CODEWITHSUNDEEP
virtualizationqemukvm
Robin
Robin

Reputation: 1190

Qemu overlay image size limit

I created a qemu ubuntu vm. Now I use overlay images as a quick way of creating vm's as needed.

But what is the size limit for an overlay image? Is it the size of the "base" image? Or can it grow as big as the host OS allows it?

Upvotes: 1

Views: 1254

Answers (1)

Will
Will

Reputation: 36

Just ran into a similar situation. I'm running a Windows 8.1 VM with overlay images. The base image is the one that sets the disk size. The overlay will have as much space as the base image was setup to have.

The base is the one that has to grow if you run out of space. The overlay take the disk size information from the base.

Unfortunately, I haven't been able to find a way for the overlay to get the update disk size if the base is modified. So I had to either start over from the base image and make a new overlay or merge down the the overlays, increase disk size, and then create a new overlay from the new base.

This page is helpful in understanding overlays: https://kashyapc.fedorapeople.org/virt/lc-2012/snapshots-handout.html

Here is an alternative solution to creating a copy of the entire overlay chain and creating a new base without modifying your existing chain: http://kashyapc.com/2014/07/06/live-disk-migration-with-libvirt-blockcopy/

Upvotes: 2

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