LVM - Reduce LV

Shrinking a root volume(Live CD):

vgchange -a y

Shrinking a non-root volume:

umount /dev/centos/var

Check for errors:

e2fsck -fy /dev/centos/var

Resize FS:

resize2fs /dev/centos/var 4G

Reduce to 5G: lvreduce -L 5G /dev/vg/disk-name

or

Reduce by 5G:

lvreduce -L -5G /dev/vg/disk-name

Use all available space:

resize2fs /dev/centos/var

Remount:

mount /dev/centos/var /mnt