To use e2label to label the second partition of the first hardisk with label DATA:
# e2label /dev/sda2 DATA
To use tune2fs to do the similar job as above:
# tune2fs -L DATA /dev/sda2
The third tool, mke2fs is actually a tool to build ext2/ext3 filesystem. So, if you want to build the partition's filesystem as ext2/ext3 and at the same time label it, this command can be used. Be careful though, because it will delete all existing data on that particular partition
# mke2fs -L DATA /dev/sda2
To view the label that you have set, there are 3 ways which are using e2label, blkid and viewing /dev/disk/by-label.
To check using e2label:
# e2label /dev/sda2
blkid tool is even more useful, because it can list out all the partitions that you have in the machine together with their labels,uuid and filesystem type:
/dev/sda1: LABEL="/" UUID="1CC08F13C08EF276" TYPE="ext3"
/dev/sda2: LABEL="DATA" UUID="2063f830-fe5d-438e-b727-571b313cb89e" TYPE="ext3"
/dev/sda3: TYPE="swap" LABEL="SWAP" UUID="3e266b53-42e0-4f09-8fe3-d1cf79cb5d37"
To view the /dev/disk/by-label
# ls -l /dev/disk/by-label
lrwxrwxrwx 1 root root 10 2009-07-24 05:38 / -> ../../sda1
lrwxrwxrwx 1 root root 10 2009-07-24 05:38 DATA -> ../../sda2
lrwxrwxrwx 1 root root 10 2009-07-24 05:38 SWAP -> ../../sda3
Note that the label will stay with the partition although the disk is moved to another computer.
To use it in /etc/fstab:
LABEL=/ / ext3 defaults 1 1
LABEL=DATA /DATA ext3 defaults 1 2
LABEL=SWAP swap swap defaults 0 0