Runs commands automatically.
The cron daemon runs shell commands at specified dates and times. The following event types are scheduled by the cron daemon:
The way these events are handled is specified by the /var/adm/cron/queuedefs file.
Regularly scheduled commands can be specified according to instructions contained in the crontab files. You can submit your crontab file with the crontab command. Use the at command to submit commands that are to be run only once. Because the cron daemon never exits, it should be run only once.
The cron daemon examines crontab files and at command files only when the cron daemon is initialized. When you make changes to the crontab files using the crontab command, a message indicating the change is sent to the cron daemon. This eliminates the overhead of checking for new or changed files at regularly scheduled intervals.
When the TZ environment variable is changed, either with the chtz command, a Web-based System Management application, or through SMIT, the cron daemon must be restarted. This enables the cron daemon to use the correct timezone and summer time change information for the new TZ environment variable.
The cron daemon creates a log of its activities in the /var/adm/cron/log file.
Auditing Events: If the auditing subsystem has been properly configured and is enabled, the cron daemon will generate the following audit record (event) every time the command is executed:
|CRON_Start||Lists the name of each job, whether the job was initiated by an at or cron command, and the time the job started.|
|CRON_Finish||Lists the user's name, process ID of the job, and the time the processing was completed.|
See "Setting up Auditing" in AIX Version 4.3 System Management Guide: Operating System and Devices for more details about how to properly select and group audit events, and how to configure audit event data collection.
|/var/adm/cron/FIFO||A named pipe that sends messages to the cron daemon when new jobs are submitted with the crontab or at commands.|
|/var/adm/cron||Specifies the main cron daemon directory.|
|/var/adm/cron/log||Specifies the accounting information.|
|Specifies the cron daemon events file.|
|/var/spool/cron||Specifies the spool area.|
|/usr||Indicates directory kept open by the cron daemon.|
|/usr/bin||Indicates directory kept open by the cron daemon.|
|/usr/lib||Indicates directory kept open by the cron daemon.|
|/etc||Indicates directory kept open by the cron daemon.|
|/tmp||Indicates directory kept open by the cron daemon.|
The at command, auditpr command, batch command, crontab command, csh command, ksh command, rc command.
The sync subroutine.
The Auditing Overview in AIX Version 4.3 System Management Guide: Operating System and Devices explains more about audits and audit events.
Setting up and running Web-based System Management in AIX Version 4.3 System Management Guide: Operating System and Devices.