To run a cron job after a system reboot in Linux, you can add the job to the system's crontab file.
The crontab file is a configuration file that specifies the commands to be run at specific times. To edit the system's crontab file, you can use the "crontab" command with the "-e" option.
For example, to run a command called "mycommand" at reboot, you can add the following line to the crontab file:
@reboot mycommand
This will run the command "mycommand" every time the system is rebooted.
You can also specify a specific time to run the command by using the crontab syntax, which consists of five fields separated by spaces: minute, hour, day of month, month, and day of week. For example, to run "mycommand" at 5:00 AM every day, you can use the following line:
0 5 * * * mycommand
This will run the command "mycommand" at 5:00 AM every day.
Note: The crontab file is specific to the user who owns it. To run a cron job as the root user, you will need to edit the root user's crontab file, which can be done using the "crontab" command with the "-u" option. For example:
sudo crontab -u root -e
This will open the root user's crontab file for editing.