systemd-services

Write a unit file in /etc/systemd/system/ with [Service] and [Install] sections, then run systemctl daemon-reload, systemctl enable, and systemctl restart. Set WantedBy=multi-user.target in the [Install] section for boot persistence.

A service without a User= directive runs as root, and git's safe.directory check blocks root from accessing user-owned repos, returning NOT_A_REPO. Fix it by adding User=<repo-owner> to the unit file and restarting the service.

System services live in /etc/systemd/system/, need sudo, and run before login; user services live in ~/.config/systemd/user/ and are managed with systemctl --user without sudo. Use user services for per-login daemons and system services for machine-wide daemons.

The ExecStart line is invoking the wrong interpreter, such as running a bash script through python. Check the script's shebang and match ExecStart to it, for example ExecStart=/bin/bash /opt/app/start.sh.

Use journalctl -u <service> -f to follow logs, journalctl -u <service> --since "10 min ago" for recent output, and systemctl status <service> for state plus recent log lines. Look for NOT_A_REPO, ModuleNotFoundError, or exit-code failures.

Lock files must live outside the watched directory, such as in /tmp, because lock file create and delete events inside the watched tree retrigger the watcher and cause event cascades. Use flock for kernel-level locking that auto-releases on exit.