Re: virsh backup-begin problem
On Thu, Jan 21, 2021 at 13:31:03 +0300, Andrey Fokin wrote:
Thanks Peter!
But is possible change XML configuration towards will be possible to do
full (push) backup?
Yes, I've included links to the documentation to do so in my previous
reply, so I'd suggest you follow it. See ...
On Wed, Jan 20, 2021 at 9:08 PM Peter Krempa
<pkrempa(a)redhat.com> wrote:
> On Wed, Jan 20, 2021 at 20:49:49 +0300, Andrey Fokin wrote:
> > Colleagues, could you please advise what a problem could be in XML file
> in
> > case of:
> > virsh backup-begin lubuntu2 ./backup.xml
> >
> > where backup.xml -
> > <domainbackup>
> > <disk name='/var/lib/libvirt/images/lubuntu2.qcow2'
type='file'>
> > <target file='$PWD/scratch1.img'/>
> > <driver type='raw'/>
> > </disk>
> > <disk name='/var/lib/libvirt/images/lubuntu2-1.qcow2'
type='file'>
> > <target file='$PWD/scratch2.img'/>
> > <driver type='raw'/>
> > </disk>
> > </domainbackup>
>
> snip ...
>
> You forgot to add what you are observing, but I presume:
>
> 'operation unsupported: incremental backup is not supported yet'
>
> Unfortunately it's what it says on the tin. The implementation of the
> incremental backup code is not finished yet, thus the feature is
> disabled.
>
> If you want to test-drive incremental backup APIs, you can enable the
> experimental feature by using the XML documented in:
>
> https://libvirt.org/drvqemu.html#xmlnsfeatures
... here. I specifically avoided giving exact steps so that you read the
documentation including the description of caveats of enabling this
_experimental_ feature.
So please make sure to read it. This is NOT meant for production use.
Anyways:
You need to add the 'qemu' namespace to your domain XML:
<domain type='kvm'
xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>
And force-on the incremental backup capability:
<qemu:capabilities>
<qemu:add capability='incremental-backup'/>
</qemu:capabilities>
This enables backups, but as I've wrote previously ...
>
> to enable a feature named 'incremental-backup'. Please make sure to read
> the caveats of doing so thoroughly.
.. observe the following:
> I also advise not to combine incremental backups with snapshots
> (virDomainSnapshot* APIs) and blockjobs (virDomainBlock* APIs) as that
> will not work properly without a patch enabling also experimental qemu
> features.
If you use them, backups will break. You get to keep the pieces, as
you've been warned.
Also this:
> I also suggest you use the latest qemu for this.