Here's the log file after the docker restart:
*** Running /etc/my_init.d/10_syslog-ng.init...
Oct 25 09:48:25 b4110ea3034a syslog-ng[13]: syslog-ng starting up; version='3.13.2'
*** Running /etc/my_init.d/firstrun.sh...
Using existing PHP database config file.
warning: commands will be executed using /bin/sh
job 3 at Thu Oct 25 09:49:00 2018
ln: failed to create symbolic link '/opt/observium/config.php': File exists
*** Booting runit daemon...
*** Runit started as PID 29
Oct 25 09:48:26 b4110ea3034a cron[34]: (CRON) INFO (pidfile fd = 3)
Oct 25 09:48:26 b4110ea3034a cron[34]: (CRON) INFO (Skipping @reboot jobs -- not system startup)
Database exists.
Starting MariaDB...
181025 09:48:26 mysqld_safe Logging to '/config/databases/b4110ea3034a.err'.
181025 09:48:26 mysqld_safe Starting mysqld daemon with databases from /config/databases
Oct 25 09:50:01 b4110ea3034a CRON[324]: (root) CMD ( /opt/observium/discovery.php -h new >> /dev/null 2>&1)
Oct 25 09:50:01 b4110ea3034a CRON[325]: (root) CMD ( /opt/observium/poller-wrapper.py 2 >> /dev/null 2>&1)