NAME

cron − The system clock daemon

SYNOPSIS

/usr/sbin/cron

DESCRIPTION

The cron daemon runs shell commands at specified dates and times.  Commands that are to run according to a regular or periodic schedule are found within the crontab files. Commands that are to run once only are found within the at files.  You submit crontab and at file entries by using the crontab and at commands.  Because the cron process exits only when killed or when the system stops, only one cron daemon should exist on the system at any given time.  Normally, you start the cron daemon from within a run command file. 

Note

Other that logging a startup entry in the /var/adm/cron/log file, the cron daemon does not log its activities.  You can use the Event Manager (EVM) to create custom events for tasks that are scheduled by the cron daemon. See EVM(5) for more information. 

During process initialization and when cron detects a change, it examines the crontab and at files. This strategy reduces the overhead of checking for new or changed files at regularly scheduled intervals. The cron daemon must be started from the system startup scripts because it must begin execution without a login user ID set. It maintains the /usr/spool cron/atjobs and the /usr spool cron/crontabs spool direcitories as multilevel directories; jobs and crontabs submitted reside in the directory associated with the sensitivity level of the process that invoked at or crontab. It uses the level of the subdirectory as the one at which to start the job.  The cron communication FIFO is graded at the System High sensitivity level. The cron daemon starts each job with the following process attributes stored with the job by the invoking process:

       •Login user ID

       •Effective and real user IDs

       •Effective and real group IDs

       •Supplementary groups

       •Sensitivity level

       •Information label

It also establishes the following attributes from the authentication profile of the account associated with the login user ID of the invoking process:

       •Audit control and disposition masks

       •Clearance

       •Kernel authorizations

       •Base privilege set

DIAGNOSTICS

The at and batch programs will refuse to accept jobs submitted from processes whose login user ID is different from the real user ID. 

FILES

/usr/sbin/cron
Specifies the command path.

/var/adm/cron
Main cron directory

/var/spool/cron/crontabs
Directory containing the crontab files.

/var/adm/cron/cron.allow
List of allowed users.

/var/adm/cron/cron.deny
List of denied users

/var/adm/cron/log
This file contains startup information. (It is not a log of cron activities).

/var/adm/cron/queuedefs
Queue description file for at, batch, and cron

SEE ALSO

Commands: at(1), crontab(1), rc0(8), rc2(8), rc3(8)

Files: queuedefs(4)

Misc: EVM(5)