UNIX for Dummies Questions & Answers

Hello,

First, a brief background: I'm fairly comfortable with working from the command line, having done so for a while in Mac OS X, but I have recently been asked to assist with an AIX system.

There is currently a backup script that is set to run via Cron, and I would like to change the interval at which it runs. I know that normally this is done with Crontab, but the problem is that I don't know which tab file actually has the entry for this job, as a previous IT department set it up.

What I've found: /var/spool/cron/crontabs contains the usual files you'd expect, each named after the user that created them, but also some others: root_bad (which contains junk), root.tools.10417 (among other root.tools.othernumber files), etc. Only a few of the root.tools.* files have an entry referring to the backup script, but my understanding is that a Crontab file had to be named for a user. Is my thinking here correct, or is it possible that Cron is actually using these files?

Thank you!

The cron file would have to match a user in /etc/passwd to be processed The duff ones may even be generating errors in the cron log file if logging is switched on (default is /var/adm/cron/log on AIX). You will need to consider when it runs and try to find a suitable record in the files you have found. Remember that the format of a cron record is:

Code:

mi hh dd mn dw command

Where mi is minutes past the hour
and hh is the hour of the day
then dd mn defines day of month and month critera
which is or-ed with the Day of Week value.

With this last thing in mind, it is possible to do some very confusing things (as I know to my cost) where you think you have set a job to run on every first Monday of the month (Day of month 1-7, Month of * and Day of week 1) but what you get is every day from 1-7 AND every Monday.

You will need to trace what each active line does for each file with an associated user account. No easy way to do this I'm afraid. Perhaps switching cron to log may help, or rather removing the flag that stops it logging.





I hope that this helps
Robin
Liverpool/Blackburn

Hello,
The best way to modify the crontab is to use (editor like vi, but it will refresh the cron demon ): crontab -e
This will check the consistency of the date format.
crontab -l to list the content, or crontab -l <user>
All other files that don't belong to a user from /etc/password in the folder /var/spool/cron/crontabs can be delete, it's normally not the best place to store scripts.

Thanks! I've got the backups running as I wanted now, and I'll be sure to move the junk files somewhere else.