Running your own program at startup: systemd

If your own program runs on the server — a bot, a job processor, a Node.js or Python website — set it up as a service. It will then start by itself after the server reboots, and come back up by itself if it crashes. The old way, adding a command to /etc/rc.local, doesn’t work by default on current systems.

The service file

Create the file /etc/systemd/system/mybot.service (use any name instead of mybot):

[Unit]
Description=My bot
After=network-online.target
Wants=network-online.target

[Service]
User=bot
WorkingDirectory=/opt/mybot
ExecStart=/usr/bin/python3 /opt/mybot/bot.py
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target

• User — the account the program runs as. It doesn’t usually need root, so create a separate user: sudo useradd -r -s /usr/sbin/nologin bot.
• ExecStart — the start command, with full paths. command -v python3 will tell you where a program is — see Where is a program located.
• Restart=on-failure — restart the program if it exits with an error.
• Don’t write passwords and keys directly in the service file — put them in a separate file with permissions of 600 and include it with the line EnvironmentFile=/etc/mybot.env.

Starting it and checking

sudo systemctl daemon-reload          # re-read the service files
sudo systemctl enable --now mybot     # start it and enable autostart
systemctl status mybot                # is it running?
journalctl -u mybot -f                # what the program is logging (Ctrl+C to exit)

If you change the service file, run daemon-reload again, then sudo systemctl restart mybot.

On FreeBSD

The simplest way is a line in the user’s crontab (crontab -e). The system’s daemon program will restart the program if it crashes:

@reboot /usr/sbin/daemon -r -o /var/log/mybot.log /usr/local/bin/python3 /opt/mybot/bot.py