From owner-freebsd-hackers@freebsd.org  Mon Nov 16 22:12:58 2015
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To: hackers@freebsd.org
Subject: Getting rid of 2*Njail sendmail processes
From: Poul-Henning Kamp <phk@phk.freebsd.dk>
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Date: Mon, 16 Nov 2015 22:12:50 +0000
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It has always bothered me to no end, to have to run two sendmail
processes in jails, just to be able to get the cron emails.

Tonight I figured out how to avoid that:

	In the hosts rc.conf:

	    sendmail_enable=YES

	That makes sendmail listen to *:25

	In the jails rc.conf:

	    sendmail_enable=NONE

	Add the magic sauce:

	Put all jail hostnames into the hosts /etc/mail/local-host-names

	The quick way:

	    jls | awk '{print $3}' > /etc/mail/local-host-names

	That makes the hosts sendmail treat all the jails as itself.

	Clean up, from the host:

	    killall sendmail

	    sh /etc/rc.d/sendmail start

	Congratulations:  You just got rid of 2*Njail sendmail processes.

Obviously this doesn't allow you to receive email in the jails, so
it is not a general solution for all jails, but only for the very
common case where the only email activity is out of the jails.

Poul-Henning

PS: Somebody please stick this in the relevant handbooks/docs...


-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.