CertiGuide to A+ (A+ 4 Real)  9  Chapter 5: The Linux Operating System       9  Command Line Functions And Administrative Utilities            9  Scheduling Processes For Later Execution

Scheduling Processes For Later Execution 1 cron/crontab - Execute Scheduled Commands

Commands can be scheduled for execution at a given time in the future by using the at command. This allows the system administrator to schedule a specific task, which may require significant system resources for execution later at a time when the system load is low. It takes the form:

at -f filename time_specification

For example:

at -f backupscript 11pm today

This example line would cause the file backupscript to be executed at 11:00pm today. The format for time specification is very flexible; for example, each of the following would work:

now + 5 minutes

8pm + two days

8pm 04/01/2007

The file backupscript should contain a series of commands 1 per line that are to be executed. In this case, if the file backupscript contained instructions to create an archive file of the /home directory, compress it (zip it or gzip it), and then copy it to the backup media. This would work if one only wanted to run the script on a one-time basis. Backups are tasks that generally occur on repetitive basis. Therfore they would be better suited to be scheduled by the next command.

Scheduling Processes For Later Execution 1 cron/crontab - Execute Scheduled Commands