Setting Up a New Service in SystemD on CentOS 7

I have a custom service that I need to start on reboot on a CentOS system running systemd.  Following the guidelines posted here, I was able to do it myself in my environment.

1. Create the following file: /etc/systemd/system/tcp-server.service
2. Put the following contents in the file:
3. [Unit]
Description=tcp-server for hhreplay Service
After=network.target
[Service]
Type=simple
User=root
Environment="OPTIONS=--logfile /tmp/tcp-server.log"
ExecStart=/home/jenkins/tcp-server.py $OPTIONS
Restart=on-abort[Install]
WantedBy=multi-user.target
4. Chown your log file: chown root:root /tmp/tcp-server.log
5. Reload systemd: sudo systemctl daemon-reload
6. Start your service to ensure it’s a functional service file: systemctl start tcp-server
7. Check status: systemctl status tcp-server
8. If it looks good, then set it to start at boot: systemctl enable tcp-server --now

MAN PAGE

In-depth information can be found in the systemd.service man page.  Read up on options such as Type, RemainAfterExit, ExecStart, WantedBy, ExecStop , Environment, etc.

Special Considerations

1. In some distributions you are required to have a ExecStart in your service file.  This can be set to /bin/true if you don’t explicitly need something there.
2. RemainAfterExit=true can be added to trick systemd into believing that the service is running.  This is helpful when you don’t have a ExecStart and still need a ExecStop to run after the service, or another service, shutsdown.
3. DefaultDependencies=no means ignore all dependencies and run “first” on start and “last” on stop.  If you have Before or After clauses, they will still be honored.

Additional References

0pointer.net – SystemD for Administrators Part XXI
freedesktop.org – systemd System and Service Manager