I’m a little confused by mixing service-startup hook concept with install/remove hooks. It’s seems we’re interested in install/remove hooks after all, as described in the bug 1661126 linked by @kyrofa.
If this is correct and we’re looking for install/remove hooks, then these hooks would be similiar to configure hook, with exceptions of course. My proposal:
-
install hook gets executed when snap is installed, refreshed or reverted. It’s run before configure hook.
- If it’s desirable to distinguish between install and revert/refresh (upgrade), then refresh and revert may have separate hooks (or we may pass extra environment variables to indicate this fact to install).
-
uninstall hook is only executed when last revision of snap is removed from the system.
- Both
install and uninstall would be run in transactions when it comes to configuration changes made via snapctl (similiar to configure).
- Failure in
install hook would abort the install, undo the tasks internally etc. However, I’m not sure if we should have an undo-install hook for failure on install during refresh. Perhaps if this was a refresh/revert, we should just run install hook of the previous revision?
- Failure in
uninstall hook would log a warning, but would not abort snap removal.
I think that implementation of the suggestion regarding running install/uninstall hooks per-user (suggested in the comments of aforementioned bug report) is out of scope for now as this is a bigger shift in snapd.
