popa3d has no option to write a PID file in standalone mode

[andy-bower]

There should be an option (or possibly standard behaviour) for the standalone mode to write to a PID file such as /run/popa3d.pid when the forked daemon has successfully started to avoid race conditions in initscripts.

Thanks!

[andy-bower]

Alternatively, add an option which does standalone mode but in the foreground without daemonizing, so that we can do something like start-stop-daemon --background --make-pidfile --pidfile /run/popda3d.pid. This would also be helpful for other init systems like runit.

[solardiz]

It feels a bit weird to update popa3d after so many years of it staying as-is, but maybe.

I agree a PID file could be useful. However, for start-stop-daemon in particular I think we did fine in Owl by using that program's --exec and --user options (when starting and stopping the service, as well as when querying its status), so it'd insist on only looking at processes from the right binary executable and running as the intended user (in this case as root). In Owl, this magic happened in the RH-compatible bash functions that I wrote, see:

https://github.com/openwall/Owl/blob/main/packages/popa3d/popa3d.init
https://github.com/openwall/Owl/blob/main/packages/owl-startup/functions

I agree "an option which does standalone mode but in the foreground without daemonizing" would also be useful, such as to let systemd manage the service more directly. In fact, not that long ago I reused this code from popa3d for LKRG logger, and reverted the meaning of -D there to be consistent with its meaning in sshd. I regret that popa3d's is different, but I thought that popa3d is mostly legacy now, whereas people will have sshd on current systems where they installed lkrg-logger, so consistency between these two was more important. See:

https://github.com/lkrg-org/lkrg/tree/main/logger

In popa3d, we'd actually need tri-state: inetd mode, daemon in background, and daemon in foreground. I am undecided yet on how to present this via command-line option choice best, especially given the already existing discrepancy of -D vs. its use in sshd.