vmlinux.bin` 打包成 `bzImage`:
```
arch/x86/boot/tools/build arch/x86/boot/setup.bin arch/x86/boot/vmlinux.bin arch/x86/boot/zoffset.h arch/x86/boot/bzImage
```
实际上 `bzImage` 就是把 `setup.bin` 和 `vmlinux.bin` 连接到一起。最终我们会看到输出结果，就和那些用源码编译过内核的同行的结果一样：
```
Setup is 16268 bytes (padded to 16384 bytes).
System is 4704 kB
CRC 94a88f9a
Kernel: arch/x86/boot/bzImage is ready (#5)
```
全部结束。
###结论
这就是本文的结尾部分。本文我们了解了编译内核的全部步骤：从执行 `make` 命令开始，到最后生成 `bzImage`。我知道，linux 内核的 makefile 和构建 linux 的过程第一眼看起来可能比较迷惑，但是这并不是很难。希望本文可以帮助你理解构建 linux 内核的整个流程。
###链接
* [GNU make util](https://en.wikipedia.org/wiki/Make_%28software%29)
* [Linux kernel top Makefile](https://github.com/torvalds/linux/blob/master/Makefile)
* [cross-compilation](https://en.wikipedia.org/wiki/Cross_compiler)
* [Ctags](https://en.wikipedia.org/wiki/Ctags)
* [sparse](https://en.wikipedia.org/wiki/Sparse)
* [bzImage](https://en.wikipedia.org/wiki/Vmlinux#bzImage)
* [uname](https://en.wikipedia.org/wiki/Uname)
* [shell](https://en.wikipedia.org/wiki/Shell_%28computing%29)
* [Kbuild](https://github.com/torvalds/linux/blob/master/Documentation/kbuild/kbuild.txt)
* [binutils](http://www.gnu.org/software/binutils/)
* [gcc](https://gcc.gnu.org/)
* [Documentation](https://github.com/torvalds/linux/blob/master/Documentation/kbuild/makefiles.txt)
* [System.map](https://en.wikipedia.org/wiki/System.map)
* [Relocation](https://en.wikipedia.org/wiki/Relocation_%28computing%29)
--------------------------------------------------------------------------------
via: https://github.com/0xAX/linux-insides/blob/master/Misc/how_kernel_compiled.md
译者：[oska874](https://github.com/oska874)
校对：[wxy](https://github.com/wxy)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](https://linux.cn/) 荣誉推出

25
translated/tech/20150817 Linux FAQs with Answers--How to fix Wireshark GUI freeze on Linux desktop.md → published/20150817 Linux FAQs with Answers--How to fix Wireshark GUI freeze on Linux desktop.md
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@ -1,14 +1,6 @@
Linux 有问必答--如何解决 Linux 桌面上的 Wireshark GUI 死机
Linux 有问必答：如何解决 Linux 上的 Wireshark 界面僵死
================================================================================
> **问题**: 当我试图在 Ubuntu 上的 Wireshark 中打开一个 pre-recorded 数据包转储时，它的 UI 突然死机，在我发起 Wireshark 的终端出现了下面的错误和警告。我该如何解决这个问题？
Wireshark 是一个基于 GUI 的数据包捕获和嗅探工具。该工具被网络管理员普遍使用，网络安全工程师或开发人员对于各种任务的 packet-level 网络分析是必需的，例如在网络故障，漏洞测试，应用程序调试，或逆向协议工程是必需的。 Wireshark 允许记录存活数据包，并通过便捷的图形用户界面浏览他们的协议首部和有效负荷。
![](https://farm1.staticflickr.com/722/20584224675_f4d7a59474_c.jpg)
这是 Wireshark 的 UI，尤其是在 Ubuntu 桌面下运行，有时会挂起或冻结出现以下错误，而你是向上或向下滚动分组列表视图时，就开始加载一个 pre-recorded 包转储文件。
> **问题**: 当我试图在 Ubuntu 上的 Wireshark 中打开一个 pre-recorded 数据包转储时，它的界面突然死机，在我运行 Wireshark 的终端出现了下面的错误和警告。我该如何解决这个问题？
(wireshark:3480): GLib-GObject-WARNING **: invalid unclassed pointer in cast to 'GObject'
(wireshark:3480): GLib-GObject-CRITICAL **: g_object_set_qdata_full: assertion 'G_IS_OBJECT (object)' failed
@ -22,6 +14,15 @@ Wireshark 是一个基于 GUI 的数据包捕获和嗅探工具。该工具被
(wireshark:3480): GLib-GObject-CRITICAL **: g_object_get_qdata: assertion 'G_IS_OBJECT (object)' failed
(wireshark:3480): Gtk-CRITICAL **: gtk_widget_set_name: assertion 'GTK_IS_WIDGET (widget)' failed
Wireshark 是一个基于 GUI 的数据包捕获和嗅探工具。该工具被网络管理员普遍使用，网络安全工程师或开发人员对于各种任务的数据包级的网络分析是必需的，例如在网络故障，漏洞测试，应用程序调试，或逆向协议工程是必需的。 Wireshark 允许实时记录数据包，并通过便捷的图形用户界面浏览他们的协议首部和有效负荷。
![](https://farm1.staticflickr.com/722/20584224675_f4d7a59474_c.jpg)
这是 Wireshark 的 UI，尤其是在 Ubuntu 桌面下运行时，当你向上或向下滚动分组列表视图时，或开始加载一个 pre-recorded 包转储文件时，有时会挂起或冻结，并出现以下错误。
![](https://farm1.staticflickr.com/589/20062177334_47c0f2aeae_c.jpg)
显然，这个错误是由 Wireshark 和叠加滚动条之间的一些不兼容造成的，在最新的 Ubuntu 桌面还没有被解决（例如，Ubuntu 15.04 的桌面）。
一种避免 Wireshark 的 UI 卡死的办法就是 **暂时禁用叠加滚动条**。在 Wireshark 上有两种方法来禁用叠加滚动条，这取决于你在桌面上如何启动 Wireshark 的。
@ -46,7 +47,7 @@ Wireshark 是一个基于 GUI 的数据包捕获和嗅探工具。该工具被
Exec=env LIBOVERLAY_SCROLLBAR=0 wireshark %f
虽然这种解决方法将有利于所有桌面用户的 system-wide，但它将无法升级 Wireshark。如果你想保留修改的 .desktop 文件，如下所示将它复制到你的主目录。
虽然这种解决方法可以在系统级帮助到所有桌面用户，但升级 Wireshark 就没用了。如果你想保留修改的 .desktop 文件，如下所示将它复制到你的主目录。
$ cp /usr/share/applications/wireshark.desktop ~/.local/share/applications/
@ -56,7 +57,7 @@ via: http://ask.xmodulo.com/fix-wireshark-gui-freeze-linux-desktop.html
作者：[Dan Nanni][a]
译者：[strugglingyouth](https://github.com/strugglingyouth)
校对：[校对者ID](https://github.com/校对者ID)
校对：[wxy](https://github.com/wxy)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](https://linux.cn/) 荣誉推出

7
translated/talk/20150819 Linuxcon--The Changing Role of the Server OS.md → published/20150819 Linuxcon--The Changing Role of the Server OS.md
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@ -1,6 +1,6 @@
LinuxCon: 服务器操作系统的转型
================================================================================
来自西雅图。容器迟早要改变世界，以及改变操作系统的角色。这是 Wim Coekaerts 带来的 LinuxCon 演讲主题，Coekaerts 是 Oracle 公司 Linux 与虚拟化工程的高级副总裁。
西雅图报道。容器迟早要改变世界，以及改变操作系统的角色。这是 Wim Coekaerts 带来的 LinuxCon 演讲主题，Coekaerts 是 Oracle 公司 Linux 与虚拟化工程的高级副总裁。
![](http://www.serverwatch.com/imagesvr_ce/6421/wim-200x150.jpg)
@ -8,7 +8,7 @@ Coekaerts 在开始演讲的时候拿出一张关于“桌面之年”的幻灯
“你需要操作系统做什么事情？”，Coekaerts 回答现场观众：“只需一件事：运行一个应用。操作系统负责管理硬件和资源，来让你的应用运行起来。”
Coakaerts 说在 Docker 容器的帮助下，我们的注意力再次集中在应用上，而在 Oracle，我们将注意力放在如何让应用更好地运行在操作系统上。
Coakaerts 补充说，在 Docker 容器的帮助下，我们的注意力再次集中在应用上，而在 Oracle，我们将注意力放在如何让应用更好地运行在操作系统上。
“许多人过去常常需要繁琐地安装应用，而现在的年轻人只需要按一个按钮就能让应用在他们的移动设备上运行起来”。
@ -20,7 +20,6 @@ Docker 的出现不代表虚拟机的淘汰，容器化过程需要经过很长
在这段时间内，容器会与虚拟机共存，并且我们需要一些工具，将应用在容器和虚拟机之间进行转换迁移。Coekaerts 举例说 Oracle 的 VirtualBox 就可以用来帮助用户运行 Docker，而它原来是被广泛用在桌面系统上的一项开源技术。现在 Docker 的 Kitematic 项目将在 Mac 上使用 VirtualBox 运行 Docker。
### The Open Compute Initiative and Write Once, Deploy Anywhere for Containers ###
### 容器的开放计算计划和一次写随处部署 ###
一个能让容器成功的关键是“一次写，随处部署”的概念。而在容器之间的互操作领域，Linux 基金会的开放计算计划（OCI）扮演一个非常关键的角色。
@ -43,7 +42,7 @@ via: http://www.serverwatch.com/server-news/linuxcon-the-changing-role-of-the-se
作者：[Sean Michael Kerner][a]
译者：[bazz2](https://github.com/bazz2)
校对：[校对者ID](https://github.com/校对者ID)
校对：[wxy](https://github.com/wxy)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](https://linux.cn/) 荣誉推出

13
translated/talk/20150824 Linux about to gain a new file system--bcachefs.md → published/20150824 Linux about to gain a new file system--bcachefs.md
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@ -1,14 +1,15 @@
Linux 界将出现一个新的文件系统：bcachefs
Linux 上将出现一个新的文件系统：bcachefs
================================================================================
这个有 5 年历史，由 Kent Oberstreet 创建，过去属于谷歌的文件系统，最近完成了关键的组件。Bcachefs 文件系统自称其性能和稳定性与 ext4 和 xfs 相同，而其他方面的功能又可以与 btrfs 和 zfs 相媲美。主要特性包括校验、压缩、多设备支持、缓存、快照与其他好用的特性。
Bcachefs 来自 **bcache**，这是一个块级缓存层，从 bcaceh 到一个功能完整的[写时复制][1]文件系统，堪称是一项质的转变。
这个有 5 年历史，由 Kent Oberstreet 创建，过去属于谷歌的文件系统，最近完成了全部关键组件。Bcachefs 文件系统自称其性能和稳定性与 ext4 和 xfs 相同，而其他方面的功能又可以与 btrfs 和 zfs 相媲美。主要特性包括校验、压缩、多设备支持、缓存、快照与其他“漂亮”的特性。
在自己提出问题“为什么要出一个新的文件系统”中，Kent Oberstreet 作了以下回答：当我还在谷歌的时候，我与其他在 bcache 上工作的同事在偶然的情况下意识到我们正在使用的东西可以成为一个成熟文件系统的功能块，我们可以用 bcache 创建一个拥有干净而优雅设计的文件系统，而最重要的一点是，bcachefs 的主要目的就是在性能和稳定性上能与 ext4 和 xfs 匹敌，同时拥有 btrfs 和 zfs 的特性。
Bcachefs 来自 **bcache**，这是一个块级缓存层。从 bcaceh 到一个功能完整的[写时复制][1]文件系统，堪称是一项质的转变。
对自己的问题“为什么要出一个新的文件系统”中，Kent Oberstreet 自问自答道：当我还在谷歌的时候，我与其他在 bcache 上工作的同事在偶然的情况下意识到我们正在使用的东西可以成为一个成熟文件系统的功能块，我们可以用 bcache 创建一个拥有干净而优雅设计的文件系统，而最重要的一点是，bcachefs 的主要目的就是在性能和稳定性上能与 ext4 和 xfs 匹敌，同时拥有 btrfs 和 zfs 的特性。
Overstreet 邀请人们在自己的系统上测试 bcachefs，可以通过邮件列表[通告]获取 bcachefs 的操作指南。
Linux 生态系统中文件系统几乎处于一家独大状态，Fedora 在第 16 版的时候就想用 btrfs 换掉 ext4 作为其默认文件系统，但是到现在（LCTT：都出到 Fedora 22 了）还在使用 ext4。而几乎所有 Debian 系的发行版（Ubuntu、Mint、elementary OS 等）也使用 ext4 作为默认文件系统，并且这些主流的发生版都没有替换默认文件系统的意思。
Linux 生态系统中文件系统几乎处于一家独大状态，Fedora 在第 16 版的时候就想用 btrfs 换掉 ext4 作为其默认文件系统，但是到现在（LCTT：都出到 Fedora 22 了）还在使用 ext4。而几乎所有 Debian 系的发行版（Ubuntu、Mint、elementary OS 等）也使用 ext4 作为默认文件系统，并且这些主流的发行版都没有替换默认文件系统的意思。
--------------------------------------------------------------------------------
@ -16,7 +17,7 @@ via: http://www.linuxveda.com/2015/08/22/linux-gain-new-file-system-bcachefs/
作者：[Paul Hill][a]
译者：[bazz2](https://github.com/bazz2)
校对：[校对者ID](https://github.com/校对者ID)
校对：[wxy](https://github.com/wxy)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](https://linux.cn/) 荣誉推出

110
sources/share/20150826 Mosh Shell--A SSH Based Client for Connecting Remote Unix or Linux Systems.md
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Mosh Shell – A SSH Based Client for Connecting Remote Unix/Linux Systems
================================================================================
Mosh, which stands for Mobile Shell is a command-line application which is used for connecting to the server from a client computer, over the Internet. It can be used as SSH and contains more feature than Secure Shell. It is an application similar to SSH, but with additional features. The application is written originally by Keith Winstein for Unix like operating system and released under GNU GPL v3.
![Mosh Shell SSH Client](http://www.tecmint.com/wp-content/uploads/2015/08/Mosh-Shell-SSH-Client.png)
Mosh Shell SSH Client
#### Features of Mosh ####
- It is a remote terminal application that supports roaming.
- Available for all major UNIX-like OS viz., Linux, FreeBSD, Solaris, Mac OS X and Android.
- Intermittent Connectivity supported.
- Provides intelligent local echo.
- Line editing of user keystrokes supported.
- Responsive design and Robust Nature over wifi, cellular and long-distance links.
- Remain Connected even when IP changes. It usages UDP in place of TCP (used by SSH). TCP time out when connect is reset or new IP assigned but UDP keeps the connection open.
- The Connection remains intact when you resume the session after a long time.
- No network lag. Shows users typed key and deletions immediately without network lag.
- Same old method to login as it was in SSH.
- Mechanism to handle packet loss.
### Installation of Mosh Shell in Linux ###
On Debian, Ubuntu and Mint alike systems, you can easily install the Mosh package with the help of [apt-get package manager][1] as shown.
# apt-get update
# apt-get install mosh
On RHEL/CentOS/Fedora based distributions, you need to turn on third party repository called [EPEL][2], in order to install mosh from this repository using [yum package manager][3] as shown.
# yum update
# yum install mosh
On Fedora 22+ version, you need to use [dnf package manager][4] to install mosh as shown.
# dnf install mosh
### How do I use Mosh Shell? ###
1. Let’s try to login into remote Linux server using mosh shell.
$ mosh root@192.168.0.150
![Mosh Shell Remote Connection](http://www.tecmint.com/wp-content/uploads/2015/08/Mosh-Shell-Remote-Connection.png)
Mosh Shell Remote Connection
**Note**: Did you see I got an error in connecting since the port was not open in my remote CentOS 7 box. A quick but not recommended solution I performed was:
# systemctl stop firewalld [on Remote Server]
The preferred way is to open a port and update firewall rules. And then connect to mosh on a predefined port. For in-depth details on firewalld you may like to visit this post.
- [How to Configure Firewalld][5]
2. Let’s assume that the default SSH port 22 was changed to port 70, in this case you can define custom port with the help of ‘-p‘ switch with mosh.
$ mosh -p 70 root@192.168.0.150
3. Check the version of installed Mosh.
$ mosh --version
![Check Mosh Version](http://www.tecmint.com/wp-content/uploads/2015/08/Check-Mosh-Version.png)
Check Mosh Version
4. You can close mosh session type ‘exit‘ on the prompt.
$ exit
5. Mosh supports a lot of options, which you may see as:
$ mosh --help
![Mosh Shell Options](http://www.tecmint.com/wp-content/uploads/2015/08/Mosh-Shell-Options.png)
Mosh Shell Options
#### Cons of Mosh Shell ####
- Mosh requires additional prerequisite for example, allow direct connection via UDP, which was not required by SSH.
- Dynamic port allocation in the range of 60000-61000. The first open fort is allocated. It requires one port per connection.
- Default port allocation is a serious security concern, especially in production.
- IPv6 connections supported, but roaming on IPv6 not supported.
- Scrollback not supported.
- No X11 forwarding supported.
- No support for ssh-agent forwarding.
### Conclusion ###
Mosh is a nice small utility which is available for download in the repository of most of the Linux Distributions. Though it has a few discrepancies specially security concern and additional requirement it’s features like remaining connected even while roaming is its plus point. My recommendation is Every Linux-er who deals with SSH should try this application and mind it, Mosh is worth a try.
--------------------------------------------------------------------------------
via: http://www.tecmint.com/install-mosh-shell-ssh-client-in-linux/
作者：[Avishek Kumar][a]
译者：[译者ID](https://github.com/译者ID)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](https://linux.cn/) 荣誉推出
[a]:http://www.tecmint.com/author/avishek/
[1]:http://www.tecmint.com/useful-basic-commands-of-apt-get-and-apt-cache-for-package-management/
[2]:http://www.tecmint.com/how-to-enable-epel-repository-for-rhel-centos-6-5/
[3]:http://www.tecmint.com/20-linux-yum-yellowdog-updater-modified-commands-for-package-mangement/
[4]:http://www.tecmint.com/dnf-commands-for-fedora-rpm-package-management/
[5]:http://www.tecmint.com/configure-firewalld-in-centos-7/

3
sources/share/20150901 5 best open source board games to play online.md
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Translating by H-mudcup
5 best open source board games to play online
================================================================================
I have always had a fascination with board games, in part because they are a device of social interaction, they challenge the mind and, most importantly, they are great fun to play. In my misspent youth, myself and a group of friends gathered together to escape the horrors of the classroom, and indulge in a little escapism. The time provided an outlet for tension and rivalry. Board games help teach diplomacy, how to make and break alliances, bring families and friends together, and learn valuable lessons.
@ -191,4 +192,4 @@ via: http://www.linuxlinks.com/article/20150830011533893/BoardGames.html
[2]:http://domination.sourceforge.net/
[3]:http://www.pychess.org/
[4]:http://sourceforge.net/projects/scrabble/
[5]:http://www.gnubg.org/
[5]:http://www.gnubg.org/

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Superclass: 15 of the world’s best living programmers
================================================================================
When developers discuss who the world’s top programmer is, these names tend to come up a lot.
![](http://images.techhive.com/images/article/2015/09/superman-620x465-100611650-orig.jpg)
Image courtesy [tom_bullock CC BY 2.0][1]
It seems like there are lots of programmers out there these days, and lots of really good programmers. But which one is the very best?
Even though there’s no way to really say who the best living programmer is, that hasn’t stopped developers from frequently kicking the topic around. ITworld has solicited input and scoured coder discussion forums to see if there was any consensus. As it turned out, a handful of names did frequently get mentioned in these discussions.
Use the arrows above to read about 15 people commonly cited as the world’s best living programmer.
![](http://images.techhive.com/images/article/2015/09/margaret_hamilton-620x465-100611764-orig.jpg)
Image courtesy [NASA][2]
### Margaret Hamilton ###
**Main claim to fame: The brains behind Apollo’s flight control software**
Credentials: As the Director of the Software Engineering Division at Charles Stark Draper Laboratory, she headed up the team which [designed and built][3] the on-board [flight control software for NASA’s Apollo][4] and Skylab missions. Based on her Apollo work, she later developed the [Universal Systems Language][5] and [Development Before the Fact][6] paradigm. Pioneered the concepts of [asynchronous software, priority scheduling, and ultra-reliable software design][7]. Coined the term “[software engineering][8].” Winner of the [Augusta Ada Lovelace Award][9] in 1986 and [NASA’s Exceptional Space Act Award in 2003][10].
Quotes: “Hamilton invented testing , she pretty much formalised Computer Engineering in the US.” [ford_beeblebrox][11]
“I think before her (and without disrespect including Knuth) computer programming was (and to an extent remains) a branch of mathematics. However a flight control system for a spacecraft clearly moves programming into a different paradigm.” [Dan Allen][12]
“... she originated the term ‘software engineering’ — and offered a great example of how to do it.” [David Hamilton][13]
“What a badass” [Drukered][14]
![](http://images.techhive.com/images/idge/imported/imageapi/2014/10/08/17/slide_donald_knuth-620x465-100502872-orig.jpg)
Image courtesy [vonguard CC BY-SA 2.0][15]
### Donald Knuth ###
**Main claim to fame: Author of The Art of Computer Programming**
Credentials: Wrote the [definitive book on the theory of programming][16]. Created the TeX digital typesetting system. [First winner of the ACM’s Grace Murray Hopper Award][17] in 1971. Winner of the ACM’s [A. M. Turing][18] Award in 1974, the [National Medal of Science][19] in 1979 and the IEEE’s [John von Neumann Medal][20] in 1995. Named a [Fellow at the Computer History Museum][21] in 1998.
Quotes: “... wrote The Art of Computer Programming which is probably the most comprehensive work on computer programming ever.” [Anonymous][22]
“There is only one large computer program I have used in which there are to a decent approximation 0 bugs: Don Knuth's TeX. That's impressive.” [Jaap Weel][23]
“Pretty awesome if you ask me.” [Mitch Rees-Jones][24]
![](http://images.techhive.com/images/idge/imported/imageapi/2014/10/08/17/slide_ken-thompson-620x465-100502874-orig.jpg)
Image courtesy [Association for Computing Machinery][25]
### Ken Thompson ###
**Main claim to fame: Creator of Unix**
Credentials: Co-creator, [along with Dennis Ritchie][26], of Unix. Creator of the [B programming language][27], the [UTF-8 character encoding scheme][28], the ed [text editor][29], and co-developer of the Go programming language. Co-winner (along with Ritchie) of the [A.M. Turing Award][30] in 1983, [IEEE Computer Pioneer Award][31] in 1994, and the [National Medal of Technology][32] in 1998. Inducted as a [fellow of the Computer History Museum][33] in 1997.
Quotes: “... probably the most accomplished programmer ever. Unix kernel, Unix tools, world-champion chess program Belle, Plan 9, Go Language.” [Pete Prokopowicz][34]
“Ken's contributions, more than anyone else I can think of, were fundamental and yet so practical and timeless they are still in daily use.“ [Jan Jannink][35]
![](http://images.techhive.com/images/idge/imported/imageapi/2014/10/08/17/slide_richard_stallman-620x465-100502868-orig.jpg)
Image courtesy Jiel Beaumadier CC BY-SA 3.0
### Richard Stallman ###
**Main claim to fame: Creator of Emacs, GCC**
Credentials: Founded the [GNU Project][36] and created many of its core tools, such as [Emacs, GCC, GDB][37], and [GNU Make][38]. Also founded the [Free Software Foundation][39]. Winner of the ACM's [Grace Murray Hopper Award][40] in 1990 and the [EFF's Pioneer Award in 1998][41].
Quotes: “... there was the time when he single-handedly outcoded several of the best Lisp hackers around, in the Symbolics vs LMI fight.” [Srinivasan Krishnan][42]
“Through his amazing mastery of programming and force of will, he created a whole sub-culture in programming and computers.” [Dan Dunay][43]
“I might disagree on many things with the great man, but he is still one of the most important programmers, alive or dead” [Marko Poutiainen][44]
“Try to imagine Linux without the prior work on the GNu project. Stallman's the bomb, yo.” [John Burnette][45]
![](http://images.techhive.com/images/idge/imported/imageapi/2014/10/08/17/slide_anders_hejlsberg-620x465-100502873-orig.jpg)
Image courtesy [D.Begley CC BY 2.0][46]
### Anders Hejlsberg ###
**Main claim to fame: Creator of Turbo Pascal**
Credentials: [The original author of what became Turbo Pascal][47], one of the most popular Pascal compilers and the first integrated development environment. Later, [led the building of Delphi][48], Turbo Pascal’s successor. [Chief designer and architect of C#][49]. Winner of [Dr. Dobb's Excellence in Programming Award][50] in 2001.
Quotes: “He wrote the [Pascal] compiler in assembly language for both of the dominant PC operating systems of the day (DOS and CPM). It was designed to compile, link and run a program in seconds rather than minutes.” [Steve Wood][51]
“I revere this guy - he created the development tools that were my favourite through three key periods along my path to becoming a professional software engineer.” [Stefan Kiryazov][52]
![](http://images.techhive.com/images/idge/imported/imageapi/2014/10/08/17/slide_doug_cutting-620x465-100502871-orig.jpg)
Image courtesy [vonguard CC BY-SA 2.0][53]
### Doug Cutting ###
**Main claim to fame: Creator of Lucene**
Credentials: [Developed the Lucene search engine, as well as Nutch][54], a web crawler, and [Hadoop][55], a set of tools for distributed processing of large data sets. A strong proponent of open-source (Lucene, Nutch and Hadoop are all open-source). Currently [a former director of the Apache Software Foundation][56].
Quotes: “... he is the same guy who has written an exceptional search framework(lucene/solr) and opened the big-data gateway to the world(hadoop).” [Rajesh Rao][57]
“His creation/work on Lucene and Hadoop (among other projects) has created a tremendous amount of wealth and employment for folks in the world….” [Amit Nithianandan][58]
![](http://images.techhive.com/images/idge/imported/imageapi/2014/10/08/17/slide_sanjay_ghemawat-620x465-100502876-orig.jpg)
Image courtesy [Association for Computing Machinery][59]
### Sanjay Ghemawat ###
**Main claim to fame: Key Google architect**
Credentials: [Helped to design and implement some of Google’s large distributed systems][60], including MapReduce, BigTable, Spanner and Google File System. [Created Unix’s ical][61] calendaring system. Elected to the [National Academy of Engineering][62] in 2009. Winner of the [ACM-Infosys Foundation Award in the Computing Sciences][63] in 2012.
Quote: “Jeff Dean's wingman.” [Ahmet Alp Balkan][64]
![](http://images.techhive.com/images/idge/imported/imageapi/2014/10/08/17/slide_jeff_dean-620x465-100502866-orig.jpg)
Image courtesy [Google][65]
### Jeff Dean ###
**Main claim to fame: The brains behind Google search indexing**
Credentials: Helped to design and implement [many of Google’s large-scale distributed systems][66], including website crawling, indexing and searching, AdSense, MapReduce, BigTable and Spanner. Elected to the [National Academy of Engineering][67] in 2009. 2012 winner of the ACM’s [SIGOPS Mark Weiser Award][68] and the [ACM-Infosys Foundation Award in the Computing Sciences][69].
Quotes: “... for bringing breakthroughs in data mining( GFS, Map and Reduce, Big Table ).” [Natu Lauchande][70]
“... conceived, built, and deployed MapReduce and BigTable, among a bazillion other things” [Erik Goldman][71]
![](http://images.techhive.com/images/article/2015/09/linus_torvalds-620x465-100611765-orig.jpg)
Image courtesy [Krd CC BY-SA 4.0][72]
### Linus Torvalds ###
**Main claim to fame: Creator of Linux**
Credentials: Created the [Linux kernel][73] and [Git][74], an open source version control system. Winner of numerous awards and honors, including the [EFF Pioneer Award][75] in 1998, the [British Computer Society’s Lovelace Medal][76] in 2000, the [Millenium Technology Prize][77] in 2012 and the [IEEE Computer Society’s Computer Pioneer Award][78] in 2014. Also inducted into the [Computer History Museum’s Hall of Fellows][79] in 2008 and the [Internet Hall of Fame][80] in 2012.
Quotes: “To put into prospective what an achievement this is, he wrote the Linux kernel in a few years while the GNU Hurd (a GNU-developed kernel) has been under development for 25 years and has still yet to release a production-ready example.” [Erich Ficker][81]
“Torvalds is probably the programmer's programmer.” [Dan Allen][82]
“He's pretty darn good.” [Alok Tripathy][83]
![](http://images.techhive.com/images/idge/imported/imageapi/2014/10/08/17/slide_john_carmack-620x465-100502867-orig.jpg)
Image courtesy [QuakeCon CC BY 2.0][84]
### John Carmack ###
**Main claim to fame: Creator of Doom**
Credentials: Cofounded id Software and [created such influential FPS games][85] as Wolfenstein 3D, Doom and Quake. Pioneered such ground-breaking computer graphic techniques [adaptive tile refresh][86], [binary space partitioning][87], and surface caching. Inducted into the [Academy of Interactive Arts and Sciences Hall of Fame][88] in 2001, [won Emmy awards][89] in the Engineering & Technology category in 2007 and 2008, and given a lifetime achievement award by the [Game Developers Choice Awards][90] in 2010.
Quotes: “He wrote his first rendering engine before he was 20 years old. The guy's a genius. I wish I were a quarter a programmer he is.” [Alex Dolinsky][91]
“... Wolfenstein 3D, Doom and Quake were revolutionary at the time and have influenced a generation of game designers.” [dniblock][92]
“He can write basically anything in a weekend....” [Greg Naughton][93]
“He is the Mozart of computer coding….” [Chris Morris][94]
![](http://images.techhive.com/images/idge/imported/imageapi/2014/10/08/17/slide_fabrice_bellard-620x465-100502870-orig.jpg)
Image courtesy [Duff][95]
### Fabrice Bellard ###
**Main claim to fame: Creator of QEMU**
Credentials: Created a [variety of well-known open-source software programs][96], including QEMU, a platform for hardware emulation and virtualization, FFmpeg, for handling multimedia data, the Tiny C Compiler and LZEXE, an executable file compressor. [Winner of the Obfuscated C Code Contest][97] in 2000 and 2001 and the [Google-O'Reilly Open Source Award][98] in 2011. Former world record holder for [calculating the most number of digits in Pi][99].
Quotes: “I find Fabrice Bellard's work remarkable and impressive.” [raphinou][100]
“Fabrice Bellard is the most productive programmer in the world....” [Pavan Yara][101]
“Hes like the Nikola Tesla of sofware engineering.” [Michael Valladolid][102]
“He's a prolific serial achiever since the 1980s.” M[ichael Biggins][103]
![](http://images.techhive.com/images/idge/imported/imageapi/2014/10/08/17/slide_jon_skeet-620x465-100502863-orig.jpg)
Image courtesy [Craig Murphy CC BY 2.0][104]
### Jon Skeet ###
**Main claim to fame: Legendary Stack Overflow contributor**
Credentials: Google engineer and author of [C# in Depth][105]. Holds [highest reputation score of all time on Stack Overflow][106], answering, on average, 390 questions per month.
Quotes: “Jon Skeet doesn't need a debugger, he just stares down the bug until the code confesses” [Steven A. Lowe][107]
“When Jon Skeet's code fails to compile the compiler apologises.” [Dan Dyer][108]
“Jon Skeet's code doesn't follow a coding convention. It is the coding convention.” [Anonymous][109]
![](http://images.techhive.com/images/idge/imported/imageapi/2014/10/08/17/slide_image_adam_dangelo-620x465-100502875-orig.jpg)
Image courtesy [Philip Neustrom CC BY 2.0][110]
### Adam D'Angelo ###
**Main claim to fame: Co-founder of Quora**
Credentials: As an engineer at Facebook, [built initial infrastructure for its news feed][111]. Went on to become CTO and VP of engineering at Facebook, before leaving to co-found Quora. [Eighth place finisher at the USA Computing Olympiad][112] as a high school student in 2001. Member of [California Institute of Technology’s silver medal winning team][113] at the ACM International Collegiate Programming Contest in 2004. [Finalist in the Algorithm Coding Competition][114] of Topcoder Collegiate Challenge in 2005.
Quotes: “An "All-Rounder" Programmer.” [Anonymous][115]
"For every good thing I make he has like six." [Mark Zuckerberg][116]
![](http://images.techhive.com/images/idge/imported/imageapi/2014/10/08/17/slide_petr_mitrichev-620x465-100502869-orig.jpg)
Image courtesy [Facebook][117]
### Petr Mitrechev ###
**Main claim to fame: One of the top competitive programmers of all time**
Credentials: [Two-time gold medal winner][118] in the International Olympiad in Informatics (2000, 2002). In 2006, [won the Google Code Jam][119] and was also the [TopCoder Open Algorithm champion][120]. Also, two-time winner of the Facebook Hacker Cup ([2011][121], [2013][122]). At the time of this writing, [the second ranked algorithm competitor on TopCoder][123] (handle: Petr) and also [ranked second by Codeforces][124]
Quote: “He is an idol in competitive programming even here in India…” [Kavish Dwivedi][125]
![](http://images.techhive.com/images/idge/imported/imageapi/2014/10/08/17/slide_gennady_korot-620x465-100502864-orig.jpg)
Image courtesy [Ishandutta2007 CC BY-SA 3.0][126]
### Gennady Korotkevich ###
**Main claim to fame: Competitive programming prodigy**
Credentials: Youngest participant ever (age 11) and [6 time gold medalist][127] (2007-2012) in the International Olympiad in Informatics. Part of [the winning team][128] at the ACM International Collegiate Programming Contest in 2013 and winner of the [2014 Facebook Hacker Cup][129]. At the time of this writing, [ranked first by Codeforces][130] (handle: Tourist) and [first among algorithm competitors by TopCoder][131].
Quotes: “A programming prodigy!” [Prateek Joshi][132]
“Gennady is definitely amazing, and visible example of why I have a large development team in Belarus.” [Chris Howard][133]
“Tourist is genius” [Nuka Shrinivas Rao][134]
--------------------------------------------------------------------------------
via: http://www.itworld.com/article/2823547/enterprise-software/158256-superclass-14-of-the-world-s-best-living-programmers.html#slide1
作者：[Phil Johnson][a]
译者：[译者ID](https://github.com/译者ID)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
[a]:http://www.itworld.com/author/Phil-Johnson/
[1]:https://www.flickr.com/photos/tombullock/15713223772
[2]:https://commons.wikimedia.org/wiki/File:Margaret_Hamilton_in_action.jpg
[3]:http://klabs.org/home_page/hamilton.htm
[4]:https://www.youtube.com/watch?v=DWcITjqZtpU&feature=youtu.be&t=3m12s
[5]:http://www.htius.com/Articles/r12ham.pdf
[6]:http://www.htius.com/Articles/Inside_DBTF.htm
[7]:http://www.nasa.gov/home/hqnews/2003/sep/HQ_03281_Hamilton_Honor.html
[8]:http://www.nasa.gov/50th/50th_magazine/scientists.html
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The Free Software Foundation: 30 years in
================================================================================
![](http://opensource.com/sites/default/files/styles/image-full-size/public/images/life/osdc_general_openfield.png?itok=tcXpYeHi)
Welcome back, folks, to a new Six Degrees column. As usual, please send your thoughts on this piece to the comment box and your suggestions for future columns to [my inbox][1].
Now, I have to be honest with you all, this column went a little differently than I expected.
A few weeks ago when thinking what to write, I mused over the notion of a piece about the [Free Software Foundation][2] celebrating its 30 year anniversary and how relevant and important its work is in today's computing climate.
To add some meat I figured I would interview [John Sullivan][3], executive director of the FSF. My plan was typical of many of my pieces: thread together an interesting narrative and quote pieces of the interview to give it color.
Well, that all went out the window when John sent me a tremendously detailed, thoughtful, and descriptive interview. I decided therefore to present it in full as the main event, and to add some commentary throughout. Thus, this is quite a long column, but I think it paints a fascinating picture of a fascinating organization. I recommend you grab a cup of something delicious and settle in for a solid read.
### The sands of change ###
The Free Software Foundation was founded in 1985. To paint a picture of what computing was like back then, the [Amiga 1000][4] was released, C++ was becoming a dominant language, [Aldus PageMaker][5] was announced, and networking was just starting to grow. Oh, and that year [Careless Whisper][6] by Wham! was a major hit.
Things have changed a lot in 30 years. Back in 1985 the FSF was primarily focused on building free pieces of software that were primarily useful to nerdy computer people. These days we have software, services, social networks, and more to consider.
I first wanted to get a sense of what John feels are most prominent risks to software freedom today.
"I think there's widespread agreement on the biggest risks for computer user freedom today, but maybe not on the names for them."
"The first is what we might as well just call 'tiny computers everywhere.' The free software movement has succeeded to the point where laptops, desktops, and servers can run fully free operating systems doing anything users of proprietary systems can do. There are still a few holes, but they'll be closed. The challenge that remains in this area is to cut through the billion dollar marketing budgets and legal regimes working against us to actually get the systems into users hands."
"However, we have a serious problem on the set of computers whose primary common trait is that they are very small. Even though a car is not especially small, the computers in it are, so I include that form factor in this category, along with phones, tablets, glasses, watches, and so on. While these computers often have a basis in free software—for example, using the kernel Linux along with other free software like Android or GNU—their primary uses are to run proprietary applications and be shims for services that replace local computing with computing done on a server over which the user has no control. Since these devices serve vital functions, with some being primary means of communication for huge populations, some sitting very close to our bodies and our actual vital functions, some bearing responsibility for our physical safety, it is imperative that they run fully free systems under their users' control. Right now, they don't."
John feels the risk here is not just the platforms and form factors, but the services integrates into them.
"The services many of these devices talk to are the second major threat we face. It does us little good booting into a free system if we do our actual work and entertainment on companies' servers running software we have no access to at all. The point of free software is that we can see, modify, and share code. The existence of those freedoms even for nontechnical users provides a shield that prevents companies from controlling us. None of these freedoms exist for users of Facebook or Salesforce or Google Docs. Even more worrisome, we see a trend where people are accepting proprietary restrictions imposed on their local machines in order to have access to certain services. Browsers—including Firefox—are now automatically installing a DRM plugin in order to appease Netflix and other video giants. We need to work harder at developing free software decentralized replacements for media distribution that can actually empower users, artists, and user-artists, and for other services as well. For Facebook we have GNU social, pump.io, Diaspora, Movim, and others. For Salesforce, we have CiviCRM. For Google Docs, we have Etherpad. For media, we have GNU MediaGoblin. But all of these projects need more help, and many services don't have any replacement contenders yet."
It is interesting that John mentions finding free software equivalents for common applications and services today. The FSF maintains a list of "High Priority Projects" that are designed to fill this gap. Unfortunately the capabilities of these projects varies tremendously and in an age where social media is so prominent, the software is only part of the problem: the real challenge is getting people to use it.
This all begs the question of where the FSF fit in today's modern computing world. I am a fan of the FSF. I think the work they do is valuable and I contribute financially to support it too. They are an important organization for building an open computing culture, but all organizations need to grow, adjust, and adapt, particularly ones in the technology space.
I wanted to get a better sense of what the FSF is doing today that it wasn't doing at it's inception.
"We're speaking to a much larger audience than we were 30 years ago, and to a much broader audience. It's no longer just hackers and developers and researchers that need to know about free software. Everyone using a computer does, and it's quickly becoming the case that everyone uses a computer."
John went on to provide some examples of these efforts.
"We're doing coordinated public advocacy campaigns on issues of concern to the free software movement. Earlier in our history, we expressed opinions on these things, and took action on a handful, but in the last ten years we've put more emphasis on formulating and carrying out coherent campaigns. We've made especially significant noise in the area of Digital Restrictions Management (DRM) with Defective by Design, which I believe played a role in getting iTunes music off DRM (now of course, Apple is bringing DRM back with Apple Music). We've made attractive and useful introductory materials for people new to free software, like our [User Liberation animated video][7] and our [Email Self-Defense Guide][8].
We're also endorsing hardware that [respects users' freedoms][9]. Hardware distributors whose devices have been certified by the FSF to contain and require only free software can display a logo saying so. Expanding the base of free software users and the free software movement has two parts: convincing people to care, and then making it possible for them to act on that. Through this initiative, we encourage manufacturers and distributors to do the right thing, and we make it easy for users who have started to care about free software to buy what they need without suffering through hours and hours of research. We've certified a home WiFi router, 3D printers, laptops, and USB WiFi adapters, with more on the way.
We're collecting all of the free software we can find in our [Free Software Directory][10]. We still have a long way to go on this—we're at only about 15,500 packages right now, and we can imagine many improvements to the design and function of the site—but I think this resource has great potential for helping users find the free software they need, especially users who aren't yet using a full GNU/Linux system. With the dangers inherent in downloading random programs off the Internet, there is a definite need for a curated collection like this. It also happens to provide a wealth of machine-readable data of use to researchers.
We're acting as the fiscal sponsor for several specific free software projects, enabling them to raise funds for development. Most of these projects are part of GNU (which we continue to provide many kinds of infrastructure for), but we also sponsor [Replicant][11], a fully free fork of Android designed to give users the free-est mobile devices currently possible.
We're helping developers use free software licenses properly, and we're following up on complaints about companies that aren't following the terms of the GPL. We help them fix their mistakes and distribute properly. RMS was in fact doing similar work with the precursors of the GPL very early on, but it's now an ongoing part of our work.
Most of the specific things the FSF does now it wasn't doing 30 years ago, but the vision is little changed from the original paperwork—we aim to create a world where everything users want to do on any computer can be done using free software; a world where users control their computers and not the other way around."
### A cult of personality ###
There is little doubt in anyone's minds about the value the FSF brings. As John just highlighted, its efforts span not just the creation and licensing of free software, but also recognizing, certifying, and advocating a culture of freedom in technology.
The head of the FSF is the inimitable Richard M. Stallman, commonly referred to as RMS.
RMS is a curious character. He has demonstrated an unbelievable level of commitment to his ideas, philosophy, and ethical devotion to freedom in software.
While he is sometimes mocked online for his social awkwardness, be it things said in his speeches, his bizarre travel requirements, or other sometimes cringeworthy moments, RMS's perspectives on software and freedom are generally rock-solid. He takes a remarkably consistent approach to his perspectives and he is clearly a careful thinker about not just his own thoughts but the wider movement he is leading. My only criticism is that I think from time to time he somewhat over-eggs the pudding with the voracity of his words. But hey, given his importance in our world, I would rather take an extra egg than no pudding for anyone. O.K., I get that the whole pudding thing here was strained...
So RMS is a key part of the FSF, but the organization is also much more than that. There are employees, a board, and many contributors. I was curious to see how much of a role RMS plays these days in the FSF. John shared this with me.
"RMS is the FSF's President, and does that work without receiving a salary from the FSF. He continues his grueling global speaking schedule, advocating for free software and computer user freedom in dozens of countries each year. In the course of that, he meets with government officials as well as local activists connected with all varieties of social movements. He also raises funds for the FSF and inspires many people to volunteer."
"In between engagements, he does deep thinking on issues facing the free software movement, and anticipates new challenges. Often this leads to new articles—he wrote a 3-part series for Wired earlier this year about free software and free hardware designs—or new ideas communicated to the FSF's staff as the basis for future projects."
As we delved into the cult of personality, I wanted to tap John's perspectives on how wide the free software movement has grown.
I remember being at the [Open Source Think Tank][12] (an event that brings together execs from various open source organizations) and there was a case study where attendees were asked to recommend license choice for a particular project. The vast majority of break-out groups recommended the Apache Software License (APL) over the GNU Public License (GPL).
This stuck in my mind as since then I have noticed that many companies seem to have opted for open licenses other than the GPL. I was curious to see if John had noticed a trend towards the APL as opposed to the GPL.
"Has there been? I'm not so sure. I gave a presentation at FOSDEM a few years ago called 'Is Copyleft Being Framed?' that showed some of the problems with the supposed data behind claims of shifts in license adoption. I'll be publishing an article soon on this, but here's some of the major problems:
- Free software license choices do not exist in a vacuum. The number of people choosing proprietary software licenses also needs to be considered in order to draw the kinds of conclusions that people want to draw. I find it much more likely that lax permissive license choices (such as the Apache License or 3-clause BSD) are trading off with proprietary license choices, rather than with the GPL.
- License counters often, ironically, don't publish the software they use to collect that data as free software. That means we can't inspect their methods or reproduce their results. Some people are now publishing the code they use, but certainly any that don't should be completely disregarded. Science has rules.
- What counts as a thing with a license? Are we really counting an app under the APL that makes funny noises as 1:1 with GNU Emacs under GPLv3? If not, how do we decide which things to treat as equals? Are we only looking at software that actually works? Are we making sure not to double- and triple- count programs that exist on multiple hosting sites, and what about ports for different OSes?
The question is interesting to ponder, but every conclusion I've seen so far has been extremely premature in light of the actual data. I'd much rather see a survey of developers asking about why they chose particular licenses for their projects than any more of these attempts to programmatically ascertain the license of programs and then ascribe human intentions on to patterns in that data.
Copyleft is as vital as it ever was. Permissively licensed software is still free software and on-face a good thing, but it is contingent and needs an accompanying strong social commitment to not incorporate it in proprietary software. If free software's major long-term impact is enabling businesses to more efficiently make products that restrict us, then we have achieved nothing for computer user freedom."
### Rising to new challenges ###
30 years is an impressive time for any organization to be around, and particularly one with such important goals that span so many different industries, professions, governments, and cultures.
As I started to wrap up the interview I wanted to get a better sense of what the FSF's primary function is today, 30 years after the mission started.
"I think the FSF is in a very interesting position of both being a steady rock and actively pushing the envelope."
"We have core documents like the [Free Software Definition][13], the [GNU General Public License][14], and the [list we maintain of free and nonfree software licenses][15], which have been keystones in the construction of the world of free software we have today. People place a great deal of trust in us to stay true to the principles outlined in those documents, and to apply them correctly and wisely in our assessments of new products or practices in computing. In this role, we hold the ladder for others to climb. As a 501(c)(3) charity held legally accountable to the public interest, and about 85% funded by individuals, we have the right structure for this."
"But we also push the envelope. We take on challenges that others say are too hard. I guess that means we also build ladders? Or maybe I should stop with the metaphors."
While John may not be great with metaphors (like I am one to talk), the FSF is great at setting a mission and demonstrating a devout commitment to it. This mission starts with a belief that free software should be everywhere.
"We are not satisfied with the idea that you can get a laptop that works with free software except for a few components. We're not satisfied that you can have a tablet that runs a lot of free software, and just uses proprietary software to communicate with networks and to accelerate video and to take pictures and to check in on your flight and to call an Über and to.. Well, we are happy about some such developments for sure, but we are also unhappy about the suggestion that we should be fully content with them. Any proprietary software on a system is both an injustice to the user and inherently a threat to users' security. These almost-free things can be stepping stones on the way to a free world, but only if we keep our feet moving."
In the early years of the FSF, we actually had to get a free operating system written. This has now been done by GNU and Linux and many collaborators, although there is always more software to write and bugs to fix. So while the FSF does still sponsor free software development in specific areas, there are thankfully many other organizations also doing this."
A key part of the challenge John is referring to is getting the right hardware into the hands of the right people.
"What we have been focusing on now are the challenges I highlighted in the first question. We are in desperate need of hardware in several different areas that fully supports free software. We have been talking a lot at the FSF about what we can do to address this, and I expect us to be making some significant moves to both increase our support for some of the projects already out there—as we having been doing to some extent through our Respects Your Freedom certification program—and possibly to launch some projects of our own. The same goes for the network service problem. I think we need to tackle them together, because having full control over the mobile components has great potential for changing how we relate to services, and decentralizing more and more services will in turn shape the mobile components."
I hope folks will support the FSF as we work to grow and tackle these challenges. Hardware is expensive and difficult, as is making usable, decentralized, federated replacements for network services. We're going to need the resources and creativity of a lot of people. But, 30 years ago, a community rallied around RMS and the concept of copyleft to write an entire operating system. I've spent my last 12 years at the FSF because I believe we can rise to the new challenges in the same way."
### Final thoughts ###
In reading John's thoughtful responses to my questions, and in knowing various FSF members, the one sense that resonates for me is the sheer level of passion that is alive and kicking in the FSF. This is not an organization that has got bored or disillusioned with its mission. Its passion and commitment is as voracious as it has ever been.
While I don't always agree with the FSF and I sometimes think its approach is a little one-dimensional at times, I have been and will continue to be a huge fan and supporter of its work. The FSF represent the ethical heartbeat of much of the free software and open source work that happens across the world. It represents a world view that is pretty hard to the left, but I believe its passion and conviction helps to bring people further to the right a little closer to the left too.
Sure, RMS can be odd, somewhat hardline, and a little sensational, but he is precisely the kind of leader that is valuable in a movement that encapsulates a mixture of technology, ethics, and culture. We need an RMS in much the same way we need a Torvalds, a Shuttleworth, a Whitehurst, and a Zemlin. These different people bring together mixture of perspectives that ultimately maps to technology that can be adaptable to almost any set of use cases, ethics, and ambitions.
So, in closing, I want to thank the FSF for its tremendous efforts, and I wish the FSF and its fearless leaders, one Richard M. Stallman and one John Sullivan, another 30 years of fighting the good fight. Go get 'em!
> This article is part of Jono Bacon's Six Degrees column, where he shares his thoughts and perspectives on culture, communities, and trends in open source.
--------------------------------------------------------------------------------
via: http://opensource.com/business/15/9/free-software-foundation-30-years
作者：[Jono Bacon][a]
译者：[译者ID](https://github.com/译者ID)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
[a]:http://opensource.com/users/jonobacon
[1]:Welcome back, folks, to a new Six Degrees column. As usual, please send your thoughts on this piece to the comment box and your suggestions for future columns to my inbox.
[2]:http://www.fsf.org/
[3]:http://twitter.com/johns_fsf/
[4]:https://en.wikipedia.org/wiki/Amiga_1000
[5]:https://en.wikipedia.org/wiki/Adobe_PageMaker
[6]:https://www.youtube.com/watch?v=izGwDsrQ1eQ
[7]:http://fsf.org/
[8]:http://emailselfdefense.fsf.org/
[9]:http://fsf.org/ryf
[10]:http://directory.fsf.org/
[11]:http://www.replicant.us/
[12]:http://www.osthinktank.com/
[13]:http://www.fsf.org/about/what-is-free-software
[14]:http://www.gnu.org/licenses/gpl-3.0.en.html
[15]:http://www.gnu.org/licenses/licenses.en.html

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ictlyh Translating
Do Simple Math In Ubuntu And elementary OS With NaSC
================================================================================
![](http://itsfoss.itsfoss.netdna-cdn.com/wp-content/uploads/2015/09/Make-Math-Simpler-with-NaSC.jpg)
[NaSC][1], abbreviation Not a Soulver Clone, is a third party app developed for elementary OS. Whatever the name suggests, NaSC is heavily inspired by [Soulver][2], an OS X app for doing maths like a normal person.
elementary OS itself draws from OS X and it is not a surprise that a number of the third party apps it has got, are also inspired by OS X apps.
Coming back to NaSC, what exactly it means by “maths like a normal person “? Well, it means to write like how you think in your mind. As per the description of the app:
> “Its an app where you do maths like a normal person. It lets you type whatever you want and smartly figures out what is math and spits out an answer on the right pane. Then you can plug those answers in to future equations and if that answer changes, so does the equations its used in.”
Still not convinced? Here, take a look at this screenshot.
![](http://itsfoss.itsfoss.netdna-cdn.com/wp-content/uploads/2015/09/NaSC.png)
Now, you see what is ‘math for normal person’? Honestly, I am not a fan of such apps but it might be useful for some of you perhaps. Let’s see how can you install NaSC in elementary OS, Ubuntu and Linux Mint.
### Install NaSC in Ubuntu, elementary OS and Mint ###
There is a PPA available for installing NaSC. The PPA says ‘daily’ which could mean daily build (i.e. unstable) but in my quick test, it worked just fine.
Open a terminal and use the following commands:
sudo apt-add-repository ppa:nasc-team/daily
sudo apt-get update
sudo apt-get install nasc
Here is a screenshot of NaSC in Ubuntu 15.04:
![](http://itsfoss.itsfoss.netdna-cdn.com/wp-content/uploads/2015/09/NaSC-Ubuntu.png)
If you want to remove it, you can use the following commands:
sudo apt-get remove nasc
sudo apt-add-repository --remove ppa:nasc-team/daily
If you try it, do share your experience with it. In addition to this, you can also try [Vocal podcast app for Linux][3] from third party elementary OS apps.
--------------------------------------------------------------------------------
via: http://itsfoss.com/math-ubuntu-nasc/
作者：[Abhishek][a]
译者：[译者ID](https://github.com/译者ID)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
[a]:http://itsfoss.com/author/abhishek/
[1]:http://parnold-x.github.io/nasc/
[2]:http://www.acqualia.com/soulver/
[3]:http://itsfoss.com/podcast-app-vocal-linux/

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How To Manage Log Files With Logrotate On Ubuntu 12.10
================================================================================
#### About Logrotate ####
Logrotate is a utility/tool that manages activities like automatic rotation, removal and compression of log files in a system. This is an excellent tool to manage your logs conserve precious disk space. By having a simple yet powerful configuration file, different parameters of logrotation can be controlled. This gives complete control over the way logs can be automatically managed and need not necessitate manual intervention.
### Prerequisites ###
As a prerequisite, we are assuming that you have gone through the article on how to set up your droplet or VPS. If not, you can find the article [here][1]. This tutorial requires you to have a VPS up and running and have you log into it.
#### Setup Logrotate ####
### Step 1—Update System and System Packages ###
Run the following command to update the package lists from apt-get and get the information on the newest versions of packages and their dependencies.
sudo apt-get update
### Step 2—Install Logrotate ###
If logrotate is not already on your VPS, install it now through apt-get.
sudo apt-get install logrotate
### Step 3 — Confirmation ###
To verify that logrotate was successfully installed, run this in the command prompt.
logrotate
Since the logrotate utility is based on configuration files, the above command will not rotate any files and will show you a brief overview of the usage and the switch options available.
### Step 4—Configure Logrotate ###
Configurations and default options for the logrotate utility are present in:
/etc/logrotate.conf
Some of the important configuration settings are : rotation-interval, log-file-size, rotation-count and compression.
Application-specific log file information (to override the defaults) are kept at:
/etc/logrotate.d/
We will have a look at a few examples to understand the concept better.
### Step 5—Example ###
An example application configuration setting would be the dpkg (Debian package management system), that is stored in /etc/logrotate.d/dpkg. One of the entries in this file would be:
/var/log/dpkg.log {
monthly
rotate 12
compress
delaycompress
missingok
notifempty
create 644 root root
}
What this means is that:
- the logrotation for dpkg monitors the /var/log/dpkg.log file and does this on a monthly basis this is the rotation interval.
- 'rotate 12' signifies that 12 days worth of logs would be kept.
- logfiles can be compressed using the gzip format by specifying 'compress' and 'delaycompress' delays the compression process till the next log rotation. 'delaycompress' will work only if 'compress' option is specified.
- 'missingok' avoids halting on any error and carries on with the next log file.
- 'notifempty' avoid log rotation if the logfile is empty.
- 'create <mode> <owner> <group>' creates a new empty file with the specified properties after log-rotation.
Though missing in the above example, 'size' is also an important setting if you want to control the sizing of the logs growing in the system.
A configuration setting of around 100MB would look like:
size 100M
Note that If both size and rotation interval are set, then size is taken as a higher priority. That is, if a configuration file has the following settings:
monthly
size 100M
then the logs are rotated once the file size reaches 100M and this need not wait for the monthly cycle.
### Step 6—Cron Job ###
You can also set the logrotation as a cron so that the manual process can be avoided and this is taken care of automatically. By specifying an entry in /etc/cron.daily/logrotate , the rotation is triggered daily.
### Step 7—Status Check and Verification ###
To verify if a particular log is indeed rotating or not and to check the last date and time of its rotation, check the /var/lib/logrotate/status file. This is a neatly formatted file that contains the log file name and the date on which it was last rotated.
cat /var/lib/logrotate/status
A few entries from this file, for example:
"/var/log/lpr.log" 2013-4-11
"/var/log/dpkg.log" 2013-4-11
"/var/log/pm-suspend.log" 2013-4-11
"/var/log/syslog" 2013-4-11
"/var/log/mail.info" 2013-4-11
"/var/log/daemon.log" 2013-4-11
"/var/log/apport.log" 2013-4-11
Congratulations! You have logrotate installed in your system. Now, change the configuration settings as per your requirements.
Try 'man logrotate' or 'logrotate -?' for more details.
--------------------------------------------------------------------------------
via: https://www.digitalocean.com/community/tutorials/how-to-manage-log-files-with-logrotate-on-ubuntu-12-10
译者：[译者ID](https://github.com/译者ID)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
[1]:https://www.digitalocean.com/community/articles/initial-server-setup-with-ubuntu-12-04

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Make Math Simple in Ubuntu / Elementary OS via NaSC
================================================================================
![](http://ubuntuhandbook.org/wp-content/uploads/2015/09/nasc-icon.png)
NaSC (Not a Soulver Clone) is an open source software designed for Elementary OS to do arithmetics. It’s kinda similar to the Mac app [Soulver][1].
> Its an app where you do maths like a normal person. It lets you type whatever you want and smartly figures out what is math and spits out an answer on the right pane. Then you can plug those answers in to future equations and if that answer changes, so does the equations its used in.
With NaSC you can for example:
- Perform calculations with strangers you can define yourself
- Change the units and values ​​(in m cm, dollar euro …)
- Knowing the surface area of ​​a planet
- Solve of second-degree polynomial
- and more …
![nasc-eos](http://ubuntuhandbook.org/wp-content/uploads/2015/09/nasc-eos.jpg)
At the first launch, NaSC offers a tutorial that details possible features. You can later click the help icon on headerbar to get more.
![nasc-help](http://ubuntuhandbook.org/wp-content/uploads/2015/09/nasc-help.jpg)
In addition, the software allows to save your file in order to continue the work. It can be also shared on Pastebin with a defined time.
### Install NaSC in Ubuntu / Elementary OS Freya: ###
For Ubuntu 15.04, Ubuntu 15.10, Elementary OS Freya, open terminal from the Dash, App Launcher and run below commands one by one:
1. Add the [NaSC PPA][2] via command:
sudo apt-add-repository ppa:nasc-team/daily
![nasc-ppa](http://ubuntuhandbook.org/wp-content/uploads/2015/09/nasc-ppa.jpg)
2. If you’ve installed Synaptic Package Manager, search for and install `nasc` via it after clicking Reload button.
Or run below commands to update system cache and install the software:
sudo apt-get update
sudo apt-get install nasc
3. **(Optional)** To remove the software as well as NaSC, run:
sudo apt-get remove nasc && sudo add-apt-repository -r ppa:nasc-team/daily
For those who don’t want to add PPA, grab the .deb package directly from [this page][3].
--------------------------------------------------------------------------------
via: http://ubuntuhandbook.org/index.php/2015/09/make-math-simple-in-ubuntu-elementary-os-via-nasc/
作者：[Ji m][a]
译者：[译者ID](https://github.com/译者ID)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
[a]:http://ubuntuhandbook.org/index.php/about/
[1]:http://www.acqualia.com/soulver/
[2]:https://launchpad.net/~nasc-team/+archive/ubuntu/daily/
[3]:http://ppa.launchpad.net/nasc-team/daily/ubuntu/pool/main/n/nasc/

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10 Useful Linux Command Line Tricks for Newbies – Part 2
================================================================================
I remember when I first started using Linux and I was used to the graphical interface of Windows, I truly hated the Linux terminal. Back then I was finding the commands hard to remember and proper use of each one of them. With time I realised the beauty, flexibility and usability of the Linux terminal and to be honest a day doesn’t pass without using. Today, I would like to share some useful tricks and tips for Linux new comers to ease their transition to Linux or simply help them learn something new (hopefully).
![10 Linux Commandline Tricks for Newbies](http://www.tecmint.com/wp-content/uploads/2015/09/10-Linux-Commandline-Tricks.jpg)
10 Linux Commandline Tricks – Part 2
- [5 Interesting Command Line Tips and Tricks in Linux – Part 1][1]
- [5 Useful Commands to Manage Linux File Types – Part 3][2]
This article intends to show you some useful tricks how to use the Linux terminal like a pro with minimum amount of skills. All you need is a Linux terminal and some free time to test these commands.
### 1. Find the right command ###
Executing the right command can be vital for your system. However in Linux there are so many different command lines that they are often hard to remember. So how do you search for the right command you need? The answer is apropos. All you need to run is:
# apropos <description>
Where you should change the “description” with the actual description of the command you are looking for. Here is a good example:
# apropos "list directory"
dir (1) - list directory contents
ls (1) - list directory contents
ntfsls (8) - list directory contents on an NTFS filesystem
vdir (1) - list directory contents
On the left you can see the commands and on the right their description.
### 2. Execute Previous Command ###
Many times you will need to execute the same command over and over again. While you can repeatedly press the Up key on your keyboard, you can use the history command instead. This command will list all commands you entered since you launched the terminal:
# history
1 fdisk -l
2 apt-get install gnome-paint
3 hostname tecmint.com
4 hostnamectl tecmint.com
5 man hostnamectl
6 hostnamectl --set-hostname tecmint.com
7 hostnamectl -set-hostname tecmint.com
8 hostnamectl set-hostname tecmint.com
9 mount -t "ntfs" -o
10 fdisk -l
11 mount -t ntfs-3g /dev/sda5 /mnt
12 mount -t rw ntfs-3g /dev/sda5 /mnt
13 mount -t -rw ntfs-3g /dev/sda5 /mnt
14 mount -t ntfs-3g /dev/sda5 /mnt
15 mount man
16 man mount
17 mount -t -o ntfs-3g /dev/sda5 /mnt
18 mount -o ntfs-3g /dev/sda5 /mnt
19 mount -ro ntfs-3g /dev/sda5 /mnt
20 cd /mnt
...
As you will see from the output above, you will receive a list of all commands that you have ran. On each line you have number indicating the row in which you have entered the command. You can recall that command by using:
!#
Where # should be changed with the actual number of the command. For better understanding, see the below example:
!501
Is equivalent to:
# history
### 3. Use midnight Commander ###
If you are not used to using commands such cd, cp, mv, rm than you can use the midnight command. It is an easy to use visual shell in which you can also use mouse:
![Midnight Commander in Action](http://www.tecmint.com/wp-content/uploads/2015/09/mc-command.jpg)
Midnight Commander in Action
Thanks to the F1 – F12 keys, you can easy perform different tasks. Simply check the legend at the bottom. To select a file or folder click the “Insert” button.
In short the midnight command is called “mc“. To install mc on your system simply run:
$ sudo apt-get install mc [On Debian based systems]
----------
# yum install mc [On Fedora based systems]
Here is a simple example of using midnight commander. Open mc by simply typing:
# mc
Now use the TAB button to switch between windows – left and right. I have a LibreOffice file that I will move to “Software” folder:
![Midnight Commander Move Files](http://www.tecmint.com/wp-content/uploads/2015/09/Midnight-Commander-Move-Files.jpg)
Midnight Commander Move Files
To move the file in the new directory press F6 button on your keyboard. MC will now ask you for confirmation:
![Move Files to New Directory](http://www.tecmint.com/wp-content/uploads/2015/09/Move-Files-to-new-Directory.png)
Move Files to New Directory
Once confirmed, the file will be moved in the new destination directory.
Read More: [How to Use Midnight Commander File Manager in Linux][4]
### 4. Shutdown Computer at Specific Time ###
Sometimes you will need to shutdown your computer some hours after your work hours have ended. You can configure your computer to shut down at specific time by using:
$ sudo shutdown 21:00
This will tell your computer to shut down at the specific time you have provided. You can also tell the system to shutdown after specific amount of minutes:
$ sudo shutdown +15
That way the system will shut down in 15 minutes.
### 5. Show Information about Known Users ###
You can use a simple command to list your Linux system users and some basic information about them. Simply use:
# lslogins
This should bring you the following output:
UID USER PWD-LOCK PWD-DENY LAST-LOGIN GECOS
0 root 0 0 Apr29/11:35 root
1 bin 0 1 bin
2 daemon 0 1 daemon
3 adm 0 1 adm
4 lp 0 1 lp
5 sync 0 1 sync
6 shutdown 0 1 Jul19/10:04 shutdown
7 halt 0 1 halt
8 mail 0 1 mail
10 uucp 0 1 uucp
11 operator 0 1 operator
12 games 0 1 games
13 gopher 0 1 gopher
14 ftp 0 1 FTP User
23 squid 0 1
25 named 0 1 Named
27 mysql 0 1 MySQL Server
47 mailnull 0 1
48 apache 0 1 Apache
...
### 6. Search for Files ###
Searching for files can sometimes be not as easy as you think. A good example for searching for files is:
# find /home/user -type f
This command will search for all files located in /home/user. The find command is extremely powerful one and you can pass more options to it to make your search even more detailed. If you want to search for files larger than given size, you can use:
# find . -type f -size 10M
The above command will search from current directory for all files that are larger than 10 MB. Make sure not to run the command from the root directory of your Linux system as this may cause high I/O on your machine.
One of the most frequently used combinations that I use find with is “exec” option, which basically allows you to run some actions on the results of the find command.
For example, lets say that we want to find all files in a directory and change their permissions. This can be easily done with:
# find /home/user/files/ -type f -exec chmod 644 {} \;
The above command will search for all files in the specified directory recursively and will executed chmod command on the found files. I am sure you will find many more uses on this command in future, for now read [35 Examples of Linux ‘find’ Command and Usage][5].
### 7. Build Directory Trees with one Command ###
You probably know that you can create new directories by using the mkdir command. So if you want to create a new folder you will run something like this:
# mkdir new_folder
But what, if you want to create 5 subfolders within that folder? Running mkdir 5 times in a row is not a good solution. Instead you can use -p option like that:
# mkdir -p new_folder/{folder_1,folder_2,folder_3,folder_4,folder_5}
In the end you should have 5 folders located in new_folder:
# ls new_folder/
folder_1 folder_2 folder_3 folder_4 folder_5
### 8. Copy File into Multiple Directories ###
File copying is usually performed with the cp command. Copying a file usually looks like this:
# cp /path-to-file/my_file.txt /path-to-new-directory/
Now imagine that you need to copy that file in multiple directories:
# cp /home/user/my_file.txt /home/user/1
# cp /home/user/my_file.txt /home/user/2
# cp /home/user/my_file.txt /home/user/3
This is a bit absurd. Instead you can solve the problem with a simple one line command:
# echo /home/user/1/ /home/user/2/ /home/user/3/ | xargs -n 1 cp /home/user/my_file.txt
### 9. Deleting Larger Files ###
Sometimes files can grow extremely large. I have seen cases where a single log file went over 250 GB large due to poor administrating skills. Removing the file with rm utility might not be sufficient in such cases due to the fact that there is extremely large amount of data that needs to be removed. The operation will be a “heavy” one and should be avoided. Instead, you can go with a really simple solution:
# > /path-to-file/huge_file.log
Where of course you will need to change the path and the file names with the exact ones to match your case. The above command will simply write an empty output to the file. In more simpler words it will empty the file without causing high I/O on your system.
### 10. Run Same Command on Multiple Linux Servers ###
Recently one of our readers asked in our [LinuxSay forum][6], how to execute single command to multiple Linux boxes at once using SSH. He had his machines IP addresses looking like this:
10.0.0.1
10.0.0.2
10.0.0.3
10.0.0.4
10.0.0.5
So here is a simple solution of this issue. Collect the IP addresses of the servers in a one file called list.txt one under other just as shown above. Then you can run:
# for in $i(cat list.txt); do ssh user@$i 'bash command'; done
In the above example you will need to change “user” with the actual user with which you will be logging and “bash command” with the actual bash command you wish to execute. The method is better working when you are [using passwordless authentication with SSH key][7] to your machines as that way you will not need to enter the password for your user over and over again.
Note that you may need to pass some additional parameters to the SSH command depending on your Linux boxes setup.
### Conclusion ###
The above examples are really simple ones and I hope they have helped you to find some of the beauty of Linux and how you can easily perform different operations that can take much more time on other operating systems.
--------------------------------------------------------------------------------
via: http://www.tecmint.com/10-useful-linux-command-line-tricks-for-newbies/
作者：[Marin Todorov][a]
译者：[译者ID](https://github.com/译者ID)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
[a]:http://www.tecmint.com/author/marintodorov89/
[1]:http://www.tecmint.com/5-linux-command-line-tricks/
[2]:http://www.tecmint.com/manage-file-types-and-set-system-time-in-linux/
[3]:http://www.tecmint.com/history-command-examples/
[4]:http://www.tecmint.com/midnight-commander-a-console-based-file-manager-for-linux/
[5]:http://www.tecmint.com/35-practical-examples-of-linux-find-command/
[6]:http://www.linuxsay.com/
[7]:http://www.tecmint.com/ssh-passwordless-login-using-ssh-keygen-in-5-easy-steps/

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5 Useful Commands to Manage File Types and System Time in Linux – Part 3
================================================================================
Adapting to using the command line or terminal can be very hard for beginners who want to learn Linux. Because the terminal gives more control over a Linux system than GUIs programs, one has to get a used to running commands on the terminal. Therefore to memorize different commands in Linux, you should use the terminal on a daily basis to understand how commands are used with different options and arguments.
![Manage File Types and Set Time in Linux](http://www.tecmint.com/wp-content/uploads/2015/09/Find-File-Types-in-Linux.jpg)
Manage File Types and Set Time in Linux – Part 3
Please go through our previous parts of this [Linux Tricks][1] series.
- [5 Interesting Command Line Tips and Tricks in Linux – Part 1][2]
- [ Useful Commandline Tricks for Newbies – Part 2][3]
In this article, we are going to look at some tips and tricks of using 10 commands to work with files and time on the terminal.
### File Types in Linux ###
In Linux, everything is considered as a file, your devices, directories and regular files are all considered as files.
There are different types of files in a Linux system:
- Regular files which may include commands, documents, music files, movies, images, archives and so on.
- Device files: which are used by the system to access your hardware components.
There are two types of device files block files that represent storage devices such as harddisks, they read data in blocks and character files read data in a character by character manner.
- Hardlinks and softlinks: they are used to access files from any where on a Linux filesystem.
- Named pipes and sockets: allow different processes to communicate with each other.
#### 1. Determining the type of a file using ‘file’ command ####
You can determine the type of a file by using the file command as follows. The screenshot below shows different examples of using the file command to determine the types of different files.
tecmint@tecmint ~/Linux-Tricks $ dir
BACKUP master.zip
crossroads-stable.tar.gz num.txt
EDWARD-MAYA-2011-2012-NEW-REMIX.mp3 reggea.xspf
Linux-Security-Optimization-Book.gif tmp-link
tecmint@tecmint ~/Linux-Tricks $ file BACKUP/
BACKUP/: directory
tecmint@tecmint ~/Linux-Tricks $ file master.zip
master.zip: Zip archive data, at least v1.0 to extract
tecmint@tecmint ~/Linux-Tricks $ file crossroads-stable.tar.gz
crossroads-stable.tar.gz: gzip compressed data, from Unix, last modified: Tue Apr 5 15:15:20 2011
tecmint@tecmint ~/Linux-Tricks $ file Linux-Security-Optimization-Book.gif
Linux-Security-Optimization-Book.gif: GIF image data, version 89a, 200 x 259
tecmint@tecmint ~/Linux-Tricks $ file EDWARD-MAYA-2011-2012-NEW-REMIX.mp3
EDWARD-MAYA-2011-2012-NEW-REMIX.mp3: Audio file with ID3 version 2.3.0, contains: MPEG ADTS, layer III, v1, 192 kbps, 44.1 kHz, JntStereo
tecmint@tecmint ~/Linux-Tricks $ file /dev/sda1
/dev/sda1: block special
tecmint@tecmint ~/Linux-Tricks $ file /dev/tty1
/dev/tty1: character special
#### 2. Determining the file type using ‘ls’ and ‘dir’ commands ####
Another way of determining the type of a file is by performing a long listing using the ls and [dir][4] commands.
Using ls -l to determine the type of a file.
When you view the file permissions, the first character shows the file type and the other charcters show the file permissions.
tecmint@tecmint ~/Linux-Tricks $ ls -l
total 6908
drwxr-xr-x 2 tecmint tecmint 4096 Sep 9 11:46 BACKUP
-rw-r--r-- 1 tecmint tecmint 1075620 Sep 9 11:47 crossroads-stable.tar.gz
-rwxr----- 1 tecmint tecmint 5916085 Sep 9 11:49 EDWARD-MAYA-2011-2012-NEW-REMIX.mp3
-rw-r--r-- 1 tecmint tecmint 42122 Sep 9 11:49 Linux-Security-Optimization-Book.gif
-rw-r--r-- 1 tecmint tecmint 17627 Sep 9 11:46 master.zip
-rw-r--r-- 1 tecmint tecmint 5 Sep 9 11:48 num.txt
-rw-r--r-- 1 tecmint tecmint 0 Sep 9 11:46 reggea.xspf
-rw-r--r-- 1 tecmint tecmint 5 Sep 9 11:47 tmp-link
Using ls -l to determine block and character files.
tecmint@tecmint ~/Linux-Tricks $ ls -l /dev/sda1
brw-rw---- 1 root disk 8, 1 Sep 9 10:53 /dev/sda1
tecmint@tecmint ~/Linux-Tricks $ ls -l /dev/tty1
crw-rw---- 1 root tty 4, 1 Sep 9 10:54 /dev/tty1
Using dir -l to determine the type of a file.
tecmint@tecmint ~/Linux-Tricks $ dir -l
total 6908
drwxr-xr-x 2 tecmint tecmint 4096 Sep 9 11:46 BACKUP
-rw-r--r-- 1 tecmint tecmint 1075620 Sep 9 11:47 crossroads-stable.tar.gz
-rwxr----- 1 tecmint tecmint 5916085 Sep 9 11:49 EDWARD-MAYA-2011-2012-NEW-REMIX.mp3
-rw-r--r-- 1 tecmint tecmint 42122 Sep 9 11:49 Linux-Security-Optimization-Book.gif
-rw-r--r-- 1 tecmint tecmint 17627 Sep 9 11:46 master.zip
-rw-r--r-- 1 tecmint tecmint 5 Sep 9 11:48 num.txt
-rw-r--r-- 1 tecmint tecmint 0 Sep 9 11:46 reggea.xspf
-rw-r--r-- 1 tecmint tecmint 5 Sep 9 11:47 tmp-link
#### 3. Counting number of files of a specific type ####
Next we shall look at tips on counting number of files of a specific type in a given directory using the ls, [grep][5] and [wc][6] commands. Communication between the commands is achieved through named piping.
- grep – command to search according to a given pattern or regular expression.
- wc – command to count lines, words and characters.
Counting number of regular files
In Linux, regular files are represented by the `–` symbol.
tecmint@tecmint ~/Linux-Tricks $ ls -l | grep ^- | wc -l
7
**Counting number of directories**
In Linux, directories are represented by the `d` symbol.
tecmint@tecmint ~/Linux-Tricks $ ls -l | grep ^d | wc -l
1
**Counting number of symbolic and hard links**
In Linux, symblic and hard links are represented by the l symbol.
tecmint@tecmint ~/Linux-Tricks $ ls -l | grep ^l | wc -l
0
**Counting number of block and character files**
In Linux, block and character files are represented by the `b` and `c` symbols respectively.
tecmint@tecmint ~/Linux-Tricks $ ls -l /dev | grep ^b | wc -l
37
tecmint@tecmint ~/Linux-Tricks $ ls -l /dev | grep ^c | wc -l
159
#### 4. Finding files on a Linux system ####
Next we shall look at some commands one can use to find files on a Linux system, these include the locate, find, whatis and which commands.
**Using the locate command to find files**
In the output below, I am trying to locate the [Samba server configuration][7] for my system.
tecmint@tecmint ~/Linux-Tricks $ locate samba.conf
/usr/lib/tmpfiles.d/samba.conf
/var/lib/dpkg/info/samba.conffiles
**Using the find command to find files**
To learn how to use the find command in Linux, you can read our following article that shows more than 30+ practical examples and usage of find command in Linux.
- [35 Examples of ‘find’ Command in Linux][8]
**Using the whatis command to locate commands**
The whatis command is mostly used to locate commands and it is special because it gives information about a command, it also finds configurations files and manual entries for a command.
tecmint@tecmint ~/Linux-Tricks $ whatis bash
bash (1) - GNU Bourne-Again SHell
tecmint@tecmint ~/Linux-Tricks $ whatis find
find (1) - search for files in a directory hierarchy
tecmint@tecmint ~/Linux-Tricks $ whatis ls
ls (1) - list directory contents
**Using which command to locate commands**
The which command is used to locate commands on the filesystem.
tecmint@tecmint ~/Linux-Tricks $ which mkdir
/bin/mkdir
tecmint@tecmint ~/Linux-Tricks $ which bash
/bin/bash
tecmint@tecmint ~/Linux-Tricks $ which find
/usr/bin/find
tecmint@tecmint ~/Linux-Tricks $ $ which ls
/bin/ls
#### 5. Working with time on your Linux system ####
When working in a networked environment, it is a good practice to keep the correct time on your Linux system. There are certain services on Linux systems that require correct time to work efficiently on a network.
We shall look at commands you can use to manage time on your machine. In Linux, time is managed in two ways: system time and hardware time.
The system time is managed by a system clock and the hardware time is managed by a hardware clock.
To view your system time, date and timezone, use the date command as follows.
tecmint@tecmint ~/Linux-Tricks $ date
Wed Sep 9 12:25:40 IST 2015
Set your system time using date -s or date –set=”STRING” as follows.
tecmint@tecmint ~/Linux-Tricks $ sudo date -s "12:27:00"
Wed Sep 9 12:27:00 IST 2015
tecmint@tecmint ~/Linux-Tricks $ sudo date --set="12:27:00"
Wed Sep 9 12:27:00 IST 2015
You can also set time and date as follows.
tecmint@tecmint ~/Linux-Tricks $ sudo date 090912302015
Wed Sep 9 12:30:00 IST 2015
Viewing current date from a calendar using cal command.
tecmint@tecmint ~/Linux-Tricks $ cal
September 2015
Su Mo Tu We Th Fr Sa
1 2 3 4 5
6 7 8 9 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30
View hardware clock time using the hwclock command.
tecmint@tecmint ~/Linux-Tricks $ sudo hwclock
Wednesday 09 September 2015 06:02:58 PM IST -0.200081 seconds
To set the hardware clock time, use hwclock –set –date=”STRING” as follows.
tecmint@tecmint ~/Linux-Tricks $ sudo hwclock --set --date="09/09/2015 12:33:00"
tecmint@tecmint ~/Linux-Tricks $ sudo hwclock
Wednesday 09 September 2015 12:33:11 PM IST -0.891163 seconds
The system time is set by the hardware clock during booting and when the system is shutting down, the hardware time is reset to the system time.
Therefore when you view system time and hardware time, they are the same unless when you change the system time. Your hardware time may be incorrect when the CMOS battery is weak.
You can also set your system time using time from the hardware clock as follows.
$ sudo hwclock --hctosys
It is also possible to set hardware clock time using the system clock time as follows.
$ sudo hwclock --systohc
To view how long your Linux system has been running, use the uptime command.
tecmint@tecmint ~/Linux-Tricks $ uptime
12:36:27 up 1:43, 2 users, load average: 1.39, 1.34, 1.45
tecmint@tecmint ~/Linux-Tricks $ uptime -p
up 1 hour, 43 minutes
tecmint@tecmint ~/Linux-Tricks $ uptime -s
2015-09-09 10:52:47
### Summary ###
Understanding file types is Linux is a good practice for begginers, and also managing time is critical especially on servers to manage services reliably and efficiently. Hope you find this guide helpful. If you have any additional information, do not forget to post a comment. Stay connected to Tecmint.
--------------------------------------------------------------------------------
via: http://www.tecmint.com/manage-file-types-and-set-system-time-in-linux/
作者：[Aaron Kili][a]
译者：[译者ID](https://github.com/译者ID)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
[a]:http://www.tecmint.com/author/aaronkili/
[1]:http://www.tecmint.com/tag/linux-tricks/
[2]:http://www.tecmint.com/free-online-linux-learning-guide-for-beginners/
[3]:http://www.tecmint.com/10-useful-linux-command-line-tricks-for-newbies/
[4]:http://www.tecmint.com/linux-dir-command-usage-with-examples/
[5]:http://www.tecmint.com/12-practical-examples-of-linux-grep-command/
[6]:http://www.tecmint.com/wc-command-examples/
[7]:http://www.tecmint.com/setup-samba-file-sharing-for-linux-windows-clients/
[8]:http://www.tecmint.com/35-practical-examples-of-linux-find-command/

209
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ictlyh Translating
Setting Up Samba and Configure FirewallD and SELinux to Allow File Sharing on Linux/Windows Clients – Part 6
================================================================================
Since computers seldom work as isolated systems, it is to be expected that as a system administrator or engineer, you know how to set up and maintain a network with multiple types of servers.
In this article and in the next of this series we will go through the essentials of setting up Samba and NFS servers with Windows/Linux and Linux clients, respectively.
![Setup Samba File Sharing on Linux](http://www.tecmint.com/wp-content/uploads/2015/09/setup-samba-file-sharing-on-linux-windows-clients.png)
RHCE: Setup Samba File Sharing – Part 6
This article will definitely come in handy if you’re called upon to set up file servers in corporate or enterprise environments where you are likely to find different operating systems and types of devices.
Since you can read about the background and the technical aspects of both Samba and NFS all over the Internet, in this article and the next we will cut right to the chase with the topic at hand.
### Step 1: Installing Samba Server ###
Our current testing environment consists of two RHEL 7 boxes and one Windows 8 machine, in that order:
1. Samba / NFS server [box1 (RHEL 7): 192.168.0.18],
2. Samba client #1 [box2 (RHEL 7): 192.168.0.20]
3. Samba client #2 [Windows 8 machine: 192.168.0.106]
![Testing Setup for Samba](http://www.tecmint.com/wp-content/uploads/2015/09/Testing-Setup-for-Samba.png)
Testing Setup for Samba
On box1, install the following packages:
# yum update && yum install samba samba-client samba-common
On box2:
# yum update && yum install samba samba-client samba-common cifs-utils
Once the installation is complete, we’re ready to configure our share.
### Step 2: Setting Up File Sharing Through Samba ###
One of the reason why Samba is so relevant is because it provides file and print services to SMB/CIFS clients, which causes those clients to see the server as if it was a Windows system (I must admit I tend to get a little emotional while writing about this topic as it was my first setup as a new Linux system administrator some years ago).
**Adding system users and setting up permissions and ownership**
To allow for group collaboration, we will create a group named finance with two users (user1 and user2) with [useradd command][1] and a directory /finance in box1.
We will also change the group owner of this directory to finance and set its permissions to 0770 (read, write, and execution permissions for the owner and the group owner):
# groupadd finance
# useradd user1
# useradd user2
# usermod -a -G finance user1
# usermod -a -G finance user2
# mkdir /finance
# chmod 0770 /finance
# chgrp finance /finance
### Step 3:​ Configuring SELinux and Firewalld ###
In preparation to configure /finance as a Samba share, we will need to either disable SELinux or set the proper boolean and security context values as follows (otherwise, SELinux will prevent clients from accessing the share):
# setsebool -P samba_export_all_ro=1 samba_export_all_rw=1
# getsebool –a | grep samba_export
# semanage fcontext –at samba_share_t "/finance(/.*)?"
# restorecon /finance
In addition, we must ensure that Samba traffic is allowed by the [firewalld][2].
# firewall-cmd --permanent --add-service=samba
# firewall-cmd --reload
### Step 4: Configure Samba Share ###
Now it’s time to dive into the configuration file /etc/samba/smb.conf and add the section for our share: we want the members of the finance group to be able to browse the contents of /finance, and save / create files or subdirectories in it (which by default will have their permission bits set to 0770 and finance will be their group owner):
**smb.conf**
----------
[finance]
comment=Directory for collaboration of the company's finance team
browsable=yes
path=/finance
public=no
valid users=@finance
write list=@finance
writeable=yes
create mask=0770
Force create mode=0770
force group=finance
Save the file and then test it with the testparm utility. If there are any errors, the output of the following command will indicate what you need to fix. Otherwise, it will display a review of your Samba server configuration:
![Test Samba Configuration](http://www.tecmint.com/wp-content/uploads/2015/09/Test-Samba-Configuration.png)
Test Samba Configuration
Should you want to add another share that is open to the public (meaning without any authentication whatsoever), create another section in /etc/samba/smb.conf and under the new share’s name copy the section above, only changing public=no to public=yes and not including the valid users and write list directives.
### Step 5: Adding Samba Users ###
Next, you will need to add user1 and user2 as Samba users. To do so, you will use the smbpasswd command, which interacts with Samba’s internal database. You will be prompted to enter a password that you will later use to connect to the share:
# smbpasswd -a user1
# smbpasswd -a user2
Finally, restart Samba, enable the service to start on boot, and make sure the share is actually available to network clients:
# systemctl start smb
# systemctl enable smb
# smbclient -L localhost –U user1
# smbclient -L localhost –U user2
![Verify Samba Share](http://www.tecmint.com/wp-content/uploads/2015/09/Verify-Samba-Share.png)
Verify Samba Share
At this point, the Samba file server has been properly installed and configured. Now it’s time to test this setup on our RHEL 7 and Windows 8 clients.
### Step 6:​ Mounting the Samba Share in Linux ###
First, make sure the Samba share is accessible from this client:
# smbclient –L 192.168.0.18 -U user2
![Mount Samba Share on Linux](http://www.tecmint.com/wp-content/uploads/2015/09/Mount-Samba-Share-on-Linux.png)
Mount Samba Share on Linux
(repeat the above command for user1)
As any other storage media, you can mount (and later unmount) this network share when needed:
# mount //192.168.0.18/finance /media/samba -o username=user1
![Mount Samba Network Share](http://www.tecmint.com/wp-content/uploads/2015/09/Mount-Samba-Network-Share.png)
Mount Samba Network Share
(where /media/samba is an existing directory)
or permanently, by adding the following entry in /etc/fstab file:
**fstab**
----------
//192.168.0.18/finance /media/samba cifs credentials=/media/samba/.smbcredentials,defaults 0 0
Where the hidden file /media/samba/.smbcredentials (whose permissions and ownership have been set to 600 and root:root, respectively) contains two lines that indicate the username and password of an account that is allowed to use the share:
**.smbcredentials**
----------
username=user1
password=PasswordForUser1
Finally, let’s create a file inside /finance and check the permissions and ownership:
# touch /media/samba/FileCreatedInRHELClient.txt
![Create File in Samba Share](http://www.tecmint.com/wp-content/uploads/2015/09/Create-File-in-Samba-Share.png)
Create File in Samba Share
As you can see, the file was created with 0770 permissions and ownership set to user1:finance.
### Step 7: Mounting the Samba Share in Windows ###
To mount the Samba share in Windows, go to My PC and choose Computer, then Map network drive. Next, assign a letter for the drive to be mapped and check Connect using different credentials (the screenshots below are in Spanish, my native language):
![Mount Samba Share in Windows](http://www.tecmint.com/wp-content/uploads/2015/09/Mount-Samba-Share-in-Windows.png)
Mount Samba Share in Windows
Finally, let’s create a file and check the permissions and ownership:
![Create Files on Windows Samba Share](http://www.tecmint.com/wp-content/uploads/2015/09/Create-Files-on-Windows-Samba-Share.png)
Create Files on Windows Samba Share
# ls -l /finance
This time the file belongs to user2 since that’s the account we used to connect from the Windows client.
### Summary ###
In this article we have explained not only how to set up a Samba server and two clients using different operating systems, but also [how to configure the firewalld][3] and [SELinux on the server][4] to allow the desired group collaboration capabilities.
Last, but not least, let me recommend the reading of the online [man page of smb.conf][5] to explore other configuration directives that may be more suitable for your case than the scenario described in this article.
As always, feel free to drop a comment using the form below if you have any comments or suggestions.
--------------------------------------------------------------------------------
via: http://www.tecmint.com/setup-samba-file-sharing-for-linux-windows-clients/
作者：[Gabriel Cánepa][a]
译者：[译者ID](https://github.com/译者ID)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
[a]:http://www.tecmint.com/author/gacanepa/
[1]:http://www.tecmint.com/add-users-in-linux/
[2]:http://www.tecmint.com/firewalld-vs-iptables-and-control-network-traffic-in-firewall/
[3]:http://www.tecmint.com/configure-firewalld-in-centos-7/
[4]:http://www.tecmint.com/selinux-essentials-and-control-filesystem-access/
[5]:https://www.samba.org/samba/docs/man/manpages-3/smb.conf.5.html

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ictlyh Translating
Setting Up NFS Server with Kerberos-based Authentication for Linux Clients – Part 7
================================================================================
In the last article of this series, we reviewed [how to set up a Samba share over a network][1] that may consist of multiple types of operating systems. Now, if you need to set up file sharing for a group of Unix-like clients you will automatically think of the Network File System, or NFS for short.
![Setting Up NFS Server with Kerberos Authentication](http://www.tecmint.com/wp-content/uploads/2015/09/Setting-Kerberos-Authentication-with-NFS.jpg)
RHCE Series: Setting Up NFS Server with Kerberos Authentication – Part 7
In this article we will walk you through the process of using Kerberos-based authentication for NFS shares. It is assumed that you already have set up a NFS server and a client. If not, please refer to [install and configure NFS server][2] – which will list the necessary packages that need to be installed and explain how to perform initial configurations on the server before proceeding further.
In addition, you will want to configure both [SELinux][3] and [firewalld][4] to allow for file sharing through NFS.
The following example assumes that your NFS share is located in /nfs in box2:
# semanage fcontext -a -t public_content_rw_t "/nfs(/.*)?"
# restorecon -R /nfs
# setsebool -P nfs_export_all_rw on
# setsebool -P nfs_export_all_ro on
(where the -P flag indicates persistence across reboots).
Finally, don’t forget to:
#### Create NFS Group and Configure NFS Share Directory ####
1. Create a group called nfs and add the nfsnobody user to it, then change the permissions of the /nfs directory to 0770 and its group owner to nfs. Thus, nfsnobody (which is mapped to the client requests) will have write permissions on the share) and you won’t need to use no_root_squash in the /etc/exports file.
# groupadd nfs
# usermod -a -G nfs nfsnobody
# chmod 0770 /nfs
# chgrp nfs /nfs
2. Modify the exports file (/etc/exports) as follows to only allow access from box1 using Kerberos security (sec=krb5).
**Note**: that the value of anongid has been set to the GID of the nfs group that we created previously:
**exports – Add NFS Share**
----------
/nfs box1(rw,sec=krb5,anongid=1004)
3. Re-export (-r) all (-a) the NFS shares. Adding verbosity to the output (-v) is a good idea since it will provide helpful information to troubleshoot the server if something goes wrong:
# exportfs -arv
4. Restart and enable the NFS server and related services. Note that you don’t have to enable nfs-lock and nfs-idmapd because they will be automatically started by the other services on boot:
# systemctl restart rpcbind nfs-server nfs-lock nfs-idmap
# systemctl enable rpcbind nfs-server
#### Testing Environment and Other Prerequisites ####
In this guide we will use the following test environment:
- Client machine [box1: 192.168.0.18]
- NFS / Kerberos server [box2: 192.168.0.20] (also known as Key Distribution Center, or KDC for short).
**Note**: that Kerberos service is crucial to the authentication scheme.
As you can see, the NFS server and the KDC are hosted in the same machine for simplicity, although you can set them up in separate machines if you have more available. Both machines are members of the `mydomain.com` domain.
Last but not least, Kerberos requires at least a basic schema of name resolution and the [Network Time Protocol][5] service to be present in both client and server since the security of Kerberos authentication is in part based upon the timestamps of tickets.
To set up name resolution, we will use the /etc/hosts file in both client and server:
**host file – Add DNS for Domain**
----------
192.168.0.18 box1.mydomain.com box1
192.168.0.20 box2.mydomain.com box2
In RHEL 7, chrony is the default software that is used for NTP synchronization:
# yum install chrony
# systemctl start chronyd
# systemctl enable chronyd
To make sure chrony is actually synchronizing your system’s time with time servers you may want to issue the following command two or three times and make sure the offset is getting nearer to zero:
# chronyc tracking
![Synchronize Server Time with Chrony](http://www.tecmint.com/wp-content/uploads/2015/09/Synchronize-Time-with-Chrony.png)
Synchronize Server Time with Chrony
### Installing and Configuring Kerberos ###
To set up the KDC, install the following packages on both server and client (omit the server package in the client):
# yum update && yum install krb5-server krb5-workstation pam_krb5
Once it is installed, edit the configuration files (/etc/krb5.conf and /var/kerberos/krb5kdc/kadm5.acl) and replace all instances of example.com (lowercase and uppercase) with `mydomain.com` as follows.
Next, enable Kerberos through the firewall and start / enable the related services.
**Important**: nfs-secure must be started and enabled on the client as well:
# firewall-cmd --permanent --add-service=kerberos
# systemctl start krb5kdc kadmin nfs-secure
# systemctl enable krb5kdc kadmin nfs-secure
Now create the Kerberos database (please note that this may take a while as it requires a some level of entropy in your system. To speed things up, I opened another terminal and ran ping -f localhost for 30-45 seconds):
# kdb5_util create -s
![Create Kerberos Database](http://www.tecmint.com/wp-content/uploads/2015/09/Create-Kerberos-Database.png)
Create Kerberos Database
Next, using the kadmin.local tool, create an admin principal for root:
# kadmin.local
# addprinc root/admin
And add the Kerberos server to the database:
# addprinc -randkey host/box2.mydomain.com
Same with the NFS service for both client (box1) and server (box2). Please note that in the screenshot below I forgot to do it for box1 before quitting:
# addprinc -randkey nfs/box2.mydomain.com
# addprinc -randkey nfs/box1.mydomain.com
And exit by typing quit and pressing Enter:
![Add Kerberos to NFS Server](http://www.tecmint.com/wp-content/uploads/2015/09/Create-Kerboros-for-NFS.png)
Add Kerberos to NFS Server
Then obtain and cache Kerberos ticket-granting ticket for root/admin:
# kinit root/admin
# klist
![Cache Kerberos](http://www.tecmint.com/wp-content/uploads/2015/09/Cache-kerberos-Ticket.png)
Cache Kerberos
The last step before actually using Kerberos is storing into a keytab file (in the server) the principals that are authorized to use Kerberos authentication:
# kdadmin.local
# ktadd host/box2.mydomain.com
# ktadd nfs/box2.mydomain.com
# ktadd nfs/box1.mydomain.com
Finally, mount the share and perform a write test:
# mount -t nfs4 -o sec=krb5 box2:/nfs /mnt
# echo "Hello from Tecmint.com" > /mnt/greeting.txt
![Mount NFS Share](http://www.tecmint.com/wp-content/uploads/2015/09/Mount-NFS-Share.png)
Mount NFS Share
Let’s now unmount the share, rename the keytab file in the client (to simulate it’s not present) and try to mount the share again:
# umount /mnt
# mv /etc/krb5.keytab /etc/krb5.keytab.orig
![Mount Unmount Kerberos NFS Share](http://www.tecmint.com/wp-content/uploads/2015/09/Mount-Unmount-Kerberos-NFS-Share.png)
Mount Unmount Kerberos NFS Share
Now you can use the NFS share with Kerberos-based authentication.
### Summary ###
In this article we have explained how to set up NFS with Kerberos authentication. Since there is much more to the topic than we can cover in a single guide, feel free to check the online [Kerberos documentation][6] and since Kerberos is a bit tricky to say the least, don’t hesitate to drop us a note using the form below if you run into any issue or need help with your testing or implementation.
--------------------------------------------------------------------------------
via: http://www.tecmint.com/setting-up-nfs-server-with-kerberos-based-authentication/
作者：[Gabriel Cánepa][a]
译者：[译者ID](https://github.com/译者ID)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
[a]:http://www.tecmint.com/author/gacanepa/
[1]:http://www.tecmint.com/setup-samba-file-sharing-for-linux-windows-clients/
[2]:http://www.tecmint.com/configure-nfs-server/
[3]:http://www.tecmint.com/selinux-essentials-and-control-filesystem-access/
[4]:http://www.tecmint.com/firewalld-rules-for-centos-7/
[5]:http://www.tecmint.com/install-ntp-server-in-centos/
[6]:http://web.mit.edu/kerberos/krb5-1.12/doc/admin/admin_commands/

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mosh - 一个基于SSH用于连接远程Unix/Linux系统的工具
================================================================================
Mosh表示移动Shell（Mobile Shell）是一个用于从客户端连接远程服务器的命令行工具。它可以像ssh那样使用并包含了更多的功能。它是一个类似ssh的程序，但是提供更多的功能。程序最初由Keith Winstein编写用于类Unix的操作系统中，发布于GNU GPL v3协议下。
![Mosh Shell SSH Client](http://www.tecmint.com/wp-content/uploads/2015/08/Mosh-Shell-SSH-Client.png)
Mosh客户端
#### Mosh的功能 ####
- 它是一个支持漫游的远程终端程序。
- 在所有主流类Unix版本中可用如Linux、FreeBSD、Solaris、Mac OS X和Android。
- 中断连接支持
- 支持智能本地echo
- 用户按键行编辑支持
- 响应式设计及在wifi、3G、长距离连接下的鲁棒性
- 在IP改变后保持连接。它使用UDP代替TCP（在SSH中使用）当连接被重置或者获得新的IP后TCP会超时但是UDP仍然保持连接。
- 在你很长之间之后恢复会话时仍然保持连接。
- 没有网络延迟。立即显示用户输入和删除而没有延迟
- 像SSH那样支持一些旧的方式登录。
- 包丢失处理机制
### Linux中mosh的安装 ###
在Debian、Ubuntu和Mint类似的系统中，你可以很容易地用[apt-get包管理器][1]安装。
# apt-get update
# apt-get install mosh
在基于RHEL/CentOS/Fedora的系统中，要使用[yum 包管理器][3]安装mosh，你需要打开第三方的[EPEL][2]。
# yum update
# yum install mosh
在Fedora 22+的版本中，你需要使用[dnf包管理器][4]来安装mosh。
# dnf install mosh
### 我该如何使用mosh？ ###
1. 让我们尝试使用mosh登录远程Linux服务器。
$ mosh root@192.168.0.150
![Mosh Shell Remote Connection](http://www.tecmint.com/wp-content/uploads/2015/08/Mosh-Shell-Remote-Connection.png)
mosh远程连接
**注意**：你有没有看到一个连接错误，因为我在CentOS 7中还有打开这个端口。一个快速但是我并不建议的解决方法是：
# systemctl stop firewalld [on Remote Server]
更好的方法是打开一个端口并更新防火墙规则。接着用mosh连接到预定义的端口中。至于更深入的细节，也许你会对下面的文章感兴趣。
- [如何配置Firewalld][5]
2. 让我们假设把默认的22端口改到70，这时使用-p选项来使用自定义端口。
$ mosh -p 70 root@192.168.0.150
3. 检查mosh的版本
$ mosh --version
![Check Mosh Version](http://www.tecmint.com/wp-content/uploads/2015/08/Check-Mosh-Version.png)
检查mosh版本
4. 你可以输入‘exit’来退出mosh会话。
$ exit
5. mosh支持很多选项，你可以用下面的方法看到：
$ mosh --help
![Mosh Shell Options](http://www.tecmint.com/wp-content/uploads/2015/08/Mosh-Shell-Options.png)
Mosh选项
#### mosh的利弊 ####
- mosh有额外的需求，比如需要允许UDP直接连接，这在SSH不需要。
- 动态分配的端口范围是60000-61000。第一个打开的端口是分配的。每个连接都需要一个端口。
- 默认端口分配是一个严重的安全问题，尤其是在生产环境中。
- 支持IPv6连接，但是不支持IPv6漫游。
- 不支持回溯
- 不支持X11转发
- 不支持ssh-agent转发
### 总结 ###
Mosh is a nice small utility which is available for download in the repository of most of the Linux Distributions. Though it has a few discrepancies specially security concern and additional requirement it’s features like remaining connected even while roaming is its plus point. My recommendation is Every Linux-er who deals with SSH should try this application and mind it, Mosh is worth a try.
mosh是一款在大多数linux发行版的仓库中可以下载的一款小工具。虽然它有一些差异尤其是安全问题和额外的需求，它的功能像漫游后保持连接是一个加分点。我的建议是任何一个使用ssh的linux用户都应该试试这个程序，mosh值得一试
--------------------------------------------------------------------------------
via: http://www.tecmint.com/install-mosh-shell-ssh-client-in-linux/
作者：[Avishek Kumar][a]
译者：[geekpi](https://github.com/geekpi)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](https://linux.cn/) 荣誉推出
[a]:http://www.tecmint.com/author/avishek/
[1]:http://www.tecmint.com/useful-basic-commands-of-apt-get-and-apt-cache-for-package-management/
[2]:http://www.tecmint.com/how-to-enable-epel-repository-for-rhel-centos-6-5/
[3]:http://www.tecmint.com/20-linux-yum-yellowdog-updater-modified-commands-for-package-mangement/
[4]:http://www.tecmint.com/dnf-commands-for-fedora-rpm-package-management/
[5]:http://www.tecmint.com/configure-firewalld-in-centos-7/

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如何构建Linux 内核
================================================================================
介绍
--------------------------------------------------------------------------------
我不会告诉你怎么在自己的电脑上去构建、安装一个定制化的Linux 内核，这样的[资料](https://encrypted.google.com/search?q=building+linux+kernel#q=building+linux+kernel+from+source+code) 太多了，它们会对你有帮助。本文会告诉你当你在内核源码路径里敲下`make` 时会发生什么。当我刚刚开始学习内核代码时，[Makefile](https://github.com/torvalds/linux/blob/master/Makefile) 是我打开的第一个文件，这个文件看起来真令人害怕 :)。那时候这个[Makefile](https://en.wikipedia.org/wiki/Make_%28software%29) 还只包含了`1591` 行代码，当我开始写本文是，这个[Makefile](https://github.com/torvalds/linux/commit/52721d9d3334c1cb1f76219a161084094ec634dc) 已经是第三个候选版本了。
这个makefile 是Linux 内核代码的根makefile ，内核构建就始于此处。是的，它的内容很多，但是如果你已经读过内核源代码，你就会发现每个包含代码的目录都有一个自己的makefile。当然了，我们不会去描述每个代码文件是怎么编译链接的。所以我们将只会挑选一些通用的例子来说明问题，而你不会在这里找到构建内核的文档、如何整洁内核代码、[tags](https://en.wikipedia.org/wiki/Ctags) 的生成和[交叉编译](https://en.wikipedia.org/wiki/Cross_compiler) 相关的说明，等等。我们将从`make` 开始，使用标准的内核配置文件，到生成了内核镜像[bzImage](https://en.wikipedia.org/wiki/Vmlinux#bzImage) 结束。
如果你已经很了解[make](https://en.wikipedia.org/wiki/Make_%28software%29) 工具那是最好，但是我也会描述本文出现的相关代码。
让我们开始吧
编译内核前的准备
---------------------------------------------------------------------------------
在开始编译前要进行很多准备工作。最主要的就是找到并配置好配置文件，`make` 命令要使用到的参数都需要从这些配置文件获取。现在就让我们深入内核的根`makefile` 吧
内核的根`Makefile` 负责构建两个主要的文件：[vmlinux](https://en.wikipedia.org/wiki/Vmlinux) （内核镜像可执行文件）和模块文件。内核的 [Makefile](https://github.com/torvalds/linux/blob/master/Makefile) 从此处开始：
```Makefile
VERSION = 4
PATCHLEVEL = 2
SUBLEVEL = 0
EXTRAVERSION = -rc3
NAME = Hurr durr I'ma sheep
```
这些变量决定了当前内核的版本，并且被使用在很多不同的地方，比如`KERNELVERSION` ：
```Makefile
KERNELVERSION = $(VERSION)$(if $(PATCHLEVEL),.$(PATCHLEVEL)$(if $(SUBLEVEL),.$(SUBLEVEL)))$(EXTRAVERSION)
```
接下来我们会看到很多`ifeq` 条件判断语句，它们负责检查传给`make` 的参数。内核的`Makefile` 提供了一个特殊的编译选项`make help` ，这个选项可以生成所有的可用目标和一些能传给`make` 的有效的命令行参数。举个例子，`make V=1` 会在构建过程中输出详细的编译信息，第一个`ifeq` 就是检查传递给make的`V=n` 选项。
```Makefile
ifeq ("$(origin V)", "command line")
KBUILD_VERBOSE = $(V)
endif
ifndef KBUILD_VERBOSE
KBUILD_VERBOSE = 0
endif
ifeq ($(KBUILD_VERBOSE),1)
quiet =
Q =
else
quiet=quiet_
Q = @
endif
export quiet Q KBUILD_VERBOSE
```
如果`V=n` 这个选项传给了`make` ，系统就会给变量`KBUILD_VERBOSE` 选项附上`V` 的值，否则的话`KBUILD_VERBOSE` 就会为`0`。然后系统会检查`KBUILD_VERBOSE` 的值，以此来决定`quiet` 和`Q` 的值。符号`@` 控制命令的输出，如果它被放在一个命令之前，这条命令的执行将会是`CC scripts/mod/empty.o`，而不是`Compiling .... scripts/mod/empty.o`（注：CC 在makefile 中一般都是编译命令）。最后系统仅仅导出所有的变量。下一个`ifeq` 语句检查的是传递给`make` 的选项`O=/dir`，这个选项允许在指定的目录`dir` 输出所有的结果文件：
```Makefile
ifeq ($(KBUILD_SRC),)
ifeq ("$(origin O)", "command line")
KBUILD_OUTPUT := $(O)
endif
ifneq ($(KBUILD_OUTPUT),)
saved-output := $(KBUILD_OUTPUT)
KBUILD_OUTPUT := $(shell mkdir -p $(KBUILD_OUTPUT) && cd $(KBUILD_OUTPUT) \
&& /bin/pwd)
$(if $(KBUILD_OUTPUT),, \
$(error failed to create output directory "$(saved-output)"))
sub-make: FORCE
$(Q)$(MAKE) -C $(KBUILD_OUTPUT) KBUILD_SRC=$(CURDIR) \
-f $(CURDIR)/Makefile $(filter-out _all sub-make,$(MAKECMDGOALS))
skip-makefile := 1
endif # ifneq ($(KBUILD_OUTPUT),)
endif # ifeq ($(KBUILD_SRC),)
```
系统会检查变量`KBUILD_SRC`，如果他是空的（第一次执行makefile 时总是空的），并且变量`KBUILD_OUTPUT` 被设成了选项`O` 的值（如果这个选项被传进来了），那么这个值就会用来代表内核源码的顶层目录。下一步会检查变量`KBUILD_OUTPUT` ，如果之前设置过这个变量，那么接下来会做以下几件事：
* 将变量`KBUILD_OUTPUT` 的值保存到临时变量`saved-output`；
* 尝试创建输出目录；
* 检查创建的输出目录，如果失败了就打印错误；
* 如果成功创建了输出目录，那么就在新目录重新执行`make` 命令（参见选项`-C`）。
下一个`ifeq` 语句会检查传递给make 的选项`C` 和`M`：
```Makefile
ifeq ("$(origin C)", "command line")
KBUILD_CHECKSRC = $(C)
endif
ifndef KBUILD_CHECKSRC
KBUILD_CHECKSRC = 0
endif
ifeq ("$(origin M)", "command line")
KBUILD_EXTMOD := $(M)
endif
```
第一个选项`C` 会告诉`makefile` 需要使用环境变量`$CHECK` 提供的工具来检查全部`c` 代码，默认情况下会使用[sparse](https://en.wikipedia.org/wiki/Sparse)。第二个选项`M` 会用来编译外部模块（本文不做讨论）。因为设置了这两个变量，系统还会检查变量`KBUILD_SRC`，如果`KBUILD_SRC` 没有被设置，系统会设置变量`srctree` 为`.`：
```Makefile
ifeq ($(KBUILD_SRC),)
srctree := .
endif
objtree := .
src := $(srctree)
obj := $(objtree)
export srctree objtree VPATH
```
这将会告诉`Makefile` 内核的源码树就在执行make 命令的目录。然后要设置`objtree` 和其他变量为执行make 命令的目录，并且将这些变量导出。接着就是要获取`SUBARCH` 的值，这个变量代表了当前的系统架构（注：一般都指CPU 架构）：
```Makefile
SUBARCH := $(shell uname -m | sed -e s/i.86/x86/ -e s/x86_64/x86/ \
-e s/sun4u/sparc64/ \
-e s/arm.*/arm/ -e s/sa110/arm/ \
-e s/s390x/s390/ -e s/parisc64/parisc/ \
-e s/ppc.*/powerpc/ -e s/mips.*/mips/ \
-e s/sh[234].*/sh/ -e s/aarch64.*/arm64/ )
```
如你所见，系统执行[uname](https://en.wikipedia.org/wiki/Uname) 得到机器、操作系统和架构的信息。因为我们得到的是`uname` 的输出，所以我们需要做一些处理在赋给变量`SUBARCH` 。获得`SUBARCH` 之后就要设置`SRCARCH` 和`hfr-arch`，`SRCARCH`提供了硬件架构相关代码的目录，`hfr-arch` 提供了相关头文件的目录：
```Makefile
ifeq ($(ARCH),i386)
SRCARCH := x86
endif
ifeq ($(ARCH),x86_64)
SRCARCH := x86
endif
hdr-arch := $(SRCARCH)
```
注意：`ARCH` 是`SUBARCH` 的别名。如果没有设置过代表内核配置文件路径的变量`KCONFIG_CONFIG`，下一步系统会设置它，默认情况下就是`.config` ：
```Makefile
KCONFIG_CONFIG ?= .config
export KCONFIG_CONFIG
```
以及编译内核过程中要用到的[shell](https://en.wikipedia.org/wiki/Shell_%28computing%29)
```Makefile
CONFIG_SHELL := $(shell if [ -x "$$BASH" ]; then echo $$BASH; \
else if [ -x /bin/bash ]; then echo /bin/bash; \
else echo sh; fi ; fi)
```
接下来就要设置一组和编译内核的编译器相关的变量。我们会设置主机的`C` 和`C++` 的编译器及相关配置项：
```Makefile
HOSTCC = gcc
HOSTCXX = g++
HOSTCFLAGS = -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 -fomit-frame-pointer -std=gnu89
HOSTCXXFLAGS = -O2
```
下一步会去适配代表编译器的变量`CC`,那为什么还要`HOST*` 这些选项呢？这是因为`CC` 是编译内核过程中要使用的目标架构的编译器，但是`HOSTCC` 是要被用来编译一组`host` 程序的（下面我们就会看到）。然后我们就看看变量`KBUILD_MODULES` 和`KBUILD_BUILTIN` 的定义，这两个变量决定了我们要编译什么东西（内核、模块还是其他）：
```Makefile
KBUILD_MODULES :=
KBUILD_BUILTIN := 1
ifeq ($(MAKECMDGOALS),modules)
KBUILD_BUILTIN := $(if $(CONFIG_MODVERSIONS),1)
endif
```
在这我们可以看到这些变量的定义，并且，如果们仅仅传递了`modules` 给`make`,变量`KBUILD_BUILTIN` 会依赖于内核配置选项`CONFIG_MODVERSIONS`。下一步操作是引入下面的文件：
```Makefile
include scripts/Kbuild.include
```
文件`kbuild` ,[Kbuild](https://github.com/torvalds/linux/blob/master/Documentation/kbuild/kbuild.txt) 或者又叫做 `Kernel Build System`是一个用来管理构建内核和模块的特殊框架。`kbuild` 文件的语法与makefile 一样。文件[scripts/Kbuild.include](https://github.com/torvalds/linux/blob/master/scripts/Kbuild.include) 为`kbuild` 系统同提供了一些原生的定义。因为我们包含了这个`kbuild` 文件，我们可以看到和不同工具关联的这些变量的定义，这些工具会在内核和模块编译过程中被使用（比如链接器、编译器、二进制工具包[binutils](http://www.gnu.org/software/binutils/)，等等）：
```Makefile
AS = $(CROSS_COMPILE)as
LD = $(CROSS_COMPILE)ld
CC = $(CROSS_COMPILE)gcc
CPP = $(CC) -E
AR = $(CROSS_COMPILE)ar
NM = $(CROSS_COMPILE)nm
STRIP = $(CROSS_COMPILE)strip
OBJCOPY = $(CROSS_COMPILE)objcopy
OBJDUMP = $(CROSS_COMPILE)objdump
AWK = awk
...
...
...
```
在这些定义好的变量后面，我们又定义了两个变量：`USERINCLUDE` 和`LINUXINCLUDE`。他们包含了头文件的路径（第一个是给用户用的，第二个是给内核用的）：
```Makefile
USERINCLUDE := \
-I$(srctree)/arch/$(hdr-arch)/include/uapi \
-Iarch/$(hdr-arch)/include/generated/uapi \
-I$(srctree)/include/uapi \
-Iinclude/generated/uapi \
-include $(srctree)/include/linux/kconfig.h
LINUXINCLUDE := \
-I$(srctree)/arch/$(hdr-arch)/include \
...
```
以及标准的C 编译器标志：
```Makefile
KBUILD_CFLAGS := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
-fno-strict-aliasing -fno-common \
-Werror-implicit-function-declaration \
-Wno-format-security \
-std=gnu89
```
这并不是最终确定的编译器标志，他们还可以在其他makefile 里面更新（比如`arch/` 里面的kbuild）。变量定义完之后，全部会被导出供其他makefile 使用。下面的两个变量`RCS_FIND_IGNORE` 和 `RCS_TAR_IGNORE` 包含了被版本控制系统忽略的文件：
```Makefile
export RCS_FIND_IGNORE := \( -name SCCS -o -name BitKeeper -o -name .svn -o \
-name CVS -o -name .pc -o -name .hg -o -name .git \) \
-prune -o
export RCS_TAR_IGNORE := --exclude SCCS --exclude BitKeeper --exclude .svn \
--exclude CVS --exclude .pc --exclude .hg --exclude .git
```
这就是全部了，我们已经完成了所有的准备工作，下一个点就是如果构建`vmlinux`.
直面构建内核
--------------------------------------------------------------------------------
现在我们已经完成了所有的准备工作，根makefile（注：内核根目录下的makefile）的下一步工作就是和编译内核相关的了。在我们执行`make` 命令之前，我们不会在终端看到任何东西。但是现在编译的第一步开始了，这里我们需要从内核根makefile的的[598](https://github.com/torvalds/linux/blob/master/Makefile#L598) 行开始，这里可以看到目标`vmlinux`：
```Makefile
all: vmlinux
include arch/$(SRCARCH)/Makefile
```
不要操心我们略过的从`export RCS_FIND_IGNORE.....` 到`all: vmlinux.....` 这一部分makefile 代码，他们只是负责根据各种配置文件生成不同目标内核的，因为之前我就说了这一部分我们只讨论构建内核的通用途径。
目标`all:` 是在命令行如果不指定具体目标时默认使用的目标。你可以看到这里包含了架构相关的makefile（在这里就指的是[arch/x86/Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/Makefile)）。从这一时刻起，我们会从这个makefile 继续进行下去。如我们所见，目标`all` 依赖于根makefile 后面声明的`vmlinux`：
```Makefile
vmlinux: scripts/link-vmlinux.sh $(vmlinux-deps) FORCE
```
`vmlinux` 是linux 内核的静态链接可执行文件格式。脚本[scripts/link-vmlinux.sh](https://github.com/torvalds/linux/blob/master/scripts/link-vmlinux.sh) 把不同的编译好的子模块链接到一起形成了vmlinux。第二个目标是`vmlinux-deps`，它的定义如下：
```Makefile
vmlinux-deps := $(KBUILD_LDS) $(KBUILD_VMLINUX_INIT) $(KBUILD_VMLINUX_MAIN)
```
它是由内核代码下的每个顶级目录的`built-in.o` 组成的。之后我们还会检查内核所有的目录，`kbuild` 会编译各个目录下所有的对应`$obj-y` 的源文件。接着调用`$(LD) -r` 把这些文件合并到一个`build-in.o` 文件里。此时我们还没有`vmloinux-deps`, 所以目标`vmlinux` 现在还不会被构建。对我而言`vmlinux-deps` 包含下面的文件
```
arch/x86/kernel/vmlinux.lds arch/x86/kernel/head_64.o
arch/x86/kernel/head64.o arch/x86/kernel/head.o
init/built-in.o usr/built-in.o
arch/x86/built-in.o kernel/built-in.o
mm/built-in.o fs/built-in.o
ipc/built-in.o security/built-in.o
crypto/built-in.o block/built-in.o
lib/lib.a arch/x86/lib/lib.a
lib/built-in.o arch/x86/lib/built-in.o
drivers/built-in.o sound/built-in.o
firmware/built-in.o arch/x86/pci/built-in.o
arch/x86/power/built-in.o arch/x86/video/built-in.o
net/built-in.o
```
下一个可以被执行的目标如下：
```Makefile
$(sort $(vmlinux-deps)): $(vmlinux-dirs) ;
$(vmlinux-dirs): prepare scripts
$(Q)$(MAKE) $(build)=$@
```
就像我们看到的，`vmlinux-dir` 依赖于两部分：`prepare` 和`scripts`。第一个`prepare` 定义在内核的根`makefile` ，准备工作分成三个阶段：
```Makefile
prepare: prepare0
prepare0: archprepare FORCE
$(Q)$(MAKE) $(build)=.
archprepare: archheaders archscripts prepare1 scripts_basic
prepare1: prepare2 $(version_h) include/generated/utsrelease.h \
include/config/auto.conf
$(cmd_crmodverdir)
prepare2: prepare3 outputmakefile asm-generic
```
第一个`prepare0` 展开到`archprepare` ，后者又展开到`archheader` 和`archscripts`，这两个变量定义在`x86_64` 相关的[Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/Makefile)。让我们看看这个文件。`x86_64` 特定的makefile从变量定义开始，这些变量都是和特定架构的配置文件 ([defconfig](https://github.com/torvalds/linux/tree/master/arch/x86/configs)，等等)有关联。变量定义之后，这个makefile 定义了编译[16-bit](https://en.wikipedia.org/wiki/Real_mode)代码的编译选项，根据变量`BITS` 的值，如果是`32`， 汇编代码、链接器、以及其它很多东西（全部的定义都可以在[arch/x86/Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/Makefile)找到）对应的参数就是`i386`,而`64`就对应的是`x86_84`。生成的系统调用列表（syscall table）的makefile 里第一个目标就是`archheaders` ：
```Makefile
archheaders:
$(Q)$(MAKE) $(build)=arch/x86/entry/syscalls all
```
这个makefile 里第二个目标就是`archscripts`：
```Makefile
archscripts: scripts_basic
$(Q)$(MAKE) $(build)=arch/x86/tools relocs
```
我们可以看到`archscripts` 是依赖于根[Makefile](https://github.com/torvalds/linux/blob/master/Makefile)里的`scripts_basic` 。首先我们可以看出`scripts_basic` 是按照[scripts/basic](https://github.com/torvalds/linux/blob/master/scripts/basic/Makefile) 的mekefile 执行make 的：
```Maklefile
scripts_basic:
$(Q)$(MAKE) $(build)=scripts/basic
```
`scripts/basic/Makefile`包含了编译两个主机程序`fixdep` 和`bin2` 的目标：
```Makefile
hostprogs-y := fixdep
hostprogs-$(CONFIG_BUILD_BIN2C) += bin2c
always := $(hostprogs-y)
$(addprefix $(obj)/,$(filter-out fixdep,$(always))): $(obj)/fixdep
```
第一个工具是`fixdep`：用来优化[gcc](https://gcc.gnu.org/) 生成的依赖列表，然后在重新编译源文件的时候告诉make。第二个工具是`bin2c`,他依赖于内核配置选项`CONFIG_BUILD_BIN2C`,并且它是一个用来将标准输入接口（注：即stdin）收到的二进制流通过标准输出接口（即：stdout）转换成C 头文件的非常小的C 程序。你可以注意到这里有些奇怪的标志，如`hostprogs-y`等。这些标志使用在所有的`kbuild` 文件，更多的信息你可以从[documentation](https://github.com/torvalds/linux/blob/master/Documentation/kbuild/makefiles.txt) 获得。在我们的用例`hostprogs-y` 中，他告诉`kbuild` 这里有个名为`fixed` 的程序，这个程序会通过和`Makefile` 相同目录的`fixdep.c` 编译而来。执行make 之后，终端的第一个输出就是`kbuild` 的结果：
```
$ make
HOSTCC scripts/basic/fixdep
```
当目标`script_basic` 被执行，目标`archscripts` 就会make [arch/x86/tools](https://github.com/torvalds/linux/blob/master/arch/x86/tools/Makefile) 下的makefile 和目标`relocs`:
```Makefile
$(Q)$(MAKE) $(build)=arch/x86/tools relocs
```
代码`relocs_32.c` 和`relocs_64.c` 包含了[重定位](https://en.wikipedia.org/wiki/Relocation_%28computing%29) 的信息，将会被编译，者可以在`make` 的输出中看到：
```Makefile
HOSTCC arch/x86/tools/relocs_32.o
HOSTCC arch/x86/tools/relocs_64.o
HOSTCC arch/x86/tools/relocs_common.o
HOSTLD arch/x86/tools/relocs
```
在编译完`relocs.c` 之后会检查`version.h`:
```Makefile
$(version_h): $(srctree)/Makefile FORCE
$(call filechk,version.h)
$(Q)rm -f $(old_version_h)
```
我们可以在输出看到它：
```
CHK include/config/kernel.release
```
以及在内核根Makefiel 使用`arch/x86/include/generated/asm`的目标`asm-generic` 来构建`generic` 汇编头文件。在目标`asm-generic` 之后，`archprepare` 就会被完成，所以目标`prepare0` 会接着被执行，如我上面所写：
```Makefile
prepare0: archprepare FORCE
$(Q)$(MAKE) $(build)=.
```
注意`build`，它是定义在文件[scripts/Kbuild.include](https://github.com/torvalds/linux/blob/master/scripts/Kbuild.include)，内容是这样的：
```Makefile
build := -f $(srctree)/scripts/Makefile.build obj
```
或者在我们的例子中，他就是当前源码目录路径——`.`：
```Makefile
$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.build obj=.
```
参数`obj` 会告诉脚本[scripts/Makefile.build](https://github.com/torvalds/linux/blob/master/scripts/Makefile.build) 那些目录包含`kbuild` 文件，脚本以此来寻找各个`kbuild` 文件：
```Makefile
include $(kbuild-file)
```
然后根据这个构建目标。我们这里`.` 包含了[Kbuild](https://github.com/torvalds/linux/blob/master/Kbuild)，就用这个文件来生成`kernel/bounds.s` 和`arch/x86/kernel/asm-offsets.s`。这样目标`prepare` 就完成了它的工作。`vmlinux-dirs` 也依赖于第二个目标——`scripts` ，`scripts`会编译接下来的几个程序：`filealias`，`mk_elfconfig`,`modpost`等等。`scripts/host-programs` 编译完之后，我们的目标`vmlinux-dirs` 就可以开始编译了。第一步，我们先来理解一下`vmlinux-dirs` 都包含了那些东西。在我们的例子中它包含了接下来要使用的内核目录的路径：
```
init usr arch/x86 kernel mm fs ipc security crypto block
drivers sound firmware arch/x86/pci arch/x86/power
arch/x86/video net lib arch/x86/lib
```
我们可以在内核的根[Makefile](https://github.com/torvalds/linux/blob/master/Makefile) 里找到`vmlinux-dirs` 的定义：
```Makefile
vmlinux-dirs := $(patsubst %/,%,$(filter %/, $(init-y) $(init-m) \
$(core-y) $(core-m) $(drivers-y) $(drivers-m) \
$(net-y) $(net-m) $(libs-y) $(libs-m)))
init-y := init/
drivers-y := drivers/ sound/ firmware/
net-y := net/
libs-y := lib/
...
...
...
```
这里我们借助函数`patsubst` 和`filter`去掉了每个目录路径里的符号`/`，并且把结果放到`vmlinux-dirs` 里。所以我们就有了`vmlinux-dirs` 里的目录的列表，以及下面的代码：
```Makefile
$(vmlinux-dirs): prepare scripts
$(Q)$(MAKE) $(build)=$@
```
符号`$@` 在这里代表了`vmlinux-dirs`，这就表明程序会递归遍历从`vmlinux-dirs` 以及它内部的全部目录（依赖于配置），并且在对应的目录下执行`make` 命令。我们可以在输出看到结果：
```
CC init/main.o
CHK include/generated/compile.h
CC init/version.o
CC init/do_mounts.o
...
CC arch/x86/crypto/glue_helper.o
AS arch/x86/crypto/aes-x86_64-asm_64.o
CC arch/x86/crypto/aes_glue.o
...
AS arch/x86/entry/entry_64.o
AS arch/x86/entry/thunk_64.o
CC arch/x86/entry/syscall_64.o
```
每个目录下的源代码将会被编译并且链接到`built-io.o` 里：
```
$ find . -name built-in.o
./arch/x86/crypto/built-in.o
./arch/x86/crypto/sha-mb/built-in.o
./arch/x86/net/built-in.o
./init/built-in.o
./usr/built-in.o
...
...
```
好了，所有的`built-in.o` 都构建完了，现在我们回到目标`vmlinux` 上。你应该还记得，目标`vmlinux` 是在内核的根makefile 里。在链接`vmlinux` 之前，系统会构建[samples](https://github.com/torvalds/linux/tree/master/samples), [Documentation](https://github.com/torvalds/linux/tree/master/Documentation)等等，但是如上文所述，我不会在本文描述这些。
```Makefile
vmlinux: scripts/link-vmlinux.sh $(vmlinux-deps) FORCE
...
...
+$(call if_changed,link-vmlinux)
```
你可以看到，`vmlinux` 的调用脚本[scripts/link-vmlinux.sh](https://github.com/torvalds/linux/blob/master/scripts/link-vmlinux.sh) 的主要目的是把所有的`built-in.o` 链接成一个静态可执行文件、生成[System.map](https://en.wikipedia.org/wiki/System.map)。 最后我们来看看下面的输出：
```
LINK vmlinux
LD vmlinux.o
MODPOST vmlinux.o
GEN .version
CHK include/generated/compile.h
UPD include/generated/compile.h
CC init/version.o
LD init/built-in.o
KSYM .tmp_kallsyms1.o
KSYM .tmp_kallsyms2.o
LD vmlinux
SORTEX vmlinux
SYSMAP System.map
```
以及内核源码树根目录下的`vmlinux` 和`System.map`
```
$ ls vmlinux System.map
System.map vmlinux
```
这就是全部了，`vmlinux` 构建好了，下一步就是创建[bzImage](https://en.wikipedia.org/wiki/Vmlinux#bzImage).
制作bzImage
--------------------------------------------------------------------------------
`bzImage` 就是压缩了的linux 内核镜像。我们可以在构建了`vmlinux` 之后通过执行`make bzImage` 获得`bzImage`。同时我们可以仅仅执行`make` 而不带任何参数也可以生成`bzImage` ，因为它是在[arch/x86/kernel/Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/Makefile) 里预定义的、默认生成的镜像：
```Makefile
all: bzImage
```
让我们看看这个目标，他能帮助我们理解这个镜像是怎么构建的。我已经说过了`bzImage` 师被定义在[arch/x86/kernel/Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/Makefile)，定义如下：
```Makefile
bzImage: vmlinux
$(Q)$(MAKE) $(build)=$(boot) $(KBUILD_IMAGE)
$(Q)mkdir -p $(objtree)/arch/$(UTS_MACHINE)/boot
$(Q)ln -fsn ../../x86/boot/bzImage $(objtree)/arch/$(UTS_MACHINE)/boot/$@
```
在这里我们可以看到第一次为boot 目录执行`make`，在我们的例子里是这样的：
```Makefile
boot := arch/x86/boot
```
现在的主要目标是编译目录`arch/x86/boot` 和`arch/x86/boot/compressed` 的代码，构建`setup.bin` 和`vmlinux.bin`，然后用这两个文件生成`bzImage`。第一个目标是定义在[arch/x86/boot/Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/boot/Makefile) 的`$(obj)/setup.elf`:
```Makefile
$(obj)/setup.elf: $(src)/setup.ld $(SETUP_OBJS) FORCE
$(call if_changed,ld)
```
我们已经在目录`arch/x86/boot`有了链接脚本`setup.ld`，并且将变量`SETUP_OBJS` 扩展到`boot` 目录下的全部源代码。我们可以看看第一个输出：
```Makefile
AS arch/x86/boot/bioscall.o
CC arch/x86/boot/cmdline.o
AS arch/x86/boot/copy.o
HOSTCC arch/x86/boot/mkcpustr
CPUSTR arch/x86/boot/cpustr.h
CC arch/x86/boot/cpu.o
CC arch/x86/boot/cpuflags.o
CC arch/x86/boot/cpucheck.o
CC arch/x86/boot/early_serial_console.o
CC arch/x86/boot/edd.o
```
下一个源码文件是[arch/x86/boot/header.S](https://github.com/torvalds/linux/blob/master/arch/x86/boot/header.S)，但是我们不能现在就编译它，因为这个目标依赖于下面两个头文件：
```Makefile
$(obj)/header.o: $(obj)/voffset.h $(obj)/zoffset.h
```
第一个头文件`voffset.h` 是使用`sed` 脚本生成的，包含用`nm` 工具从`vmlinux` 获取的两个地址：
```C
#define VO__end 0xffffffff82ab0000
#define VO__text 0xffffffff81000000
```
这两个地址是内核的起始和结束地址。第二个头文件`zoffset.h` 在[arch/x86/boot/compressed/Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/boot/compressed/Makefile) 可以看出是依赖于目标`vmlinux`的：
```Makefile
$(obj)/zoffset.h: $(obj)/compressed/vmlinux FORCE
$(call if_changed,zoffset)
```
目标`$(obj)/compressed/vmlinux` 依赖于变量`vmlinux-objs-y` —— 说明需要编译目录[arch/x86/boot/compressed](https://github.com/torvalds/linux/tree/master/arch/x86/boot/compressed) 下的源代码，然后生成`vmlinux.bin`, `vmlinux.bin.bz2`, 和编译工具 - `mkpiggy`。我们可以在下面的输出看出来：
```Makefile
LDS arch/x86/boot/compressed/vmlinux.lds
AS arch/x86/boot/compressed/head_64.o
CC arch/x86/boot/compressed/misc.o
CC arch/x86/boot/compressed/string.o
CC arch/x86/boot/compressed/cmdline.o
OBJCOPY arch/x86/boot/compressed/vmlinux.bin
BZIP2 arch/x86/boot/compressed/vmlinux.bin.bz2
HOSTCC arch/x86/boot/compressed/mkpiggy
```
`vmlinux.bin` 是去掉了调试信息和注释的`vmlinux` 二进制文件，加上了占用了`u32` （注：即4-Byte）的长度信息的`vmlinux.bin.all` 压缩后就是`vmlinux.bin.bz2`。其中`vmlinux.bin.all` 包含了`vmlinux.bin` 和`vmlinux.relocs`（注：vmlinux 的重定位信息），其中`vmlinux.relocs` 是`vmlinux` 经过程序`relocs` 处理之后的`vmlinux` 镜像（见上文所述）。我们现在已经获取到了这些文件，汇编文件`piggy.S` 将会被`mkpiggy` 生成、然后编译：
```Makefile
MKPIGGY arch/x86/boot/compressed/piggy.S
AS arch/x86/boot/compressed/piggy.o
```
这个汇编文件会包含经过计算得来的、压缩内核的偏移信息。处理完这个汇编文件，我们就可以看到`zoffset` 生成了：
```Makefile
ZOFFSET arch/x86/boot/zoffset.h
```
现在`zoffset.h` 和`voffset.h` 已经生成了，[arch/x86/boot](https://github.com/torvalds/linux/tree/master/arch/x86/boot/) 里的源文件可以继续编译：
```Makefile
AS arch/x86/boot/header.o
CC arch/x86/boot/main.o
CC arch/x86/boot/mca.o
CC arch/x86/boot/memory.o
CC arch/x86/boot/pm.o
AS arch/x86/boot/pmjump.o
CC arch/x86/boot/printf.o
CC arch/x86/boot/regs.o
CC arch/x86/boot/string.o
CC arch/x86/boot/tty.o
CC arch/x86/boot/video.o
CC arch/x86/boot/video-mode.o
CC arch/x86/boot/video-vga.o
CC arch/x86/boot/video-vesa.o
CC arch/x86/boot/video-bios.o
```
所有的源代码会被编译，他们最终会被链接到`setup.elf` ：
```Makefile
LD arch/x86/boot/setup.elf
```
或者：
```
ld -m elf_x86_64 -T arch/x86/boot/setup.ld arch/x86/boot/a20.o arch/x86/boot/bioscall.o arch/x86/boot/cmdline.o arch/x86/boot/copy.o arch/x86/boot/cpu.o arch/x86/boot/cpuflags.o arch/x86/boot/cpucheck.o arch/x86/boot/early_serial_console.o arch/x86/boot/edd.o arch/x86/boot/header.o arch/x86/boot/main.o arch/x86/boot/mca.o arch/x86/boot/memory.o arch/x86/boot/pm.o arch/x86/boot/pmjump.o arch/x86/boot/printf.o arch/x86/boot/regs.o arch/x86/boot/string.o arch/x86/boot/tty.o arch/x86/boot/video.o arch/x86/boot/video-mode.o arch/x86/boot/version.o arch/x86/boot/video-vga.o arch/x86/boot/video-vesa.o arch/x86/boot/video-bios.o -o arch/x86/boot/setup.elf
```
最后两件事是创建包含目录`arch/x86/boot/*` 下的编译过的代码的`setup.bin`：
```
objcopy -O binary arch/x86/boot/setup.elf arch/x86/boot/setup.bin
```
以及从`vmlinux` 生成`vmlinux.bin` :
```
objcopy -O binary -R .note -R .comment -S arch/x86/boot/compressed/vmlinux arch/x86/boot/vmlinux.bin
```
最后，我们编译主机程序[arch/x86/boot/tools/build.c](https://github.com/torvalds/linux/blob/master/arch/x86/boot/tools/build.c)，它将会用来把`setup.bin` 和`vmlinux.bin` 打包成`bzImage`:
```
arch/x86/boot/tools/build arch/x86/boot/setup.bin arch/x86/boot/vmlinux.bin arch/x86/boot/zoffset.h arch/x86/boot/bzImage
```
实际上`bzImage` 就是把`setup.bin` 和`vmlinux.bin` 连接到一起。最终我们会看到输出结果，就和那些用源码编译过内核的同行的结果一样：
```
Setup is 16268 bytes (padded to 16384 bytes).
System is 4704 kB
CRC 94a88f9a
Kernel: arch/x86/boot/bzImage is ready (#5)
```
全部结束。
结论
================================================================================
这就是本文的最后一节。本文我们了解了编译内核的全部步骤：从执行`make` 命令开始，到最后生成`bzImage`。我知道，linux 内核的makefiles 和构建linux 的过程第一眼看起来可能比较迷惑，但是这并不是很难。希望本文可以帮助你理解构建linux 内核的整个流程。
链接
================================================================================
* [GNU make util](https://en.wikipedia.org/wiki/Make_%28software%29)
* [Linux kernel top Makefile](https://github.com/torvalds/linux/blob/master/Makefile)
* [cross-compilation](https://en.wikipedia.org/wiki/Cross_compiler)
* [Ctags](https://en.wikipedia.org/wiki/Ctags)
* [sparse](https://en.wikipedia.org/wiki/Sparse)
* [bzImage](https://en.wikipedia.org/wiki/Vmlinux#bzImage)
* [uname](https://en.wikipedia.org/wiki/Uname)
* [shell](https://en.wikipedia.org/wiki/Shell_%28computing%29)
* [Kbuild](https://github.com/torvalds/linux/blob/master/Documentation/kbuild/kbuild.txt)
* [binutils](http://www.gnu.org/software/binutils/)
* [gcc](https://gcc.gnu.org/)
* [Documentation](https://github.com/torvalds/linux/blob/master/Documentation/kbuild/makefiles.txt)
* [System.map](https://en.wikipedia.org/wiki/System.map)
* [Relocation](https://en.wikipedia.org/wiki/Relocation_%28computing%29)
--------------------------------------------------------------------------------
via: https://github.com/0xAX/linux-insides/blob/master/Misc/how_kernel_compiled.md
译者：[译者ID](https://github.com/oska874)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](https://linux.cn/) 荣誉推出

53
translated/tech/20150906 Do Simple Math In Ubuntu And elementary OS With NaSC.md Normal file
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在 Ubuntu 和 Elementary OS 上使用 NaSC 进行简单数学运算
================================================================================
![](http://itsfoss.itsfoss.netdna-cdn.com/wp-content/uploads/2015/09/Make-Math-Simpler-with-NaSC.jpg)
[NaSC][1]，Not a Soulver Clone 的缩写，是为 elementary 操作系统开发的第三方应用程序。正如名字暗示的那样，NaSC 的灵感来源于 [Soulver][2]，后者是像普通人一样进行数学计算的 OS X 应用。
Elementary OS 它自己本身借鉴了 OS X，也就不奇怪它的很多第三方应用灵感都来自于 OS X 应用。
回到 NaSC，“像普通人一样进行数学计算”到底是什么意思呢？事实上，它意味着正如你想的那样去书写。按照该应用程序的介绍：
> “它能使你像平常那样进行计算。它允许你输入任何你想输入的，智能识别其中的数学部分并在右边面板打印出结果。然后你可以在后面的等式中使用这些结果，如果结果发生了改变，等式中使用的也会同样变化。”
还不相信？让我们来看一个截图。
![](http://itsfoss.itsfoss.netdna-cdn.com/wp-content/uploads/2015/09/NaSC.png)
现在，你明白什么是 “像普通人一样做数学” 了吗？坦白地说，我并不是这类应用程序的粉丝，但对你们中的某些人可能会有用。让我们来看看怎么在 Elementary OS、Ubuntu 和 Linux Mint 上安装 NaSC。
### 在 Ubuntu、Elementary OS 和 Mint 上安装 NaSC ###
安装 NaSC 有一个可用的 PPA。PPA 中说 ‘每日’，意味着所有构建（包括不稳定），但作为我的快速测试，并没什么影响。
打卡一个终端并运行下面的命令：
sudo apt-add-repository ppa:nasc-team/daily
sudo apt-get update
sudo apt-get install nasc
这是 Ubuntu 15.04 中使用 NaSC 的一个截图：
![](http://itsfoss.itsfoss.netdna-cdn.com/wp-content/uploads/2015/09/NaSC-Ubuntu.png)
如果你想卸载它，可以使用下面的命令：
sudo apt-get remove nasc
sudo apt-add-repository --remove ppa:nasc-team/daily
如果你试用了这个软件，要分享你的经验哦。除此之外，你也可以在第三方 Elementary OS 应用中体验[Vocal podcast app for Linux][3]。
--------------------------------------------------------------------------------
via: http://itsfoss.com/math-ubuntu-nasc/
作者：[Abhishek][a]
译者：[ictlyh](http://www.mutouxiaogui.cn/blog/)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
[a]:http://itsfoss.com/author/abhishek/
[1]:http://parnold-x.github.io/nasc/
[2]:http://www.acqualia.com/soulver/
[3]:http://itsfoss.com/podcast-app-vocal-linux/

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在 Ubuntu 和 Elementary 上使用 NaSC 做简单数学运算
================================================================================
![](http://ubuntuhandbook.org/wp-content/uploads/2015/09/nasc-icon.png)
NaSC（Not a Soulver Clone，并非 Soulver 的克隆品）是为 Elementary 操作系统进行数学计算而设计的一款开源软件。类似于 Mac 上的 [Soulver][1]。
> 它能使你像平常那样进行计算。它允许你输入任何你想输入的，智能识别其中的数学部分并在右边面板打印出结果。然后你可以在后面的等式中使用这些结果，如果结果发生了改变，等式中使用的也会同样变化。
用 NaSC，你可以：
- 自己定义复杂的计算
- 改变单位和值（英尺、米、厘米，美元、欧元等）
- 了解行星的表面积
- 解二次多项式
- 以及其它
![nasc-eos](http://ubuntuhandbook.org/wp-content/uploads/2015/09/nasc-eos.jpg)
第一次启动时，NaSC 提供了一个关于现有功能的教程。以后你还可以通过点击标题栏上的帮助图标再次查看。
![nasc-help](http://ubuntuhandbook.org/wp-content/uploads/2015/09/nasc-help.jpg)
另外，这个软件还允许你保存文件以便以后继续工作。还可以在一定时间内通过粘贴板共用。
### 在 Ubuntu 或 Elementary OS Freya 上安装 NaSC： ###
对于 Ubuntu 15.04，Ubuntu 15.10，Elementary OS Freya，从 Dash 或应用启动器中打开终端，逐条运行下面的命令：
1. 通过命令添加 [NaSC PPA][2]：
sudo apt-add-repository ppa:nasc-team/daily
![nasc-ppa](http://ubuntuhandbook.org/wp-content/uploads/2015/09/nasc-ppa.jpg)
2. 如果安装了 Synaptic 软件包管理器，点击 ‘Reload’ 后搜索并安装 ‘nasc’。
或者运行下面的命令更新系统缓存并安装软件：
sudo apt-get update
sudo apt-get install nasc
3. **(可选)** 要卸载软件以及 NaSC，运行：
sudo apt-get remove nasc && sudo add-apt-repository -r ppa:nasc-team/daily
对于不想添加 PPA 的人，可以直接从[该网页][3]获取 .deb 安装包。、
--------------------------------------------------------------------------------
via: http://ubuntuhandbook.org/index.php/2015/09/make-math-simple-in-ubuntu-elementary-os-via-nasc/
作者：[Ji m][a]
译者：[ictlyh](http://www.mutouxiaogui.cn/blog/)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
[a]:http://ubuntuhandbook.org/index.php/about/
[1]:http://www.acqualia.com/soulver/
[2]:https://launchpad.net/~nasc-team/+archive/ubuntu/daily/
[3]:http://ppa.launchpad.net/nasc-team/daily/ubuntu/pool/main/n/nasc/

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RHCSA 系列: 如何管理RHEL7的用户和组 – Part 3
RHCSA 系列（三）: 如何管理 RHEL7 的用户和组
================================================================================
和管理其他Linux服务器一样，管理一个 RHEL 7 服务器 要求你能够添加，修改，暂停或删除用户帐户，并且授予他们文件,目录，其他系统资源所必要的权限。
和管理其它Linux服务器一样，管理一个 RHEL 7 服务器要求你能够添加、修改、暂停或删除用户帐户，并且授予他们执行其分配的任务所需的文件、目录、其它系统资源所必要的权限。
![User and Group Management in Linux](http://www.tecmint.com/wp-content/uploads/2015/03/User-and-Group-Management-in-Linux.png)
RHCSA: 用户和组管理 – Part 3
*RHCSA: 用户和组管理 – Part 3*
### 管理用户帐户##
###管理用户帐户##
如果想要给RHEL 7 服务器添加账户，你需要以root用户执行如下两条命令
如果想要给RHEL 7 服务器添加账户，你需要以root用户执行如下两条命令之一：
# adduser [new_account]
# useradd [new_account]
当添加新的用户帐户时，默认会执行下列操作。
- 他/她 的主目录就会被创建(一般是"/home/用户名"，除非你特别设置)
- 一些隐藏文件 如`.bash_logout`, `.bash_profile` 以及 `.bashrc` 会被复制到用户的主目录，并且会为用户的回话提供环境变量.你可以进一步查看他们的相关细节。
- 会为您的账号添加一个邮件池目录
- 会创建一个和用户名同样的组
- 它/她的主目录就会被创建(一般是"/home/用户名"，除非你特别设置)
- 一些隐藏文件 如`.bash_logout`, `.bash_profile` 以及 `.bashrc` 会被复制到用户的主目录，它们会为用户的回话提供环境变量。你可以进一步查看它们的相关细节。
- 会为您的账号添加一个邮件池目录。
- 会创建一个和用户名同样的组（LCTT 译注：除非你给新创建的用户指定了组）。
用户帐户的全部信息被保存在`/etc/passwd`文件。这个文件以如下格式保存了每一个系统帐户的所有信息(字段以“:”分割)
用户帐户的全部信息被保存在`/etc/passwd `文件。这个文件以如下格式保存了每一个系统帐户的所有信息(以:分割)
[username]:[x]:[UID]:[GID]:[Comment]:[Home directory]:[Default shell]
- `[username]` 和`[Comment]` 是用于自我解释的
- ‘x’表示帐户的密码保护(详细在`/etc/shadow`文件)，就是我们用于登录的`[username]`.
- `[UID]` 和`[GID]`是用于显示`[username]` 的 用户认证和主用户组。
- `[username]` 和`[Comment]` 其意自明，就是用户名和备注
- 第二个‘x’表示帐户的启用了密码保护(记录在`/etc/shadow`文件)，密码用于登录`[username]`
- `[UID]` 和`[GID]`是整数，它们表明了`[username]`的用户ID 和所属的主组ID
最后,
最后。
- `[Home directory]`显示`[username]`的主目录的绝对路径
- `[Default shell]` 是当用户登录系统后使用的默认shell
另外一个你必须要熟悉的重要的文件是存储组信息的`/etc/group`.因为和`/etc/passwd`类似，所以也是由:分割
另外一个你必须要熟悉的重要的文件是存储组信息的`/etc/group`。和`/etc/passwd`类似，也是每行一个记录，字段由“:”分割
[Group name]:[Group password]:[GID]:[Group members]
- `[Group name]` 是组名
- 这个组是否使用了密码 (如果是"X"意味着没有).
- 这个组是否使用了密码 (如果是"x"意味着没有)
- `[GID]`: 和`/etc/passwd`中一样
- `[Group members]`:用户列表，使用,隔开。里面包含组内的所有用户
- `[Group members]`:用户列表，使用“,”隔开。里面包含组内的所有用户
添加过帐户后，任何时候你都可以通过 usermod 命令来修改用户账户信息，基本的语法如下:
添加过帐户后，任何时候你都可以通过 usermod 命令来修改用户战壕沟，基础的语法如下:
# usermod [options] [username]
相关阅读
- [15 ‘useradd’ Command Examples][1]
- [15 ‘usermod’ Command Examples][2]
- [15 ‘useradd’ 命令示例][1]
- [15 ‘usermod’ 命令示例][2]
#### 示例1 : 设置帐户的过期时间 ####
如果你的公司有一些短期使用的帐户或者你相应帐户在有限时间内使用，你可以使用 `--expiredate` 参数 ，后加YYYY-MM-DD格式的日期。为了查看是否生效，你可以使用如下命令查看
如果你的公司有一些短期使用的帐户或者你要在有限时间内授予访问，你可以使用 `--expiredate` 参数 ，后加YYYY-MM-DD 格式的日期。为了查看是否生效，你可以使用如下命令查看
# chage -l [username]
帐户更新前后的变动如下图所示
![Change User Account Information](http://www.tecmint.com/wp-content/uploads/2015/03/Change-User-Account-Information.png)
修改用户信息
*修改用户信息*
#### 示例 2: 向组内追加用户 ####
除了创建用户时的主用户组，一个用户还能被添加到别的组。你需要使用 -aG或 -append -group 选项，后跟逗号分隔的组名
除了创建用户时的主用户组，一个用户还能被添加到别的组。你需要使用 -aG或 -append -group 选项，后跟逗号分隔的组名。
#### 示例 3: 修改用户主目录或默认Shell ####
如果因为一些原因，你需要修改默认的用户主目录(一般为 /home/用户名)，你需要使用 -d 或 -home 参数，后跟绝对路径来修改主目录
如果有用户想要使用其他的shell来取代bash(比如sh ),一般默认是bash .使用 usermod ，并使用 -shell 的参数，后加新的shell的路径
如果因为一些原因，你需要修改默认的用户主目录(一般为 /home/用户名)，你需要使用 -d 或 -home 参数，后跟绝对路径来修改主目录。
如果有用户想要使用其它的shell来取代默认的bash(比如zsh)。使用 usermod ，并使用 -shell 的参数，后加新的shell的路径。
#### 示例 4: 展示组内的用户 ####
当把用户添加到组中后，你可以使用如下命令验证属于哪一个组
@ -73,17 +81,17 @@ RHCSA: 用户和组管理 – Part 3
# groups [username]
# id [username]
下面图片的演示了示例2到示例四
下面图片的演示了示例2到示例4
![Adding User to Supplementary Group](http://www.tecmint.com/wp-content/uploads/2015/03/Adding-User-to-Supplementary-Group.png)
添加用户到额外的组
*添加用户到额外的组*
在上面的示例中:
# usermod --append --groups gacanepa,users --home /tmp --shell /bin/sh tecmint
如果想要从组内删除用户，省略 `--append` 切换，并且可以使用 `--groups` 来列举组内的用户
如果想要从组内删除用户，取消 `--append` 选项，并使用 `--groups` 和你要用户属于的组的列表。
#### 示例 5: 通过锁定密码来停用帐户 ####
@ -91,120 +99,136 @@ RHCSA: 用户和组管理 – Part 3
#### 示例 6: 解锁密码 ####
当你想要重新启用帐户让他可以继续登录时，属于 -u 或 –unlock 选项来解锁用户的密码，就像示例5 介绍的那样
当你想要重新启用帐户让它可以继续登录时，使用 -u 或 –unlock 选项来解锁用户的密码，就像示例5 介绍的那样
# usermod --unlock tecmint
下面的图片展示了示例5和示例6
下面的图片展示了示例5和示例6：
![Lock Unlock User Account](http://www.tecmint.com/wp-content/uploads/2015/03/Lock-Unlock-User-Account.png)
锁定上锁用户
*锁定上锁用户*
#### 示例 7:删除组和用户 ####
如果要删除一个组，你需要使用 groupdel ，如果需要删除用户 你需要使用 userdel (添加 -r 可以删除主目录和邮件池的内容)
如果要删除一个组，你需要使用 groupdel ，如果需要删除用户 你需要使用 userdel (添加 -r 可以删除主目录和邮件池的内容)。
# groupdel [group_name] # 删除组
# userdel -r [user_name] # 删除用户，并删除主目录和邮件池
如果一些文件属于组，他们将不会被删除。但是组拥有者将会被设置为删除掉的组的GID
### 列举，设置，并且修改 ugo/rwx 权限 ###
如果一些文件属于该组，删除组时它们不会也被删除。但是组拥有者的名字将会被设置为删除掉的组的GID。
著名的 [ls 命令][3] 是管理员最好的助手. 当我们使用 -l 参数, 这个工具允许您查看一个目录中的内容（或详细格式).
### 列举，设置，并且修改标准 ugo/rwx 权限 ###
著名的 [ls 命令][3] 是管理员最好的助手. 当我们使用 -l 参数, 这个工具允许您以长格式（或详细格式)查看一个目录中的内容。
而且，该命令还可以用于单个文件中。无论哪种方式，在“ls”输出中的前10个字符表示每个文件的属性。
而且，该命令还可以应用于单个文件中。无论哪种方式，在“ls”输出中的前10个字符表示每个文件的属性。
这10个字符序列的第一个字符用于表示文件类型：
- – (连字符): 一个标准文件
- d: 一个目录
- l: 一个符号链接
- c: 字符设备（将数据作为字节流，即一个终端）
- b: 块设备（处理数据块，即存储设备）
- c: 字符设备（将数据作为字节流，例如终端）
- b: 块设备（以块的方式处理数据，例如存储设备）
文件属性的接下来的九个字符，分为三个组，被称为文件模式，并注明读（r）、写（w）、和执行（x）权限授予文件的所有者、文件的所有组、和其它的用户（通常被称为“世界”）。
同文件上的读取权限允许文件被打开和读取一样，如果目录同时有执行权限时，就允许其目录内容被列出。此外，如果一个文件有执行权限，就允许它作为一个程序运行。
文件属性的下一个九个字符，分为三个组，被称为文件模式，并注明读（r），写（w），并执行（x）授予文件的所有者，文件的所有组，和其他的用户（通常被称为“世界”）。
在文件的读取权限允许打开和读取相同的权限时，允许其内容被列出，如果还设置了执行权限，还允许它作为一个程序和运行。
文件权限是通过chmod命令改变的，它的基本语法如下：
# chmod [new_mode] file
new_mode是一个八进制数或表达式，用于指定新的权限。适合每一个随意的案例。或者您已经有了一个更好的方式来设置文件的权限，所以你觉得可以自由地使用最适合你自己的方法。
八进制数可以基于二进制等效计算，可以从所需的文件权限的文件的所有者，所有组，和世界。一定权限的存在等于2的幂（R = 22，W = 21，x = 20），没有时意为0。例如：
new_mode 是一个八进制数或表达式，用于指定新的权限。随意试试各种权限看看是什么效果。或者您已经有了一个更好的方式来设置文件的权限，你也可以用你自己的方式自由地试试。
八进制数可以基于二进制等价计算，可以从所需的文件权限的文件的所有者、所有组、和世界组合成。每种权限都等于2的幂（R = 2\^2，W = 2\^1，x = 2\^0），没有时即为0。例如：
![File Permissions](http://www.tecmint.com/wp-content/uploads/2015/03/File-Permissions.png)
文件权限
*文件权限*
在八进制形式下设置文件的权限，如上图所示
# chmod 744 myfile
请用一分钟来对比一下我们以前的计算，在更改文件的权限后，我们的实际输出为：
请用马上来对比一下我们以前的计算，在更改文件的权限后，我们的实际输出为：
![Long List Format](http://www.tecmint.com/wp-content/uploads/2015/03/Long-List-Format.png)
长列表格式
*长列表格式*
#### 示例 8: 寻找777权限的文件 ####
出于安全考虑，你应该确保在正常情况下，尽可能避免777权限（读、写、执行的文件）。虽然我们会在以后的教程中教你如何更有效地找到所有的文件在您的系统的权限集的说明，你现在仍可以使用LS grep获取这种信息。
在下面的例子，我们会寻找 /etc 目录下的777权限文件. 注意，我们要使用第二章讲到的管道的知识[第二章：文件和目录管理][4]:
出于安全考虑，你应该确保在正常情况下，尽可能避免777权限（任何人可读、可写、可执行的文件）。虽然我们会在以后的教程中教你如何更有效地找到您的系统的具有特定权限的全部文件，你现在仍可以组合使用ls 和 grep来获取这种信息。
在下面的例子，我们会寻找 /etc 目录下的777权限文件。注意，我们要使用[第二章：文件和目录管理][4]中讲到的管道的知识：
# ls -l /etc | grep rwxrwxrwx
![Find All Files with 777 Permission](http://www.tecmint.com/wp-content/uploads/2015/03/Find-All-777-Files.png)
查找所有777权限的文件
*查找所有777权限的文件*
#### 示例 9: 为所有用户指定特定权限 ####
shell脚本，以及一些二进制文件，所有用户都应该有权访问（不只是其相应的所有者和组），应该有相应的执行权限（我们会讨论特殊情况下的问题）：
# chmod a+x script.sh
**注意**: 我们可以设置文件模式使用表示用户权限的字母如“u”，组所有者权限的字母“g”，其余的为o 。所有权限为a.权限可以通过`+` 或 `-` 来管理。
**注意**: 我们可以使用表达式设置文件模式，表示用户权限的字母如“u”，组所有者权限的字母“g”，其余的为“o” ，同时具有所有权限为“a”。权限可以通过`+` 或 `-` 来授予和收回。
![Set Execute Permission on File](http://www.tecmint.com/wp-content/uploads/2015/03/Set-Execute-Permission-on-File.png)
为文件设置执行权限
*为文件设置执行权限*
长目录列表还显示了该文件的所有者和其在第一和第二列中的组主。此功能可作为系统中文件的第一级访问控制方法：
长目录列表还用两列显示了该文件的所有者和所有组。此功能可作为系统中文件的第一级访问控制方法：
![Check File Owner and Group](http://www.tecmint.com/wp-content/uploads/2015/03/Check-File-Owner-and-Group.png)
检查文件的属主和属组
*检查文件的所有者和所有组*
改变文件的所有者，您应该使用chown命令。请注意，您可以在同时或分别更改文件的所有组：
改变文件的所有者，您将使用chown命令。请注意，您可以在同一时间或单独的更改文件的所有权：
# chown user:group file
虽然可以在同一时间更改用户或组，或在同一时间的两个属性，但是不要忘记冒号区分，如果你想要更新其他属性，让另外的选项保持空白：
# chown :group file # Change group ownership only
# chown user: file # Change user ownership only
你可以更改用户或组，或在同时更改两个属性，但是不要忘记冒号区分，如果你想要更新其它属性，让另外的部分为空：
# chown :group file # 仅改变所有组
# chown user: file # 仅改变所有者
#### 示例 10:从一个文件复制权限到另一个文件####
If you would like to “clone” ownership from one file to another, you can do so using the –reference flag, as follows:
如果你想“克隆”一个文件的所有权到另一个，你可以这样做，使用–reference参数，如下：
# chown --reference=ref_file file
ref_file的所有信息会复制给 file
![Clone File Ownership](http://www.tecmint.com/wp-content/uploads/2015/03/Clone-File-Ownership.png)
复制文件属主信息
*复制文件属主信息*
### 设置 SETGID 协作目录 ###
你应该授予在一个特定的目录中拥有访问所有的文件的权限给一个特点的用户组，你将有可能使用目录设置setgid的方法。当setgid后设置，真实用户的有效GID成为团队的主人。
因此，任何用户都可以访问该文件的组所有者授予的权限的文件。此外，当setgid设置在一个目录中，新创建的文件继承同一组目录，和新创建的子目录也将继承父目录的setgid。
假如你需要授予在一个特定的目录中拥有访问所有的文件的权限给一个特定的用户组，你有可能需要使用给目录设置setgid的方法。当setgid设置后，该真实用户的有效GID会变成属主的GID。
因此，任何访问该文件的用户会被授予该文件的属组的权限。此外，当setgid设置在一个目录中，新创建的文件继承组该目录的组，而且新创建的子目录也将继承父目录的setgid权限。
# chmod g+s [filename]
为了设置 setgid 在八进制形式，预先准备好数字2 来给基本的权限
要以八进制形式设置 setgid，需要在基本权限前缀以2。
# chmod 2755 [directory]
### 总结 ###
扎实的用户和组管理知识，符合规则的,Linux权限管理，以及部分实践，可以帮你快速解决RHEL 7 服务器的文件权限。
我向你保证，当你按照本文所概述的步骤和使用系统文档(和第一章解释的那样 [Part 1: Reviewing Essential Commands & System Documentation][5] of this series) 你将掌握基本的系统管理的能力。
扎实的用户和组管理知识，以及标准和特殊的 Linux权限管理，通过实践，可以帮你快速解决 RHEL 7 服务器的文件权限问题。
请随时让我们知道你是否有任何问题或意见使用下面的表格。
我向你保证，当你按照本文所概述的步骤和使用系统文档(在本系列的[第一章 回顾基础命令及系统文档][5]中讲到)， 你将掌握基本的系统管理的能力。
请随时使用下面的评论框让我们知道你是否有任何问题或意见。
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@ -212,13 +236,13 @@ via: http://www.tecmint.com/rhcsa-exam-manage-users-and-groups/
作者：[Gabriel Cánepa][a]
译者：[xiqingongzi](https://github.com/xiqingongzi)
校对：[校对者ID](https://github.com/校对者ID)
校对：[wxy](https://github.com/wxy)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](https://linux.cn/) 荣誉推出
[a]:http://www.tecmint.com/author/gacanepa/
[1]:http://www.tecmint.com/add-users-in-linux/
[2]:http://www.tecmint.com/usermod-command-examples/
[3]:http://www.tecmint.com/ls-interview-questions/
[4]:http://www.tecmint.com/file-and-directory-management-in-linux/
[3]:http://linux.cn/article-5349-1.html
[4]:https://www.linux.cn/article-6155-1.html
[5]:http://www.tecmint.com/rhcsa-exam-reviewing-essential-commands-system-documentation/