anacron

[sktsee]

On Tue, 2006-05-09 at 21:41 +0100, Toby Kelsey wrote:
> Derek Broughton wrote:
> 
> > Anacron exists to ensure that scheduled jobs run _sometime_.  So it runs at
> > boot _and then stops_.  It also runs at set times of day (specified by
> > cron) to execute the cron.*ly schedules.  If you want something to _always_
> > run at an exact time, you put it in a crontab, if you want something to
> > always get run, even if your system isn't up when scheduled, you use
> > anacron.
> 
> Or better, use fcron, as has been suggested.
> 
> > "Description: a cron-like program that doesn't go by time" seems to be
> 
> Given the etymology and function of cron, it is a confused and
> self-contradictory description.  What is cron if not a "by time" program?
> 
> The man page has a better summary "anacron - runs commands periodically"
> 
> > pretty clear that you _can't_ expect it to run at set times.  It's _not_
> > advertised as a replacement for cron, either.  It's a supplement to cron -
> > mostly for those of us with laptops, or desktop machines we shut down when
> > not in use.
> 
> Here's the default Breezy /etc/crontab:
> 
> # /etc/crontab: system-wide crontab
> # Unlike any other crontab you don't have to run the `crontab'
> # command to install the new version when you edit this file.
> # This file also has a username field, that none of the other crontabs do.
> 
> SHELL=/bin/sh
> PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
> 
> # m h dom mon dow user  command
> 17 *    * * *   root    run-parts --report /etc/cron.hourly
> 25 6    * * *   root    test -x /usr/sbin/anacron || run-parts --report
> /etc/cron.daily
> 47 6    * * 7   root    test -x /usr/sbin/anacron || run-parts --report
> /etc/cron.weekly
> 52 6    1 * *   root    test -x /usr/sbin/anacron || run-parts --report
> /etc/cron.monthly
> #
> 
> Clearly, when anacron is installed it _usurps_ the usual cron directories
> /etc/cron.*ly.  Yes you can still edit the crontab but for the more
> user-friendly directories it's not a supplement but is installed as a
> replacement.  So both end-users and Ubuntu-designers are confused by its name
> into thinking it's a replacement for cron.  It should be called
> something different like 'periodic' and use its own directories.
> 
> Toby
> 
>From /usr/share/doc/anacron/README.gz

"What Anacron is not ?
     ---------------------

   Anacron is not an attempt to make cron redundant.  It cannot
currently be used to schedule commands at intervals smaller than days.
It also does not guarantee that the commands will be executed at any
specific day or hour.

   It isn't a full-time daemon.  It has to be executed from boot
scripts, from cron-jobs, or explicitly."

Sometimes reading the man page isn't enough. Anacron does what it's
advertised to do.


-- 
sktsee