The following steps will show you how to shrink an LVM volume. In this example we will be shrinking volume VolGroup00-LogVol00 down to 20GB. Note: This can and will cause data loss if performed improperly or on a volume that you attempt to shrink below the current volume usage. With that said, the steps are as follows:
umount /dev/mapper/VolGroup00-LogVol00 e2fsck -f /dev/mapper/VolGroup00-LogVol00 resize2fs /dev/mapper/VolGroup00-LogVol00 20G lvreduce -L 20G /dev/mapper/VolGroup00-LogVol00 e2fsck -f /dev/mapper/VolGroup00-LogVol00
The process is similar when expanding a logical volume except the lvextend command is used in place of lvreduce.