How to reduce (lvreduce) the Logical Volume in Linux Server

How to reduce (lvreduce) the Logical Volume in Linux Server.

Situation

Here, /app1 is 100GB filesystem. We need to reduce it to 70GB 

[root@testserver ~]# df -hP
Filesystem                                                 Size  Used Avail Use% Mounted on
/dev/mapper/vg_main-lv_root                   31G  2.0G    28G   7%    /
tmpfs                                                        3.7G     0      3.7G   0%   /dev/shm
/dev/xvdb1                                              477M   93M  355M  21%  /boot
/dev/mapper/vg_DPFERT-lv_app1           99G   11G    84G  11%   /app1


[root@testserver ~]# vgs
  VG                #PV #LV #SN Attr      VSize    VFree
  vg_DPFERT    1   1      0    wz--n-  100.00g    0
  vg_main           1   2      0    wz--n-    31.50g   0

[root@testserver ~]# fdisk -l /dev/xvdc

Disk /dev/xvdc: 107.4 GB, 107374182400 bytes
255 heads, 63 sectors/track, 13054 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

    Device Boot      Start         End      Blocks   Id  System
/dev/xvdc1               1       13054   104856254+  8e  Linux LVM

STEP 1 : First Unmount the LV

STEP 2 : Run e2fsck command to check the file system

[root@testserver ~]# e2fsck -f /dev/vg_DPFERT/lv_app1
e2fsck 1.43-WIP (20-Jun-2013)
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/vg_DPFERT/lv_app1: 57971/6553600 files (0.2% non-contiguous), 3073907/26213376 blocks


STEP 3 : Run resize2fs command for resizing the file system.

[root@testserver ~]# resize2fs /dev/vg_DPFERT/lv_app1 70G 
resize2fs 1.43-WIP (20-Jun-2013)
Resizing the filesystem on /dev/vg_DPFERT/lv_app1 to 18350080 (4k) blocks.
The filesystem on /dev/vg_DPFERT/lv_app1 is now 18350080 blocks long.

STEP 4 : Run lvreduce command to resuce the lvsize.

[root@testserver ~]# lvreduce -L 70G /dev/vg_DPFERT/lv_app1
  WARNING: Reducing active logical volume to 70.00 GiB
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce lv_app1? [y/n]: y
  Size of logical volume vg_DPFERT/lv_app1 changed from 100.00 GiB (25599 extents) to 70.00 GiB (17920 extents).
  Logical volume lv_app1 successfully resized
[root@testserver ~]#

STEP 5 : Mount the LV
[root@testserver ~]# lvs
  LV          VG                  Attr          LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  lv_app1  vg_DPFERT  -wi-a-----  70.00g
  lv_root    vg_main       -wi-ao----  31.22g
  lv_swap  vg_main       -wi-ao---- 288.00m

[root@testserver ~]# vgs
  VG                  #PV #LV #SN Attr       VSize      VFree
  vg_DPFERT    1      1      0    wz--n-  100.00g   30.00g
  vg_main           1      2     0     wz--n-  31.50g     0
  
[root@testserver home]# df -hP
Filesystem                                          Size  Used Avail Use% Mounted on
/dev/mapper/vg_main-lv_root             31G   2.0G   28G   7%   /
tmpfs                                                  3.7G     0      3.7G   0%  /dev/shm
/dev/xvdb1                                        477M   93M  355M  21% /boot
/dev/mapper/vg_DPFERT-lv_app1     69G   11G   56G   16%  /app1

Hope it helps.