Crontab

2008-06-19T06:54:42Z

78.143.200.245: /* External links */

Scheduling jobs on [[linux]] requires two parts. The first part is having the crond daemon running. The second part is using the [[crontab]] command to create a schedule. The schedule is a list of jobs with times that you'd like to have run.

There are two versions of the command that you will use most of the time.

crontab -e
To edit your crontab file.

crontab -l
To list your crontab file.

crontab -l > crontabbackup.txt
Another useful variation of the -l, list your crontab, allows you to send the schedule to a file.

crontab crontabbackup.txt
If you use the crontab -l option and send the output to a file as was shown in the prior command example, you can take that schedule and import it into another schedule. All you have to do is use [[crontab]] and supply your backed up schedule file. This is a great trick for [[knoppix]]. The creative use of this format of the command would be import your schedule from a [[USB]] thumb drive or a hard drive partion. You could even store the file on a MS Windows partition as long as the file is in [[linux]] format verse MS Dos format.

man 5 crontab
Use this man command read about the formatting requirements for your '''/etc/crontab''' file.

Note: Two classes of user will use this command. <br>
A user or the "root" user. Although, almost every Linux system, I've ran '''crontab -e''' as "root" '''does not''' support it. <br>
In other words, if you are Sys Admin (root). Just '''vi /etc/crontab'''.

== External links ==
* [http://www.math-linux.com/spip.php?article45 Crontab : Scheduling Tasks]
[[Category:Useful Linux Commands]]

* [http://www.hxpi.com/cron_sandbox.php A safe place to experiment with crontab commands is Cron Sandbox at HxPI where you can see straightaway a future schedule of run times for whatever crontab parameters you type in.]

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Crontab