Bug#930105: systemd: prerm fail breaks apt and renders system hard to recover

[Michael Biebl]

Control: severity -1 normal

Am 07.06.19 um 00:55 schrieb Adam Borowski:
> Source: systemd
> Version: 241-5
> Severity: critical
> Justification: breaks the whole system
> 
> 
> When trying to switch to any other init system (and d-i offers no way to
> start with anything but systemd), prerm refuses to uninstall _in the middle
> of the apt run_.  This leaves the system in a broken state, with a good part
> of tools refusing to start (including apt itself), and for obvious reasons
> unbootable.  Anyone without a good knowledge of dpkg's internals would be
> unable to recover the system at all.  To even attempt recovery, one has to
> rm -rf /run/systemd or otherwise neuter the prerm script.
> 
> Thus, what's even the point of this prerm check?  The way dependencies
> between systemd components are written, getting apt to even attempt removing
> systemd requires a pretty deliberate action.  If, unlike other init systems,
> systemd can't cleanly shut down, it's a problem but for any remotely
> adequate modern piece of software not a fatal one: any filesystem from this
> millenium won't corrupt data on an unexpected power loss, any database
> worth its salt won't corrupt data without intentionally defeating fsync, and
> so on.   Ie, without the prerm check you may need a SysRq-B or power cycle,
> with it you currently end with up with system that can't even run apt.

The prerm check is there for a reason (to be able to cleanly shutdown)
and switch over.
Once that is done, you can opt to remove the systemd package if you so
desire.


-- 
Why is it that all of the instruments seeking intelligent life in the
universe are pointed away from Earth?

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