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|Oracle Solaris Administration: Common Tasks Oracle Solaris 11 Information Library|
You can set up many system tasks to execute automatically. Some of these tasks should occur at regular intervals. Other tasks need to run only once, perhaps during off hours such as evenings or weekends.
This section contains overview information about two commands, crontab and at, which enable you to schedule routine tasks to execute automatically. The crontab command schedules repetitive commands. The at command schedules tasks that execute once.
Table 14-1 Command Summary: Scheduling System Tasks
You can schedule routine system administration tasks to execute daily, weekly, or monthly by using the crontab command.
Removing files more than a few days old from temporary directories
Executing accounting summary commands
Taking snapshots of the system by using the df and ps commands
Performing daily security monitoring
Running system backups
Rebuilding the catman database for use by the man -k command
Listing files not used during a specific month
Producing monthly accounting reports
For step-by-step instructions on scheduling crontab jobs, see How to Create or Edit a crontab File.
Similar to crontab, the at command allows you to schedule the automatic execution of routine tasks. However, unlike crontab files, at files execute their tasks once. Then, they are removed from their directory. Therefore, the at command is most useful for running simple commands or scripts that direct output into separate files for later examination.
Submitting an at job involves typing a command and following the at command syntax to specify options to schedule the time your job will be executed. For more information about submitting at jobs, see Description of the at Command.
The at command stores the command or script you ran, along with a copy of your current environment variable, in the /var/spool/cron/atjobs directory. Your at job file name is given a long number that specifies its location in the at queue, followed by the .a extension, such as 793962000.a.
The cron daemon checks for at jobs at startup and listens for new jobs that are submitted. After the cron daemon executes an at job, the at job's file is removed from the atjobs directory. For more information, see the at(1) man page.
For step-by-step instructions on scheduling at jobs, see How to Create an at Job.