mirror of
https://github.com/LCTT/TranslateProject.git
synced 2024-12-29 21:41:00 +08:00
Jindong Huang
commit
f766fea8ac
@ -1,24 +1,25 @@
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在 Linux 中安装 Google 环聊桌面客户端
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================================================================================
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先前，我们已经介绍了如何[在 Linux 中安装 Facebook Messenger][1] 和[WhatsApp 桌面客户端][2]。这些应用都是非官方的应用。今天，我将为你推荐另一款非官方的应用，它就是 [Google 环聊][3]
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当然，你可以在 Web 浏览器中使用 Google 环聊，但相比于此，使用桌面客户端会更加有趣。好奇吗？那就跟着我看看如何 **在 Linux 中安装 Google 环聊** 以及如何使用它把。
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当然，你可以在 Web 浏览器中使用 Google 环聊，但相比于此，使用桌面客户端会更加有趣。好奇吗？那就跟着我看看如何 **在 Linux 中安装 Google 环聊** 以及如何使用它吧。
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### 在 Linux 中安装 Google 环聊 ###
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我们将使用一个名为 [yakyak][4] 的开源项目，它是一个针对 Linux，Windows 和 OS X 平台的非官方 Google 环聊客户端。我将向你展示如何在 Ubuntu 中使用 yakyak，但我相信在其他的 Linux 发行版本中，你可以使用同样的方法来使用它。在了解如何使用它之前，让我们先看看 yakyak 的主要特点：
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- 发送和接受聊天信息
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- 创建和更改对话 (重命名, 添加人物)
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- 创建和更改对话 (重命名, 添加参与者)
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- 离开或删除对话
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- 桌面提醒通知
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- 打开或关闭通知
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- 针对图片上传，支持拖放，复制粘贴或使用上传按钮
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- Hangupsbot 房间同步(实际的用户图片) (注: 这里翻译不到位，希望改善一下)
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- 对于图片上传，支持拖放，复制粘贴或使用上传按钮
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- Hangupsbot 房间同步(使用用户实际的图片)
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- 展示行内图片
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- 历史回放
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- 翻阅历史
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听起来不错吧，你可以从下面的链接下载到该软件的安装文件:
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@ -36,7 +37,7 @@
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假如你想看看对话的配置图，你可以选择 `查看-> 展示对话缩略图`
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假如你想在联系人里面显示用户头像，你可以选择 `查看-> 展示对话缩略图`
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@ -54,7 +55,7 @@ via: http://itsfoss.com/install-google-hangouts-linux/
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作者：[Abhishek][a]
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译者：[FSSlc](https://github.com/FSSlc)
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校对：[校对者ID](https://github.com/校对者ID)
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校对：[wxy](https://github.com/wxy)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](https://linux.cn/) 荣誉推出
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@ -1,10 +1,9 @@
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如何修复ubuntu 14.04中检测到系统程序错误的问题
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如何修复 ubuntu 中检测到系统程序错误的问题
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================================================================================
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在过去的几个星期，（几乎）每次都有消息 **Ubuntu 15.04在启动时检测到系统程序错误（system program problem detected on startup in Ubuntu 15.04)** 跑出来“欢迎”我。那时我是直接忽略掉它的，但是这种情况到了某个时刻，它就让人觉得非常烦人了！
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在过去的几个星期，（几乎）每次都有消息 **Ubuntu 15.04在启动时检测到系统程序错误** 跑出来“欢迎”我。那时我是直接忽略掉它的，但是这种情况到了某个时刻，它就让人觉得非常烦人了！
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> 检测到系统程序错误(System program problem detected)
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>
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@ -18,15 +17,16 @@
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#### 那么这个通知到底是关于什么的？ ####
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大体上讲，它是在告知你，你的系统的一部分崩溃了。可别因为“崩溃”这个词而恐慌。这不是一个严重的问题，你的系统还是完完全全可用的。只是在以前的某个时刻某个程序崩溃了，而Ubuntu想让你决定要不要把这个问题报告给开发者，这样他们就能够修复这个问题。
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大体上讲，它是在告知你，你的系统的一部分崩溃了。可别因为“崩溃”这个词而恐慌。这不是一个严重的问题，你的系统还是完完全全可用的。只是在之前的某个时刻某个程序崩溃了，而Ubuntu想让你决定要不要把这个问题报告给开发者，这样他们就能够修复这个问题。
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#### 那么，我们点了“报告错误”的按钮后，它以后就不再显示了？####
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不，不是的！即使你点了“报告错误”按钮，最后你还是会被一个如下的弹窗再次“欢迎”一下：
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不，不是的！即使你点了“报告错误”按钮，最后你还是会被一个如下的弹窗再次“欢迎”：
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[对不起，Ubuntu发生了一个内部错误(Sorry, Ubuntu has experienced an internal error)][1]是一个Apport(Apport是Ubuntu中错误信息的收集报告系统,详见Ubuntu Wiki中的Apport篇,译者注)，它将会进一步的打开网页浏览器，然后你可以通过登录或创建[Launchpad][2]帐户来填写一份漏洞（Bug)报告文件。你看,这是一个复杂的过程,它要花整整四步来完成.
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[对不起，Ubuntu发生了一个内部错误][1]是个Apport（LCTT 译注：Apport是Ubuntu中错误信息的收集报告系统，详见Ubuntu Wiki中的Apport篇），它将会进一步的打开网页浏览器，然后你可以通过登录或创建[Launchpad][2]帐户来填写一份漏洞（Bug)报告文件。你看，这是一个复杂的过程，它要花整整四步来完成。
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#### 但是我想帮助开发者，让他们知道这个漏洞啊 !####
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你这样想的确非常地周到体贴,而且这样做也是正确的。但是这样做的话，存在两个问题。第一，存在非常高的概率，这个漏洞已经被报告过了；第二，即使你报告了个这次崩溃，也无法保证你不会再看到它。
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@ -34,35 +34,38 @@
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#### 那么，你的意思就是说别报告这次崩溃了？####
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对，也不对。如果你想的话，在你第一次看到它的时候报告它。你可以在上面图片显示的“显示细节（Show Details)”中，查看崩溃的程序。但是如果你总是看到它，或者你不想报告漏洞（Bug)，那么我建议你还是一次性摆脱这个问题吧。
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### 修复Ubuntu中“检测到系统程序错误”的错误 ###
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这些错误报告被存放在Ubuntu中目录/var/crash中。如果你翻看这个目录的话，应该可以看到有一些以crash结尾的文件。
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我的建议是删除这些错误报告。打开一个终端，执行下面的命令：
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sudo rm /var/crash/*
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这个操作会删除所有在/var/crash目录下的所有内容。这样你就不会再被这些报告以前程序错误的弹窗所扰。但是如果有一个程序又崩溃了，你就会再次看到“检测到系统程序错误”的错误。你可以再次删除这些报告文件，或者你可以禁用Apport来彻底地摆脱这个错误弹窗。
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这个操作会删除所有在/var/crash目录下的所有内容。这样你就不会再被这些报告以前程序错误的弹窗所扰。但是如果又有一个程序崩溃了，你就会再次看到“检测到系统程序错误”的错误。你可以再次删除这些报告文件，或者你可以禁用Apport来彻底地摆脱这个错误弹窗。
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#### 彻底地摆脱Ubuntu中的系统错误弹窗 ####
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如果你这样做，系统中任何程序崩溃时，系统都不会再通知你。如果你想问问我的看法的话，我会说，这不是一件坏事，除非你愿意填写错误报告。如果你不想填写错误报告，那么这些错误通知存不存在都不会有什么区别。
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要禁止Apport，并且彻底地摆脱Ubuntu系统中的程序崩溃报告，打开一个终端，输入以下命令：
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gksu gedit /etc/default/apport
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这个文件的内容是：
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# set this to 0 to disable apport, or to 1 to enable it
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# 设置0表示禁用Apportw，或者1开启它。译者注，下同。
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# you can temporarily override this with
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# 设置0表示禁用Apportw，或者1开启它。
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# 你可以用下面的命令暂时关闭它：
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# sudo service apport start force_start=1
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enabled=1
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把**enabled=1**改为**enabled=0**.保存并关闭文件。完成之后你就再也不会看到弹窗报告错误了。很显然，如果我们想重新开启错误报告功能，只要再打开这个文件，把enabled设置为1就可以了。
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把**enabled=1**改为**enabled=0**。保存并关闭文件。完成之后你就再也不会看到弹窗报告错误了。很显然，如果我们想重新开启错误报告功能，只要再打开这个文件，把enabled设置为1就可以了。
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#### 你的有效吗？ ####
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我希望这篇教程能够帮助你修复Ubuntu 14.04和Ubuntu 15.04中检测到系统程序错误的问题。如果这个小窍门帮你摆脱了这个烦人的问题，请让我知道。
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--------------------------------------------------------------------------------
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@ -71,7 +74,7 @@ via: http://itsfoss.com/how-to-fix-system-program-problem-detected-ubuntu/
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作者：[Abhishek][a]
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译者：[XLCYun](https://github.com/XLCYun)
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校对：[校对者ID](https://github.com/校对者ID)
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校对：[wxy](https://github.com/wxy)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](https://linux.cn/) 荣誉推出
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@ -1,10 +1,12 @@
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Linux命令行中使用和执行PHP代码——第一部分
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在 Linux 命令行中使用和执行 PHP 代码（一）
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================================================================================
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PHP是一个开元服务器端脚本语言，最初这三个字母代表的是“Personal Home Page”，而现在则代表的是“PHP：Hypertext Preprocessor”，它是个递归首字母缩写。它是一个跨平台脚本语言，深受C、C++和Java的影响。
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Linux命令行中运行PHP代码——第一部分
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PHP是一个开源服务器端脚本语言，最初这三个字母代表的是“Personal Home Page”，而现在则代表的是“PHP：Hypertext Preprocessor”，它是个递归首字母缩写。它是一个跨平台脚本语言，深受C、C++和Java的影响。
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PHP的语法和C、Java以及带有一些PHP特性的Perl变成语言中的语法十分相似，它眼下大约正被2.6亿个网站所使用，当前最新的稳定版本是PHP版本5.6.10。
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*在 Linux 命令行中运行 PHP 代码*
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PHP的语法和C、Java以及带有一些PHP特性的Perl变成语言中的语法十分相似，它当下大约正被2.6亿个网站所使用，当前最新的稳定版本是PHP版本5.6.10。
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PHP是HTML的嵌入脚本，它便于开发人员快速写出动态生成的页面。PHP主要用于服务器端（而Javascript则用于客户端）以通过HTTP生成动态网页，然而，当你知道可以在Linux终端中不需要网页浏览器来执行PHP时，你或许会大为惊讶。
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@ -12,40 +14,44 @@ PHP是HTML的嵌入脚本，它便于开发人员快速写出动态生成的页
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**1. 在安装完PHP和Apache2后，我们需要安装PHP命令行解释器。**
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# apt-get install php5-cli [Debian and alike System)
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# yum install php-cli [CentOS and alike System)
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# apt-get install php5-cli [Debian 及类似系统]
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# yum install php-cli [CentOS 及类似系统]
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接下来我们通常要做的是，在‘/var/www/html‘（这是 Apache2 在大多数发行版中的工作目录）这个位置创建一个内容为 ‘<?php phpinfo(); ?>‘，名为 ‘infophp.php‘ 的文件来测试（是否安装正确），执行以下命令即可。
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接下来我们通常要做的是，在`/var/www/html`（这是 Apache2 在大多数发行版中的工作目录）这个位置创建一个内容为 `<?php phpinfo(); ?>`，名为 `infophp.php` 的文件来测试（PHP是否安装正确），执行以下命令即可。
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# echo '<?php phpinfo(); ?>' > /var/www/html/infophp.php
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然后，将浏览器指向http://127.0.0.1/infophp.php， 这将会在网络浏览器中打开该文件。
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然后，将浏览器访问 http://127.0.0.1/infophp.php ，这将会在网络浏览器中打开该文件。
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检查PHP信息
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不需要任何浏览器，在Linux终端中也可以获得相同的结果。在Linux命令行中执行‘/var/www/html/infophp.php‘，如：
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*检查PHP信息*
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不需要任何浏览器，在Linux终端中也可以获得相同的结果。在Linux命令行中执行`/var/www/html/infophp.php`，如：
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# php -f /var/www/html/infophp.php
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从命令行检查PHP信息
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由于输出结果太大，我们可以通过管道将上述输出结果输送给 ‘less‘ 命令，这样就可以一次输出一屏了，命令如下：
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*从命令行检查PHP信息*
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由于输出结果太大，我们可以通过管道将上述输出结果输送给 `less` 命令，这样就可以一次输出一屏了，命令如下：
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# php -f /var/www/html/infophp.php | less
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检查所有PHP信息
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这里，‘-f‘选项解析病执行命令后跟随的文件。
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*检查所有PHP信息*
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这里，‘-f‘选项解析并执行命令后跟随的文件。
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**2. 我们可以直接在Linux命令行使用`phpinfo()`这个十分有价值的调试工具而不需要从文件来调用，只需执行以下命令：**
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# php -r 'phpinfo();'
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PHP调试工具
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*PHP调试工具*
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这里，‘-r‘ 选项会让PHP代码在Linux终端中不带`<`和`>`标记直接执行。
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@ -74,13 +80,14 @@ PHP调试工具
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输入 ‘exit‘ 或者按下 ‘ctrl+c‘ 来关闭PHP交互模式。
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启用PHP交互模式
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*启用PHP交互模式*
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**4. 你可以仅仅将PHP脚本作为shell脚本来运行。首先，创建在你当前工作目录中创建一个PHP样例脚本。**
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# echo -e '#!/usr/bin/php\n<?php phpinfo(); ?>' > phpscript.php
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注意，我们在该PHP脚本的第一行使用#!/usr/bin/php，就像在shell脚本中那样（/bin/bash）。第一行的#!/usr/bin/php告诉Linux命令行将该脚本文件解析到PHP解释器中。
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注意，我们在该PHP脚本的第一行使用`#!/usr/bin/php`，就像在shell脚本中那样（`/bin/bash`）。第一行的`#!/usr/bin/php`告诉Linux命令行用 PHP 解释器来解析该脚本文件。
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其次，让该脚本可执行：
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@ -96,7 +103,7 @@ PHP调试工具
|
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# php -a
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创建一个函授，将它命名为 addition。同时，声明两个变量 $a 和 $b。
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创建一个函数，将它命名为 `addition`。同时，声明两个变量 `$a` 和 `$b`。
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php > function addition ($a, $b)
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@ -133,7 +140,8 @@ PHP调试工具
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12.3NULL
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创建PHP函数
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*创建PHP函数*
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你可以一直运行该函数，直至退出交互模式（ctrl+z）。同时，你也应该注意到了，上面输出结果中返回的数据类型为 NULL。这个问题可以通过要求 php 交互 shell用 return 代替 echo 返回结果来修复。
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@ -152,11 +160,12 @@ PHP调试工具
|
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这里是一个样例，在该样例的输出结果中返回了正确的数据类型。
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PHP函数
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*PHP函数*
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永远都记住，用户定义的函数不会从一个shell会话保留到下一个shell会话，因此，一旦你退出交互shell，它就会丢失了。
|
||||
|
||||
希望你喜欢此次会话。保持连线，你会获得更多此类文章。保持关注，保持健康。请在下面的评论中为我们提供有价值的反馈。点赞并分享，帮助我们扩散。
|
||||
希望你喜欢此次教程。保持连线，你会获得更多此类文章。保持关注，保持健康。请在下面的评论中为我们提供有价值的反馈。点赞并分享，帮助我们扩散。
|
||||
|
||||
还请阅读： [12个Linux终端中有用的的PHP命令行用法——第二部分][1]
|
||||
|
||||
@ -164,9 +173,9 @@ PHP函数
|
||||
|
||||
via: http://www.tecmint.com/run-php-codes-from-linux-commandline/
|
||||
|
||||
作者：[vishek Kumar][a]
|
||||
作者：[Avishek Kumar][a]
|
||||
译者：[GOLinux](https://github.com/GOLinux)
|
||||
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
|
||||
|
||||
@ -1,3 +1,4 @@
|
||||
zpl1025
|
||||
Interviews: Linus Torvalds Answers Your Question
|
||||
================================================================================
|
||||
Last Thursday you had a chance to [ask Linus Torvalds][1] about programming, hardware, and all things Linux. You can read his answers to those questions below. If you'd like to see what he had to say the last time we sat down with him, [you can do so here][2].
|
||||
@ -181,4 +182,4 @@ via: http://linux.slashdot.org/story/15/06/30/0058243/interviews-linus-torvalds-
|
||||
[a]:samzenpus@slashdot.org
|
||||
[1]:http://interviews.slashdot.org/story/15/06/24/1718247/interview-ask-linus-torvalds-a-question
|
||||
[2]:http://meta.slashdot.org/story/12/10/11/0030249/linus-torvalds-answers-your-questions
|
||||
[3]:https://lwn.net/Articles/604695/
|
||||
[3]:https://lwn.net/Articles/604695/
|
||||
|
||||
@ -0,0 +1,90 @@
|
||||
Easy Backup, Restore and Migrate Containers in Docker
|
||||
================================================================================
|
||||
Today we'll learn how we can easily backup, restore and migrate docker containers out of the box. [Docker][1] is an open source platform that automates the deployment of applications with fast and easy way to pack, ship and run it under a lightweight layer of software called container. It makes the applications platform independent as it acts an additional layer of abstraction and automation of operating system level virtualization on Linux. It utilizes resource isolation features of Linux Kernel with its components cgroups and namespace for avoiding the overhead of virtual machines. It makes the great building blocks for deploying and scaling web apps, databases, and back-end services without depending on a particular stack or provider. Containers are those software layers which are created from a docker image that contains the respective linux filesystem and applications out of the box. If we have a docker container running in our box and need to backup those containers for future use or wanna migrate those containers, then this tutorial will help you how we can backup, restore and migrate docker containers in linux operating system.
|
||||
|
||||
Here are some easy steps on how we can backup, restore and migrate the docker containers in linux.
|
||||
|
||||
### 1. Backing up the Containers ###
|
||||
|
||||
First of all, in order to backup the containers in docker, we'll wanna see the list of containers that we wanna backup. To do so, we'll need to run docker ps in our linux machine running docker engine with containers already created.
|
||||
|
||||
# docker ps
|
||||
|
||||
|
||||
|
||||
After that, we'll choose the containers we wanna backup and then we'll go for creating the snapshot of the container. We can use docker commit command in order to create the snapshot.
|
||||
|
||||
# docker commit -p 30b8f18f20b4 container-backup
|
||||
|
||||
|
||||
|
||||
This will generated a snapshot of the container as the docker image. We can see the docker image by running the command docker images as shown below.
|
||||
|
||||
# docker images
|
||||
|
||||
|
||||
|
||||
As we can see the snapshot that was taken above has been preserved as docker image. Now, inorder to backup that snapshot, we have two options, one is that we can login into the docker registry hub and push the image and the next is that we can backup the docker image as tarballs for further use.
|
||||
|
||||
If we wanna upload or backup the image in the [docker registry hub][2], we can simply run docker login command to login into the docker registry hub and then push the required image.
|
||||
|
||||
# docker login
|
||||
|
||||
|
||||
|
||||
# docker tag a25ddfec4d2a arunpyasi/container-backup:test
|
||||
# docker push arunpyasi/container-backup
|
||||
|
||||
|
||||
|
||||
If we don't wanna backup to the docker registry hub and wanna save the image for future use in the machine locally then we can backup the image as tarballs. To do so, we'll need to run the following docker save command.
|
||||
|
||||
# docker save -o ~/container-backup.tar container-backup
|
||||
|
||||
|
||||
|
||||
To verify if the tarball has been generated or not, we can simply run docker ls inside the directory where we saved the tarball.
|
||||
|
||||
### 2. Restoring the Containers ###
|
||||
|
||||
Next, after we have successfully backed up our docker containers, we'll now go for restoring those contianers which are snapshotted as docker images. If we have pushed those docker images in the registry hub, then we can simply pull that docker image and run it out of the box.
|
||||
|
||||
# docker pull arunpyasi/container-backup:test
|
||||
|
||||
|
||||
|
||||
But if we have backed up those docker images locally as tarball file, then we can easy load that docker image using docker load command followed by the backed up tarball.
|
||||
|
||||
# docker load -i ~/container-backup.tar
|
||||
|
||||
Now, to ensure that those docker images have been loaded successfully, we'll run docker images command.
|
||||
|
||||
# docker images
|
||||
|
||||
After the images have been loaded, we'll gonna run the docker container from the loaded image.
|
||||
|
||||
# docker run -d -p 80:80 container-backup
|
||||
|
||||
|
||||
|
||||
### 3. Migrating the Docker Containers ###
|
||||
|
||||
Migrating the containers involve both the above process ie Backup and Restore. We can migrate any docker container from one machine to another. In the process of migration, first we take the backup of the container as snapshot docker image. Then, that docker image is either pushed to the docker registry hub or saved as tarball files in the locally. If we have pushed the image to the docker registry hub, we can easily restore and run the container using docker run command from any machine we want. But if we have saved the image as tarballs locally, we can simply copy or move the image to the machine where we want to load image and run the required container.
|
||||
|
||||
### Conclusion ###
|
||||
|
||||
Finally, we have learned how we can backup, restore and migrate the docker containers out of the box. This tutorial is exactly same for every platform of operating system where docker runs successfully. Really, docker is pretty simple and easy to use but very powerful tool. It has pretty easy to remember commands which are short enough with many simple but powerful flags and parameters. The above methods makes us comfortable to backup our containers so that we can restore them when needed in future. This can help us recover our containers and images even if our host system crashes or gets wiped out accidentally. If you have any questions, suggestions, feedback please write them in the comment box below so that we can improve or update our contents. Thank you ! Enjoy :-)
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: http://linoxide.com/linux-how-to/backup-restore-migrate-containers-docker/
|
||||
|
||||
作者：[Arun Pyasi][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://linoxide.com/author/arunp/
|
||||
[1]:http://docker.com/
|
||||
[2]:https://registry.hub.docker.com/
|
||||
674
sources/tech/20150728 Process of the Linux kernel building.md
Normal file
674
sources/tech/20150728 Process of the Linux kernel building.md
Normal file
@ -0,0 +1,674 @@
|
||||
Process of the Linux kernel building
|
||||
================================================================================
|
||||
Introduction
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
I will not tell you how to build and install custom Linux kernel on your machine, you can find many many [resources](https://encrypted.google.com/search?q=building+linux+kernel#q=building+linux+kernel+from+source+code) that will help you to do it. Instead, we will know what does occur when you are typed `make` in the directory with Linux kernel source code in this part. When I just started to learn source code of the Linux kernel, the [Makefile](https://github.com/torvalds/linux/blob/master/Makefile) file was a first file that I've opened. And it was scary :) This [makefile](https://en.wikipedia.org/wiki/Make_%28software%29) contains `1591` lines of code at the time when I wrote this part and it was [third](https://github.com/torvalds/linux/commit/52721d9d3334c1cb1f76219a161084094ec634dc) release candidate.
|
||||
|
||||
This makefile is the the top makefile in the Linux kernel source code and kernel build starts here. Yes, it is big, but moreover, if you've read the source code of the Linux kernel you can noted that all directories with a source code has an own makefile. Of course it is not real to describe how each source files compiled and linked. So, we will see compilation only for the standard case. You will not find here building of the kernel's documentation, cleaning of the kernel source code, [tags](https://en.wikipedia.org/wiki/Ctags) generation, [cross-compilation](https://en.wikipedia.org/wiki/Cross_compiler) related stuff and etc. We will start from the `make` execution with the standard kernel configuration file and will finish with the building of the [bzImage](https://en.wikipedia.org/wiki/Vmlinux#bzImage).
|
||||
|
||||
It would be good if you're already familiar with the [make](https://en.wikipedia.org/wiki/Make_%28software%29) util, but I will anyway try to describe all code that will be in this part.
|
||||
|
||||
So let's start.
|
||||
|
||||
Preparation before the kernel compilation
|
||||
---------------------------------------------------------------------------------
|
||||
|
||||
There are many things to preparate before the kernel compilation will be started. The main point here is to find and configure
|
||||
the type of compilation, to parse command line arguments that are passed to the `make` util and etc. So let's dive into the top `Makefile` of the Linux kernel.
|
||||
|
||||
The Linux kernel top `Makefile` is responsible for building two major products: [vmlinux](https://en.wikipedia.org/wiki/Vmlinux) (the resident kernel image) and the modules (any module files). The [Makefile](https://github.com/torvalds/linux/blob/master/Makefile) of the Linux kernel starts from the definition of the following variables:
|
||||
|
||||
```Makefile
|
||||
VERSION = 4
|
||||
PATCHLEVEL = 2
|
||||
SUBLEVEL = 0
|
||||
EXTRAVERSION = -rc3
|
||||
NAME = Hurr durr I'ma sheep
|
||||
```
|
||||
|
||||
These variables determine the current version of the Linux kernel and are used in the different places, for example in the forming of the `KERNELVERSION` variable:
|
||||
|
||||
```Makefile
|
||||
KERNELVERSION = $(VERSION)$(if $(PATCHLEVEL),.$(PATCHLEVEL)$(if $(SUBLEVEL),.$(SUBLEVEL)))$(EXTRAVERSION)
|
||||
```
|
||||
|
||||
After this we can see a couple of the `ifeq` condition that check some of the parameters passed to `make`. The Linux kernel `makefiles` provides a special `make help` target that prints all available targets and some of the command line arguments that can be passed to `make`. For example: `make V=1` - provides verbose builds. The first `ifeq` condition checks if the `V=n` option is passed to make:
|
||||
|
||||
```Makefile
|
||||
ifeq ("$(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
|
||||
```
|
||||
|
||||
If this option is passed to `make` we set the `KBUILD_VERBOSE` variable to the value of the `V` option. Otherwise we set the `KBUILD_VERBOSE` variable to zero. After this we check value of the `KBUILD_VERBOSE` variable and set values of the `quiet` and `Q` variables depends on the `KBUILD_VERBOSE` value. The `@` symbols suppress the output of the command and if it will be set before a command we will see something like this: `CC scripts/mod/empty.o` instead of the `Compiling .... scripts/mod/empty.o`. In the end we just export all of these variables. The next `ifeq` statement checks that `O=/dir` option was passed to the `make`. This option allows to locate all output files in the given `dir`:
|
||||
|
||||
```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),)
|
||||
```
|
||||
|
||||
We check the `KBUILD_SRC` that represent top directory of the source code of the linux kernel and if it is empty (it is empty every time while makefile executes first time) and the set the `KBUILD_OUTPUT` variable to the value that passed with the `O` option (if this option was passed). In the next step we check this `KBUILD_OUTPUT` variable and if we set it, we do following things:
|
||||
|
||||
* Store value of the `KBUILD_OUTPUT` in the temp `saved-output` variable;
|
||||
* Try to create given output directory;
|
||||
* Check that directory created, in other way print error;
|
||||
* If custom output directory created sucessfully, execute `make` again with the new directory (see `-C` option).
|
||||
|
||||
The next `ifeq` statements checks that `C` or `M` options was passed to the make:
|
||||
|
||||
```Makefile
|
||||
ifeq ("$(origin C)", "command line")
|
||||
KBUILD_CHECKSRC = $(C)
|
||||
endif
|
||||
ifndef KBUILD_CHECKSRC
|
||||
KBUILD_CHECKSRC = 0
|
||||
endif
|
||||
|
||||
ifeq ("$(origin M)", "command line")
|
||||
KBUILD_EXTMOD := $(M)
|
||||
endif
|
||||
```
|
||||
|
||||
The first `C` option tells to the `makefile` that need to check all `c` source code with a tool provided by the `$CHECK` environment variable, by default it is [sparse](https://en.wikipedia.org/wiki/Sparse). The second `M` option provides build for the external modules (will not see this case in this part). As we set this variables we make a check of the `KBUILD_SRC` variable and if it is not set we set `srctree` variable to `.`:
|
||||
|
||||
```Makefile
|
||||
ifeq ($(KBUILD_SRC),)
|
||||
srctree := .
|
||||
endif
|
||||
|
||||
objtree := .
|
||||
src := $(srctree)
|
||||
obj := $(objtree)
|
||||
|
||||
export srctree objtree VPATH
|
||||
```
|
||||
|
||||
That tells to `Makefile` that source tree of the Linux kernel will be in the current directory where `make` command was executed. After this we set `objtree` and other variables to this directory and export these variables. The next step is the getting value for the `SUBARCH` variable that will represent tewhat the underlying archicecture is:
|
||||
|
||||
```Makefile
|
||||
SUBARCH := $(shell uname -m | sed -e s/i.86/x86/ -e s/x86_64/x86/ \
|
||||
-e s/sun4u/sparc64/ \
|
||||
-e s/arm.*/arm/ -e s/sa110/arm/ \
|
||||
-e s/s390x/s390/ -e s/parisc64/parisc/ \
|
||||
-e s/ppc.*/powerpc/ -e s/mips.*/mips/ \
|
||||
-e s/sh[234].*/sh/ -e s/aarch64.*/arm64/ )
|
||||
```
|
||||
|
||||
As you can see it executes [uname](https://en.wikipedia.org/wiki/Uname) utils that prints information about machine, operating system and architecture. As it will get output of the `uname` util, it will parse it and assign to the `SUBARCH` variable. As we got `SUBARCH`, we set the `SRCARCH` variable that provides directory of the certain architecture and `hfr-arch` that provides directory for the header files:
|
||||
|
||||
```Makefile
|
||||
ifeq ($(ARCH),i386)
|
||||
SRCARCH := x86
|
||||
endif
|
||||
ifeq ($(ARCH),x86_64)
|
||||
SRCARCH := x86
|
||||
endif
|
||||
|
||||
hdr-arch := $(SRCARCH)
|
||||
```
|
||||
|
||||
Note that `ARCH` is the alias for the `SUBARCH`. In the next step we set the `KCONFIG_CONFIG` variable that represents path to the kernel configuration file and if it was not set before, it will be `.config` by default:
|
||||
|
||||
```Makefile
|
||||
KCONFIG_CONFIG ?= .config
|
||||
export KCONFIG_CONFIG
|
||||
```
|
||||
|
||||
and the [shell](https://en.wikipedia.org/wiki/Shell_%28computing%29) that will be used during kernel compilation:
|
||||
|
||||
```Makefile
|
||||
CONFIG_SHELL := $(shell if [ -x "$$BASH" ]; then echo $$BASH; \
|
||||
else if [ -x /bin/bash ]; then echo /bin/bash; \
|
||||
else echo sh; fi ; fi)
|
||||
```
|
||||
|
||||
The next set of variables related to the compiler that will be used during Linux kernel compilation. We set the host compilers for the `c` and `c++` and flags for it:
|
||||
|
||||
```Makefile
|
||||
HOSTCC = gcc
|
||||
HOSTCXX = g++
|
||||
HOSTCFLAGS = -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 -fomit-frame-pointer -std=gnu89
|
||||
HOSTCXXFLAGS = -O2
|
||||
```
|
||||
|
||||
Next we will meet the `CC` variable that represent compiler too, so why do we need in the `HOST*` variables? The `CC` is the target compiler that will be used during kernel compilation, but `HOSTCC` will be used during compilation of the set of the `host` programs (we will see it soon). After this we can see definition of the `KBUILD_MODULES` and `KBUILD_BUILTIN` variables that are used for the determination of the what to compile (kernel, modules or both):
|
||||
|
||||
```Makefile
|
||||
KBUILD_MODULES :=
|
||||
KBUILD_BUILTIN := 1
|
||||
|
||||
ifeq ($(MAKECMDGOALS),modules)
|
||||
KBUILD_BUILTIN := $(if $(CONFIG_MODVERSIONS),1)
|
||||
endif
|
||||
```
|
||||
|
||||
Here we can see definition of these variables and the value of the `KBUILD_BUILTIN` will depens on the `CONFIG_MODVERSIONS` kernel configuration parameter if we pass only `modules` to the `make`. The next step is including of the:
|
||||
|
||||
```Makefile
|
||||
include scripts/Kbuild.include
|
||||
```
|
||||
|
||||
`kbuild` file. The [Kbuild](https://github.com/torvalds/linux/blob/master/Documentation/kbuild/kbuild.txt) or `Kernel Build System` is the special infrastructure to manage building of the kernel and its modules. The `kbuild` files has the same syntax that makefiles. The [scripts/Kbuild.include](https://github.com/torvalds/linux/blob/master/scripts/Kbuild.include) file provides some generic definitions for the `kbuild` system. As we included this `kbuild` files we can see definition of the variables that are related to the different tools that will be used during kernel and modules compilation (like linker, compilers, utils from the [binutils](http://www.gnu.org/software/binutils/) and etc...):
|
||||
|
||||
```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 = $(CROSS_COMPILE)objdump
|
||||
AWK = awk
|
||||
...
|
||||
...
|
||||
...
|
||||
```
|
||||
|
||||
After definition of these variables we define two variables: `USERINCLUDE` and `LINUXINCLUDE`. They will contain paths of the directories with headers (public for users in the first case and for kernel in the second case):
|
||||
|
||||
```Makefile
|
||||
USERINCLUDE := \
|
||||
-I$(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 \
|
||||
...
|
||||
```
|
||||
|
||||
And the standard flags for the C compiler:
|
||||
|
||||
```Makefile
|
||||
KBUILD_CFLAGS := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
|
||||
-fno-strict-aliasing -fno-common \
|
||||
-Werror-implicit-function-declaration \
|
||||
-Wno-format-security \
|
||||
-std=gnu89
|
||||
```
|
||||
|
||||
It is the not last compiler flags, they can be updated by the other makefiles (for example kbuilds from `arch/`). After all of these, all variables will be exported to be available in the other makefiles. The following two the `RCS_FIND_IGNORE` and the `RCS_TAR_IGNORE` variables will contain files that will be ignored in the version control system:
|
||||
|
||||
```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
|
||||
```
|
||||
|
||||
That's all. We have finished with the all preparations, next point is the building of `vmlinux`.
|
||||
|
||||
Directly to the kernel build
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
As we have finished all preparations, next step in the root makefile is related to the kernel build. Before this moment we will not see in the our terminal after the execution of the `make` command. But now first steps of the compilation are started. In this moment we need to go on the [598](https://github.com/torvalds/linux/blob/master/Makefile#L598) line of the Linux kernel top makefile and we will see `vmlinux` target there:
|
||||
|
||||
```Makefile
|
||||
all: vmlinux
|
||||
include arch/$(SRCARCH)/Makefile
|
||||
```
|
||||
|
||||
Don't worry that we have missed many lines in Makefile that are placed after `export RCS_FIND_IGNORE.....` and before `all: vmlinux.....`. This part of the makefile is responsible for the `make *.config` targets and as I wrote in the beginning of this part we will see only building of the kernel in a general way.
|
||||
|
||||
The `all:` target is the default when no target is given on the command line. You can see here that we include architecture specific makefile there (in our case it will be [arch/x86/Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/Makefile)). From this moment we will continue from this makefile. As we can see `all` target depends on the `vmlinux` target that defined a little lower in the top makefile:
|
||||
|
||||
```Makefile
|
||||
vmlinux: scripts/link-vmlinux.sh $(vmlinux-deps) FORCE
|
||||
```
|
||||
|
||||
The `vmlinux` is is the Linux kernel in an statically linked executable file format. The [scripts/link-vmlinux.sh](https://github.com/torvalds/linux/blob/master/scripts/link-vmlinux.sh) script links combines different compiled subsystems into vmlinux. The second target is the `vmlinux-deps` that defined as:
|
||||
|
||||
```Makefile
|
||||
vmlinux-deps := $(KBUILD_LDS) $(KBUILD_VMLINUX_INIT) $(KBUILD_VMLINUX_MAIN)
|
||||
```
|
||||
|
||||
and consists from the set of the `built-in.o` from the each top directory of the Linux kernel. Later, when we will go through all directories in the Linux kernel, the `Kbuild` will compile all the `$(obj-y)` files. It then calls `$(LD) -r` to merge these files into one `built-in.o` file. For this moment we have no `vmlinux-deps`, so the `vmlinux` target will not be executed now. For me `vmlinux-deps` contains following files:
|
||||
|
||||
```
|
||||
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
|
||||
```
|
||||
|
||||
The next target that can be executed is following:
|
||||
|
||||
```Makefile
|
||||
$(sort $(vmlinux-deps)): $(vmlinux-dirs) ;
|
||||
$(vmlinux-dirs): prepare scripts
|
||||
$(Q)$(MAKE) $(build)=$@
|
||||
```
|
||||
|
||||
As we can see the `vmlinux-dirs` depends on the two targets: `prepare` and `scripts`. The first `prepare` defined in the top `Makefile` of the Linux kernel and executes three stages of preparations:
|
||||
|
||||
```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
|
||||
```
|
||||
|
||||
The first `prepare0` expands to the `archprepare` that exapnds to the `archheaders` and `archscripts` that defined in the `x86_64` specific [Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/Makefile). Let's look on it. The `x86_64` specific makefile starts from the definition of the variables that are related to the archicteture-specific configs ([defconfig](https://github.com/torvalds/linux/tree/master/arch/x86/configs) and etc.). After this it defines flags for the compiling of the [16-bit](https://en.wikipedia.org/wiki/Real_mode) code, calculating of the `BITS` variable that can be `32` for `i386` or `64` for the `x86_64` flags for the assembly source code, flags for the linker and many many more (all definitions you can find in the [arch/x86/Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/Makefile)). The first target is `archheaders` in the makefile generates syscall table:
|
||||
|
||||
```Makefile
|
||||
archheaders:
|
||||
$(Q)$(MAKE) $(build)=arch/x86/entry/syscalls all
|
||||
```
|
||||
|
||||
And the second target is `archscripts` in this makefile is:
|
||||
|
||||
```Makefile
|
||||
archscripts: scripts_basic
|
||||
$(Q)$(MAKE) $(build)=arch/x86/tools relocs
|
||||
```
|
||||
|
||||
We can see that it depends on the `scripts_basic` target from the top [Makefile](https://github.com/torvalds/linux/blob/master/Makefile). At the first we can see the `scripts_basic` target that executes make for the [scripts/basic](https://github.com/torvalds/linux/blob/master/scripts/basic/Makefile) makefile:
|
||||
|
||||
```Maklefile
|
||||
scripts_basic:
|
||||
$(Q)$(MAKE) $(build)=scripts/basic
|
||||
```
|
||||
|
||||
The `scripts/basic/Makefile` contains targets for compilation of the two host programs: `fixdep` and `bin2`:
|
||||
|
||||
```Makefile
|
||||
hostprogs-y := fixdep
|
||||
hostprogs-$(CONFIG_BUILD_BIN2C) += bin2c
|
||||
always := $(hostprogs-y)
|
||||
|
||||
$(addprefix $(obj)/,$(filter-out fixdep,$(always))): $(obj)/fixdep
|
||||
```
|
||||
|
||||
First program is `fixdep` - optimizes list of dependencies generated by the [gcc](https://gcc.gnu.org/) that tells make when to remake a source code file. The second program is `bin2c` depends on the value of the `CONFIG_BUILD_BIN2C` kernel configuration option and very little C program that allows to convert a binary on stdin to a C include on stdout. You can note here strange notation: `hostprogs-y` and etc. This notation is used in the all `kbuild` files and more about it you can read in the [documentation](https://github.com/torvalds/linux/blob/master/Documentation/kbuild/makefiles.txt). In our case the `hostprogs-y` tells to the `kbuild` that there is one host program named `fixdep` that will be built from the will be built from `fixdep.c` that located in the same directory that `Makefile`. The first output after we will execute `make` command in our terminal will be result of this `kbuild` file:
|
||||
|
||||
```
|
||||
$ make
|
||||
HOSTCC scripts/basic/fixdep
|
||||
```
|
||||
|
||||
As `script_basic` target was executed, the `archscripts` target will execute `make` for the [arch/x86/tools](https://github.com/torvalds/linux/blob/master/arch/x86/tools/Makefile) makefile with the `relocs` target:
|
||||
|
||||
```Makefile
|
||||
$(Q)$(MAKE) $(build)=arch/x86/tools relocs
|
||||
```
|
||||
|
||||
The `relocs_32.c` and the `relocs_64.c` will be compiled that will contain [relocation](https://en.wikipedia.org/wiki/Relocation_%28computing%29) information and we will see it in the `make` output:
|
||||
|
||||
```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
|
||||
```
|
||||
|
||||
There is checking of the `version.h` after compiling of the `relocs.c`:
|
||||
|
||||
```Makefile
|
||||
$(version_h): $(srctree)/Makefile FORCE
|
||||
$(call filechk,version.h)
|
||||
$(Q)rm -f $(old_version_h)
|
||||
```
|
||||
|
||||
We can see it in the output:
|
||||
|
||||
```
|
||||
CHK include/config/kernel.release
|
||||
```
|
||||
|
||||
and the building of the `generic` assembly headers with the `asm-generic` target from the `arch/x86/include/generated/asm` that generated in the top Makefile of the Linux kernel. After the `asm-generic` target the `archprepare` will be done, so the `prepare0` target will be executed. As I wrote above:
|
||||
|
||||
```Makefile
|
||||
prepare0: archprepare FORCE
|
||||
$(Q)$(MAKE) $(build)=.
|
||||
```
|
||||
|
||||
Note on the `build`. It defined in the [scripts/Kbuild.include](https://github.com/torvalds/linux/blob/master/scripts/Kbuild.include) and looks like this:
|
||||
|
||||
```Makefile
|
||||
build := -f $(srctree)/scripts/Makefile.build obj
|
||||
```
|
||||
|
||||
or in our case it is current source directory - `.`:
|
||||
|
||||
```Makefile
|
||||
$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.build obj=.
|
||||
```
|
||||
|
||||
The [scripts/Makefile.build](https://github.com/torvalds/linux/blob/master/scripts/Makefile.build) tries to find the `Kbuild` file by the given directory via the `obj` parameter, include this `Kbuild` files:
|
||||
|
||||
```Makefile
|
||||
include $(kbuild-file)
|
||||
```
|
||||
|
||||
and build targets from it. In our case `.` contains the [Kbuild](https://github.com/torvalds/linux/blob/master/Kbuild) file that generates the `kernel/bounds.s` and the `arch/x86/kernel/asm-offsets.s`. After this the `prepare` target finished to work. The `vmlinux-dirs` also depends on the second target - `scripts` that compiles following programs: `file2alias`, `mk_elfconfig`, `modpost` and etc... After scripts/host-programs compilation our `vmlinux-dirs` target can be executed. First of all let's try to understand what does `vmlinux-dirs` contain. For my case it contains paths of the following kernel directories:
|
||||
|
||||
```
|
||||
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
|
||||
```
|
||||
|
||||
We can find definition of the `vmlinux-dirs` in the top [Makefile](https://github.com/torvalds/linux/blob/master/Makefile) of the Linux kernel:
|
||||
|
||||
```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/
|
||||
...
|
||||
...
|
||||
...
|
||||
```
|
||||
|
||||
Here we remove the `/` symbol from the each directory with the help of the `patsubst` and `filter` functions and put it to the `vmlinux-dirs`. So we have list of directories in the `vmlinux-dirs` and the following code:
|
||||
|
||||
```Makefile
|
||||
$(vmlinux-dirs): prepare scripts
|
||||
$(Q)$(MAKE) $(build)=$@
|
||||
```
|
||||
|
||||
The `$@` represents `vmlinux-dirs` here that means that it will go recursively over all directories from the `vmlinux-dirs` and its internal directories (depens on configuration) and will execute `make` in there. We can see it in the output:
|
||||
|
||||
```
|
||||
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
|
||||
```
|
||||
|
||||
Source code in each directory will be compiled and linked to the `built-in.o`:
|
||||
|
||||
```
|
||||
$ 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
|
||||
...
|
||||
...
|
||||
```
|
||||
|
||||
Ok, all buint-in.o(s) built, now we can back to the `vmlinux` target. As you remember, the `vmlinux` target is in the top Makefile of the Linux kernel. Before the linking of the `vmlinux` it builds [samples](https://github.com/torvalds/linux/tree/master/samples), [Documentation](https://github.com/torvalds/linux/tree/master/Documentation) and etc., but I will not describe it in this part as I wrote in the beginning of this part.
|
||||
|
||||
```Makefile
|
||||
vmlinux: scripts/link-vmlinux.sh $(vmlinux-deps) FORCE
|
||||
...
|
||||
...
|
||||
+$(call if_changed,link-vmlinux)
|
||||
```
|
||||
|
||||
As you can see main purpose of it is a call of the [scripts/link-vmlinux.sh](https://github.com/torvalds/linux/blob/master/scripts/link-vmlinux.sh) script is linking of the all `built-in.o`(s) to the one statically linked executable and creation of the [System.map](https://en.wikipedia.org/wiki/System.map). In the end we will see following output:
|
||||
|
||||
```
|
||||
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
|
||||
```
|
||||
|
||||
and `vmlinux` and `System.map` in the root of the Linux kernel source tree:
|
||||
|
||||
```
|
||||
$ ls vmlinux System.map
|
||||
System.map vmlinux
|
||||
```
|
||||
|
||||
That's all, `vmlinux` is ready. The next step is creation of the [bzImage](https://en.wikipedia.org/wiki/Vmlinux#bzImage).
|
||||
|
||||
Building bzImage
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
The `bzImage` is the compressed Linux kernel image. We can get it with the execution of the `make bzImage` after the `vmlinux` built. In other way we can just execute `make` without arguments and will get `bzImage` anyway because it is default image:
|
||||
|
||||
```Makefile
|
||||
all: bzImage
|
||||
```
|
||||
|
||||
in the [arch/x86/kernel/Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/Makefile). Let's look on this target, it will help us to understand how this image builds. As I already said the `bzImage` target defined in the [arch/x86/kernel/Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/Makefile) and looks like this:
|
||||
|
||||
```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/$@
|
||||
```
|
||||
|
||||
We can see here, that first of all called `make` for the boot directory, in our case it is:
|
||||
|
||||
```Makefile
|
||||
boot := arch/x86/boot
|
||||
```
|
||||
|
||||
The main goal now to build source code in the `arch/x86/boot` and `arch/x86/boot/compressed` directories, build `setup.bin` and `vmlinux.bin`, and build the `bzImage` from they in the end. First target in the [arch/x86/boot/Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/boot/Makefile) is the `$(obj)/setup.elf`:
|
||||
|
||||
```Makefile
|
||||
$(obj)/setup.elf: $(src)/setup.ld $(SETUP_OBJS) FORCE
|
||||
$(call if_changed,ld)
|
||||
```
|
||||
|
||||
We already have the `setup.ld` linker script in the `arch/x86/boot` directory and the `SETUP_OBJS` expands to the all source files from the `boot` directory. We can see first output:
|
||||
|
||||
```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
|
||||
```
|
||||
|
||||
The next source code file is the [arch/x86/boot/header.S](https://github.com/torvalds/linux/blob/master/arch/x86/boot/header.S), but we can't build it now because this target depends on the following two header files:
|
||||
|
||||
```Makefile
|
||||
$(obj)/header.o: $(obj)/voffset.h $(obj)/zoffset.h
|
||||
```
|
||||
|
||||
The first is `voffset.h` generated by the `sed` script that gets two addresses from the `vmlinux` with the `nm` util:
|
||||
|
||||
```C
|
||||
#define VO__end 0xffffffff82ab0000
|
||||
#define VO__text 0xffffffff81000000
|
||||
```
|
||||
|
||||
They are start and end of the kernel. The second is `zoffset.h` depens on the `vmlinux` target from the [arch/x86/boot/compressed/Makefile](https://github.com/torvalds/linux/blob/master/arch/x86/boot/compressed/Makefile):
|
||||
|
||||
```Makefile
|
||||
$(obj)/zoffset.h: $(obj)/compressed/vmlinux FORCE
|
||||
$(call if_changed,zoffset)
|
||||
```
|
||||
|
||||
The `$(obj)/compressed/vmlinux` target depends on the `vmlinux-objs-y` that compiles source code files from the [arch/x86/boot/compressed](https://github.com/torvalds/linux/tree/master/arch/x86/boot/compressed) directory and generates `vmlinux.bin`, `vmlinux.bin.bz2`, and compiles programm - `mkpiggy`. We can see this in the output:
|
||||
|
||||
```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
|
||||
```
|
||||
|
||||
Where the `vmlinux.bin` is the `vmlinux` with striped debuging information and comments and the `vmlinux.bin.bz2` compressed `vmlinux.bin.all` + `u32` size of `vmlinux.bin.all`. The `vmlinux.bin.all` is `vmlinux.bin + vmlinux.relocs`, where `vmlinux.relocs` is the `vmlinux` that was handled by the `relocs` program (see above). As we got these files, the `piggy.S` assembly files will be generated with the `mkpiggy` program and compiled:
|
||||
|
||||
```Makefile
|
||||
MKPIGGY arch/x86/boot/compressed/piggy.S
|
||||
AS arch/x86/boot/compressed/piggy.o
|
||||
```
|
||||
|
||||
This assembly files will contain computed offset from a compressed kernel. After this we can see that `zoffset` generated:
|
||||
|
||||
```Makefile
|
||||
ZOFFSET arch/x86/boot/zoffset.h
|
||||
```
|
||||
|
||||
As the `zoffset.h` and the `voffset.h` are generated, compilation of the source code files from the [arch/x86/boot](https://github.com/torvalds/linux/tree/master/arch/x86/boot/) can be continued:
|
||||
|
||||
```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
|
||||
```
|
||||
|
||||
As all source code files will be compiled, they will be linked to the `setup.elf`:
|
||||
|
||||
```Makefile
|
||||
LD arch/x86/boot/setup.elf
|
||||
```
|
||||
|
||||
or:
|
||||
|
||||
```
|
||||
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
|
||||
```
|
||||
|
||||
The last two things is the creation of the `setup.bin` that will contain compiled code from the `arch/x86/boot/*` directory:
|
||||
|
||||
```
|
||||
objcopy -O binary arch/x86/boot/setup.elf arch/x86/boot/setup.bin
|
||||
```
|
||||
|
||||
and the creation of the `vmlinux.bin` from the `vmlinux`:
|
||||
|
||||
```
|
||||
objcopy -O binary -R .note -R .comment -S arch/x86/boot/compressed/vmlinux arch/x86/boot/vmlinux.bin
|
||||
```
|
||||
|
||||
In the end we compile host program: [arch/x86/boot/tools/build.c](https://github.com/torvalds/linux/blob/master/arch/x86/boot/tools/build.c) that will create our `bzImage` from the `setup.bin` and the `vmlinux.bin`:
|
||||
|
||||
```
|
||||
arch/x86/boot/tools/build arch/x86/boot/setup.bin arch/x86/boot/vmlinux.bin arch/x86/boot/zoffset.h arch/x86/boot/bzImage
|
||||
```
|
||||
|
||||
Actually the `bzImage` is the concatenated `setup.bin` and the `vmlinux.bin`. In the end we will see the output which familiar to all who once build the Linux kernel from source:
|
||||
|
||||
```
|
||||
Setup is 16268 bytes (padded to 16384 bytes).
|
||||
System is 4704 kB
|
||||
CRC 94a88f9a
|
||||
Kernel: arch/x86/boot/bzImage is ready (#5)
|
||||
```
|
||||
|
||||
That's all.
|
||||
|
||||
Conclusion
|
||||
================================================================================
|
||||
|
||||
It is the end of this part and here we saw all steps from the execution of the `make` command to the generation of the `bzImage`. I know, the Linux kernel makefiles and process of the Linux kernel building may seem confusing at first glance, but it is not so hard. Hope this part will help you to understand process of the Linux kernel building.
|
||||
|
||||
Links
|
||||
================================================================================
|
||||
|
||||
* [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/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
|
||||
@ -0,0 +1,129 @@
|
||||
Tips to Create ISO from CD, Watch User Activity and Check Memory Usages of Browser
|
||||
================================================================================
|
||||
Here again, I have written another post on [Linux Tips and Tricks][1] series. Since beginning the objective of this post is to make you aware of those small tips and hacks that lets you manage your system/server efficiently.
|
||||
|
||||
|
||||
|
||||
Create Cdrom ISO Image and Monitor Users in Linux
|
||||
|
||||
In this post we will see how to create ISO image from the contents of CD/DVD loaded in the drive, Open random man pages for learning, know details of other logged-in users and what they are doing and monitoring the memory usages of a browser, and all these using native tools/commands without any third-party application/utility. Here we go…
|
||||
|
||||
### Create ISO image from a CD ###
|
||||
|
||||
Often we need to backup/copy the content of CD/DVD. If you are on Linux platform you do not need any additional software. All you need is the access to Linux console.
|
||||
|
||||
To create ISO image of the files in your CD/DVD ROM, you need two things. The first thing is you need to find the name of your CD/DVD drive. To find the name of your CD/DVD drive, you may choose any of the below three methods.
|
||||
|
||||
**1. Run command lsblk (list block devices) from your terminal/console.**
|
||||
|
||||
$ lsblk
|
||||
|
||||
|
||||
|
||||
Find Block Devices
|
||||
|
||||
**2. To see information about CD-ROM, you may use commands like less or more.**
|
||||
|
||||
$ less /proc/sys/dev/cdrom/info
|
||||
|
||||
|
||||
|
||||
Check Cdrom Information
|
||||
|
||||
**3. You may get the same information from [dmesg command][2] and customize the output using egrep.**
|
||||
|
||||
The command ‘dmesg‘ print/control the kernel buffer ring. ‘egrep‘ command is used to print lines that matches a pattern. Option -i and –color with egrep is used to ignore case sensitive search and highlight the matching string respectively.
|
||||
|
||||
$ dmesg | egrep -i --color 'cdrom|dvd|cd/rw|writer'
|
||||
|
||||
|
||||
|
||||
Find Device Information
|
||||
|
||||
Once you know the name of your CD/DVD, you can use following command to create a ISO image of your cdrom in Linux.
|
||||
|
||||
$ cat /dev/sr0 > /path/to/output/folder/iso_name.iso
|
||||
|
||||
Here ‘sr0‘ is the name of my CD/DVD drive. You should replace this with the name of your CD/DVD. This will help you in creating ISO image and backup contents of CD/DVD without any third-party application.
|
||||
|
||||
|
||||
|
||||
Create ISO Image of CDROM
|
||||
|
||||
### Open a man page randomly for Reading ###
|
||||
|
||||
If you are new to Linux and want to learn commands and switches, this tweak is for you. Put the below line of code at the end of your `~/.bashrc` file.
|
||||
|
||||
/use/bin/man $(ls /bin | shuf | head -1)
|
||||
|
||||
Remember to put the above one line script in users’s `.bashrc` file and not in the .bashrc file of root. So when the next you login either locally or remotely using SSH you will see a man page randomly opened for you to read. For the newbies who want to learn commands and command-line switches, this will prove helpful.
|
||||
|
||||
Here is what I got in my terminal after logging in to session for two times back-to-back.
|
||||
|
||||
|
||||
|
||||
LoadKeys Man Pages
|
||||
|
||||
|
||||
|
||||
Zgrep Man Pages
|
||||
|
||||
### Check Activity of Logged-in Users ###
|
||||
|
||||
Know what other users are doing on your shared server.
|
||||
|
||||
In most general case, either you are a user of Shared Linux Server or the Admin. If you are concerned about your server and want to check what other users are doing, you may try command ‘w‘.
|
||||
|
||||
This command lets you know if someone is executing any malicious code or tampering the server, slowing it down or anything else. ‘w‘ is the preferred way of keeping an eye on logged on users and what they are doing.
|
||||
|
||||
To see logged on users and what they re doing, run command ‘w’ from terminal, preferably as root.
|
||||
|
||||
# w
|
||||
|
||||
|
||||
|
||||
Check Linux User Activity
|
||||
|
||||
### Check Memory usages by Browser ###
|
||||
|
||||
These days a lot of jokes are cracked on Google-chrome and its demand of memory. If you want to know the memory usages of a browser, you can list the name of the process, its PID and Memory usages of it. To check memory usages of a browser, just enter the “about:memory” in the address bar without quotes.
|
||||
|
||||
I have tested it on Google-Chrome and Mozilla Firefox web browser. If you can check it on any other browser and it works well you may acknowledge us in the comments below. Also you may kill the browser process simply as if you have done for any Linux terminal process/service.
|
||||
|
||||
In Google Chrome, type `about:memory` in address bar, you should get something similar to below image.
|
||||
|
||||
|
||||
|
||||
Check Chrome Memory Usage
|
||||
|
||||
In Mozilla Firefox, type `about:memory` in address bar, you should get something similar to below image.
|
||||
|
||||
|
||||
|
||||
Check Firefox Memory Usage
|
||||
|
||||
Out of these options you may select any of them, if you understand what it is. To check memory usages, click the left most option ‘Measure‘.
|
||||
|
||||
|
||||
|
||||
Firefox Main Process
|
||||
|
||||
It shows tree like process-memory usages by browser.
|
||||
|
||||
That’s all for now. Hope all the above tips will help you at some point of time. If you have one (or more) tips/tricks that will help Linux Users to manage their Linux System/Server more efficiently ans is lesser known, you may like to share it with us.
|
||||
|
||||
I’ll be here with another post soon, till then stay tuned and connected to TecMint. Provide us with your valuable feedback in the comments below. Like and share us and help us get spread.
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: http://www.tecmint.com/creating-cdrom-iso-image-watch-user-activity-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/tag/linux-tricks/
|
||||
[2]:http://www.tecmint.com/dmesg-commands/
|
||||
@ -0,0 +1,118 @@
|
||||
Understanding Shell Commands Easily Using “Explain Shell” Script in Linux
|
||||
================================================================================
|
||||
While working on Linux platform all of us need help on shell commands, at some point of time. Although inbuilt help like man pages, whatis command is helpful, but man pages output are too lengthy and until and unless one has some experience with Linux, it is very difficult to get any help from massive man pages. The output of whatis command is rarely more than one line which is not sufficient for newbies.
|
||||
|
||||
|
||||
|
||||
Explain Shell Commands in Linux Shell
|
||||
|
||||
There are third-party application like ‘cheat‘, which we have covered here “[Commandline Cheat Sheet for Linux Users][1]. Although Cheat is an exceptionally good application which shows help on shell command even when computer is not connected to Internet, it shows help on predefined commands only.
|
||||
|
||||
There is a small piece of code written by Jackson which is able to explain shell commands within the bash shell very effectively and guess what the best part is you don’t need to install any third party package. He named the file containing this piece of code as `'explain.sh'`.
|
||||
|
||||
#### Features of Explain Utility ####
|
||||
|
||||
- Easy Code Embedding.
|
||||
- No third-party utility needed to be installed.
|
||||
- Output just enough information in course of explanation.
|
||||
- Requires internet connection to work.
|
||||
- Pure command-line utility.
|
||||
- Able to explain most of the shell commands in bash shell.
|
||||
- No root Account involvement required.
|
||||
|
||||
**Prerequisite**
|
||||
|
||||
The only requirement is `'curl'` package. In most of the today’s latest Linux distributions, curl package comes pre-installed, if not you can install it using package manager as shown below.
|
||||
|
||||
# apt-get install curl [On Debian systems]
|
||||
# yum install curl [On CentOS systems]
|
||||
|
||||
### Installation of explain.sh Utility in Linux ###
|
||||
|
||||
We have to insert the below piece of code as it is in the `~/.bashrc` file. The code should be inserted for each user and each `.bashrc` file. It is suggested to insert the code to the user’s .bashrc file only and not in the .bashrc of root user.
|
||||
|
||||
Notice the first line of code that starts with hash `(#)` is optional and added just to differentiate rest of the codes of .bashrc.
|
||||
|
||||
# explain.sh marks the beginning of the codes, we are inserting in .bashrc file at the bottom of this file.
|
||||
|
||||
# explain.sh begins
|
||||
explain () {
|
||||
if [ "$#" -eq 0 ]; then
|
||||
while read -p "Command: " cmd; do
|
||||
curl -Gs "https://www.mankier.com/api/explain/?cols="$(tput cols) --data-urlencode "q=$cmd"
|
||||
done
|
||||
echo "Bye!"
|
||||
elif [ "$#" -eq 1 ]; then
|
||||
curl -Gs "https://www.mankier.com/api/explain/?cols="$(tput cols) --data-urlencode "q=$1"
|
||||
else
|
||||
echo "Usage"
|
||||
echo "explain interactive mode."
|
||||
echo "explain 'cmd -o | ...' one quoted command to explain it."
|
||||
fi
|
||||
}
|
||||
|
||||
### Working of explain.sh Utility ###
|
||||
|
||||
After inserting the code and saving it, you must logout of the current session and login back to make the changes taken into effect. Every thing is taken care of by the ‘curl’ command which transfer the input command and flag that need explanation to the mankier server and then print just necessary information to the Linux command-line. Not to mention to use this utility you must be connected to internet always.
|
||||
|
||||
Let’s test few examples of command which I don’t know the meaning with explain.sh script.
|
||||
|
||||
**1. I forgot what ‘du -h‘ does. All I need to do is:**
|
||||
|
||||
$ explain 'du -h'
|
||||
|
||||
|
||||
|
||||
Get Help on du Command
|
||||
|
||||
**2. If you forgot what ‘tar -zxvf‘ does, you may simply do:**
|
||||
|
||||
$ explain 'tar -zxvf'
|
||||
|
||||
|
||||
|
||||
Tar Command Help
|
||||
|
||||
**3. One of my friend often confuse the use of ‘whatis‘ and ‘whereis‘ command, so I advised him.**
|
||||
|
||||
Go to Interactive Mode by simply typing explain command on the terminal.
|
||||
|
||||
$ explain
|
||||
|
||||
and then type the commands one after another to see what they do in one window, as:
|
||||
|
||||
Command: whatis
|
||||
Command: whereis
|
||||
|
||||
|
||||
|
||||
Whatis Whereis Commands Help
|
||||
|
||||
To exit interactive mode he just need to do Ctrl + c.
|
||||
|
||||
**4. You can ask to explain more than one command chained by pipeline.**
|
||||
|
||||
$ explain 'ls -l | grep -i Desktop'
|
||||
|
||||
|
||||
|
||||
Get Help on Multiple Commands
|
||||
|
||||
Similarly you can ask your shell to explain any shell command. All you need is a working Internet connection. The output is generated based upon the explanation needed from the server and hence the output result is not customizable.
|
||||
|
||||
For me this utility is really helpful and it has been honored being added to my .bashrc. Let me know what is your thought on this project? How it can useful for you? Is the explanation satisfactory?
|
||||
|
||||
Provide us with your valuable feedback in the comments below. Like and share us and help us get spread.
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: http://www.tecmint.com/explain-shell-commands-in-the-linux-shell/
|
||||
|
||||
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/cheat-command-line-cheat-sheet-for-linux-users/
|
||||
Loading…
Reference in New Issue
Block a user