How to expand the /tmp file system on a Linux server

Problem: /tmp needs more space.
It is placed in the root directory of the server:

[root@myserver ~]# df -h /
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_system-Root
               5.8G  4.0G  1.5G  73% /

Use vgdisplay to check how much free space exist in the volume group by looking at Free PE / Size:

[root@myserver]# vgdisplay
  --- Volume group ---
  VG Name               vg_system
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  11
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                5
  Open LV               5
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               24.00 GiB <-- total size of VG
  PE Size               4.00 MiB
  Total PE              6143
  Alloc PE / Size       5631 / 22.00 GiB
  Free  PE / Size       512 / 4.00 GiB <-- 4 GB free
  VG UUID               d0OgTw-stMx-GfyT-N1zA-cEv8-1OGY-2qZ8D4

Increase size of logical volume by 2GB:

lvextend -L +2G /dev/vg_system/Root 

 Size of logical volume vg_system/Root changed from 8.00 GiB (2047 extents) to 10.00 GiB (2559 extents).
  Logical volume Root successfully resized.

Finally increase size of file system:

resize2fs /dev/mapper/vg_system-Root 

resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/mapper/vg_system-Root is mounted on /; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 1
Performing an on-line resize of /dev/mapper/vg_system-Root to 2620416 (4k) blocks.
The filesystem on /dev/mapper/vg_system-Root is now 2620416 blocks long.

In this example:

vg_system = volume group name

/dev/vg_system/Root = Logical volume Path

/dev/mapper/vg_system-Root = file system name

The file system name you will find in /etc/fstab:

/dev/mapper/vg_system-Root      /       ext4    defaults        1       1