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sys文件系统

2022-08-03 18:10:00 【天糊土】

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前言

Linux2.6版本的内核引入了sys文件系统。
在 proc文件系统介绍和使用中，介绍了sys文件系统与proc文件系统的差异。它们都是虚拟文件系统，都是内核中的数据结构的可视化接口。它们分别挂载在/sys目录、/proc目录下。
与proc文件系统类似，通过sys文件系统可以查看系统相关的信息。
sys文件系统中与设备驱动相关的文件节点，可视为 /dev 文件系统的替代者。
sys文件系统的主要作用，是对系统上的设备与总线进行组织与管理，以形成分级的文件。用户空间可以访问或配置这些文件，进而得知系统状态或者控制系统。

目录含义

下面简述/sys目录中的目录所代表的含义。

[email protected]:/sys# tree -L 1
.
├── block
├── bus
├── class 
├── dev
├── devices
├── firmware
├── fs
├── hypervisor
├── kernel
├── module
└── power

11 directories, 0 files
[email protected]:/sys# ls

1、class目录

将设备按照功能分类。

如/sys/class/net包括了所有网络接口。

其中 power_supply 可以查看充电相关的信息。

[email protected]:/sys/class# ls
ata_device  dma       i2c-adapter  powercap      scsi_device    tty
ata_link    dmi       input        power_supply  scsi_disk      vc
ata_port    drm       leds         ppdev         scsi_generic   virtio-ports
backlight   extcon    mdio_bus     ppp           scsi_host      vtconsole
bdi         firmware  mem          printer       sound          watchdog
block       gpio      misc         pwm           spi_host
bluetooth   graphics  mmc_host     regulator     spi_master
bsg         hidraw    net          rfkill        spi_transport
devfreq     hwmon     pci_bus      rtc           thermal
[email protected]:/sys/class# cd net
[email protected]:/sys/class/net# ls
eth0  lo
[email protected]:/sys/class/net# ls -l
总用量 0
lrwxrwxrwx 1 root root 0 Jul  4 20:50 eth0 -> ../../devices/pci0000:00/0000:00:11.0/0000:02:01.0/net/eth0
lrwxrwxrwx 1 root root 0 Aug  2 00:03 lo -> ../../devices/virtual/net/lo
[email protected]:/sys/class/net# cd eth0
[email protected]:/sys/class/net/eth0# ls
addr_assign_type  device   ifalias    netdev_group  speed         uevent
address           dev_id   ifindex    operstate     statistics
addr_len          dormant  iflink     phys_port_id  subsystem
broadcast         duplex   link_mode  power         tx_queue_len
carrier           flags    mtu        queues        type
[email protected]:/sys/class/net/eth0#

2、block目录

每个子目录中又包含一些属性文件，它们描述了这个块设备的各方面的属性，比如设备大小。另外，loop块设备是使用文件来模拟的。

通过查看该目录下的详细信息，得知它们都是链接文件，指向/sys/devices/下的设备。

[email protected]:/sys/block# ls
loop0  loop3  loop6  ram1   ram12  ram15  ram4  ram7  sda
loop1  loop4  loop7  ram10  ram13  ram2   ram5  ram8  sr0
loop2  loop5  ram0   ram11  ram14  ram3   ram6  ram9  sr1
[email protected]:/sys/block# cd sr0
[email protected]:/sys/block/sr0# ls
alignment_offset  discard_alignment  holders   removable  subsystem
bdi               events             inflight  ro         trace
capability        events_async       power     size       uevent
dev               events_poll_msecs  queue     slaves
device            ext_range          range     stat
[email protected]:/sys/block/sr0# cat size 
2097151
[email protected]:/sys/block/sr0# cd ..
[email protected]:/sys/block# ls -l sda
lrwxrwxrwx 1 root root 0 Jul  4 20:50 sda -> ../devices/pci0000:00/0000:00:10.0/host32/target32:0:0/32:0:0:0/block/sda
[email protected]:/sys/block# ls -l sr0
lrwxrwxrwx 1 root root 0 Aug  2 00:03 sr0 -> ../devices/pci0000:00/0000:00:11.0/0000:02:05.0/ata3/host2/target2:0:0/2:0:0:0/block/sr0
[email protected]:/sys/block# ls -l sr1
lrwxrwxrwx 1 root root 0 Aug  2 00:03 sr1 -> ../devices/pci0000:00/0000:00:11.0/0000:02:05.0/ata4/host3/target3:0:0/3:0:0:0/block/sr1
[email protected]:/sys/block# ls -l ram1
lrwxrwxrwx 1 root root 0 Aug  2 00:03 ram1 -> ../devices/virtual/block/ram1
[email protected]:/sys/block# ls -l loop1
lrwxrwxrwx 1 root root 0 Aug  2 00:03 loop1 -> ../devices/virtual/block/loop1
[email protected]:/sys/block#

3、bus目录

在内核注册的每条总线，在该目录下对应一个子目录，比如i2c、spi、pci、scsi、usb等等。

其中每个总线目录又包含两个子目录devices和drivers。devices目录包含了在整个系统中发现的、属于该总线类型的设备。drivers目录包含了注册到该总线的所有驱动。

[email protected]:/sys/bus# ls
ac97         cpu           hid           mdio_bus     platform  sdio   virtio
acpi         eisa          i2c           mmc          pnp       serio  workqueue
clockevents  event_source  isa           pci          rapidio   spi    xen
clocksource  gameport      machinecheck  pci_express  scsi      usb    xen-backend
[email protected]:/sys/bus# cd cpu
[email protected]:/sys/bus/cpu# ls
devices  drivers  drivers_autoprobe  drivers_probe  uevent
[email protected]:/sys/bus/cpu# cd devices/
[email protected]:/sys/bus/cpu/devices# ls
cpu0  cpu1
[email protected]:/sys/bus/cpu/devices# cd cpu0
[email protected]:/sys/bus/cpu/devices/cpu0# ls
cache        crash_notes_size  firmware_node  power      topology
crash_notes  driver            microcode      subsystem  uevent
[email protected]:/sys/bus/cpu/devices/cpu0# cd ../../drivers
[email protected]:/sys/bus/cpu/drivers# ls
processor
[email protected]:/sys/bus/cpu/drivers# cd processor/
[email protected]:/sys/bus/cpu/drivers/processor# ls
bind  cpu0  cpu1  uevent  unbind
[email protected]:/sys/bus/cpu/drivers/processor#

4、devices目录

包含系统的所有设备。（它和/sys/dev目录有啥区别呢？）

[email protected]:/sys# ls
block  bus  class  dev  devices  firmware  fs  hypervisor  kernel  module  power
[email protected]:/sys# cd dev
[email protected]:/sys/dev# l
block/  char/
[email protected]:/sys/dev# cd char/
[email protected]:/sys/dev/char# ls //下面的都是一些链接，指向/sys/devices相关设备
10:1    10:60   13:32    189:140  4:10  4:24  4:38  4:51  4:65  4:79  4:92
10:175  10:61   13:33    1:9      4:11  4:25  4:39  4:52  4:66  4:8   4:93  
//省略部分
[email protected]:/sys/dev/char# cd ../../devices/
[email protected]:/sys/devices# ls
breakpoint  isa          pci0000:00  pnp0  rapidio   system      virtual
cpu         LNXSYSTM:00  platform    pnp1  software  tracepoint
[email protected]:/sys/devices# cd pci0000\:00/
[email protected]:/sys/devices/pci0000:00# ls
0000:00:00.0  0000:00:15.0  0000:00:16.1  0000:00:17.2  0000:00:18.3
0000:00:01.0  0000:00:15.1  0000:00:16.2  0000:00:17.3  0000:00:18.4
0000:00:07.0  0000:00:15.2  0000:00:16.3  0000:00:17.4  0000:00:18.5
0000:00:07.1  0000:00:15.3  0000:00:16.4  0000:00:17.5  0000:00:18.6
0000:00:07.3  0000:00:15.4  0000:00:16.5  0000:00:17.6  0000:00:18.7
0000:00:07.7  0000:00:15.5  0000:00:16.6  0000:00:17.7  firmware_node
0000:00:0f.0  0000:00:15.6  0000:00:16.7  0000:00:18.0  pci_bus
0000:00:10.0  0000:00:15.7  0000:00:17.0  0000:00:18.1  power
0000:00:11.0  0000:00:16.0  0000:00:17.1  0000:00:18.2  uevent
[email protected]:/sys/devices/pci0000:00# cd ../cpu
[email protected]:/sys/devices/cpu# ls
events format perf_event_mux_interval_ms  power  rdpmc subsystem type  uevent
[email protected]:/sys/devices/cpu#