Re: [gentoo-user] OT crontab not understood

[Alan McKinnon]

On Mon, 09 Jan 2012 13:10:50 +0100
Daniel Troeder <daniel@×××××××××.com> wrote:

> Hi :)
>
> It seems I don't understand something about cron(tab). Can someone
> help me pls:
>
> I want to run flexbackup with the following backup plan:
>   * monthly full
>   * weekly diff
>   * daily incr
>
> So I have installed sys-process/vixie-cron-4.1-r12 (and virtual/cron-0
> and sys-process/cronbase-0.3.3).
>
> My crontab (created with "crontab -e") contains:
>
> 00 03 2-31 * 1-6     /usr/bin/flexbackup -set root -level incremental
> 00 03 2-31 * 0       /usr/bin/flexbackup -set root -level differential
> 00 03 1    * *       /usr/bin/flexbackup -set root -level full
>
> The problem I'm facing is, that incr and diff are executed each day
> _both_ at the same time (which flexbackup luckily handles well).
>
> From my understanding the 2nd line (diff) should only be run on
> sundays, and the 1st line (inc) should not run sundays.
>
>
> Can someone please explain me what I'm doing wrong?

You are combining fields 3 and 5, those two work funny.

Unlike the other datetime specs, they are not ANDed, they are ORed.

Taking the first one, you obviously want the cron to run at 3 am
between the 2nd and 31st of the month AND if the day is Mon-Sat.

What it is doing is running at 3am every day between the 2nd and 31st
and also every day Mon-Sat (even if that is the 1st of the month).

Vixie cron does not directly allow you to do what you want. It's
designed to run things periodically on a set schedule and doesn't do
"except" very well.

A better approach would be to fire off a wrapper script every day at
3am. This script will then check for date, time and day of week and
launch the app with the appropriate options. 

>
> Thank you,
> Daniel
>



-- 
Alan McKinnnon
alan.mckinnon@×××××.com