Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wasatch!cs.utexas.edu!uunet!auspex!guy
From: guy@auspex.auspex.com (Guy Harris)
Newsgroups: comp.mail.uucp
Subject: Re: su uucp in crontabs/root ?
Keywords: root uucp crontab su
Message-ID: <1559@auspex.auspex.com>
Date: 4 May 89 07:13:06 GMT
References: <75@norsat.UUCP> <2008@egvideo.UUCP> <1524@auspex.auspex.com> <483@sequoia.UUCP> <1545@auspex.auspex.com> <487@sequoia.UUCP>
Reply-To: guy@auspex.auspex.com (Guy Harris)
Distribution: na
Organization: Auspex Systems, Santa Clara
Lines: 22

>I asked about the mechanism because I wished to understand it,

Well, as was indicated in the part of my posting you didn't cite,
"crontab" sends a message over a named pipe.  The named pipe is
generally named "FIFO"; its location differs.  The message basically
tells "cron" that a "crontab" file is to be reread, and which file it
is.  (Other messages are used for deleting "crontab" files and for
submitting and deleting "at" jobs.)

>Occasionally someone does some things without RTFM though, and it
>would be nice to be able to send a signal or whatever to quickly
>fix a problem if that were a known way to get things back on track.

The way to quickly fix the problem is to resubmit the "crontab" file
through "crontab" - if the only copy left is the one in
"crontabs/<wherever>", make a copy of it and hand it to "crontab" -
standard procedure.  You really don't need to know the
subject-to-change-without-notice details of how "crontab" works to do
this.  (And one problem with people knowing about it is that it becomes
harder to change - that's one reason why Sun never published the ND
protocol; they didn't want anybody to use it themselves and make it hard
for them to nuke ND.)