C. Scott Ananian
cscott at laptop.org
Wed Nov 4 17:12:41 EST 2009
On Wed, Nov 4, 2009 at 5:01 PM, Paul Fox <pgf at laptop.org> wrote:
> c. scott ananian wrote:
> > Keep in mind that some of cron's duties are done by anacron (or were
> > when I had a hand in the distro), which is laptop-friendly.
> > Anacron only handles daily/weekly/monthly tasks, though; you do need
> > cron running if you want tasks with sub-day scheduling.
> as dsd pointed out to me on IRC, anacron is driven by cron -- at
> least these days it seems to be. so without cron, anacron probably
> won't work either. (i was under the impression they were
> separate, but perhaps that's ancient history, or i was just
That's *mostly* right. Anacron is idempotent, it just needs to be
triggered at least once a day so it can check to see if there's stuff
to do. It's invoked from initscripts/upstart at power up, and is
often invoked on resume-from-suspend as well. But if you actually
leave the machine on and unsuspended for >1 day, you need to trigger
it from cron as well to make sure it gets a chance to do its thing.
It never hurts to invoke anacron, you just need to ensure a certain
minimum frequency of invocation -- and cron is usually used to do
this. But you don't always immediately notice if cron is missing,
because anacron will still do its thing on startup, etc.
( http://cscott.net/ )
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