Bug#746577: closed by Michael Biebl <biebl at debian.org> (Re: Bug#746577: systemd-sysv: for upgrade safety, systemd-sysv and sysvinit-core must be coinstallable)

[Michael Stapelberg]

Hi Zack,

Fundamentally we agree with you of course. The devil is in the detail,
though: sysvinit-core and systemd are coinstallable, for all the reasons
you explained.

However, you seem to be using a package which depends on libpam-systemd,
which, translated to English, means the package is using some
functionality that can only be provided when logind is running. To
ensure that logind is running, we had to make libpam-systemd depend on
“systemd-sysv | systemd-shim”. It had to be systemd-sysv to not just
ensure systemd is _present_, but to ensure it is _running_. If we don’t
add this dependency, the package in question is broken, which may well
be the bigger deal to most users than being able to roll back and forth
between init systems :).

So, if you want to keep systemd as an option and use/fall back to
sysvinit, just install systemd-shim and sysvinit-core. If that’s not
okay with you, figure out which package it is that depends on
libpam-systemd and uninstall that. I’m afraid we don’t have any other
options than that (AFAICT).

-- 
Best regards,
Michael