libvirt users - Sep 2016 - Re: internal snapshot question

I take an internal snapshot (VM is 'shutdown' when taking it) of a qcow2
image like this:

   $ qemu-img snapshot -c sn1 [my_image].qcow2

I see that snapshot when asking for:

   $ qemu-img info [my_image].qcow   

but do NOT see it with: 

   $ virsh domblklist [my_domain]

is that how it is meant to be?

On Sat, Sep 03, 2016 at 03:07:37PM +0800, vrms@netcologne.de
wrote:
>I take an internal snapshot (VM is 'shutdown' when taking it) of a
qcow2 image like this:
>
>   $ qemu-img snapshot -c sn1 [my_image].qcow2
>
>I see that snapshot when asking for:
>
>   $ qemu-img info [my_image].qcow
>
Firstly, you are doing this behind libvirt's back, so libvirt will most
likely not know about that snapshot.
>but do NOT see it with:
>
>   $ virsh domblklist [my_domain]
>
Well, what would you expect to see there?  Have a look at the man page,
virsh(1) says:

domblklist domain [--inactive] [--details]
    Print a table showing the brief information of all block devices associated
with
    domain. If --inactive is specified, query the block devices that will be
used on
    the next boot, rather than those currently in use by a running domain. If
    --details is specified, disk type and device value will also be printed.
Other
    contexts that require a block device name (such as domblkinfo or
snapshot-create
    for disk snapshots) will accept either target or unique source names printed
by
    this command.
>is that how it is meant to be?
>
Well, yeah (if the above is really what you wanted to run)...
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hi Martin, 

thanks again for the feedback. maybe you have noted that I am not yet all too
familiar with those tools.

this is now sort of working for me. But I sense that you seem this method to be
less then ideal.
Reading through the virsh manual it looks like ...

   $ virsh snapshot-create [domain] --disk-only --live

... might be doing a similar thing. Maybe more elegant (pure virsh) and on a
running machine
what I can't qite figure out is where to squeeze in the name (or
description, even) for the snapshot

> On September 3, 2016 at 3:37 PM Martin Kletzander
<mkletzan@redhat.com> wrote:
> 
> On Sat, Sep 03, 2016 at 03:07:37PM +0800, vrms@netcologne.de wrote:
> 
> > I take an internal snapshot (VM is 'shutdown' when taking it)
of a qcow2 image like this:
> > 
> > $ qemu-img snapshot -c sn1 [my_image].qcow2
> > 
> > I see that snapshot when asking for:
> > 
> > $ qemu-img info [my_image].qcow
> 
> Firstly, you are doing this behind libvirt's back, so libvirt will most
> likely not know about that snapshot.
> 
> > but do NOT see it with:
> > 
> > $ virsh domblklist [my_domain]
> 
> Well, what would you expect to see there? Have a look at the man page,
> virsh(1) says:
> 
> domblklist domain [--inactive] [--details]
>  Print a table showing the brief information of all block devices
associated with
>  domain. If --inactive is specified, query the block devices that will be
used on
>  the next boot, rather than those currently in use by a running domain. If
>  --details is specified, disk type and device value will also be printed.
Other
>  contexts that require a block device name (such as domblkinfo or
snapshot-create
>  for disk snapshots) will accept either target or unique source names
printed by
>  this command.
> 
> > is that how it is meant to be?
> 
> Well, yeah (if the above is really what you wanted to run)...
> 
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