Re: LUG: Anything wrong with this cron entry? - Fri, 07 Oct 2011 16:52:59 -0400

Subject : Re: LUG: Anything wrong with this cron entry?

From : Kevin Hunter <hunteke@earlham.[redacted]>

Date : Fri, 07 Oct 2011 16:52:59 -0400

At 3:11pm -0400 Wed, 05 Oct 2011, Daniel Underwood wrote:
> For some reason, the "/usr/bin/rsnapshot monthly" entry in the cron
> listing below was not executed on this past October 1st. It's
> supposed to be executed once a month on the first day of the month.
> (I added the monthly run just a few days prior to October 1st, so I
> don't have any history of it working.) Does anyone see a problem with
> the cron listing below?
>
> [BEGIN TEXT FROM CRON]
> # m h dom mon dow command
> 0 * * * * /usr/bin/rsnapshot hourly
> 30 23 * * * /usr/bin/rsnapshot daily
> 0 0 1 * * /usr/bin/rsnapshot monthly
> [END TEXT FROM CRON]

Nothing looks immediately out of place. What debugging measures have
you tried? Some thoughts:

-----
1. Are you sure cron is still running? A process listing can do wonders
for problem discovery:

$ ps -eF
(or 'ps waux' for some older timers)

And for some newer members of this list, who may not yet have learned
about piping, this makes it easier to browse:

$ ps -eF | less

2. Are you able to execute a simple echo and mail to yourself on, say, a
minute to minute basis? Something like this:

* * * * * /bin/echo "Hi Mom." | /usr/bin/mail -s "Test from crontab"
root@localhost

As you appear to have already done, note that it's often easiest to
debug if you use the full path to all executables rather than relying on
a may-not-be-what-you-expect-in-crontab PATH variable.

3. In a dedicated window, consider using the "tail -F" command on
/var/log/syslog while you do your various crontab works.

4. If it's /really/ bothering, consider installing yourself a quick and
limited version of the distro inside of a VirtualBox session. Then
update the time to just before the month rollover, and see if you can
recreate the erroneous results
-----

With the first 3 measures, you'll likely be far more successful tracking
down your issue that will we without direct access to your machine, or
face-to-face contact, and the 4th measure is the frickin' sledgehammer
for if you *must solve it now.*

Cheers and good luck,

Kevin

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