[systemd-devel] SysVInit service migration to systemd

[Cristian Rodríguez]

On Mon, Jun 29, 2015 at 10:58 AM, Lesley Kimmel <ljkimmel99 at hotmail.com> wrote:
> Jonathan;
>
> Thanks for the background and information. Since you clearly seem to have a
> grasp of systemd please humour me with a few more questions (some of them
> slightly ignorant):
>
> a) Why are PID bad?

Because they pretend to work but they really don't.
This is because only a tiny portion of software implements pid file
creation correctly,
this is in part due to the lack of a FREEBSD-like pidfile_*()
interface that at least tries to be correct.

> b) Why are lock files bad?

Mostly because at least till the *very recent* advent of File-private
POSIX locks (un-POSIX locks)
the OS facilities were terrible.

> c) If a/b are so bad why did they persist for so many years in SysVInit?

Because sysvinit is unable to track processes, in that case you need
at least to know what is the PID of the deamon, in order to be able to
kill it: