>What's the cleanest way to wait on s6-svscan to shut down after issuing of
>a SIGTERM (say s6 via-svscanctl -t)?
Be its parent, and wait for it. :)
On SIGTERM, s6-svscan will not exit until the supervision tree is
entirely down, so that will work.
If you're not the parent, then you'll have to wait for a notification
somehow, but that's easy:
When s6-svscan wants to exit, it doesn't exit right away, but
tries to exec into the .s6-svscan/finish script. So you have a clear
indicator here: when .s6-svscan/finish runs, it means the supervision
tree is down.
So, for instance, make a finish script that writes a byte in a fifo,
and have your jail shutdown script read on that fifo. Something like:
.s6-svscan/finish:
#!/bin/sh
exec echo > /run/blah/fifo
shutdown script:
#!/bin/sh
...
rm -f /run/blah/fifo
mkfifo /run/blah/fifo
read < /run/blah/fifo &
s6-svscanctl -t /run/service
wait
...
(read on the fifo before running s6-svscanctl, to avoid the small
race condition.)
>Looking at the documentation, my only option appears to be to check if the
>return code of s6-svscanctl is 100, or maybe to monitor for the existence
>of .s6-svscan/control (not sure if it's removed on exit). Are there any
>other ways to monitor s6-svscan?
Ew. Don't poll.
Use .s6-svscan/finish to do anything you want to do at s6-svscan
death time.
--
Laurent
Received on Thu Feb 24 2022 - 06:04:02 CET