Auto-Run Scripts on Linux Boot: rc.local, crontab @reboot, and systemd Service

Method 1: Edit /etc/rc.d/rc.local

The /etc/rc.d/rc.local file runs after all system services have started, making it a convenient place to launch custom scripts. Ensure the file is executable, then add the script path at the end of the file. chmod +x /etc/rc.d/rc.local Create a simple script that writes the date and hostname to a file in the home directory:

vim auto_run_script.sh
#!/bin/bash
date >> /home/alvin/output.txt
hostname >> /home/alvin/output.txt

Make the script executable: chmod +x auto_run_script.sh Append the script call to /etc/rc.d/rc.local (the last line before exit 0 if present):

vim /etc/rc.d/rc.local
/home/alvin/auto_run_script.sh

Reboot the system ( sudo reboot) and verify that output.txt contains the expected data.

Method 2: Use crontab with @reboot

The crontab utility can schedule tasks; the special @reboot keyword runs a command each time the system boots.

crontab -e
@reboot /home/alvin/auto_run_script.sh

Save the file and reboot; the script will execute automatically, producing the same result as Method 1.

Method 3: Create a systemd Service

First confirm the host uses systemd by checking the PID 1 process: ps aux | grep "1 .*systemd" Create a service unit file named auto_run_script.service:

vim /etc/systemd/system/auto_run_script.service
[Unit]
Description=Run a Custom Script at Startup
After=default.target

[Service]
ExecStart=/home/alvin/auto_run_script.sh

[Install]
WantedBy=default.target

Reload the systemd manager configuration and enable the service to start at boot:

systemctl daemon-reload
systemctl enable auto_run_script.service

Finally, reboot the machine ( reboot) and verify that the script runs as expected.