Scenario: Decrease Logical Volume /home to 1GB size in CentOS/RHEL 6
System: CentOS/RHEL 6

Steps:
– Check the drive and LV Path:

[root@centos6 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolumeGroup-lv_root 9.9G 1.8G 7.6G 20% /
tmpfs 931M 0 931M 0% /dev/shm
/dev/sda1 485M 39M 421M 9% /boot
/dev/mapper/VolumeGroup-lv_home 2.5G 68M 2.3G 3% /home
/dev/mapper/VolumeGroup-lv_opt 2.5G 68M 2.3G 3% /opt
/dev/mapper/VolumeGroup-lv_var 9.9G 199M 9.2G 3% /var
[root@centos6 ~]# lvdisplay | grep Path
 LV Path /dev/VolumeGroup/lv_root
 LV Path /dev/VolumeGroup/lv_swap
 LV Path /dev/VolumeGroup/lv_var
 LV Path /dev/VolumeGroup/lv_opt
 LV Path /dev/VolumeGroup/lv_home
[root@centos6 ~]# vgs
 VG #PV #LV #SN Attr VSize VFree
 VolumeGroup 1 5 0 wz--n- 39.51g 10.51g
[root@centos6 ~]#

got the logical volume home path is /dev/VolumeGroup/lv_home with 2.5GB size.

– Unmount logical volume home and run fuser to kill process that using home directory

[root@centos6 ~]# umount -l /dev/VolumeGroup/lv_home
[root@centos6 ~]# fuser -v /dev/VolumeGroup/lv_home
[root@centos6 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolumeGroup-lv_root 9.9G 1.8G 7.6G 20% /
tmpfs 931M 0 931M 0% /dev/shm
/dev/sda1 485M 39M 421M 9% /boot
/dev/mapper/VolumeGroup-lv_opt 2.5G 68M 2.3G 3% /opt
/dev/mapper/VolumeGroup-lv_var 9.9G 199M 9.2G 3% /var
[root@centos6 ~]#

– Run e2fsck to check logical volume

[root@centos6 ~]# e2fsck -ff /dev/VolumeGroup/lv_home
e2fsck 1.41.12 (17-May-2010)
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/VolumeGroup/lv_home: 11/163840 files (0.0% non-contiguous), 27636/655360 blocks
[root@centos6 ~]#

– Decrease logical volume home to 1GB size

[root@centos6 ~]# resize2fs /dev/VolumeGroup/lv_home 1G
resize2fs 1.41.12 (17-May-2010)
Resizing the filesystem on /dev/VolumeGroup/lv_home to 262144 (4k) blocks.
The filesystem on /dev/VolumeGroup/lv_home is now 262144 blocks long.

[root@centos6 ~]# lvreduce -L 1G /dev/VolumeGroup/lv_home
 WARNING: Reducing active logical volume to 1.00 GiB
 THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce lv_home? [y/n]: y
 Reducing logical volume lv_home to 1.00 GiB
 Logical volume lv_home successfully resized
[root@centos6 ~]# 

– Finish, mount the logical volume home then check the final result

[root@centos6 ~]# mount -a
[root@centos6 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolumeGroup-lv_root 9.9G 1.8G 7.6G 20% /
tmpfs 931M 0 931M 0% /dev/shm
/dev/sda1 485M 39M 421M 9% /boot
/dev/mapper/VolumeGroup-lv_opt 2.5G 68M 2.3G 3% /opt
/dev/mapper/VolumeGroup-lv_var 9.9G 199M 9.2G 3% /var
/dev/mapper/VolumeGroup-lv_home 1008M 68M 890M 8% /home
[root@centos6 ~]# vgs
 VG #PV #LV #SN Attr VSize VFree
 VolumeGroup 1 5 0 wz--n- 39.51g 12.01g
[root@centos6 ~]#