Relocate kvm images directory

relocatelibvirtimages.md

Relocate an existing libvirtd (KVM) images directory

By default, KVM (libvirtd) images on Ubuntu and most other Linux distributions are found in /var/lib/libvirt/images. This can be inconvenient if you don't have a separate /var partition that can grow over time to accommodate multiple large images.

You can simply rename the images folder to something else and then symlink to a larger space with it (e.g. ln -s /data1/libvirt/images /var/lib/libvirt/images). That's what I used to do.

But that can lead to all sorts of unanticipated trouble. The right way to have your images on a bigger disk is to change the path for libvirt's default storage pool to a partition on that big disk, which is logically where KVM is going to create them.

First check to make sure a default pool exists:

$ virsh pool-list --all
 Name      State    Autostart
-------------------------------
 default   active   yes

NOTE: If no default pool exists, follow the instructions in this gist to create one on your preferred storage volume.

Assuming a default pool exists, find the current default pool's path:

$ virsh pool-dumpxml default
<pool type='dir'>
  <name>default</name>
  <uuid>91c6d1b3-4e42-4a1f-989e-89b2127da056</uuid>
  <capacity unit='bytes'>133070688256</capacity>
  <allocation unit='bytes'>25177309184</allocation>
  <available unit='bytes'>107893379072</available>
  <source>
  </source>
  <target>
    <path>/var/lib/libvirt/images</path>
    <permissions>
      <mode>0711</mode>
      <owner>64055</owner>
      <group>108</group>
    </permissions>
  </target>
</pool>

Before going further it is best to shut down ("destroy") all existing virtual machines).

Now use virsh edit to change the disk path in each virtual machines's configuration to the default pool's new location. Assuming this will be "/data1/libvirt/images", you would proceed like this:

$ virsh edit example
...
<disk type='file' device='disk'>
    <driver name='qemu' type='qcow2'/>
-   <source file='/var/lib/libvirt/images/example.qcow2'/>
+   <source file='/data1/libvirt/images/example.qcow2'/>

(the line will then read <source file='/data1/libvirt/images/example.qcow2'

Next, the default pool should be completely shut down:

$ virsh pool-destroy default

Then, undefined:

$ virsh pool-undefine default

NOTE: By default, virt-manager creates additional pools automatically for things like iso files. These should also be destroyed and undefined before proceeding, to free things up for redefining the default pool (if you don't, the system will spit out "error: operation failed: Storage source conflict with pool" messages when you try redefining).

Now, recreate the default pool anew and start:

$ virsh pool-define-as default dir --target "/data1/libvirt/images"
$ virsh pool-build default
$ virsh pool-start default
$ virsh pool-autostart default

Check the status with virsh-info:

$ virsh pool-info default

And then the configuration with pool-dumpxml:

$ virsh pool-dumpxml default

Finally, move any existing disk images from /var/lib/libvirt/images to the new location (e.g. /data1/libvirt/images).

Better late than never. This is a good point. I've updated my notes to reflect it.

Hello, I relocated the default location: /home/user/Stocks/libvirt/images
which I own
And now :
Unable to complete install: 'internal error: QEMU unexpectedly closed the monitor (vm='archlinux'): 2024-07-18T10:14:38.159379Z qemu-system-x86_64: -blockdev {"node-name":"libvirt-2-format","read-only":false,"discard":"unmap","driver":"qcow2","file":"libvirt-2-storage","backing":null}: Could not open '/home/user/Stocks/libvirt/images/archlinux.qcow2': Permission denied'