How to automatically execute shell script at startup boot on systemd Linux

Automating tasks to run during system startup is essential in many server environments. This guide covers setting up a systemd service unit to execute a custom shell script at boot time for tasks such as starting services, checking disk space, or creating backups.

In this tutorial you will learn:

• How to create a systemd service unit
• How to write a shell script for checking disk space
• How to configure and enable the systemd service to run at boot time

Systemd Service Unit

1. Create the Systemd Service File: Start by creating the systemd service unit file. Store the service file as /etc/systemd/system/disk-space-check.service.

   [Unit]
   Description=Check Disk Space on /home directory at Startup
   After=mysql.service
   
   [Service]
   ExecStart=/usr/local/bin/disk-space-check.sh
   
   [Install]
   WantedBy=default.target
   

   This script sets up a service that will execute after the MySQL service has started, running a script to check disk space.

2. Write the Shell Script: Write the shell script that the systemd service will execute. Store the scrip as /usr/local/bin/disk-space-check.sh.

   #!/bin/bash
   echo "Checking disk space on /home directory:"
   date > /root/disk_space_report.txt
   du -sh /home/ >> /root/disk_space_report.txt

   This script writes the current date to a file and appends the disk space usage of the /home directory to it.

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3. Set Permissions and Enable Service: Set the necessary permissions and enable the systemd service to run at boot.

   $ sudo chmod 744 /usr/local/bin/disk-space-check.sh
   $ sudo chmod 664 /etc/systemd/system/disk-space-check.service
   $ sudo systemctl daemon-reload
   $ sudo systemctl enable disk-space-check.service
   

   These commands make the script executable, set appropriate permissions for the service file, reload the systemd manager configuration, and enable the service to start at boot.

4. Test the Systemd Service: Verify that the script works by manually starting the service.

   $ sudo systemctl start disk-space-check.service
   $ sudo cat /root/disk_space_report.txt
   

   Execute the service manually using the systemctl start command. After running the service, check the contents of the disk space report by viewing the disk_space_report.txt file located in the /root/ directory. This file should contain the date and the disk space usage of the /home/ directory, confirming that the script executed successfully.

   

Conclusion

By following these steps, your Linux system will automatically perform the specified checks at boot time, facilitating automated maintenance and monitoring without requiring manual intervention.