CRON(8) Maintenance Commands and Procedures CRON(8)

NAME

cron - clock daemon

SYNOPSIS

/usr/sbin/cron

DESCRIPTION

cron starts a process that executes commands at specified dates and
times.


You can specify regularly scheduled commands to cron according to
instructions found in crontab files in the directory
/var/spool/cron/crontabs. Users can submit their own crontab file using
the crontab(1) command. Commands which are to be executed only once can
be submitted using the at(1) command.


cron only examines crontab or at command files during its own process
initialization phase and when the crontab or at command is run. This
reduces the overhead of checking for new or changed files at regularly
scheduled intervals.


As cron never exits, it should be executed only once. This is done
routinely by way of the svc:/system/cron:default service. The file
/etc/cron.d/FIFO file is used as a lock file to prevent the execution of
more than one instance of cron.


cron captures the output of the job's stdout and stderr streams, and, if
it is not empty, mails the output to the user. If the job does not
produce output, no mail is sent to the user. An exception is if the job
is an at(1) job and the -m option was specified when the job was
submitted.


cron and at jobs are not executed if your account is locked. The
shadow(5) file defines which accounts are not locked and will have their
jobs executed.

Setting cron Jobs Across Timezones

The timezone of the cron daemon sets the system-wide timezone for cron
entries. This, in turn, is by set by default system-wide using
/etc/default/init. The timezone for cron entries can be overridden in a
user's crontab file; see crontab(1).


If some form of daylight savings or summer/winter time is in effect, then
jobs scheduled during the switchover period could be executed once,
twice, or not at all.

Setting cron Defaults

To keep a log of all actions taken by cron, you must specify CRONLOG=YES
in the /etc/default/cron file. If you specify CRONLOG=NO, no logging is
done. Keeping the log is a user configurable option since cron usually
creates huge log files.


You can specify the PATH for user cron jobs by using PATH= in
/etc/default/cron. You can set the PATH for root cron jobs using SUPATH=
in /etc/default/cron. Carefully consider the security implications of
setting PATH and SUPATH.


Example /etc/default/cron file:

CRONLOG=YES
PATH=/usr/bin:/usr/ucb:


This example enables logging and sets the default PATH used by non-root
jobs to /usr/bin:/usr/ucb:. Root jobs continue to use /usr/sbin:/usr/bin.


The cron log file is periodically rotated by logadm(8).

FILES

/etc/cron.d
Main cron directory


/etc/cron.d/FIFO
Lock file


/etc/default/cron
cron default settings file


/var/cron/log
cron history information


/var/spool/cron
Spool area


/etc/cron.d/queuedefs
Queue description file for at, batch, and cron


/etc/logadm.conf
Configuration file for logadm

SEE ALSO

at(1), crontab(1), sh(1), svcs(1), queuedefs(5), shadow(5),
attributes(7), rbac(7), smf(7), smf_security(7), logadm(8), svcadm(8)

NOTES

The cron service is managed by the service management facility, smf(7),
under the service identifier:

svc:/system/cron:default


Administrative actions on this service, such as enabling, disabling, or
requesting restart, can be performed using svcadm(8). The service's
status can be queried using the svcs(1) command. Most administrative
actions may be delegated to users with the solaris.smf.manage.cron
authorization (see rbac(7) and smf_security(7)).

DIAGNOSTICS

A history of all actions taken by cron is stored in /var/cron/log and
possibly in /var/cron/olog.

March 30, 2017 CRON(8)