Subject: Linux-Activists - DOC Channel digest. 95-2-4-20:58
From: Linux Activists <[email-masked]>
To: Linux-Activists <[email-masked]>
Date: Sun, 5 Mar 1995 02:38:56 +0200

Topics:
	 caching named howto

----------------------------------------------------------------------

From: "Nicolai Langfeldt" <[email-masked]>
Subject: caching named howto
Date: Sat, 04 Mar 1995 18:53:18 +0100

I've written a caching named mini howto.  This is useful for anyone
running thru a modem connection with slip/ppp or other ip connection.
I've gotten a few ppl to use it and all but one (which had a TOTAL
failure to get anything to work) have reported that it's good.

Before I submit it to general public I'd like some more ppl to test
it, so if you would read it, and maybe even follow the instructions...
And then e-mail me some feedback, and please - reply only to
[email-masked], not the whole list of recipients.

Thanks
  Nicolai

Here it is:
- - ------------------------------------------------------------------
Caching named mini howto.

Version 0.3

(C)opyright 1995 Nicolai Langfeldt.  Do not modify without amending
copyright, distribute freely but retain copyright message.

Please send money, comments and/or questions to [email-masked].

I would appreciate it if someone sent me a section 3 for (c)slip
users.

1. Introduction

This mini howto describes how to set up set up a caching name server.
This is primarily usefull for people connected to the net with a
(dialup) modem because name lookups can be slow due to the slownes of
modem comunications.

Just to be clear: When I say 'your machine' I mean the macine/host you
dial up to the net from, for most people this is their home machine.
There is room for confusion because quite people dial up to their own
internet connected machine at work, _that_ is not the machine I talk
of in this howto.  Not at all.

Before you start on this you should configure your machine so that you
can telnet in and out of it, and make successfuly make all kinds of
connections to the net.  This includes having good /etc/host.conf,
/etc/resolve.conf and /etc/hosts files.  If you don't already have
this working the networking howto explains how to set it up.

Name serving on unix is done by a program called named.  This is a
part of the bind package that's coordinated by Paul Vixie.  This can
be gotten on Linux ftp sites, but chances are that you already have a
named.  It's usualy called /usr/sbin/named.  You can use that if you
already have it.

If you need to set up named for more than just caching, for example
for setting up your own internet domain I sugest you get the book "DNS
and BIND" by C.  Liu and P. Albitz from O'Reilly & Associates,
Sebastopol, CA, ISBN 0-937175-82-X 1992.  There are also docs in the
bind distribution, including a FAQ and a manual as well as papers.

2. Setting it up

Tip: Make backup copies of all the files I instruct you to change if
you already have them, so if after going thru this nothing works you
can get it back to your old, working state.

First you need a file called /etc/named.boot.  This is read when named
starts.  For our purpose it should simply contain (remove leading
spaces):

  ;  Boot file for nicolais caching name server
  ;
  directory /etc
  ;
  ; type          domian                          source file or host
  cache           .                               root.cache

A file named /etc/root.cache is named in this.  /etc/root.cache should
contain this (remove leading spaces again):

  ; ---- Root cache dump ----
  .       IN      NS      NS.INTERNIC.NET.
  .       IN      NS      AOS.ARL.ARMY.MIL.
  .       IN      NS      NS1.ISI.EDU.
  .       IN      NS      C.PSI.NET.
  .       IN      NS      TERP.UMD.EDU.
  .       IN      NS      NS.NASA.GOV.
  .       IN      NS      NIC.NORDU.NET.
  .       IN      NS	  NS.ISC.ORG.
  ;
  ;  Prep the cache (hardwire the addresses).  Order does not matter
  ;
  NS.INTERNIC.NET.	999999	IN	A	198.41.0.4
  AOS.ARL.ARMY.MIL.	999999	IN	A	128.63.4.82
  AOS.ARL.ARMY.MIL.	999999	IN	A	192.5.25.82
  NS1.ISI.EDU.		999999	IN	A	128.9.0.107
  C.PSI.NET.		999999	IN	A	192.33.4.12
  TERP.UMD.EDU.		999999	IN	A	128.8.10.90
  NS.NASA.GOV.		999999	IN	A	128.102.16.10
  NS.NASA.GOV.		999999	IN	A	192.52.195.10
  NIC.NORDU.NET		999999	IN	A	192.36.148.17
  NS.ISC.ORG		999999	IN	A	192.5.5.241

It describes the root name servers in the world.  This changes over
time, see below for how to get updated data.

These two files are supposedly described in the named man page.  I say
supposedly because that man page is probably one of the least clear
man pages in creation if you don't already know how to set up named.

Next, when you're connected to the net you need a /etc/resolv.conf
looking like this:

  search ifi.uio.no uio.no math.uio.no
  nameserver 127.0.0.1

The 'search' line tells the name resolving routines in libc to search
for the host names in the domains ifi.uio.no, uio.no and
math.uio.no. It would normaly not contain your top domain ('no' in my
case). I have math.uio.no in the list because I regularly log into
machines there.  If you belong in 'ots.utexas.edu' you would probably
want to put 'ots.utexas.edu' and 'utexas.edu' in the list.  But you
can put any domains you like in the list.  The 'nameserver' line says
that the nameserver is at 127.0.0.1 (the loopback address, i.e. your
own machine).

The last file you have to fix is /etc/host.conf.  There should be a
line starting with 'order' and it should look like this:

  order hosts,bind

If there is no order line you should stick one in.  It tells the host
name resolving routinges to first look in /etc/hosts, then ask the
name server (which you in resolve.conf said is at 127.0.0.1)

These two latest files are documented in the resolv(8) manpage (do
'man 8 resolv').  That man page is IMHO readable, and everyone should
read it.

Now you can connect to the world and test your setup.  Dial up and
establish your connection the usual way.  Once the connection is
established (and /etc/resolve.conf has the right 'nameserver' line)
you start /usr/sbin/named.  If you look in your syslog message file
(usualy called /var/adm/messages, use the command 'tail
/var/adm/messages' to see it's end) after you start named you should
see something like:

  Jan 14 23:13:14 roke named[671]: starting.  named 4.9.3-BETA9 Sat Jan 14 
21:19:55 MET 1995    janl@roke:/usr/src/bind-4.9.3-BETA9/named
  Jan 14 23:13:14 roke named[672]: Ready to answer queries. 

If there is any messages about errors then there is a mistake
somewhere in the file named named in the message (one of named.boot
and root.cache I hope :-) Kill named and go back and check the files.

Once named does not complain you can start querying it.  The program
designed for this is nslookup. Start it by giving linux the command
'nslookup':

  $ nslookup
  Default Server:  localhost
  Address:  127.0.0.1

  > 

Now you can enter a query.  Try looking up some machine close to you.
mnemosyne.uio.no is a Linux machine I run at the university:

  > mnemosyne.uio.no
  Server:  localhost
  Address:  127.0.0.1

  Name:    mnemosyne.uio.no
  Address:  129.240.21.233

nslookup now asked your named to look for the machine
mnemosyne.uio.no.  It then contacted one of the name server machines
named in your root.cache file, and asked it's way from there.  It
might take some seconds before you get the result as it searches all
the domains you named in /etc/resolve.conf.  If you try again you get
this:

  > mnemosyne.uio.no
  Server:  localhost
  Address:  127.0.0.1

  Non-authoritative answer:
  Name:    mnemosyne.uio.no
  Address:  129.240.21.233

Note 'Non-authoritative answer:'.  That means that named did not go
out on the network to ask this time, it instead looked in it's cache
and found it there.  But the cached information _might_ be out of date
(also called 'stale').  So you are informed of this by it saying
'Non-authorative answer:'.  So when nslookup says this the second time
you ask for a host it's a sign it caches the information and the
desired effect of setting up the named has been reached. You exit
nslookup by giving the command 'exit'.

A warning: It is not smart to run named when you are not connected to
the net, this is because named will try to send queries to the net and
it has a long timeout, and you have to wait for this timeout every
time some program tries to resolve a name.  The next section explains
how I deal with seting up and taking down named when connecting and
disconnecting to the net.

So now you know how to set up different configuration files so named
works.

3. Automatic setup when connecting (and disconnecting).

This section explains how I have set things up to automate everything.
My way might not suit you at all, but you might get a idea from
something I've done.  Also, I use ppp for dialup, while many use slip
or cslip, so almost everything in your setup can be different from
mine. But slip's dip program should be able to do many of the things I
do.

Normaly, when I'm not connected to the net I have a resolv.conf file
simply containing the line

  domain uio.no

This ensures I don't have to wait for the hostname resolving library
to try to connect to a nameserver that can't help me.  But when I
connect I want to start my named and have a resolv.conf looking like
the one described above.  I have solved this by keeping two
resolv.conf 'template' files named resolv.conf.local and
resolve.conf.connected.  The latter looks like the resolve.conf
described before in this document.

To automaticaly connect to the net I run a script called 'ppp-on':

  #!/bin/sh
  cp -v /etc/resolv.conf.connected /etc/resolv.conf
  echo calling...
  pppd

pppd has a file called 'options' that tells it the particulars of how
to get connected.  Once my ppp connection is up the pppd starts a
script called ip-up (this is described in the pppd man page).  This is
parts of the script:

  #!/bin/sh
  ...
  echo 1>&2 PPP: IP upp
  ...
  /usr/sbin/named
  echo PPP: ip-up finished

I.e. I start my named there.  When ppp is disconnected pppd runs a
script called ip-down:

  #!/bin/sh
  echo 1>&2 PPP: IP down
  cp /etc/resolv.conf.local /etc/resolv.conf
  kill `cat /var/run/named.pid`

So this gets things configured and up when connecting and
disconfigured and down when disconnecting.

4. Getting a new root.cache file.

I mentioned that the root.cache information changes from time to time.
So you might want to update it once in a long while.  Start nslookup
and give the command

  > set type=ns

Which means that nslookup should ask for 'ns' (or NameServer) records
(it usualy asks for A, or address records).

  > .

Which means, get me root information.  In a unix filesystem the root
is '/', in the name server system the root is '.' and is often written
so.  The answer to my query was:

  Server:  localhost
  Address:  127.0.0.1

  Non-authoritative answer:
  (root)  nameserver = AOS.ARL.ARMY.MIL
  (root)  nameserver = NS1.ISI.EDU
  (root)  nameserver = C.PSI.NET
  (root)  nameserver = TERP.UMD.EDU
  (root)  nameserver = NS.NASA.GOV
  (root)  nameserver = NIC.NORDU.NET
  (root)  nameserver = NS.ISC.ORG
  (root)  nameserver = NS.NIC.DDN.MIL
  (root)  nameserver = NS.INTERNIC.NET

  Authoritative answers can be found from:
  (root)  nameserver = AOS.ARL.ARMY.MIL
  (root)  nameserver = NS1.ISI.EDU
  (root)  nameserver = C.PSI.NET
  (root)  nameserver = TERP.UMD.EDU
  (root)  nameserver = NS.NASA.GOV
  (root)  nameserver = NIC.NORDU.NET
  (root)  nameserver = NS.ISC.ORG
  (root)  nameserver = NS.NIC.DDN.MIL
  (root)  nameserver = NS.INTERNIC.NET
  AOS.ARL.ARMY.MIL        internet address = 128.63.4.82
  AOS.ARL.ARMY.MIL        internet address = 192.5.25.82
  NS1.ISI.EDU     internet address = 128.9.0.107
  C.PSI.NET       internet address = 192.33.4.12
  TERP.UMD.EDU    internet address = 128.8.10.90
  NS.NASA.GOV     internet address = 128.102.16.10
  NS.NASA.GOV     internet address = 192.52.195.10
  NIC.NORDU.NET   internet address = 192.36.148.17
  NS.ISC.ORG      internet address = 192.5.5.241
  NS.NIC.DDN.MIL  internet address = 192.112.36.4

It says that the answer is non-authorative, and that an authorative
answer can be gotten from one of a list of hosts.  We want a
authorative answer so we tell nslookup to use one of the named
servers.  I pick nic.nordu.net because nordunet is the Nordic research
network and is thus close to me (I'm in Norway).  You can choose any
you fancy.

  > server nic.nordu.net
  Default Server:  NIC.NORDU.NET
  Address:  192.36.148.17

Now to ask for the root ns records again:

  > .
  Server:  NIC.NORDU.NET
  Address:  192.36.148.17

  (root)  nameserver = TERP.UMD.EDU
  (root)  nameserver = NS.NASA.GOV
  (root)  nameserver = NIC.NORDU.NET
  (root)  nameserver = NS.ISC.ORG
  (root)  nameserver = NS.NIC.DDN.MIL
  (root)  nameserver = NS.INTERNIC.NET
  (root)  nameserver = AOS.ARL.ARMY.MIL
  (root)  nameserver = NS1.ISI.EDU
  (root)  nameserver = C.PSI.NET
  (root)  nameserver = TERP.UMD.EDU
  (root)  nameserver = NS.NASA.GOV
  (root)  nameserver = NIC.NORDU.NET
  (root)  nameserver = NS.ISC.ORG
  (root)  nameserver = NS.NIC.DDN.MIL
  (root)  nameserver = NS.INTERNIC.NET
  (root)  nameserver = AOS.ARL.ARMY.MIL
  (root)  nameserver = NS1.ISI.EDU
  (root)  nameserver = C.PSI.NET
  TERP.UMD.EDU    internet address = 128.8.10.90
  NS.NASA.GOV     internet address = 128.102.16.10
  NS.NASA.GOV     internet address = 192.52.195.10
  NIC.NORDU.NET   internet address = 192.36.148.17
  NS.ISC.ORG      internet address = 192.5.5.241
  NS.NIC.DDN.MIL  internet address = 192.112.36.4
  NS.INTERNIC.NET internet address = 198.41.0.4
  AOS.ARL.ARMY.MIL        internet address = 192.5.25.82
  AOS.ARL.ARMY.MIL        internet address = 128.63.4.82
  NS1.ISI.EDU     internet address = 128.9.0.107

If you change '(root) nameserver =' to '. IN NS' then the first part
is exactly like the first part of the root.cache file and if you
change 'internet address =' with '999999 IN A' in the second part you
have something exactly like the second part of the root.cache file.
So, this corresponds to the root.conf file.  Run
/usr/sbin/named.reload or restart named once you have updated the
root.cache file.

------------------------------

End of DOC Digest
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