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[update] Use systemd to Start a Linux Service at Boot #7221

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[update] Use systemd to Start a Linux Service at Boot
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162 changes: 93 additions & 69 deletions docs/guides/quick-answers/linux/start-service-at-boot/index.md
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@ description: The systemd daemon allows you to control Linux system services. Thi
authors: ["Linode"]
contributors: ["Linode"]
published: 2018-05-01
modified: 2025-03-27
keywords: ["systemd","service","enable service","Linux system service"]
license: '[CC BY-ND 4.0](https://creativecommons.org/licenses/by-nd/4.0)'
external_resources:
Expand All @@ -25,118 +26,141 @@ It is simple to create a custom systemd service that will run any script or proc

1. Create a script or executable that the service will manage. This guide uses a simple Bash script as an example:

{{< file "test_service.sh" bash >}}
DATE=`date '+%Y-%m-%d %H:%M:%S'`
echo "Example service started at ${DATE}" | systemd-cat -p info
```file {title="test_service.sh" lang="bash"}
DATE=`date '+%Y-%m-%d %H:%M:%S'`
echo "Example service started at ${DATE}" | systemd-cat -p info

while :
do
echo "Looping...";
sleep 30;
done
{{< /file >}}
while :
do
echo "Looping...";
sleep 30;
done
```

This script will log the time at which it is initialized, then loop infinitely to keep the service running.

2. Copy the script to `/usr/bin` and make it executable:

sudo cp test_service.sh /usr/bin/test_service.sh
sudo chmod +x /usr/bin/test_service.sh
```command
sudo cp test_service.sh /usr/bin/test_service.sh
sudo chmod +x /usr/bin/test_service.sh
```

3. Create a **Unit file** to define a systemd service:
3. Create a **Unit file** to define a systemd service in your application, where `/opt/myapp/` is the path to your application directory.

{{< file "/lib/systemd/system/myservice.service" conf >}}
[Unit]
Description=Example systemd service.
```file {title="/opt/myapp/myservice.service"}
[Unit]
Description=Example systemd service.

[Service]
Type=simple
ExecStart=/bin/bash /usr/bin/test_service.sh
[Service]
Type=simple
ExecStart=/bin/bash /usr/bin/test_service.sh

[Install]
WantedBy=multi-user.target
{{< /file >}}
[Install]
WantedBy=multi-user.target
```

This defines a simple service. The critical part is the `ExecStart` directive, which specifies the command that will be run to start the service.
* This defines a simple service that runs `/usr/bin/test_service.sh` through Bash.
* The `ExecStart` directive specifies the command to run.
* The `[Install]` section allows the service to be enabled at boot.

4. Copy the unit file to `/etc/systemd/system` and give it permissions:
4. Link the unit file from your application directory. This approach can streamline deployments by keeping the service definition with your codebase:

sudo cp myservice.service /etc/systemd/system/myservice.service
sudo chmod 644 /etc/systemd/system/myservice.service
```command
sudo systemctl enable /opt/myapp/myservice.service
```

If the `[Install]` section is present, this creates the necessary symlinks in `/etc/systemd/system/`.

Alternatively, copy the unit file to `/etc/systemd/system/`, and adjust the permissions:

```command
sudo cp myservice.service /etc/systemd/system/myservice.service
sudo chmod 644 /etc/systemd/system/myservice.service
```

For more information about the unit file and its available configuration options, see the [systemd documentation](https://www.freedesktop.org/wiki/Software/systemd/).

## Start and Enable the Service

1. Once you have a unit file, you are ready to test the service:

sudo systemctl start myservice

```command
sudo systemctl start myservice
```

2. Check the status of the service:

sudo systemctl status myservice
```command
sudo systemctl status myservice
```

If the service is running correctly, the output should resemble the following:

{{< output >}}
● myservice.service - Example systemd service.
Loaded: loaded (/lib/systemd/system/myservice.service; enabled; vendor preset: enabled)
Active: active (running) since Tue 2018-05-01 18:17:14 UTC; 4s ago
Main PID: 16266 (bash)
Tasks: 2
Memory: 748.0K
CPU: 4ms
CGroup: /system.slice/myservice.service
├─16266 /bin/bash /usr/bin/test_service.sh
└─16270 sleep 30

May 01 18:17:14 localhost systemd[1]: Started Example systemd service..
May 01 18:17:14 localhost cat[16269]: Example service started at 2018-05-01 18:17:14
May 01 18:17:14 localhost bash[16266]: Looping...
{{< /output >}}
```output
● myservice.service - Example systemd service.
Loaded: loaded (/lib/systemd/system/myservice.service; enabled; vendor preset: enabled)
Active: active (running) since Tue 2018-05-01 18:17:14 UTC; 4s ago
Main PID: 16266 (bash)
Tasks: 2
Memory: 748.0K
CPU: 4ms
CGroup: /system.slice/myservice.service
├─16266 /bin/bash /usr/bin/test_service.sh
└─16270 sleep 30

May 01 18:17:14 localhost systemd[1]: Started Example systemd service..
May 01 18:17:14 localhost cat[16269]: Example service started at 2018-05-01 18:17:14
May 01 18:17:14 localhost bash[16266]: Looping...
```

3. The service can be stopped or restarted using standard systemd commands:

sudo systemctl stop myservice
sudo systemctl restart myservice
```command
sudo systemctl stop myservice
sudo systemctl restart myservice
```

4. Finally, use the `enable` command to ensure that the service starts whenever the system boots:

sudo systemctl enable myservice
```command
sudo systemctl enable myservice
```

{{< output >}}
Created symlink from /etc/systemd/system/multi-user.target.wants/myservice.service to /lib/systemd/system/myservice.service.
{{< /output >}}
```output
Created symlink from /etc/systemd/system/multi-user.target.wants/myservice.service to /lib/systemd/system/myservice.service.
```

5. Reboot your Linode from the Linode Manager and check the status of the service:

sudo systemctl status myservice
```command
sudo systemctl status myservice
```

You should see that the service logged its start time immediately after booting:

{{< output >}}
● myservice.service - Example systemd service.
Loaded: loaded (/usr/lib/systemd/system/myservice.service; enabled; vendor preset: disabled)
Active: active (running) since Wed 2018-05-02 15:03:07 UTC; 48s ago
Main PID: 2973 (bash)
CGroup: /system.slice/myservice.service
├─2973 /bin/bash /usr/bin/test_service.sh
└─3371 sleep 30

May 02 15:03:07 localhost systemd[1]: Started Example systemd service..
May 02 15:03:07 localhost systemd[1]: Starting Example systemd service....
May 02 15:03:07 localhost bash[2973]: Looping...
May 02 15:03:37 localhost bash[2973]: Looping...
{{< /output >}}
```output
● myservice.service - Example systemd service.
Loaded: loaded (/usr/lib/systemd/system/myservice.service; enabled; vendor preset: disabled)
Active: active (running) since Wed 2018-05-02 15:03:07 UTC; 48s ago
Main PID: 2973 (bash)
CGroup: /system.slice/myservice.service
├─2973 /bin/bash /usr/bin/test_service.sh
└─3371 sleep 30

For more information about using `systemctl` commands, see the [systemctl guide](/docs/guides/introduction-to-systemctl).
May 02 15:03:07 localhost systemd[1]: Started Example systemd service..
May 02 15:03:07 localhost systemd[1]: Starting Example systemd service....
May 02 15:03:07 localhost bash[2973]: Looping...
May 02 15:03:37 localhost bash[2973]: Looping...
```

For more information about using `systemctl` commands, see the [systemctl guide](/docs/guides/introduction-to-systemctl).

## Troubleshooting

- "Example service started at ..." line does not appear in the output of the status command. The `systemd-cat` output is not reliable because of a race condition. As a workaround update the `test_service.sh` file as follows:
{{< file "test_service.sh" bash >}}
If the `Example service started at ...` line does not appear in the output of the status command, the `systemd-cat` output may not be reliable because of a race condition. As a workaround, you can update the `test_service.sh` file as follows:

```file {title="test_service.sh" lang="bash"}
info=/tmp/myservice-systemd-cat-pipe-info
mkfifo "$info"
trap "exec 3>&-; rm $info" EXIT
Expand All @@ -151,4 +175,4 @@ do
echo "Looping...";
sleep 30;
done
{{< /file >}}
```