Bug 1020489

Reviewing this part:

https://documentation-devel.engineering.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6-Beta/html/Virtualization_Administration_Guide/sub-sect-Managing_guest_virtual_machines_with_virsh-Managing_snapshots.html

I see that --live was removed (which is good), but I think that --quiesce and a few other parts of the documentation there don't make sense anymore considering that live-snapshots are not supported. But I would leave this for someone from libvirt to review and suggest editions.

The rest looks good to me.

(In reply to Ademar Reis from comment #7)
> Reviewing this part:
> 
> https://documentation-devel.engineering.redhat.com/site/documentation/en-US/
> Red_Hat_Enterprise_Linux/6-Beta/html/Virtualization_Administration_Guide/sub-
> sect-Managing_guest_virtual_machines_with_virsh-Managing_snapshots.html
> 
> I see that --live was removed (which is good), but I think that --quiesce
> and a few other parts of the documentation there don't make sense anymore
> considering that live-snapshots are not supported. But I would leave this
> for someone from libvirt to review and suggest editions.
> 
> The rest looks good to me.

Correction: this part needs to be reviewed as well (same reason as above):

https://documentation-devel.engineering.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6-Beta/html/Virtualization_Administration_Guide/sect-ext-snapshot-workaround.html

(In reply to Ademar Reis from comment #7)
> Reviewing this part:
> 
> https://documentation-devel.engineering.redhat.com/site/documentation/en-US/
> Red_Hat_Enterprise_Linux/6-Beta/html/Virtualization_Administration_Guide/sub-
> sect-Managing_guest_virtual_machines_with_virsh-Managing_snapshots.html
> 
> I see that --live was removed (which is good), but I think that --quiesce
> and a few other parts of the documentation there don't make sense anymore
> considering that live-snapshots are not supported. But I would leave this
> for someone from libvirt to review and suggest editions.
> 
> The rest looks good to me.

You are correct that --quiesce doesn't work if live disk snapshots aren't supported.

I just looked at the sections Ademar pointed out, and have the following additional comments:

#snapshot-create <domain> <xmlfile> [--redefine [--current] [--no-metadata] [--halt] [--disk-only] [--reuse-external] [--quiesce] [--atomic]

Missing a closing ] on --redefine.

I guess that is output that matches what libvirt outputs (because I recall that we fixed the missing ] at some point), modified to remove --live.  But it is more than just --live that requires qemu help - even --disk-only is a no-op for an offline domain, but can't work for a running domain.  Libvirt isn't going to remove the options; so about the only sane thing you can do is document ALL the options that libvirt provides, along with a caveat that the options are known to cause a graceful error message when driving a qemu that does not support the feature.

--halt, --disk-only, --quiesce, --atomic, and --live are all flags that really only matter when taking a snapshot of a running domain.

"--disk-only - causes the rest of the fields to be ignored, and automatically filled in by libvirt." - not quite.  Really, it is a flag that says that for a running domain, only disk state needs to be saved; it is redundant with snapshot XML that uses   <memory snapshot='no'/> (<memory was added to the XML after the flag had first been implemented).

All offline snapshots are disk-only, and because the guest is offline at the time, there is no need to do fsck or journal replay to get the disk image consistent again (assuming the guest was put offline via normal shutdown).

In section 22, the --memspec option of snapshot-create-as is applicable only to running domain snapshots.

This change is now available in the Red Hat Enterprise Linux 6.6 documentation at https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/.