How can you ensure a script runs at startup?

To ensure a script runs at startup, adding it to /etc/rc.local is a valid and historically common method. The /etc/rc.local file is executed at the end of the boot process in many Linux distributions, making it an appropriate place to start custom scripts that you want to run when the system boots up.

When you add your script to /etc/rc.local, you typically need to ensure that the script is executable and possibly add a line that explicitly calls the script. This method is straightforward and does not require complex configurations, which can be advantageous for simple startup tasks. Furthermore, since /etc/rc.local is called during the boot sequence, it ensures that your script runs just before the multi-user level is reached, which is useful for services that need to be available immediately after the system boots.

While creating a cron job can be used to schedule tasks at specific times or intervals, it is not intended for ensuring immediate execution upon system startup. Similarly, placing a script in /etc/init.d would typically be associated with systems using SysVinit, but it's not a standalone method for ensuring execution at startup without additional configuration, such as symlinking it to the appropriate runlevel directories. Adding it to /etc/systemd/system