`qubes-vm-update`: support targeting used templates only

[3hhh]

How to file a helpful issue

The problem you're addressing (if any)

qubes-vm-update can currently only target all installed templates.

However many templates on a regular system are not used by any AppVMs and therefore don't always need updates. Often the user forgot to remove them or only kept them for backup reasons.
For example I currently have 11 template VMs out of which I only use 2.

The solution you'd like

Add some command-line switch to only target templates which are in use by existing AppVMs.

The value to a user and who that user might be

Faster updates / updating only what is needed.

Completion criteria checklist

(This section is for developer use only. Please do not modify it.)

[marmarek]

However many templates on a regular system are not used by any AppVMs

Is this really normal? Why don't you just remove unused templates, if you aren't using them?

[RandyTheOtter]

Perhaps instead of targeting options qubes-vm-update should be capable of taking targets from STDIN while qvm-ls could have either more filter options or some interesting fields to better align with UNIX shell workflow pattern:

qvm-ls --class TemplateVM | qubes-vm-update -

or for this case

qvm-ls --class AppVM -O template --raw-data \
| sort -u \
| qubes-vm-update --force-update -

or maybe even someday

qvm-ls -cT --used | qubes-vm-update -

Sure you can do the same with a subshell but I think this is more better for no reason at all.

edit: my bad, I misread used as unused

[unman]

Why is `qubes-vm-update --targets ` not sufficient? Also for the templates with no attached qubes, `qubes-vm-update --templates --update-if-available` should prune out the templates with no qubes since these will not report updates.

[3hhh]

However many templates on a regular system are not used by any AppVMs

Is this really normal? Why don't you just remove unused templates, if you aren't using them?

I don't know for sure.

Sometimes for example I have customers with really ancient OS versions that I need to work for and I'm happy when I still have these available as templates.
Sometimes I also want to test my own software against old OS versions.
Oftentimes my mind tells me to keep it around "just in case" - especially since storage was cheap in the past.

Perhaps instead of targeting options qubes-vm-update should be capable of taking targets from STDIN

I agree that this is the more generic pattern and would cover my use case just fine via e.g. qvm-ls --class AppVM -O template --raw-data | sort -u | qubes-vm-update --force-update --targets-from-stdin, which is currently covered by the rather ugly qvm-ls --class AppVM -O template --raw-data | sort -u | tr '\n' ',' | sed 's/,$//' | xargs qubes-vm-update --force-update --targets.

So your proposal is a good solution as well imho.

qubes-vm-update --templates --update-if-available should prune out the templates with no qubes since these will not report updates.

This won't work for me with update checks disabled, see #9749.

[GWeck]

Setting qvm-feature VMNAME skip-updates 1 should do the trick - or am I completely wrong here?