CRON(8) Maintenance Commands and Procedures CRON(8)
NAME
cron - clock daemon
SYNOPSIS
/usr/sbin/cronDESCRIPTION
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
logadmSEE 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)
