Re: [Qemu-devel] segfault while booting from saved snapshot

[Kevin Wolf]

Am 15.04.2014 um 16:55 hat Shehbaz Jaffer geschrieben:
> Thankyou for your reply. I do not face the error using qemu.1.7.1 version.
> 
> 1 quick question:
> 
> I want to create a qcow2 image file after my VM has completed booting; i.e.,
> when I boot from this new snapshot, I should directly get to my VMs login
> prompt. How can i create such a qcow2 snapshot?
> 
> I tried stopped the VM using QMP after the VM had completed booting, and then
> using host CLI to create a qcow2 image :
> 
> qemu-img create -b ubuntu.qcow2 -f qcow2 newsnap.qcow2
> 
> This created a new qcow2 file - newsnap.qcow2 on top of ubuntu.qcow2, however
> when I boot using newsnap.qcow2, It takes me again through the complete boot
> process - till the login prompt.
> 
> Is there a way to create the qcow2 snapshot after VM has completed booting?

The reason for this is that you only create a snapshot of the disk this
way, not of the VM state (i.e. RAM contents, device states, etc.)

The most convenient way when you're using qemu directly is probably
using internal snapshots. This is what the savevm/loadvm HMP commands
provide (not sure if there is a QMP equivalent); you can also use the
-loadvm command line parameter to start a VM from a snapshot.

Another option is that you take an external snapshot in a new qcow2 file
like you did, but you additionally do a live migration into a file. When
restarting the VM, you need to use the -incoming option and feed that
file back to qemu. As this is a bit more cumbersome, this is probably
more an option for management tools than for manual use.

Kevin