wierd cron behavior

[Isaac Dunham]

On Mon, Jan 18, 2016 at 12:37:14PM -0500, David Henderson wrote:
> Good morning all, so I'm continuing in my attempt to get cron working.
> I have worked around some of the deficiencies of the BB implementation
> (e.g. @startup, /etc/cron.d), however, I can't seem to get cron to
> work with local times instead of UTC - meaning that I have to create
> crontabs using UTC time (not desired) and not local time (desired).
> At first I thought it was either the system time or hardware clock not
> being set correctly, so I began adjusting times with both of those:
> 
> $ unset TZ
> $ ntpd -n -q -p pool.ntp.org
> $ hwclock -w -u
> $ export TZ='EST+5EDT'
> $ date -u; hwclock -u
> Mon Jan 18 17:08:15 UTC
> Mon Jan 18 12:08:16 2016 -0.687957 seconds
> $ date; hwclock --localtime
> Mon Jan 18 12:08:18 EST
> Mon Jan 18 17:08:19 2016 -0.176678 seconds
> $ cat /var/spool/cron/crontabs/root
> 9 12 * * * date > /tmp/test.txt
> 
> The above job failed, but when I change it to:
> 
> $ cat /var/spool/cron/crontabs/root
> 10 17 * * * date > /tmp/test.txt
> 
> It seems to work.  So I figured, lets see what happens when I set the
> hardware clock to local time:
> 
> $ unset TZ
> $ ntpd -n -q -p pool.ntp.org
> $ export TZ='EST+5EDT'
> $ hwclock -w --localtime
> $ date; hwclock
> Mon Jan 18 12:17:58 EST 2016
> Mon Jan 18 12:17:59 2016 -0.312997 seconds
> $ date -u; hwclock -u
> Mon Jan 18 17:18:15 UTC 2016
> Mon Jan 18 07:18:16 2016 -0.781702 seconds
> 
> The above job works correctly when using:
> 
> 19 17 * * * date > /tmp/test.txt
> 
> But not when using:
> 
> 21 12 * * * date > /tmp/test.txt
> 
> Any help would greatly be appreciated!

When testing these, do you restart *crond* so that the timezone applies?
Do you use /etc/localtime for setting the system timezone?


To check the environment of crond, you can do (as root):
# tr '\0' '\n' < /proc/`pidof crond`/environ 

HTH,
Isaac Dunham