Re: Update early logger logging path after remounting root as rw

From: Laurent Bercot <>
Date: Sat, 05 Sep 2020 19:45:57 +0000

>I'm configuring my linux to use s6-rc. It works fairly well so far. One
>thing I want to improve though, is that the early logger logs to
>/run/uncaught-logs. It's nice to have a log file during early boot and it
>helped my debugging easier. But it would be cool to able to change the
>location to a permanent location like /var/log after the root has been
>remounted as read-write.

  Well the catch-all logger is supposed to be just that: a catch-all
logger. That means that ideally, every service should have its own
dedicated logger, typically writing to /var/log/something, and the
catch-all logger is only used for exceptional stuff such as error
messages from the supervision tree, so it doesn't matter that its logs
are stored under /run.

>Is it possible to update the log path of early/catch-all s6-log process to
>a new location, and perhaps copying the early logs there as well? Or if
>not, is it possible to spawn a new s6-log process that acts as a catch-all

  It's difficult to do. It's possible in theory: you could have a oneshot
that modifies /run/service/s6-svscan-log/run, replacing the
"/run/uncaught-logs" string with the new location you want, then
copies /run/uncaught-logs into that new location and restarting the
s6-svscan-log service. But in practice you would add complexity to the
log infrastructure, and you need to pay close attention to all the
failure cases because you don't want to have a broken catch-all logger
for any reason at all. I don't think the benefits are worth the
additional effort; but feel free to disagree and write such a "log
mover" service.

>BTW, is there a command to restart service managed by s6-rc? I've been
>using "s6-rc -v2 -d change sv && s6-rc -v2 -u change sv" but I feel there
>might be something simpler.

  For oneshots, no - but you rarely want to "restart" oneshots.
  For longruns, unless you want to also restart everything that depends
on the service, you can just bypass the s6-rc layer and directly tell s6
to restart your process: s6-svc -r /run/service/$sv

  Hope this helps,

Received on Sat Sep 05 2020 - 19:45:57 UTC

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