Anacron - cron utility for desktop machines

[Asheville Joe]

I turn my computer off at night, etc., so cron jobs don't always get run 
when they should.  I found a utility called anacron that seems to be 
exactly what I want.

I installed the latest Mandrake version - no problem.

I *think* I understand how it works now.  It was pretty confusing when I 
first installed it.  Instead of being separate from cron, it works with 
it.  Since it took me a while to puzzle this out, I thought it might be 
interesting to others - especially since  this is a Linux on the desktop 
sort of thing and not for servers that run for years like many of you 
seem to work with.

If I'm right about how this works, all you really have to do is install 
it like the rpm did for me and just forget about it.  From then on, 
either cron will do it's job or anacron will catch what it missed and 
run it.  The last piece of the puzzle was in  /etc/rc.d/init.d/anacron 
which  gets anacron to run in the first place as part of startup.

Please take a look at this and correct me if I've made any errors.

The sample anacrontab that was installed is: (I'm going to change 
SHELL=/bin/sh to /bin/bash.)

# /etc/anacrontab: configuration file for anacron

# See anacron(8) and anacrontab(5) for details.

SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin

# These entries are useful for a Mandrake system.
1    5    cron.daily        run-parts /etc/cron.daily
7    10    cron.weekly        run-parts /etc/cron.weekly
30    15    cron.monthly    run-parts /etc/cron.monthly

The table format is Period (in days) |  Delay (in minutes) |  Job 
Identifier | Command
or Enviroment-variable=Value.

That's simple enough.  I guess the rest of the line after the third 
field is the command e.g. "run-parts /etc/cron/daily".
What this does is run the daily, weekly, and monthly cron scripts using 
/usr/bin/run-parts.  However, it has a safety check to make sure things 
don't get run twice (by cron and then by anacron) - see below.

I also looked at /etc/cron.daily .
In there is a file called 0anacron which contains:

#!/bin/sh
#
# anacron's cron script
#
# This script updates anacron time stamps. It is called through run-parts
# either by anacron itself or by cron.
#
# The script is called "0anacron" to assure that it will be executed
# _before_ all other scripts.

anacron -u cron.daily

What this does is tell anacron that cron got there first by updating 
anacron's timestamp files to today's date so it will think it's job 
"cron.daily" doesn't need to run.  Similar files are in cron.weekly and 
cron.monthly.

Hope this was interesting.

Joe


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"The work of the poet comes to meet the spiritual need of the society in which he lives, and for this reason his work means more to him than his personal fate, whether he is aware of this or not." ~C.G. Jung, Modern Man In Search Of A Soul