Resize KVM qcow2 image live

KVM VMs backed by qcow2 image can be live resized with the virsh blockresize command.

Example, we had a VM with only 10 GB root disk:

[root@VM ~]# lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS vda 252:0 0 10G 0 disk ├─vda1 252:1 0 1M 0 part ├─vda2 252:2 0 200M 0 part /efi │ /boot/efi ├─vda3 252:3 0 1G 0 part /boot └─vda4 252:4 0 8.8G 0 part /

From the hypervisor, we then resized the qcow2 image:

[root@hypervisor ~]## virsh blockresize VMname /path/to/image.qcow2 128G Block device '/path/to/image.qcow2' is resized

then back in the VM, we could immediately see that the disk is now the new size:

[root@VM ~]# lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS vda 252:0 0 128G 0 disk ├─vda1 252:1 0 1M 0 part ├─vda2 252:2 0 200M 0 part /efi │ /boot/efi ├─vda3 252:3 0 1G 0 part /boot └─vda4 252:4 0 8.8G 0 part /

and then file system could be resized by growing partition and file system:

[root@VM ~]# growpart /dev/vda 4 CHANGED: partition=4 start=2510848 old: size=18460639 end=20971486 new: size=265924575 end=268435422 [root@VM ~]# xfs_growfs /dev/vda4 meta-data=/dev/vda4 isize=512 agcount=4, agsize=576895 blks = sectsz=512 attr=2, projid32bit=1 = crc=1 finobt=1, sparse=1, rmapbt=0 = reflink=1 bigtime=1 inobtcount=1 nrext64=0 data = bsize=4096 blocks=2307579, imaxpct=25 = sunit=0 swidth=0 blks naming =version 2 bsize=4096 ascii-ci=0, ftype=1 log =internal log bsize=4096 blocks=16384, version=2 = sectsz=512 sunit=0 blks, lazy-count=1 realtime =none extsz=4096 blocks=0, rtextents=0 data blocks changed from 2307579 to 33240571 [root@VM ~]# df -h / Filesystem Size Used Avail Use% Mounted on /dev/vda4 127G 8.6G 119G 7% /`

We were probably lucky in that this was the last partition. Guess it wouldn’t have been that easy to resize the earlier partitions…