Re: cron on a system without a hardware persistant clock
On Tuesday 27 Sep 2011, Camaleón wrote:
> On Tue, 27 Sep 2011 10:11:33 +0100, David Goodenough wrote:
> > I have some small single board systems on which I run Debian. They have
> > clocks, but they are not battery backed and so reset to zero for each
> > run.
>
> You mean that system always starts with no date set? :-o
Absolutely yes, that is my problem. No battery backup for the time
when the box is powered down, so on boot the time is always the 1st
Jan 1970 00:00am.
>
> > I then set the time using NTP once I have a network connection -
> > wireless as it happens and therefore not entirely predictable in how
> > quickly it will connect.
>
> Mmm... I would be careful with this, NTP may refuse to sync if the offset
> between current/real date and system date is too wide.
by NTP I mean using the NTP protocols, I use ntpdate which does not suffer
from this problem.
>
> > I would like to make sure that cron (and I am quite happy to looks at
> > other crons if that makes like easy) does not use an unset clock as the
> > basis for firing commands.
>
> There are also "/etc/cron.hourly|daily|weekly" folders where you can put
> your scripts which will be run by cron at no "specific" time, not sure if
> this can be useful to your purpose or you seek instead for a system wide
> solution to your timing issues.
>
> > I could use update-rc.d to disable cron, and only enable it once
> > wpa_supplicant has established the connection, but then what if the
> > wireless link goes down and back up while the hardware is powered up, in
> > which case it would get restarted unnecessarily.
> >
> > Does anyone know if there is a way to tell and of the crons to ignore
> > unset times?
>
> Having a system configured with bad time may experience stability issues
> as most of the base scripts rely on the right time to run their jobs by
> means of cron and/or other scheduler daemons.
which is why I want to disable the cron type activities until I have
set the time/date to a real one.
David
>
> Greetings,
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