TBH - I haven't taken the former comment as a call for further action.
It was more of a summary how docs and output could be better.

Let me answer:

1. document that --bypass-cache would help

Yeah it might be nice, but then it is just such a general thing.
It only affects apparmor users (not all libvirt users).
It only affects /tmp wi
I wonder how such a hint might look like.
Checking the doc there is a Note on disk corruption for virsh restore - maybe 
there as another Note entry.
But I'm still not all in for this.

2. on older releases "error out or warn in Libvirt when performing save
in denial paths"

It is not really possible to predetect and differentiate if such a denial was 
the reason.
Looking into the future I think we might use per-guest overrides.


I was thinking on that more, the fact that all other but /tmp (for the explicit 
deny) just work, like:
 $ virsh save xenial-testshutdown-0 /var/anythingbuttmp.state
 $ virsh restore /var/anythingbuttmp.state
That annoys me a lot.

I'd suggest otherwise, we keep the past as it is without modifying man pages or 
anything like it (after all it is no regression I can SRU and a very special 
case choosing /tmp only).
But I want to make it better thinking forward.
I thought about it again and again, and revisited the old bug that added those 
deny rules.
I think it is time to take them out in the next release.

That would mean it would generally work, and even if there is a deny it would 
at least be in the log.
See also:
- https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1403648/comments/6
- https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1403648/comments/12

I think the old assumptions don't hold true.
So for the current and stable-releases we keep it as is, to not regress anyone 
(with too much logs).
But forward I'd drop the deny rules and then all of this (and similar things 
where users WANT e.g. images in /tmp) would work.

Part of it would be to check (way more modern and recent) openstack that
it no more has those issues and if it has as part of the fix look for
something better e.g. adapt how openstack sets the ceph config to no
more trigger /tmp /tmp/var access.

There are also rules like owner /tmp/pulse-*/ rw, in the meantime which get 
trumped by the deny.
TL;DR - taking out the deny and making the save/restore case of this bug no 
more a special case would be much better IMHO.

If you are ok with that I'd create a new bug to:
1. take out the deny rules to /tmp early in Ubuntu 18.10
2. do an analysis with recent openstack+ceph if they still trigger access there

So are you ok with that approach?

P.S. If you really really (...really*) want/need a man page entry for
this special case we could work something out, but I think that would
not qualify as an SRU [1] so thinking forward is much better anyway.

[1]: https://wiki.ubuntu.com/StableReleaseUpdates

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https://bugs.launchpad.net/bugs/1719579

Title:
  [Ubuntu 18.04] [libvirt] virsh restore fails from state file saved in
  /var/tmp folder using virsh save

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