cron(8)cron(8)NAMEcron - The system clock daemon
SYNOPSIS
/usr/sbin/cron
DESCRIPTION
The cron daemon runs shell commands at specified dates and times. Com‐
mands 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 exam‐
ines 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 direcito‐
ries 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 invok‐
ing 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
Specifies the command path. Main cron directory Directory containing
the crontab files. List of allowed users. List of denied users This
file contains startup information. (It is not a log of cron activi‐
ties). Queue description file for at, batch, and cronSEE ALSO
Commands: at(1), crontab(1), rc0(8), rc2(8), rc3(8)
Files: queuedefs(4)
Misc: EVM(5)cron(8)