Understanding how to run your daemon as a managed Linux service is crucial for reliability, automation, and integration with the operating system. On modern Linux systems, systemd is the standard service manager that controls how daemons are started, stopped, restarted, and monitored. To make your daemon a first, class service, you need to write a systemd unit file, a configuration file that tells systemd exactly how to launch and manage your process. Unit files are simple text files with a specific structure and a set of directives that control service behavior.

Each section and directive in the unit file controls a specific aspect of how systemd manages your daemon. The [Unit] section provides metadata and dependencies; Description gives a human-readable name, while After=network.target ensures your daemon starts only after the network is available. The [Service] section is where you define how to run your daemon. Type=simple is the most common type for custom daemons—it tells systemd to consider the service started as soon as the process launches. ExecStart specifies the exact command to run your daemon, including any arguments or configuration files. Restart=on-failure makes systemd automatically restart your daemon if it crashes, and RestartSec=5 sets a delay before restarting. The Environment directive lets you set environment variables for your daemon process, which is useful for passing configuration or operational modes. User and Group ensure your daemon runs with restricted privileges, improving security. The [Install] section tells systemd when this service should be started automatically; WantedBy=multi-user.target means it will launch during normal system startup in multi-user mode.