I'm running several VMs within Xen, and now I'm trying to create/revert snapshots of my VMs.
Along with Xen and blktap2, another utility, vhd-util is also delivered, and according to its description, I guess I can use it to create/revert VM snapshots.
To create a snapshot is actually easy, I just call:
vhd-util snapshot -n aSnapShot.vhd -p theVMtoBackup.vhd
But when it comes to reverting a snapshot, things get really annoying.
The "revert" command requires a mandatory argument "journal", like this:
vhd-util revert -n aSnapShot.vhd -j someThingCalledJournalOfWhichIHaveNoIdea
And vhd-util expects some info from the journal, which means it's not some empty file you can write logs in.
But I've went through the code and the internet, still get no idea where this Journal comes from.
Similar question is asked http://xen.1045712.n5.nabble.com/snapshots-with-vhd-util-blktap2-td4639476.html but poor guy never get answered.
Hope someone here could help me out.
You don't need to use revert, all you need to do is shut down the VM, rename aSnapShot.vhd to theVMtoBackup.vhd and restart the VM.