What is a QUEDEFS file (cron)?

[dcm at sfsup.UUCP]

In article <815 at investor.UUCP> root at investor.UUCP writes:
>When I set up /usr/lib/cron/log on my system,  each command is
>preceded by the following:
>
>! cannot stat QUEDEFS file current date and time
>
>I cannot find a reference to this file anywhere in the manuals.
>Anybody know what it is and how to set it up?

First, a little something about the SysV cron.  
This is an impressive piece of work!  The cron daemon has the
capability of maintaining 26 different event queues.  Presently
only 3 are being used.  Queue 'a' is for 'at(1)' jobs, queue 'b'
is for 'batch(1)' jobs, and queue 'c' is for cron jobs.  (For those
not running SysV, saying "batch" is almost like saying "at now", but
it uses a different queue and at would respond with "at: too late".)
So, that means that there are 23 queues presently unused.
Unfortunately, there is no way to use these other queues without
rewriting a portion of cron, but that's a story for another day.

Now, regarding QUEDEFS.  This is in reference to the file 
"/usr/lib/cron/queuedefs".  This file defines certain aspects of
the event queues.  The default contents should look something like:

$ cat /usr/lib/cron/queuedefs
a.4j1n
b.2j2n90w
$

The format of these lines is "queue.[#j][#n][#w][#u]".
Queue is the name of one of the queues ('a' thru 'z').  The four
fields following the period are all optional.  The '#' represents
an integer decimal value.  The '#j' field limits the number of
concurrently running jobs permitted for that queue.  The '#n'
specifies the nice for all non su jobs on that queue.  The '#w'
field specifies how long to wait, in seconds,  before rescheduling
when the number of running jobs is >= '#j'.  Finally, the '#u'
field prevents scheduling of events when the number of users on
the system exceeds this number.  A zero value means no restriction.

The default values are "10j2n60w0u".

As a closing note, cronjobs (as opposed to atobs or batchjobs)
bypass the queuedefs.  So setting a queue definition for queue 'c'
will have no effect.

				Dave
--

David C. Miller, consultant
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