Snapd needs user-level hooks

[Kyle Fazzari]

Snapd currently contains a number of hooks that are run during installation/refresh, such as the install hook, configure hook, and {pre,post}-refresh hooks. If any of these hooks return non-zero during a refresh, snapd rolls the update back (or aborts the initial install), which is nice, and makes these hooks a good place to run a health check of some kind to ensure the update works. However, doing that only works if what one needs to health check is some sort of headless system service. It doesn't work well for user applications (e.g. skype, slack) because the hooks run as root. It also means hooks can never do anything meaningful in $SNAP_USER_{COMMON,DATA}.

[Evan (ev)]

If it's just about needing an X server, I wonder if we could come up with an interim example that users root-level hooks with xvfb-run.

[Evan (ev)]

The Snapcraft team and I spoke about this more and pulling in xvfb-run would also pull in the X stack, which is too much.

[Zygmunt Krynicki (zyga)]

I think health checks need more work in general and should be tailored to behave better for desktop applications. I don't know if we should solve it with user-level hooks though (exact semantics is unclear to me).