Path: utzoo!attcan!uunet!samsung!munnari.oz.au!metro!news
From: jimr@metro (Jim Richardson)
Newsgroups: comp.sys.apollo
Subject: Re: Problems with email
Message-ID: <1990Jul9.085515.25351@metro.ucc.su.OZ.AU>
Date: 9 Jul 90 08:55:15 GMT
References: <1664@tuvie>
Sender: news@metro.ucc.su.OZ.AU (news)
Organization: Dept of Pure Mathematics, University of Sydney
Lines: 90

In article <1664@tuvie>, mike@tuvie (Inst.f.Techn.Informatik) writes:
> Our mail works OK as long as the registry is available, but
> when the registry is down (we do not have slave registries), then 
> /bsd4.3/bin/mail will not deliver mail to the recipients. Now the 
> problem seems to be that the mailer cannot acquire the gid of mail, 
> but about this I'm not too sure. The mailer does not seem to return 
> an error code (or does /usr/lib/sendmail ignore it ?), whenever 
> this happens. The log file contains the status report Stat=Sent, but
> the mail is nowhere to be found (except on /dev/null).
> Has anybody had a similar problem and if so, how was it solved 
> (without resorting to slave registries)?

This does happen to us when the registry dies completely or gets that kind of
registry disease where the password file appears to be empty.  Another cause
is when /usr/spool/mail is unavailable: for historical reasons involving backup
/usr/spool/mail on our mail gateway machine is a soft link to a directory on
another node (avoid this if you can!).

We run a script like the following continuously on the gateway node.  It detects
either of these problems and kills the sendmail daemon if they occur.  If you
call it "netcheck" you can start it as root via "/etc/server -p netcheck &".  It
chews up some CPU time but it's worth it for the peace of mind!

#! /bin/ksh
#
#  Check Apollo system is fit to receive incoming mail messages

exec >> /sys/node_data/system_logs/netcheck.log 2>&1

print "netcheck starting at $( /bin/date )"

SLEEP_TIME=60
REPORT_INTERVAL=60
STOPPED_FLAG="/usr/spool/mail/STOPPED_FLAG"

shutsm() {
	/bin/ps aux
	print "$( /bin/date ) stopping sendmail daemon: $*"
	pids="$( /bin/ps ax | /bin/awk '/\/usr\/lib\/sendmail -bd -q[0-9]*m$/ {print $1}' )"
	print "Killing $pids"
	/bin/kill $pids
	/usr/ucb/logger -t netcheck "sendmail daemon(s) $pids stopped: $*"
	/usr/bin/touch ${STOPPED_FLAG}
	/bin/ps aux
}

typeset -i count=$REPORT_INTERVAL

while :
do
	if [ ! -f ${STOPPED_FLAG} ]
	then
		if [ ! -d /usr/spool/mail ]
		then
			shutsm "/usr/spool/mail unavailable"
		fi
		
		if [ ! -s /etc/passwd ]
		then
			shutsm "/etc/passwd missing or empty"
			/bin/ls -l /etc/passwd
		fi
	fi

	count=count-1
		
	if [ count -le 0 ]
	then
		# log the date periodically
		/bin/date
		# force new test next time even if stop flag exists
		/bin/rm -f ${STOPPED_FLAG}
		count=$REPORT_INTERVAL
	fi

	sleep $SLEEP_TIME
done

This will only work for you if /etc/passwd appears to have size zero whenever
the registry is down.  Furthermore, your sendmail daemon needs to look like
"/usr/lib/sendmail -bd -q[0-9]*m" to a "ps ax" command: if you use something
else like "-q1h -bd" adjust the script accordingly.  

Finally, the actual script we run does some other local stuff and I've hacked
it down to give the above, which may therefore have a flaw or too.  But you
should get the idea.
--
Jim Richardson
Department of Pure Mathematics, University of Sydney, NSW 2006, Australia
Internet: jimr@maths.su.oz.au  ACSNET: jimr@maths.su.oz  FAX: +61 2 692 4534