TranslateProject/translated/tech/20190501 Looking into Linux modules.md

[#]: collector: (lujun9972)
[#]: translator: (LazyWolfLin)
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[#]: subject: (Looking into Linux modules)
[#]: via: (https://www.networkworld.com/article/3391362/looking-into-linux-modules.html#tk.rss_all)
[#]: author: (Sandra Henry-Stocker https://www.networkworld.com/author/Sandra-Henry_Stocker/)

深入学习 Linux 内核模块
======
lsmod 命令能够告诉你当前系统上加载了哪些内核模块，以及关于使用它们的一些有趣的细节。
![Rob Oo \(CC BY 2.0\)][1]

### 什么是 Linux 内核模块？

内核模块是根据需要加载到内核中或从内核中卸载的代码块，因此无需重启就可以扩展内核的功能。事实上，除非用户使用类似 **lsmod** 这样的命令来查询模块，否则用户不太可能知道内核发生的任何变化。

需要理解的重要一点是，在你的 Linux 系统上总会有_很多_模块可用，并且如果你想深入了解细节，那么有很多细节可以获得。

lsmod 的主要用途之一是在系统不能正常工作时检查模块。然而，大多数情况下，模块是根据需要加载的，而且用户不需要知道它们如何工作。

**[ Also see:[Must-know Linux Commands][2] ]**

### 显示内核模块

显示内核模块最简单的方法是使用 **lsmod** 命令。虽然这个命令包含了很多细节，但输出却是最用户友好。

```
$ lsmod
Module                  Size  Used by
snd_hda_codec_realtek 114688  1
snd_hda_codec_generic  77824  1 snd_hda_codec_realtek
ledtrig_audio          16384  2 snd_hda_codec_generic,snd_hda_codec_realtek
snd_hda_codec_hdmi     53248  1
snd_hda_intel          40960  2
snd_hda_codec         131072  4 snd_hda_codec_generic,snd_hda_codec_hdmi,snd_hda_intel
                                ,snd_hda_codec_realtek
snd_hda_core           86016  5 snd_hda_codec_generic,snd_hda_codec_hdmi,snd_hda_intel
                                ,snd_hda_codec,snd_hda_codec_realtek
snd_hwdep              20480  1 snd_hda_codec
snd_pcm               102400  4 snd_hda_codec_hdmi,snd_hda_intel,snd_hda_codec,snd_hda
                                _core
snd_seq_midi           20480  0
snd_seq_midi_event     16384  1 snd_seq_midi
dcdbas                 20480  0
snd_rawmidi            36864  1 snd_seq_midi
snd_seq                69632  2 snd_seq_midi,snd_seq_midi_event
coretemp               20480  0
snd_seq_device         16384  3 snd_seq,snd_seq_midi,snd_rawmidi
snd_timer              36864  2 snd_seq,snd_pcm
kvm_intel             241664  0
kvm                   626688  1 kvm_intel
radeon               1454080  10
irqbypass              16384  1 kvm
joydev                 24576  0
input_leds             16384  0
ttm                   102400  1 radeon
drm_kms_helper        180224  1 radeon
drm                   475136  13 drm_kms_helper,radeon,ttm
snd                    81920  15 snd_hda_codec_generic,snd_seq,snd_seq_device,snd_hda
                                 _codec_hdmi,snd_hwdep,snd_hda_intel,snd_hda_codec,snd
                                 _hda_codec_realtek,snd_timer,snd_pcm,snd_rawmidi
i2c_algo_bit           16384  1 radeon
fb_sys_fops            16384  1 drm_kms_helper
syscopyarea            16384  1 drm_kms_helper
serio_raw              20480  0
sysfillrect            16384  1 drm_kms_helper
sysimgblt              16384  1 drm_kms_helper
soundcore              16384  1 snd
mac_hid                16384  0
sch_fq_codel           20480  2
parport_pc             40960  0
ppdev                  24576  0
lp                     20480  0
parport                53248  3 parport_pc,lp,ppdev
ip_tables              28672  0
x_tables               40960  1 ip_tables
autofs4                45056  2
raid10                 57344  0
raid456               155648  0
async_raid6_recov      24576  1 raid456
async_memcpy           20480  2 raid456,async_raid6_recov
async_pq               24576  2 raid456,async_raid6_recov
async_xor              20480  3 async_pq,raid456,async_raid6_recov
async_tx               20480  5 async_pq,async_memcpy,async_xor,raid456,async_raid6_re
                                cov
xor                    24576  1 async_xor
raid6_pq              114688  3 async_pq,raid456,async_raid6_recov
libcrc32c              16384  1 raid456
raid1                  45056  0
raid0                  24576  0
multipath              20480  0
linear                 20480  0
hid_generic            16384  0
psmouse               151552  0
i2c_i801               32768  0
pata_acpi              16384  0
lpc_ich                24576  0
usbhid                 53248  0
hid                   126976  2 usbhid,hid_generic
e1000e                245760  0
floppy                 81920  0
```

在上面的输出中：

  * “Module”显示每个模块的名称
  * “Size”显示每个模块的大小（并不是它们使占的内存大小）
  * “Used by”显示每个模块的被使用的计数和使用它们的模块



显然，这有_很多_模块。加载的模块数取决于你的系统和版本以及正在运行的内容。我们可以这样计数：

```
$ lsmod | wc -l
67
```

要查看系统中可用的模块数（不止运行当中的），试试这个命令：

```
$ modprobe -c | wc -l
41272
```

### 与内核模块相关的其他命令

Linux 提供了几条用于罗列，加载及卸载，测试，以及检查模块状态的命令。

  * depmod —— 生成 modules.dep 和映射文件
  * insmod —— 一个往 Linux 内核插入模块的程序
  * lsmod —— 显示 Linux 内核中模块状态
  * modinfo —— 显示 Linux 内核模块信息
  * modprobe —— 添加或移除 Linux 内核模块
  * rmmod —— 一个从 Linux 内核移除模块的程序



### 列出内置的内核模块

As mentioned above, the **lsmod** command is the most convenient command for listing modules. There are, however, other ways to examine them. The modules.builtin file lists all modules that are built into the kernel and is used by modprobe when trying to load one of these modules. Note that **$(uname -r)** in the commands below provides the name of the kernel release.

```
$ more /lib/modules/$(uname -r)/modules.builtin | head -10
kernel/arch/x86/crypto/crc32c-intel.ko
kernel/arch/x86/events/intel/intel-uncore.ko
kernel/arch/x86/platform/intel/iosf_mbi.ko
kernel/mm/zpool.ko
kernel/mm/zbud.ko
kernel/mm/zsmalloc.ko
kernel/fs/binfmt_script.ko
kernel/fs/mbcache.ko
kernel/fs/configfs/configfs.ko
kernel/fs/crypto/fscrypto.ko
```

You can get some additional detail on a module by using the **modinfo** command, though nothing that qualifies as an easy explanation of what service the module provides. The omitted details from the output below include a lengthy signature.

```
$ modinfo floppy | head -16
filename:       /lib/modules/5.0.0-13-generic/kernel/drivers/block/floppy.ko
alias:          block-major-2-*
license:        GPL
author:         Alain L. Knaff
srcversion:     EBEAA26742DF61790588FD9
alias:          acpi*:PNP0700:*
alias:          pnp:dPNP0700*
depends:
retpoline:      Y
intree:         Y
name:           floppy
vermagic:       5.0.0-13-generic SMP mod_unload
sig_id:         PKCS#7
signer:
sig_key:
sig_hashalgo:   md4
```

You can load or unload a module using the **modprobe** command. Using a command like the one below, you can locate the kernel object associated with a particular module:

```
$ find /lib/modules/$(uname -r) -name floppy*
/lib/modules/5.0.0-13-generic/kernel/drivers/block/floppy.ko
```

If you needed to load the module, you could use a command like this one:

```
$ sudo modprobe floppy
```

### 总结一下

Clearly the loading and unloading of modules is a big deal. It makes Linux systems considerably more flexible and efficient than if they ran with a one-size-fits-all kernel. It also means you can make significant changes — including adding hardware — without rebooting.

**[ Two-Minute Linux Tips:[Learn how to master a host of Linux commands in these 2-minute video tutorials][3] ]**

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--------------------------------------------------------------------------------

via: https://www.networkworld.com/article/3391362/looking-into-linux-modules.html#tk.rss_all

作者：[Sandra Henry-Stocker][a]
选题：[lujun9972][b]
译者：[LazyWolfLin](https://github.com/LazyWolfLin)
校对：[校对者ID](https://github.com/校对者ID)

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[b]: https://github.com/lujun9972
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