Run Bun as a daemon with systemd

systemd is an init system and service manager for Linux. It manages the startup and control of system processes and services.

To run a Bun application as a daemon with systemd, create a service file in /etc/systemd/system/.

cd /etc/systemd/system
touch my-app.service

Here is a typical service file that runs an application on system start. Use it as a template for your own service. Replace YOUR_USER with the name of the user to run the application as. To run as root, replace YOUR_USER with root and /home/YOUR_USER with /root (root's home directory). For security reasons, we don't recommend running as root.

Refer to the systemd documentation for details on each setting.

[Unit]
# describe the app
Description=My App
# start the app after the network management stack has started
# (this does not wait for the network to be up, see https://systemd.io/NETWORK_ONLINE)
After=network.target

[Service]
# usually you'll use 'simple'
# one of https://www.freedesktop.org/software/systemd/man/systemd.service.html#Type=
Type=simple
# which user to use when starting the app
User=YOUR_USER
# path to your application's root directory
WorkingDirectory=/home/YOUR_USER/path/to/my-app
# the command to start the app
# requires absolute paths
ExecStart=/home/YOUR_USER/.bun/bin/bun run index.ts
# restart policy
# one of {no|on-success|on-failure|on-abnormal|on-watchdog|on-abort|always}
Restart=always

[Install]
# start the app automatically
WantedBy=multi-user.target

If your application starts a webserver, non-root users cannot listen on ports 80 or 443 by default. To allow Bun to listen on these ports when run by a non-root user, use the following command. The command requires sudo permissions. This step isn't necessary when running as root.

setcap CAP_NET_BIND_SERVICE=+eip /home/YOUR_USER/.bun/bin/bun

The command attaches the capability to the bun binary itself. Replacing the binary, for example with bun upgrade, removes the capability. Re-run the command after upgrading. Alternatively, add AmbientCapabilities=CAP_NET_BIND_SERVICE to the [Service] section of the service file instead.

With the service file configured, enable the service. Once enabled, it starts automatically on reboot. Enabling the service requires sudo permissions.

systemctl enable my-app

To start the service without rebooting, start it manually.

systemctl start my-app

Check the status of your application with systemctl status. If the app started successfully, the output looks like this:

systemctl status my-app

● my-app.service - My App
     Loaded: loaded (/etc/systemd/system/my-app.service; enabled; preset: enabled)
     Active: active (running) since Thu 2023-10-12 11:34:08 UTC; 1h 8min ago
   Main PID: 309641 (bun)
      Tasks: 3 (limit: 503)
     Memory: 40.9M
        CPU: 1.093s
     CGroup: /system.slice/my-app.service
             └─309641 /home/YOUR_USER/.bun/bin/bun run index.ts

To update the service, edit the service file, then reload the daemon.

systemctl daemon-reload

For a complete guide to service unit configuration, see the systemd.service documentation. Or use this cheatsheet of common commands:

systemctl daemon-reload # tell systemd that some files got changed
systemctl enable my-app # enable the app (to allow auto-start)
systemctl disable my-app # disable the app (turns off auto-start)
systemctl start my-app # start the app if is stopped
systemctl stop my-app # stop the app
systemctl restart my-app # restart the app