8.8 KiB
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。
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 ]
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 ]
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作者：Sandra Henry-Stocker 选题：lujun9972 译者：LazyWolfLin 校对：校对者ID