Shulou(Shulou.com)06/01 Report--

What is the match key and RAW of UDEV rules? for this question, this article introduces the corresponding analysis and solution in detail, hoping to help more partners who want to solve this problem to find a more simple and feasible method.

The udevadm command can see the specific information udevadm info-- attribute-walk-- name=/dev/sda

Some common directory information involved in UDEV

Ll / sys/class/block/

Ll / dev/raw

Ll / dev/mapper

Ll / dev/block

Ll / dev/disk/by-path

Ll / dev/disk/by-id

Ll / dev/disk/by-uuid

Match field properties of UDEV rules

ACTION matches the action name of the event, for example: add (add device), remove (remove device).

The DEVPATH matches the device-relative path of the event. For example, the devpath for sda is / dev/sda,sda2 and the devpath is / dev/sda2.

KERNEL matches the name of the device for the event, such as sdb, such as sd* for any SCSI disk device

The NAME matches the name of the network interface or device node. NAME can only be used after the previous rule has been assigned.

The SYMLINK matches the name of the symbol chain of the device node. SYMLINK can only be used after the previous rule has been assigned. There can be multiple symlinks, and only one needs to be matched.

SUBSYSTEM matching equipment subsystem

DRIVER matches the device driver name of the device in devpath, for example: ide-cdrom.

The bus name of the BUS device in devpath, for example: usb.

Identification number of ID device in devpath

ENV {key} environment variable. ENV {MAJOR} = = "8" and ENV {MINOR} = = "1" for sda1

PROGRAM executes a program. If the program returns successfully, key is true. The properties of the device are placed in the environment variable of the executing process, and the output of the program is stdout, which can be read from the key of RESULT.

RESULT matches the return string from the most recent PROGRAM call. It should be used after PROGRAM.

OWNER matches the subordinate group of the device file

GROUP matches the group in which the device file is located.

MODE matches the permissions of the device file, using octal

MAJOR represents the disk number

MINOR represents the partition number under the disk

UDEV rules match field properties and callable replacement operators

$kernel,% k: the kernel device name of the device, for example: sda, cdrom.

$number,% n: the kernel number of the device, for example: the kernel number of sda3 is 3.

$devpath,% p: the devpath path of the device.

$id,% b: the ID number of the device in devpath.

$sysfs {file},% s {file}: the contents of the file in the sysfs of the device. It is actually the property value of the device.

$env {key},% E {key}: the value of an environment variable.

$major,% M: major number of the device.

$minor% m: minor number of the device.

$result, the result returned by% c:PROGRAM.

$parent,% P: the device file name of the parent device.

$root, the value of% r:udev_root, defaults to / dev/.

$tempnode,% N: temporary device name.

%%: symbol% itself.

$: symbol $itself.

Special description of ENV {key}

The different devices indicated in the linux kernel are implemented through major and minor number, and the corresponding drivers are loaded through major and minor Number.

The major number of both sda and sdb is 8. SDA's minor number starts with 0 and sdb's minor number starts with 16.

ENV {major} major indicates different device types

ENV {minor} minor represents different partitions of the same device

ACTION== "add", KERNEL== "sda", RUN+= "/ bin/raw / dev/raw/raw1 N"

ACTION== "add", ENV {MAJOR} = = "8", ENV {MINOR} = = "1", RUN+= "/ bin/raw / dev/raw/raw2% M% m"

Raw command (in the past, the RHEL4 version used more, now RHEL6 uses less, but RHEL6 can also use this way)

You can bind a bare device directly through the raw command, but it will be lost after reboot. It needs to be written in / etc/sysconfig/rawdevices file, such as / dev/raw/raw1 / dev/sdb1.

[root@localhost ~] # ll / dev/raw

Total dosage 0

Crw-rw----. 1 root disk 162,06 June 23 16:58 rawctl

[root@localhost ~] # raw

Usage:

Raw/ dev/raw/rawN

Raw/ dev/raw/rawN / dev/

Raw-Q / dev/raw/rawN

Raw-qa

[root@localhost ~] # raw/ dev/raw/raw1 / dev/sdb1

/ dev/raw/raw1: bound to major 8, minor 17

[root@localhost ~] # ll / dev/ | grep sdb

Brw-rw----. 1 root disk 8, 16 June 23 16:59 sdb

Brw-rw----. 1 root disk 8, 17 June 23 16:59 sdb1

[root@localhost ~] # raw-qa

/ dev/raw/raw1: bound to major 8, minor 17

[root@localhost] # raw-Q / dev/raw/raw1

/ dev/raw/raw1: bound to major 8, minor 17

[root@localhost ~] # ll / dev/raw

Total dosage 0

Crw-rw----. 1 root disk 162,16 June 23 17:25 raw1

Crw-rw----. 1 root disk 162,06 June 23 16:58 rawctl

[root@localhost ~] # cat / etc/issue

CentOS release 6.5 (Final)

Kernel\ r on an\ m

This is the answer to the match key of UDEV rules and what is RAW. I hope the above content can be of some help to you. If you still have a lot of doubts to be solved, you can follow the industry information channel to learn more about it.

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