Linux udev

Persistent network interface names

If you have no /etc/udev/rules.d/70-persistent-net.rules just create one:

# lshw -C network | awk '/logical name:/{iface=$NF;}/serial:/{mac=$NF;printf "SUBSYSTEM==\"net\", ACTION==\"add\", DRIVERS==\"?*\", ATTR{address}==\"%s\", ATTR{dev_id}==\"0x0\", ATTR{type}==\"1\", KERNEL==\"eth*\", NAME=\"%s\"\n",mac,iface;}' >> /etc/udev/rules.d/70-persistent-net.rules

or add a specific interface to /etc/udev/rules.d/70-persistent-net.rules:

# MATCHADDR="00:50:56:a1:20:22" INTERFACE=eth2 /lib/udev/write_net_rules

Change order with:

# vi /etc/udev/rules.d/70-persistent-net.rules

Then let udev reread the file:

# udevadm trigger --action=add --subsystem-match=net  --verbose

udev for MySQL on LVM with InnoDB on raw devices

Make your rule

root@mysql:~# cat /etc/udev/rules.d/99-lvm-mysql-permissions.rules
# udevadm info --query=all --name /dev/vg-data/lv-rawdisk-innodb01
# DM_VG_NAME=vg-data
# DM_LV_NAME=lv-rawdisk-innodb01
ENV{DM_VG_NAME}=="vg-data" ENV{DM_LV_NAME}=="lv-rawdisk-innodb*" OWNER="mysql" GROUP="mysql"

Test your rule

root@mysql:~# ls -al /dev/vg-data/lv-rawdisk-innodb01
lrwxrwxrwx 1 root root 7 Aug 12 14:45 /dev/vg-data/lv-rawdisk-innodb01 -> ../dm-0

root@mysql:~# udevadm test /class/block/dm-0
...
read rules file: /etc/udev/rules.d/99-lvm-mysql-permissions.rules
specified user 'mysql' unknown
...

OK user mysql unknown... maybe I should install MySQL ;-).

After that:

root@mysql:~# id -a mysql
uid=108(mysql) gid=114(mysql) groups=114(mysql)

root@mysql:~# udevadm test /class/block/dm-0
...
OWNER 108 /etc/udev/rules.d/99-lvm-mysql-permissions.rules:4
GROUP 114 /etc/udev/rules.d/99-lvm-mysql-permissions.rules:4
handling device node '/dev/dm-0', devnum=b252:0, mode=0660, uid=108, gid=114
set permissions /dev/dm-0, 060660, uid=108, gid=114
...

Trigger your rule

root@mysql:~# udevadm trigger
root@mysql:~# ls -alL /dev/vg-data/lv-rawdisk-innodb01 
brw-rw---- 1 mysql mysql 252, 0 Aug 12 15:07 /dev/vg-data/lv-rawdisk-innodb01