The Universally Unique Identifier can be used to identify a device independent form its mount point or device name. This is more and more important as many devices today support hot-plugging or are external anyway. Therefore it makes sometimes sense to access a device (for example in fstab
) not by device name but by the UUID.
There are several ways to get the UUID. The first one uses the /dev/
directory. While you are on is you might want to check other by-*
directories, I never knew of them.
[root@jira ~]# ls -l /dev/disk/by-uuid
total 0
lrwxrwxrwx. 1 root root 10 May 14 12:06 24136044-94a0-4106-9f06-1be49356b1d5 -> ../../sdc1
lrwxrwxrwx. 1 root root 10 May 14 11:55 69354ec2-9edd-48ed-833b-575bfe25622f -> ../../sdb1
lrwxrwxrwx. 1 root root 10 May 14 11:55 6f5ef646-a484-4b4e-9007-c58bdc85faff -> ../../sda3
lrwxrwxrwx. 1 root root 10 May 14 11:55 93acd8b4-5442-4f42-a4c9-a9ae45e165ef -> ../../sda1
lrwxrwxrwx. 1 root root 10 May 14 11:55 9798da8e-f4a8-4ada-91d9-3a2bda4285e5 -> ../../sda2
[root@jira ~]# cat /etc/fstab
#
# /etc/fstab
# Created by anaconda on Mon May 14 11:17:45 2012
#
# Accessible filesystems, by reference, are maintained under ‘/dev/disk’
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
UUID=6f5ef646-a484-4b4e-9007-c58bdc85faff / ext4 defaults 1 1
UUID=93acd8b4-5442-4f42-a4c9-a9ae45e165ef /boot ext4 defaults 1 2
UUID=69354ec2-9edd-48ed-833b-575bfe25622f /data01 ext4 defaults 1 2
UUID=9798da8e-f4a8-4ada-91d9-3a2bda4285e5 swap swap defaults 0 0
tmpfs /dev/shm tmpfs defaults 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
sysfs /sys sysfs defaults 0 0
proc /proc proc defaults 0 0
[root@jira ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 67G 2.8G 61G 5% /
tmpfs 3.9G 100K 3.9G 1% /dev/shm
/dev/sda1 194M 30M 154M 17% /boot
/dev/sdb1 493G 198M 467G 1% /data01
/dev/sdc1 493G 198M 467G 1% /data02
[root@jira ~]# blkid /dev/sda*
/dev/sda1: UUID=”93acd8b4-5442-4f42-a4c9-a9ae45e165ef” TYPE=”ext4″
/dev/sda2: UUID=”9798da8e-f4a8-4ada-91d9-3a2bda4285e5″ TYPE=”swap”
/dev/sda3: UUID=”6f5ef646-a484-4b4e-9007-c58bdc85faff” TYPE=”ext4″
[root@jira ~]#
[root@jira ~]#