systemctl - service exit codes and status information explanation

Question

When checking a service status via systemctl

systemctl status docker

the output is something like

● docker.service - Docker Application Container Engine
  Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
  Active: inactive (dead) (Result: exit-code) since Mon 2018-03-19 13:52:21 CST; 4min 32s ago
  Docs: https://docs.docker.com
  Process: 6001 ExecStart=/usr/bin/dockerd -H fd:// (code=exited, status=205/LIMITS)
  Main PID: 6001 (code=exited, status=205/LIMITS)

The question is about the part in bold: the main process exit code and status information.
Is there a list of all the codes and statuses along with their explanation ?

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^{I know that most times it's self-explanatory (and I know the answer to the question here) but lately we get this question a lot at work (some people search via google but can't find it, other people open the systemd.service man page, search for e.g. code 203 and don't find it...) so I thought I might as well put it here so it's easier for people to find the answer via google.}

Answer 1

Yes, but only since 2017 when Jan Synacek finally documented them in the systemd manual. Your work colleagues are simply reading the wrong page of the manual. ☺

Further reading

• Lennart Poettering (2017). "Process exit codes: systemd-specific exit codes". systemd.exec. systemd manual pages. Freedesktop.org.
• Jan Synacek (2016-06-15) Document service status codes. systemd bug #3545. GitHub.

Answer 2

Here is the list of status codes for systemctl

https://www.freedesktop.org/software/systemd/man/systemctl.html#Exit%20status