How to Increase or reduce volume size on Centos

Increase virtual Hard Disk space running on ext4 file system

1. Identify the partition type:
# fdkisk -l
Device Boot         Start         End      Blocks   Id  System
/dev/sda1   *        2048     2099199     1048576   83  Linux
/dev/sda2         2099200  1953523711   975712256   8e  Linux LVM

Disk /dev/mapper/cl-root: 53.7 GB, 53687091200 bytes, 104857600 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

2. Check Disk information
# df -ah
/dev/mapper/cl-root   50G  6.4G   44G  13% /


3. Add/create additional volume then scan with this command
#partprobe -s

# fdkisk -l
Device Boot         Start         End      Blocks   Id  System
/dev/sda1   *        2048     2099199     1048576   83  Linux
/dev/sda2         2099200  1953523711   975712256   8e  Linux LVM
/dev/sda3      1953523711  1953524102    10485760   8e  Linux LVM

4. Increase the Logical Volume
#pvcreate /dev/sda3
Physical volume "/dev/sda3" successfully created

5. confirm name of the current volume group
# vgdisplay
--- Volume group ---
  VG Name               cl
VG Size               53.7 GiB

6. Extend 'cl' volume group  by adding physical volume /dev/sda3
# vgextend cl /dev/sda3
Volume group "Mega" successfully extended

7. Scan all disks for physical volumes
# pvscan
PV /dev/sda2   VG cl              lvm2 [53.7 GiB / 4.00 MiB free]
PV /dev/sda3   VG cl              lvm2 [10.00 GiB / 4.00 MiB free]
Total: 2 [63.7 GiB] / in use: 2 [63.7 GiB] / in no VG: 0 [0   ]


8. confirm the path of the logical volume
#lvdisplay
  --- Logical volume ---
  LV Path                /dev/cl/root

9. Extend the logical volume with lvextend command
# lvextend /dev/cl/root /dev/sda3
  Extending logical volume root to 63.7 GiB
  Logical volume root successfully resized
alternatively you can also extend logical volume with different sizes:
# lvextend -L +10G /dev/cl/root

 
10. Resize the file system using resize2fs command for ext based file system.
# resize2fs /dev/cl/root
resize2fs 1.42.9 (28-Dec-2013)
Filesystem at /dev/cl/root is mounted on /; on-line resizing required
old desc_blocks = 2, new_desc_blocks = 2
Performing an on-line resize of /dev/cl/root to 7576576 (4k) blocks.
The filesystem on /dev/cl/root is now 7576576 blocks long.

 
Note : if you are using XFS file system (default on RHEL7/CentOS7) you can extend the file system with this command:
# xfs_growfs /dev/cl/root




Reduce logical volume device size

To reduce logical volume we need to be careful and take backup if any data
1. check file system information
# lvs
LV    VG  Attr        LSize   Pool Origin Data%  Meta%  
data  cl  -wi-ao----  876.63g                                                    
root  cl   -wi-ao----  50.00g                                                    
swap  cl  -wi-ao----  3.88g                                                    

# df -ah
Filesystem           Size  Used Avail Use% Mounted on
/dev/mapper/cl-data  877G  8.4G  868G   1% /data

2. unmount mount point of the volume which needs to be reduced
umount -v /dev/mapper/cl-data /data

3. check for file-system errors using this command
# e2fsck -ff /dev/mapper/cl-data
e2fsck 1.42.9 (28-Dec-2013)
/dev/mapper/cl-data

Note: Must pass in every 5 steps of file-system check if not there might be some issue with your file-system.

To check hard drive related information and logs run this command
# smartctl -a /dev/sda

4. Now reduce the file system
# resize2fs /dev/mapper/cl-data  10GB

reduce the logical volume using this command
# lvreduce -L -8G /dev/mapper/cl-data


5. Resize the file system back
# resize2fs /dev/cl/data

6. Mount the file system back to same mount point
# mount  /dev/cl/data  /data

7. Check the size of the partition
# #lvdisplay
  --- Logical volume ---
LV Path                /dev/cl/data
LV Size   866.73 GiB

Thats it..