Logical Volume Manager is great, you can manage your disks and partitions in volumes. The most common task is to extend a volume or reduce one.
You can extend a volume while the system is running, which is preaty great. Here�s how:
1. Let say your physical disk is /dev/sda, you already have two partitions (/dev/sda1 and /dev/sda2) and want to extend the rest of the free space. fdisk /dev/sda and create a new partition /dev/sda3
vgextend VolGroup00 /dev/sda3
lvextend /dev/VolGroup00/LogVol00 /dev/sda3
Now, asume that we want to reduce. This is a little bit tricky, you can not do it on the fly. You have to boot with a rescue cd (can be CentOS cd1 and type linux rescue at prompt).
lvm vgchange -a y
e2fsck -f /dev/VolGroup00/LogVol00
resize2fs -f /dev/VolGroup00/LogVol00 20G
lvm lvreduce -L10G /dev/VolGroup00/LogVol00
Happy resizing !