How to create custom script to run automatically during boot CentOS / RHEL 7?

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

 

Here,

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

 

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