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Imported from https://www.github.com/BytemarkHosting/symbiosis/issues/129

The symbiosis-monit script will return an exit code of 75 for a few reasons: if it's been disabled, if the machine is still booting, if the load is higher than the number of CPU cores, or if dpkg is running:

root@jessie:~# grep -c processor /proc/cpuinfo     

root@jessie:~# cat /proc/loadavg
4.00 4.00 3.87 5/130 5696
root@jessie:~# /usr/sbin/symbiosis-monit -t email /etc/symbiosis/monit.d -a
root@jessie:~# echo $?
75

In Symbiosis Stretch, this will be printed to syslog:

upgrade2 systemd[1]: symbiosis-monit.service: Main process exited, code=exited, status=75/n/a

upgrade2 systemd[1]: symbiosis-monit.service: Unit entered failed state.

upgrade2 systemd[1]: symbiosis-monit.service: Failed with result 'exit-code'.

And also as an email:

Subject: Symbiosis monitor detected service failure
root : TTY=unknown ; PWD=/ ; USER=nobody ; COMMAND=/usr/bin/tee /var/tmp/symbiosis-monit.cursor
pam_unix(sudo:session): session opened for user nobody by (uid=0)
Started Symbiosis monitor.
symbiosis-monit.service: Main process exited, code=exited, status=75/n/a
symbiosis-monit.service: Unit entered failed state.
symbiosis-monit.service: Triggering OnFailure= dependencies.
symbiosis-monit.service: Failed with result 'exit-code'.

Server load will frequently rise above the number of CPU cores on busy servers, generating a large amount of emails. Printing to syslog is useful if there are problems with the symbiosis-monit service itself, but we should probably only send a failure email when an individual test has failed (e.g. apache2), rather than the entire service.