Cron Jobs - UNIX for Dummies Questions & Answers

dereckbc · #1 (**permalink**) 01-18-2005

Where can someone find info on Cron Jobs? Very new to UNIX and the PC I inherited looks to have several of them. Looks like they are some kind of background program that runs automatically at specified times. Would like to delete some of them and know more about them.

zazzybob · #2 (**permalink**) 01-18-2005

Search this site and google.com for starters. A search for "cron" on google.com gives 3 *million* results. Searching for "cron tutorial" gives 194,000 results.

man cron and man crontab are also must-reads.

Quote:

Originally Posted by man cron

cron executes commands at specified dates and times. Regularly
scheduled commands can be specified according to instructions placed
in crontab files. Users can submit their own crontab files with a
crontab command (see crontab(1)). Users can submit commands that are
to be executed only once with an at or batch command.

Cheers
ZB

dereckbc · #3 (**permalink**) 01-18-2005

Thanks Bob, I did search google and got overwhelmed by the number of hits.

zazzybob · #4 (**permalink**) 01-18-2005

There seem to be a couple of introductions at these links (note: i haven't checked these out...)

http://www.unixgeeks.org/security/ne...ix/cron-1.html
http://www.linuxhelp.net/guides/cron/
http://www.linux.com/article.pl?sid=04/04/04/1544250
http://weather.ou.edu/~billston/crontab/
http://www.linuxforums.org/forum/ptopic4440.html
http://www.adminschoice.com/docs/crontab.htm

Also; take a look at the following article from our FAQ section.

That and the man pages should get you going

Cheers
ZB

dereckbc · #5 (**permalink**) 01-18-2005

THX Bob. That has got me rolling. I entered "crontab -l" and see some of the actions, however not the ones I am getting errors on e-mail. Are there more than one crontab file, and if so how would I find it. I know the path and file name of the errored e-mail messages.

locustfurnace · #6 (**permalink**) 01-18-2005

Try as su or root
crontab -l root to see roots crontab, which is most likely the backup processes. If, you decide to delete those, you can by issuing;
crontab -d root

wayneb · #7 (**permalink**) 01-19-2005

If you change to the crontab directory it will give you a list of al the crontab user files.
Type in cd /usr/spool/cron/crontabs
then ls -l in the directory, it should show you all the files with the names being the user.
You will then need to type
crontab -u filename -l
This will then display all the jobs due to run under each user.

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