How to Create a systemd Service File in Linux: Step-by-Step Guide

Systemd is the init system on most modern Linux distributions. A service file (also called a unit file) tells systemd how to start, stop, and manage a process. Creating one is the correct way to run a custom script or application as a managed service with automatic restart, boot integration, and proper logging.

Service files use the .service extension and are plain text files in ini format. Place custom files in /etc/systemd/system/. Files there take priority over package-installed units in /usr/lib/systemd/system/ and survive package upgrades. Never edit files in /usr/lib/systemd/system/ directly — copy them to /etc/systemd/system/ to override.

How to Create and Install a systemd Service File

Create the file:

bashsudo nano /etc/systemd/system/myapp.service

A minimal working service file:

ini[Unit]Description=My Custom ApplicationAfter=network.target[Service]Type=simpleExecStart=/usr/local/bin/myapp.shRestart=on-failureRestartSec=5[Install]WantedBy=multi-user.target

After saving, reload systemd and enable the service:

bashsudo systemctl daemon-reloadsudo systemctl enable --now myapp

Run daemon-reload after every edit to the unit file. Systemd reads the file at reload time, not at start time. Skipping this step is the most common reason why changes have no effect.

Check status and logs:

bashsudo systemctl status myappsudo journalctl -u myapp          # full log historysudo journalctl -fu myapp         # live log stream

Service File Sections: [Unit], [Service], and [Install] Explained

[Unit] contains metadata and dependency declarations:

• Description= — the name shown in systemctl status output
• After= — start this service after the listed units are active; this is ordering only, not a dependency
• Requires= — hard dependency; if the listed unit fails, this service also fails
• Wants= — soft dependency; service still starts even if the listed unit fails

After=network.target means “wait for networking to be ready” but does not make networking a hard requirement. For a hard requirement, combine After= with Requires=.

[Service] defines the process:

• ExecStart= — the command to run; must be an absolute path. Use which binary to find the full path if unsure
• Type= — see the table below
• Restart= and RestartSec= — restart behavior and delay
• User= and Group= — run as a specific user instead of root
• Environment= — set environment variables: Environment="NODE_ENV=production"

[Install] controls enablement:

• WantedBy=multi-user.target — the standard value for services that start on normal multi-user boot

Service Types, Restart Policies, and Non-Root Execution

Type= tells systemd how the process behaves at startup:

Restart= controls when systemd automatically restarts the service:

• on-failure — restart on non-zero exit code, signal, or timeout; most common choice
• always — restart after any exit, including a clean exit code 0
• no — never restart (default)

The default RestartSec= is 100ms. Set it to a higher value like RestartSec=5 to avoid rapid restart loops.

Running as a non-root user. Running services as root is a security risk. Use User= and Group= in [Service] and create a dedicated system account first:

bashsudo useradd -r -s /usr/sbin/nologin myappuser

Add to the service file:

iniUser=myappuserGroup=myappuser

If the service is compromised, the process cannot escalate to root privileges.

Place the file in /etc/systemd/system/, run daemon-reload after every change, and check logs with journalctl -u. Use Type=simple and Restart=on-failure for most custom applications, and always run services under a dedicated non-root user. Leave a comment below if you run into any issues.