[ale] RHL9 crond doesn't read in new crontab entries

[Danny Cox]

On Tue, 2006-08-22 at 08:38 -0400, Chris Ricker wrote:
> You're not the only one
> 
> I've seen similar on both Linux and on Solaris. Usually, it was either 
> because of a weird interaction with a naming service or because of nscd 
> (if you use nscd, start it before cron and never restart it without also 
> restarting cron)
> 
> One of the other Unix admins here is paranoid enough about this that he 
> *always* restarts the cron daemon after editing any root crontab ;-)

	Okay, I'll weigh in on this too.  I've long suspected that modern
cronds implemented another mechanism for notification besides kill -HUP
that Edition 7 Unix had (showing my age, huh? ;-).  I just did an "ls
-l /proc/1724/fd" on my system (crond's PID), and one interesting fd is
"4 -> socket:[4514]".

	I speculate ('cause I've not read the code) that crontab may "nudge"
crond to reread a just-modified crontab via the socket.  That would also
explain why simply editing a crontab in place would have no effect;
crond never notices.

	The current man page for crond says that a HUP will cause it to close
and reopen it's log file.  It mentions nothing about rereading the
crontabs.

	Yeah, now my curiosity is up.  I'll have to download the source and
poke around at it.  Linux mysteries.  Blech! ;-)

-- 
Daniel S. Cox
Internet Commerce Corporation