System Scheduler-Cron Notes

Features:
1. Permits scheduling of scripts(shell/perl/python/ruby/PHP/etc.)/tasks on a per-user basis via individual cron tables.
2. Permits recurring execution of tasks
3. Permits one-time execution of tasks via 'at'
4. Logs results(exit status but can be full output) of executed tasks
5. Facilitates restrictions/permissions via - cron.deny,cron.allow,at.*

Directory Layout for Cron daemon:
/var/spool/cron - and sub-directories of to store cron & at entries
/var/spool/cron/atjobs - houses one-off, atjobs
- 787546321.a - corresponds to a user's atjob

/var/spool/cron/crontabs - houses recurring jobs for users
- username - these files house recurring tasks for each user


Cron command:
crontab - facilitates the management of cron table files
-crontab -l - lists the cron table for current user -
- reads /var/spool/cron/crontabs/root

###Cron table format###

m(0-59) h(0-23) dom(1-31) m(1-12) dow(0-6) command
10 3 * * * /usr/sbin/logadm - 3:10AM - every day
15 3 * * 0 /usr/lib/fs/nfs/nfsfind - 3:15 - every Sunday
30 3 * * * [ -x /usr/lib/gss/gsscred_clean ] && /usr/lib/gss/gsscred_clean
1 2 * * * [ -x /usr/sbin/rtc ] && /usr/sbin/rtc -c > /dev/null 2>&1

m(0-59) h(0-23) dom(1-31) m(1-12) dow(0-6) command
Note: (date/time/command) MUST be on 1 line
m = minute(0-59)
h = hour(0-23)
dom = day of the month(1-31)
m = month(1-12)
dow = day of the week(0-6) - 0=Sunday

Note: each line contains 6 fields/columns - 5 pertain to date & time of execution, and the 6th pertains to command to execute

#m h dom m dow
10 3 * * * /usr/sbin/logadm - 3:10AM - every day
* * * * * /usr/sbin/logadm - every minute,hour,dom,m,dow
*/5 * * * * /usr/sbin/logadm - every 5 minutes(0,5,10,15...)
1 0-4 * * * /usr/sbin/logadm - 1 minute after the hours 0-4
0 0,2,4,6,9 * * * /usr/sbin/logadm - top of the hours 0,2,4,6,9

1-9 0,2,4,6,9 * * * /usr/sbin/logadm - 1-9 minutes of hours 0,2,4,6,9

Note: Separate columns/fields using whitespace or tabs

###Create crontabs for root & unixcbt###
Note: ALWAYS test commands prior to crontab/at submission

11 * * * * repquota -va >> /reports/`date +%F`.quota.report

Note: set EDITOR variable to desired editor
export EDITOR=vim

###unixcbt - execute quota -v###
#!/usr/bin/bash
HOME=/export/home/unixcbt
quota -v >> $HOME/`date +%F`.unixcbt.quota.report
#END

Note: aim to reference scripts(shell/perl/python/ruby/PHP,etc.) instead of the various characters

Note:
Default Solaris install creates 'at.deny' & 'cron.deny'
You MUST not be included in either file to be able to submit at & cron entries

Conversely, if cron.allow and at.allow files exist, you MUST belong to either file to submit at or cron entries

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