Handle possible zombie processes

[itzg]

Such as introducing https://github.com/krallin/tini as the entry point.

Discussed in Discord

I logged into my docker server and it notified me that I had an orphan process. I was able to trace it down to the mc-backup image. I'm not super familiar with how it does what it's doing but do you have any idea why it seems it left an orphan process? The following (I hope it looks decent) was found with ps -elf --forest | grep -C5 '<[d]efunct>':

0 S root        2741       1  0  80   0 - 308308 -     10:04 ?        00:00:00 /usr/bin/containerd-shim-runc-v2 -namespace moby -id 3b03647950031d6893b14ac345044b113b6c0d39743bf89ff9936f0d71871f29 -address /run/containerd/containerd.sock
4 S root        2765    2741  0  80   0 - 306691 -     10:04 ?        00:00:00  \_ /opt/entrypoint-demoter --match /backups /opt/backup-loop.sh
4 S root        2804    2765  0  80   0 -   879 -      10:04 ?        00:00:00      \_ /bin/bash /opt/backup-loop.sh
0 S root        3527    2804  0  80   0 -  1920 -      10:05 ?        00:00:00      |   \_ sleep 5m
4 Z root        2815    2765  0  80   0 -     0 -      10:04 ?        00:00:00      \_ [cat] <defunct>

Maybe https://github.com/itzg/entrypoint-demoter needs to be enhanced to catch and reap the zombie processes since that's the one calling backup script.

[itzg]

Start by looking here

https://github.com/itzg/entrypoint-demoter/blob/72a8c25413b5fc395cb06223383bd4594fda7c5a/run.go#L63

[itzg]

Further discussion