1cron(1M) System Administration Commands cron(1M)
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6 cron - clock daemon
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9 /usr/sbin/cron
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13 cron starts a process that executes commands at specified dates and
14 times.
15 You can specify regularly scheduled commands to cron according to
18 instructions found in crontab files in the directory
19 /var/spool/cron/crontabs. Users can submit their own crontab file using
20 the crontab(1) command. Commands which are to be executed only once can
21 be submitted using the at(1) command.
22 cron only examines crontab or at command files during its own process
25 initialization phase and when the crontab or at command is run. This
26 reduces the overhead of checking for new or changed files at regularly
27 scheduled intervals.
28 As cron never exits, it should be executed only once. This is done rou‐
31 tinely by way of the svc:/system/cron:default service. The file
32 /etc/cron.d/FIFO file is used as a lock file to prevent the execution
33 of more than one instance of cron.
34 cron captures the output of the job's stdout and stderr streams, and,
37 if it is not empty, mails the output to the user. If the job does not
38 produce output, no mail is sent to the user. An exception is if the job
39 is an at(1) job and the -m option was specified when the job was sub‐
40 mitted.
41 cron and at jobs are not executed if your account is locked. Jobs and
44 processses execute. The shadow(4) file defines which accounts are not
45 locked and will have their jobs and processes executed.
46 Setting cron Jobs Across Timezones
48 The timezone of the cron daemon sets the system-wide timezone for cron
49 entries. This, in turn, is by set by default system-wide using
50 /etc/default/init. The timezone for cron entries can be overridden in a
51 user's crontab file; see crontab(1).
52 If some form of daylight savings or summer/winter time is in effect,
55 then jobs scheduled during the switchover period could be executed
56 once, twice, or not at all.
57 Setting cron Defaults
59 To keep a log of all actions taken by cron, you must specify CRON‐
60 LOG=YES in the /etc/default/cron file. If you specify CRONLOG=NO, no
61 logging is done. Keeping the log is a user configurable option since
62 cron usually creates huge log files.
63 You can specify the PATH for user cron jobs by using PATH= in
66 /etc/default/cron. You can set the PATH for root cron jobs using
67 SUPATH= in /etc/default/cron. Carefully consider the security implica‐
68 tions of setting PATH and SUPATH.
69 Example /etc/default/cron file:
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