|
# Tested on RHEL 6 & 7
# 3.- Name a network interface bearing a given mac-address (/etc/udev/rules.d/70-persistent-net.rules)# 'udev' is a mechanism for maintaining device nodes on a server. It handles the management # of the devices nodes through the 'udevd' daemon as well as rules defined on the system. # This way we can manage the creation of device nodes and their properties and names. # Once a device is recognized by the kernel it triggers a series of events. First it # populates /sys structures, then the kernel sends a uevent received by 'udev' and, # finally, 'udev' creates a device node for the new device or parses the 'udev' rules files, # under /etc/udev/rules.d/, in alphanumeric order, to decide what action should be taken. # To query the 'udev' database for device information or the properties of a device from its # sysfs representation we can use 'udevadm info': # Export the content of the udev database: udevadm info --export-db # Print all sysfs properties of the specified device that can be used in 'udev' rules to match # the specified device. It prints all devices along the chain, up to the root of sysfs that # can be used in 'udev' rules. udevadm info --attribute-walk --name=/dev/<sdc> # For a scsi device, we may use its unique SCSI identifier # 'udevd' watch for any changes in rules files and will automatically apply any changes to # those files. If that's not the case, one can ask 'udevd' to reload the rules files # (reloading rules does not apply any changes to already existing devices) by: udevadm control --reload-rules # Request to trigger the execution of all 'udev' rules: udevadm trigger # Writing a simple custom rule # ------------------------------------------------------------------------------------------ # A 'udev' rule has two parts: one part that tests certain conditions and one part that # assigns variables (name, permissions, symbolic links, etc) when all conditions are # fulfilled # 'udev' rule operators # --------------------- # # == Compare for equality # != Compare for inequality # = Assign a value to a key # += Add the value to a key that holds a list of entries # := Assign a value to a key and lock the key to prevent any further modification # Some examples of udev rules: vi /etc/udev/rules.d/<99-my-custom.rules> # 1.- Create a symbolic link under /dev/mydisks/ for each matching sd device SUBSYSTEM=="block", KERNEL=="sd*", SYMLINK:="mydisks/%k" # If the new device is a block device, then we test if the internal kernel name starts # with 'sd'. If both match, we add 'mydisks/%k' to the list of symbolic links to be created # for this device # 2.- Create a symbolic link and run a command for each sd matching device KERNEL=="sd[b-d]", SUBSYSTEM=="block", SUBSYSTEMS=="scsi", DRIVERS=="sd", SYMLINK+="shared/%k", RUN+="/usr/bin/wall MESSAGE: shared/%k --> $tempnode" ll /dev/sd* brw-rw---- 1 root disk 8, 0 Jul 2 17:18 /dev/sda brw-rw---- 1 root disk 8, 1 Jul 2 17:18 /dev/sda1 brw-rw---- 1 root disk 8, 2 Jul 2 17:18 /dev/sda2 brw-rw---- 1 root disk 8, 16 Jul 2 17:18 /dev/sdb brw-rw---- 1 root disk 8, 32 Jul 2 17:18 /dev/sdc brw-rw---- 1 root disk 8, 48 Jul 2 17:18 /dev/sdd udevadm trigger Broadcast message from root@mynode (Wed Jul 2 17:18:44 2014): MESSAGE: /dev/sdd Broadcast message from root@mynode (Wed Jul 2 17:18:45 2014): MESSAGE: /dev/sdb Broadcast message from root@mynode (Wed Jul 2 17:18:46 2014): MESSAGE: /dev/sdc ll /dev/shared/ total 0 lrwxrwxrwx 1 root root 6 Jul 2 17:18 sdb -> ../sdb lrwxrwxrwx 1 root root 6 Jul 2 17:18 sdc -> ../sdc lrwxrwxrwx 1 root root 6 Jul 2 17:18 sdd -> ../sdd SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="08:00:27:48:a7:ef", ATTR{type}=="1", KERNEL=="eth*", NAME="my_eth0"
# 4.- Create a symbolic link and run a command for a device matching a given SCSI identifier SUBSYSTEM=="block", KERNEL=="sd?", PROGRAM=="/usr/lib/udev/scsi_id -g -u -d /dev/%k", RESULT=="1ATA_VBOX_HARDDISK_VB0d221c89-8b845902", SYMLINK:="shared/disk01" ll /dev/shared total 0 lrwxrwxrwx 1 root root 6 Feb 8 16:18 disk01 -> ../sdb # 5.- Creating Oracle ASM devices under /dev/oracle/ using disks' SCSI identifiers ACTION=="add", BUS=="scsi", ENV{ID_SERIAL}=="360c22lm4rr4nzf88df13aa9a0c8", NAME="oracle/DGTEST_01", OWNER="oracle", GROUP="dba", MODE="0660" |