Common Commands#

List all service units that are configured to start automatically at boot.

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systemctl list-unit-files --type=service --state=enabled

List all currently running services.

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systemctl list-units --type=service --state=running

Check whether a service is enabled at boot and whether it is currently running.

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systemctl is-enabled nginx.service
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systemctl is-active nginx.service

Start, stop, restart, enable, and check the status of a service.

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systemctl start nginx
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systemctl stop nginx
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systemctl restart nginx
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systemctl enable nginx
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systemctl status nginx

Create a Custom Spring Boot Service#

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cat <<'EOF' >/etc/systemd/system/hello.service
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[Unit]
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Description=Spring Boot HelloWorld
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After=syslog.target
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After=network.target
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[Service]
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User=username
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Type=simple
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ExecStart=/usr/bin/java -jar /root/hello.jar
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Restart=always
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StandardOutput=syslog
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StandardError=syslog
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SyslogIdentifier=helloworld
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[Install]
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WantedBy=multi-user.target
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EOF

Default Locations of systemd Unit Files#

(See man systemd.unit for more details.)

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Table 1. Load path when running in system mode (--system).
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┌────────────────────┬─────────────────────────────┐
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│ Path               │ Description                 │
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├────────────────────┼─────────────────────────────┤
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│ /etc/systemd/system│ Local configuration         │
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├────────────────────┼─────────────────────────────┤
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│ /run/systemd/system│ Runtime units               │
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├────────────────────┼─────────────────────────────┤
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│ /lib/systemd/system│ Units of installed packages │
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└────────────────────┴─────────────────────────────┘

NOTE

• /etc/systemd/system contains locally created or customized unit files.
• /lib/systemd/system (or /usr/lib/systemd/system on many modern distributions) contains unit files installed by software packages.
• /run/systemd/system is used for runtime-generated or temporary unit files.

Reload systemd After Modifying a Unit#

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systemctl daemon-reload

Whenever you create or modify a unit file, you should reload the systemd manager.

Reloading the configuration does not restart the service automatically, so you will usually need to run:

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systemctl restart hello.service

Verify the Syntax of a Unit File#

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systemd-analyze verify /etc/systemd/system/hello.service

List Failed Units#

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systemctl --failed

List only failed services.

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systemctl --failed --type=service

View Service Logs#

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journalctl -u hello.service
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journalctl -u hello.service -b
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journalctl -u hello.service -f
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journalctl -u hello.service --since "30 minutes ago"

Clear the Failed State#

If a service still shows as failed after fixing the issue:

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systemctl reset-failed hello.service

Then start the service again:

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systemctl start hello.service

Use Drop-in Overrides Instead of Editing Package Files#

Avoid modifying package-managed unit files directly, such as:

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/lib/systemd/system/nginx.service

Your changes may be overwritten during package upgrades.

Instead, create a drop-in override:

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systemctl edit nginx.service

Example:

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[Service]
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Restart=on-failure
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RestartSec=5s

View the merged configuration:

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systemctl cat nginx.service

Remove all local overrides and restore the original configuration:

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systemctl revert nginx.service

Find Which Package Installed a Unit File#

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dpkg-query -S /lib/systemd/system/* | sort -u

Example output:

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dpkg-query: no path found matching pattern /lib/systemd/system/ecs_mq.service
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dpkg-query: no path found matching pattern /lib/systemd/system/SplunkForwarder.service
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dpkg-query: no path found matching pattern /lib/systemd/system/system-systemd\x2dcryptsetup.slice
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accountsservice: /lib/systemd/system/accounts-daemon.service
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apparmor: /lib/systemd/system/apparmor.service
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apt: /lib/systemd/system/apt-daily.service
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apt: /lib/systemd/system/apt-daily.timer
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apt: /lib/systemd/system/apt-daily-upgrade.service
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apt: /lib/systemd/system/apt-daily-upgrade.timer
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at: /lib/systemd/system/atd.service
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auditd: /lib/systemd/system/auditd.service
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base-files: /lib/systemd/system/motd-news.service
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base-files: /lib/systemd/system/motd-news.timer

NOTE

If dpkg-query cannot find a matching package, it simply means that no package recorded ownership of that path in the dpkg database. The unit file may have been created manually, installed by a third-party installer, generated by a package installation script, or generated dynamically by a systemd generator. Installing a package manually with dpkg -i does not normally prevent dpkg-query -S from identifying files that belong to that package.