Make rsyslog container aware remove pidfile on start
- 08 Apr 2018: Post was created (diff)
There was a commit to rsyslogd that made the rsyslog daemon container-aware by checking if it was running as PID 1. If so, it will avoid writing a pidfile to disk. This is very handy when using it in a container environment where you might have a lot of container restarts or recreations, and you don’t want the daemon to check if a pidfile exists, because when it does, rsyslogd will refuse to start.
I am using Debian Stretch in my Docker image, but a version of rsyslog including this commit does not exists in the Debian apt repositories.
A work-around is to delete the pidfile manually whenever a container starts up by using a custom
ENTRYPOINT, which is what I ended up with. In which case, here’s a file to include in your custom rsyslog image
#!/bin/sh # Clear the pid file from old runs. It doesn't restart otherwise. # NOTE: This won't be necessary after upgrading to version 8.34.0 of rsyslogd rm /var/run/rsyslogd.pid # Run command after configuration exec $@
Then reference this file in the
# Use stretch-backports to get rsyslog version with mongodb uristr option FROM debian:stretch-backports RUN apt update && apt -t stretch-backports install -y \ rsyslog \ rsyslog-relp \ rsyslog-mongodb # This must be updated if more protocols are added EXPOSE 514/tcp # rsyslogd will die on QUIT, TERM or INT (man rsyslogd) STOPSIGNAL SIGTERM COPY rsyslog.conf /etc/rsyslog.conf COPY bin/configure.sh /usr/bin ENTRYPOINT ["configure.sh"] # This will enable debug output toggling with SIGUSR1 (requires -d) #ENV RSYSLOG_DEBUG=DebugOnDemand # -n : Avoid auto-backgrounding # -d : Enable debug mode CMD ["rsyslogd", "-n", "-d"]
An alternative to this is to build your own image of rsyslog from source, but I didn’t want to do that.