DNS HOWTO : A resolving, caching name server.
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3. A resolving, caching name server.

A first stab at DNS config, very useful for dialup, cable-modem and ADSL users.

On Red Hat and Red Hat related distributions you can achieve the same practical result as this HOWTO's first section by installing the packages bind, bind-utils and caching-nameserver. If you use Debian simply install bind and bind-doc. Of course just installing those packages won't teach you as much as reading this HOWTO. So install the packages, and then read along verifying the files they installed.

A caching only name server will find the answer to name queries and remember the answer the next time you need it. This will shorten the waiting time the next time significantly, especially if you're on a slow connection.

First you need a file called /etc/namedb/named.conf. This is read when named starts. For now it should simply contain:


// Config file for caching only name server

options {
	directory "/etc/namedb";

	// Uncommenting this might help if you have to go through a
	// firewall and things are not working out.  But you probably
	// need to talk to your firewall admin.

	// query-source port 53;
};

zone "." {
        type hint;
        file "named.root";
};

zone "0.0.127.in-addr.arpa" {
        type master;
        file "localhost.rev";
};

The FreeBSD distribution packages may use different file names for each kind of file mentioned here; they will still contain about the same things.

The `directory' line tells named where to look for files. All files named subsequently will be relative to this. /etc/namedb is the standard directory according to the hier(7) manpage.

The file named /etc/namedb/named.root is named in this. /etc/namedb/named.root should contain this: (If you cut and paste this file from an electronic version of this document, please note that there should be no leading spaces in the file, i.e. all the lines should start with a non-blank character. Some document processing software will insert spaces at beginning of the lines, causing some confusion. In that case please remove the leading spaces)


;
; There might be opening comments here if you already have this file.
; If not don't worry.
;
.                       6D IN NS        M.ROOT-SERVERS.NET.
.                       6D IN NS        I.ROOT-SERVERS.NET.
.                       6D IN NS        E.ROOT-SERVERS.NET.
.                       6D IN NS        D.ROOT-SERVERS.NET.
.                       6D IN NS        A.ROOT-SERVERS.NET.
.                       6D IN NS        H.ROOT-SERVERS.NET.
.                       6D IN NS        C.ROOT-SERVERS.NET.
.                       6D IN NS        G.ROOT-SERVERS.NET.
.                       6D IN NS        F.ROOT-SERVERS.NET.
.                       6D IN NS        B.ROOT-SERVERS.NET.
.                       6D IN NS        J.ROOT-SERVERS.NET.
.                       6D IN NS        K.ROOT-SERVERS.NET.
.                       6D IN NS        L.ROOT-SERVERS.NET.
;
M.ROOT-SERVERS.NET.     6D IN A         202.12.27.33
I.ROOT-SERVERS.NET.     6D IN A         192.36.148.17
E.ROOT-SERVERS.NET.     6D IN A         192.203.230.10
D.ROOT-SERVERS.NET.     6D IN A         128.8.10.90
A.ROOT-SERVERS.NET.     6D IN A         198.41.0.4
H.ROOT-SERVERS.NET.     6D IN A         128.63.2.53
C.ROOT-SERVERS.NET.     6D IN A         192.33.4.12
G.ROOT-SERVERS.NET.     6D IN A         192.112.36.4
F.ROOT-SERVERS.NET.     6D IN A         192.5.5.241
B.ROOT-SERVERS.NET.     6D IN A         128.9.0.107
J.ROOT-SERVERS.NET.     6D IN A         198.41.0.10
K.ROOT-SERVERS.NET.     6D IN A         193.0.14.129
L.ROOT-SERVERS.NET.     6D IN A         198.32.64.12

The file describes the root name servers in the world. The servers change over time and must be maintained now and then. See the maintenance section for how to keep it up to date.

The next section in named.conf is the last zone. I will explain its use in a later chapter; for now just make this a file named localhost.rev in the subdirectory etc/namedb/: (Again, please remove leading spaces if you cut and paste this)


$TTL 3D
@               IN      SOA     ns.freebsd.bogus. hostmaster.freebsd.bogus. (
				1       ; Serial
				8H	; Refresh
				2H      ; Retry
				4W	; Expire
				1D)	; Minimum TTL
			NS      ns.freebsd.bogus.
1			PTR	localhost.

Next, you need a /etc/resolv.conf looking something like this: (Again: Remove spaces!)


search subdomain.your-domain.edu your-domain.edu
nameserver 127.0.0.1

The `search' line specifies what domains should be searched for any host names you want to connect to. The `nameserver' line specifies the address of your nameserver, in this case your own machine since that is where your named runs (127.0.0.1 is right, no matter if your machine has another address too). If you want to list several name servers put in one `nameserver' line for each. (Note: Named never reads this file, the resolver that uses named does. Note 2: In some resolv.conf files you find a line saying "domain". That's fine, but don't use both "search" and "domain", only one of them will work).

To illustrate what this file does: If a client tries to look up foo, then foo.subdomain.your-domain.edu is tried first, then foo.your-domain.edu, and finally foo. You may not want to put in too many domains in the search line, as it takes time to search them all.

The example assumes you belong in the domain subdomain.your-domain.edu; your machine, then, is probably called your-machine.subdomain.your-domain.edu. The search line should not contain your TLD (Top Level Domain, `edu' in this case). If you frequently need to connect to hosts in another domain you can add that domain to the search line like this: (Remember to remove the leading spaces, if any)


search subdomain.your-domain.edu your-domain.edu other-domain.com

and so on. Obviously you need to put real domain names in instead. Please note the lack of periods at the end of the domain names. This is important; please note the lack of periods at the end of the domain names.

3.1. Starting named

3.2. Resolvers

3.3. Congratulations


DNS HOWTO : A resolving, caching name server.
Previous: Introduction.
Next: Starting named