[Pkg-systemd-maintainers] Bug#741496: Switching between packages providing the same Alias is broken (see syslog.service handling)

[Michael Biebl]

Package: init-system-helpers
Version: 1.18
Severity: important

Both syslog-ng and rsyslog are socket-activated.
/lib/systemd/system/syslog.socket is shipped by systemd itself and the
currently installed (and active) syslog implementation is supposed to
create a symlink like
/etc/systemd/system/syslog.service ->
/lib/systemd/system/rsyslog.service
via
/--------------------
|[Install]
|Alias=syslog.service
\--------------------
in its service file.


If rsyslog is removed, but not purged, i-s-h does *not* remove that symlink.

Consider that rsyslog is installed and active, and you run
"apt-get install syslog-ng". This will cause rsyslog to be uninstalled
(since those packages conflict with each other).
Still, after syslog-ng has been installed, the
/etc/systemd/system/syslog.service symlink still points to
rsyslog.service.

This is obviously broken.

I'm not sure how to address this. We switched i-s-h to not remove symlinks
on "remove" but only on "purge", but I don't remember all the details
anymore, why we did that. Michael, do you remember?

I fear, switching i-s-h back to remove the symlinks on "remove" might
break certain cases again.

In this particular case, I assume i-s-h doesn't update the
/etc/systemd/system/syslog.service symlink, because it already exists.

Any clever idea how to fix this?


Michael
-- System Information:
Debian Release: jessie/sid
  APT prefers unstable
  APT policy: (500, 'unstable'), (200, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 3.13-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=de_DE.utf8, LC_CTYPE=de_DE.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages init-system-helpers depends on:
ii  perl  5.18.2-2+b1

init-system-helpers recommends no packages.

init-system-helpers suggests no packages.

-- no debconf information