How to Expand an LVM Volume and Filesystem

We’ve got a virtual server that’s low on disk space. The system administrator responsible for the virtual machine has expanded the disk. Now we need to expand the filesystem to include the additional disk space.

TIP: There are two ways we can do this. 1) Don’t expand the disk but rather add a second disk and use that disk for whatever is taking up the most space such as “/var/www/html” on a web-server. That is the lowest risk option. 2) Create a new partition (using “fdisk” of type “8e”) on the expanded disk to use up the remaining space and then create a new LVM disk (using “pvcreate /dev/sdaX”). Then expand the LVM volume group to include the new disk (using “vgextend NAME-X /dev/sdaX”). Then expand the Volume LVM_NAME to include the new volume (using “lvextend /dev/mapper/NAME-Y /dev/sdaX”). Finally we expand the filesystem to include the new/unused disk space (using “resize2fs /dev/mapper/NAME-Y”).

We’re using option 2 here. It’s more risky because it involves working on live disks (potentially) so make sure to have a plan if all goes bad.

Let’s start with a view of the disks. In the following we can see there is a 100G disk but only about 30G has been used.

[root@server ~]# lsblk
NAME                        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda                           8:0    0  100G  0 disk 
├─sda1                        8:1    0  500M  0 part /boot
└─sda2                        8:2    0 29.5G  0 part 
  ├─VolGroup-lv_root (dm-0) 253:0    0 26.5G  0 lvm  /
  └─VolGroup-lv_swap (dm-1) 253:1    0    3G  0 lvm  [SWAP]
sr0                          11:0    1 1024M  0 rom

Create the new partition on “/dev/sda”. it will be called “/dev/sda3” as that’s the next partition. Remember to make the new partition a “type 8e” partition.

fdisk /dev/sda

It will look similar to this:

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          64      512000   83  Linux
/dev/sda2              64        3917    30944256   8e  Linux LVM
/dev/sda3            3917       13054    73398975   8e  Linux LVM

Convert the new filesystem into an LVM volume:

pvcreate /dev/sda3

If the above gives an error such as “Device /dev/sda3 not found (or ignored by filtering)” you’ll likely need to reboot.

Run “vgs” to get the Volume Group name:

[root@server ~]# vgs
  VG       #PV #LV #SN Attr   VSize  VFree
  VolGroup   1   2   0 wz--n- 29.51g    0

We can see above that ‘my’ Volume Group is called “VolGroup”. To include our new volume into the “VolGroup” Volume Group, run this:

vgextend VolGroup /dev/sda3

Now we expand to include all available disk space offer by the new physical volume. This is a two step process. We need the Volume path and then we extend over it.

[root@server ~]# df -h /
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root
                       26G   14G   12G  55% /

The full path is “/dev/mapper/VolGroup-lv_root”. Now extend it with the following command:

lvextend /dev/mapper/VolGroup-lv_root /dev/sda3

Finally we extend the filesystem over the larger disk:

resize2fs /dev/mapper/VolGroup-lv_root

Confirm it has worked with these two commands “df -h” and “lsblk”:

[root@server ~]# lsblk
NAME                        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda                           8:0    0  100G  0 disk 
├─sda1                        8:1    0  500M  0 part /boot
├─sda2                        8:2    0 29.5G  0 part 
│ ├─VolGroup-lv_root (dm-0) 253:0    0 96.5G  0 lvm  /
│ └─VolGroup-lv_swap (dm-1) 253:1    0    3G  0 lvm  [SWAP]
└─sda3                        8:3    0   70G  0 part 
  └─VolGroup-lv_root (dm-0) 253:0    0 96.5G  0 lvm  /
sr0                          11:0    1 1024M  0 rom  

… and …

[root@server ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root
                       95G   14G   77G  16% /
tmpfs                 7.6G     0  7.6G   0% /dev/shm
/dev/sda1             477M  114M  339M  26% /boot

Resources:

• https://www.rootusers.com/how-to-increase-the-size-of-a-linux-lvm-by-expanding-the-virtual-machine-disk/