How to Shrink or reduce size of LVM partitons in RHEL/CentOS

1. Check disk partitions size
# df -hT

Filesystem	Type	Size	Used	Avail	Use%	Mounted on
/dev/mapper/VolGroup00-LogVol00	ext3	34G	6.6G	26G	21%	/
/dev/mapper/VolGroup00-LogVol03	ext3	34G	29G	27G	52%	/usr
/dev/mapper/VolGroup00-LogVol04	ext3	97G	89G	2.7G	98%	/var
/dev/sda1	ext3	99M	27M	67M	29%	/boot
tmpfs	tmpfs	56G	0	56G	0%	/dev/shm
/dev/mapper/VolGroup00-LogVol02	ext3	56G	9.1G	65G	13%	/backup

2. Unmount the partitions that want to shrink or reduce
# umount /dev/mapper/VolGroup00-LogVol02

3. Check a Linux ext2/ext3/ext4 file system partition.
# /sbin/e2fsck -f /dev/mapper/VolGroup00-LogVol02
e2fsck 1.39 (29-May-2006)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
/lost+found not found.  Create<y>? yes
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/mapper/VolGroup00-LogVol02: ***** FILE SYSTEM WAS MODIFIED *****
/dev/mapper/VolGroup00-LogVol02: 2887/20971520 files (14.9% non-contiguous), 3019764/20971520 blocks
4. Resize the partition to 30 GB
# /sbin/resize2fs -p /dev/mapper/VolGroup00-LogVol02 30G
resize2fs 1.39 (29-May-2006)
Resizing the filesystem on /dev/mapper/VolGroup00-LogVol02 to 7864320 (4k) blocks.
Begin pass 2 (max = 1690914)
Relocating blocks             XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
Begin pass 3 (max = 640)
Scanning inode table          XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
Begin pass 4 (max = 201)
Updating inode references     XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
The filesystem on /dev/mapper/VolGroup00-LogVol02 is now 7864320 blocks long.
5. Reduce the size of a logical volume upto 30 GB
# /usr/sbin/lvreduce -L 30G /dev/mapper/VolGroup00-LogVol02
  WARNING: Reducing active logical volume to 30.00 GB
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
  Do you really want to reduce LogVol02? [y/n]: y
  Reducing logical volume LogVol02 to 30.00 GB
  Logical volume LogVol02 successfully resized
6. Recheck  again, Linux ext2/ext3/ext4 file system partition.
# /sbin/e2fsck -f /dev/mapper/VolGroup00-LogVol02
e2fsck 1.39 (29-May-2006)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/mapper/VolGroup00-LogVol02: 2887/7864320 files (14.9% non-contiguous), 2606289/7864320 blocks
7. Resize the partition to 30 GB
# /sbin/resize2fs -p /dev/mapper/VolGroup00-LogVol02
resize2fs 1.39 (29-May-2006)
The filesystem is already 7864320 blocks long.  Nothing to do!
8. Now, Mount the partition.
# mount /dev/mapper/VolGroup00-LogVol02  /backup
9. Again, Check disk partitions size
# df -hT

Filesystem	Type	Size	Used	Avail	Use%	Mounted on
/dev/mapper/VolGroup00-LogVol00	ext3	34G	6.6G	26G	21%	/
/dev/mapper/VolGroup00-LogVol03	ext3	34G	29G	27G	52%	/usr
/dev/mapper/VolGroup00-LogVol04	ext3	97G	89G	2.7G	98%	/var
/dev/sda1	ext3	99M	27M	67M	29%	/boot
tmpfs	tmpfs	56G	0	56G	0%	/dev/shm
/dev/mapper/VolGroup00-LogVol02	ext3	30G	9.1G	19G	33%	/backup

Its Done !!!