[Bug 717397] Re: package squid 2.7.STABLE7-1ubuntu12.1 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1

[Clint Byrum]

The branch lp:~clint-fewbar/ubuntu/lucid/fix-upgrades-after-reload fixes
the problem by checking to see if the problem the recent update is
trying to correct has actually happened, and if so, doing a stop/start
on the service using invoke-rc.d Between the stop/start, it also kills
the errant pid (but only if invoke-rc.d worked, so policy is still
respected).

I test this on a lucid vm in the following scenarios:

* bare bones no updates with just 'apt-get install squid' version 2.7.STABLE7-1ubuntu12
 - When preinst is run, the upstart pid and the pidfile agree, and so it exits doing nothing.

* same, but also running 'sudo reload squid', verifying that squid is not tracked by upstart anymore with 'status squid' showing stop/waiting, but 'ps auxw | grep squid' showing a running squid.
 - the job is stopped, the old squid is killed, squid is started again

* start squid, reload, kill -9, leaving stale pid file.
 - Code stops because /proc/`cat pidfile` does not exist.

* modify /etc/init/squid.conf to not use expect fork, and pass -N (basically manually putting in the new job file). This simulates the chance that a user may have applied the fix manually.
 - Code stops because the upstart pid matches the pidfile.

* stopped service before hand
 - pidfile is gone, code is not run

* removed upstart file
 - code checks for that, does not run.

Since creating the merge proposal I also tried testing it with a
/usr/sbin/policy-rc.d that exitted with 102, the appropriate way to
disable a service's stop/starting, and the code was skipped. When the
policy-rc.d returned 0, the code worked as intended (invoke-rc.d's
behavior was basically unchanged).

** Also affects: squid-deb-proxy (Ubuntu)
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/717397

Title:
  package squid 2.7.STABLE7-1ubuntu12.1 failed to install/upgrade:
  subprocess installed post-installation script returned error exit
  status 1