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早期freebsd实现

		     NINIT -- NAMED INIT PROGRAM
			     May 13, 1991

WHAT NINIT DOES
===============

ninit starts named in nofork mode and waits for it to exit.  When it
exits, ninit restarts a new named.  In addition, every 5 minutes,
ninit wakes up and sends a SIGIOT to named.  This causes named to dump
statistical information to /usr/tmp/named.stats.  Every 60 seconds,
ninit tries to do a name resolution using the local named.  If it
fails to get an answer back in some short amount of time, it kills the
existing named and starts a new one.

We are running this on the MIT nameservers and our mailhub.  We find
that ninit is extremely useful in catching named's that die mysteriously,
or which get hung for some unknown reason.  It's especially useful on our
mailhub, since our mail queue will explode if we lose name resolution
even for a short time.  

MODIFICATIONS TO NAMED
======================

In order to use ninit, you will need to modify your named so that it
understands the -n flag, which tells it not to fork upon startup.  The
patch to do that can be found in ns_main.c.patch.  

If you don't have source code to your named, you can also solve the
problem by adding the #define FORKING_NAMED.  This solves the problem
by starting the named with the -d option, which tells named not to
fork, but which also tells it to start a debugging log in
/usr/tmp/named.run.  As soon as the the named is finished
initializing, ninit will send a SIGUSR1 signal to tell it to turn off
debugging.  (It can't send the signal before that because the signal
handlers aren't established before that point.)  The down side of this
is that named will be writing debugging information while it is
initializing itself.  

I would suggest modifying named if you have the source.  If you don't
FORKING_NAMED will work --- it's an ugly solution, though.

HOW TO INSTALL NINIT
====================

1)  Edit ninit.c and check the configuration options near the
beginning of the file.  You will almost certainly need to change
TEST_HOST.  You may or may not need to change the configuration
variables.

2) Compile ninit and place the executable in /etc.

3) Pick a port for the "nstats" service and install it in /etc/services.
Modify the named_stats script to use the port number you've picked as the 
$default_nstats_port.

5) Add the following line /etc/inetd.conf

nstats stream tcp nowait unswitched daemon /bin/cat   cat /usr/tmp/named.stats

6) Modify /etc/rc so that it starts /etc/ninit instead of /etc/named
upon reboot.

7) As root, run /etc/ninit.  It will kill off the existing named and
run a new named under its control.

If you like, you may wish to edit /etc/syslog.conf to direct the ninit
logging information to a logfile, or to some centeral logging host, or
wherever you choose.

You will also need to modify named_stats so that it checks whatever
hosts you desire.

BUGS
====

	None known.  (Yet!)

	If you find any problems, please let me know:

		Theodore Ts'o
		[e-mail].

I hope you find ninit useful!

Theodore Ts'o
May 13, 1991.