Centos Rhel 7 How To Make Custom Script To Run Automatically During Boot As A Systemd Service

30 Mar 2020

CentOS / RHEL 7 : How to create custom script to run automatically during boot as a systemd service

Reference: https://www.thegeekdiary.com/centos-rhel-7-how-to-make-custom-script-to-run-automatically-during-boot/

In RHEL 5 and 6, we were using automatic startup feature of RHEL through /etc/rc.d/init.d to run any script at system boot. Starting with RHEL 7 init is replaced by systemd and the prior method is now deprecated. There is another way in RHEL 7 to do the same.

Creating the custom script

1. Let us first create a sample custom script to be run at system boot automatically.

   vi /var/tmp/test_script.sh

    #!/bin/bash
    echo "This is a sample script to test auto run during boot" > /var/tmp/script.out
    echo "The time the script run was -->  `date`" >> /var/tmp/script.out
   

2. Check and verify the file permission.

   ls -lrt /usr/local/sbin/myscript.sh

3. Add execute permission(if it’s not already set).

   chmod +x /var/tmp/test_script.sh

Creating new systemd service unit

Create a new service unit file at /etc/systemd/system/sample.service with below content. The name of the service unit is user defined and can be any name of your choice.

`vi /etc/systemd/system/sample.service`


[Unit]
Description=Description for sample script goes here
After=network.target

[Service]
Type=simple
ExecStart=/var/tmp/test_script.sh
TimeoutStartSec=0

[Install]
WantedBy=default.target

After= : If the script needs any other system facilities (networking, etc), modify the [Unit] section to include appropriate After=, Wants=, or Requires= directives. Type= : Switch Type=simple for Type=idle in the [Service] section to delay execution of the script until all other jobs are dispatched WantedBy= : target to run the sample script in

Enable the systemd service unit

1. Reload the systemd process to consider newly created sample.service OR every time when sample.service gets modified.

   systemctl daemon-reload

2. Enable this service to start after reboot automatically.

   systemctl enable sample.service

3. Start the service.

   systemctl start sample.service

4. Reboot the host to verify whether the scripts are starting as expected during system boot.

   systemctl reboot