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--- linux_wiki:cron [2017/09/03 17:20]
billdozor [Format of User Crontabs]
+++ linux_wiki:cron [2019/05/25 23:50]
@@ Line 1: / Line 1: @@
-====== Cron ======
-**General Information**
-Automating tasks with cron (the daemon that executes scheduled commands).
-**Checklist**
-  * Distro(s): Any
-----
-====== User Crontabs ======
-Individual users can create/edit their own cron jobs.
-\\
-List your user's crontab jobs
-<code bash>
-crontab -l
-</code>
-\\
-Edit your crontab
-<code bash>
-crontab -e
-</code>
-\\
-User crontabs are stored at:
-  * /var/spool/cron/<username>
-===== Files That Control Crontab Access =====
-  * /etc/cron.allow
-  * /etc/cron.deny
-About these files:
-  * One username per line
-  * Root can always use crontab, regardless of file existence below
-^  cron.allow  ^  cron.deny  ^  Result  ^
-|  file exists  |  file exists  |  Only users in cron.allow are allowed  |
-|  no file  |  file exists  |  All users allowed except those in cron.deny  |
-|  file exists  |  no file  |  Only users in cron.allow are allowed  |
-|  no file  |  no file  |  Only root is allowed to use crontab  |
-----
-===== Format of User Crontabs =====
-For any below, asterisk means all values.
-<code bash>
-# .---------------- minute (0 - 59)
-# |  .------------- hour (0 - 23)
-# |  |  .---------- day of month (1 - 31)
-# |  |  |  .------- month (1 - 12) OR jan,feb,mar,apr ...
-# |  |  |  |  .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat
-# |  |  |  |  |
-# *  *  *  *  *  command to be executed
-</code>
-----
-===== Crontab Examples =====
-Executes script.sh at 0600,0630,1200,and 1230 every day of the month, every month, and everyday of the week.
-<code bash>
-,30 6,12 * * * /home/user/script.sh
-</code>
-Executes script.sh every minute.
-<code bash>
-* * * * * /home/user/script.sh
-</code>
-Executes script.sh every 5 minutes.
-<code bash>
-*/5 * * * * /home/user/script.sh
-</code>
-Executes script.sh on system startup.
-<code bash>
-@reboot /home/user/script.sh
-</code>
-----
-====== System Cron Jobs ======
-To run jobs in the system directories, look to /etc.
-  * /etc/cron.d/ = system executed jobs (format like crontab)
-  * /etc/cron.daily/ = daily executed scripts (format bash script)
-  * /etc/cron.hourly/ = hourly executed scripts (format bash script)
-  * /etc/cron.monthly/ = monthly executed scripts (format bash script)
-  * /etc/cron.weekly/ = weekly executed scripts (format bash script)
-  * /etc/crontab = system wide crontab
-It is recommended to drop scripts into one of the /etc/cron.* directories instead of editing the system wide crontab file.
-All formats are bash scripts, except for the /etc/cron.d/ directory, which accepts crontab formatted files, with the addition of specifying a username.
-For example, /etc/cron.d/crashplan-mirror:
-<code bash>
-# Rsync the crashplan backups to another usb drive for redundancy
-2,14 * * * root /root/scripts/rsync_cp_mirror.sh
-</code>
-The above executes at 0200 and 1400, runs as the user root, the script specified.
-----
-====== Cron Keywords ======
-Keywords that can be used in place of a specific time/date schedule.
-  * @reboot - Run once at start up.
-  * @yearly - Run once a year.
-  * @annually - Same as yearly.
-  * @monthly - Run once a month.
-  * @weekly - Run once a week.
-  * @daily - Run once a day.
-  * @midnight - Same as daily.
-  * @hourly - Run once an hour.
-----