Add a feature to block starting a qube

[marmarek]

How to file a helpful issue

The problem you're addressing (if any)

Sometimes user wants to prevent starting a qube. A qube may be started in several way (explicit qvm-start call, menu entry, a qrexec call, updater, etc). Disabling each of those methods separately is tedious and often easy to miss some.

The solution you'd like

Add a feature to prevent starting a qube with specific message.

The value to a user, and who that user might be

Useful for qubes that user want to not start for any reason. Some examples include:

• templates user really wants to keep in the original, unmodified state
• known compromised qubes, waiting for some forensics analysis or restoring
• qube that user wants to re-configure and need not running for this (for example change its template) but the qube is a target of a frequent qrexec calls

Completion criteria checklist

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

• decide on a specific mechanism, my proposal is disabled "feature" (with a content being free-form reason why it's disabled), but I'm open for other options, including "property" instead of a "feature"
• check for this flag in the start() method and raise an exception if the flag is set (including the user-provided reason in the message)
• add a test

[HW42]

+1 in general.

• decide on a specific mechanism, my proposal is disabled "feature" (with a content being free-form reason why it's disabled), but I'm open for other options, including "property" instead of a "feature"

Using a feature sounds fine (although positive logical naming would be nicer). But I would suggest naming it no-start or similar. disabled is a bit vague (for example should you be able to change properties of a "disabled" qube?), especially if we get some other features in the future that block certain actions on a qube.

[GammaSQ]

Just adding that keeping a qube paused has similar advantages and UI-challenges.

[ddevz]

If this feature is implemented, it would be helpful to also be able to document why the qube shouldn't be started.

I added "notes for qubes" as a seperate, but related feature request

#9770

Note: 9770 was closed as a duplicate of: #899

[alimirjamali]

The PR for Qube Manager is done.

Here are the snapshots:

I will work on the core next