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DNS setup

Few people run local Unix DNS servers today. I have a few customers who use Windows Server to provide local DNS, but I don't think I've seen a Unix box with anything more than resolv.conf in some time.

The configuration was not difficult, but it did require careful attention to detail and editing of text files. That's probably the biggest reason people had trouble - a simple mistype could cripple you.

From: simon at ccomms dot demon dot co dot uk (Simon Hobson)
Newsgroups: comp.unix.sco.misc
Subject: Re: DNS
Date: Sat, 07 Aug 1999 14:38:07 +0100
Message-ID: <B3D1F54F966815F6EC@simonsmac.colony.com> 
References: <7oep3l$2jo6@enews1.newsguy.com> 
X-NNTP-Posting-Host: colonyuk.demon.co.uk:158.152.173.186

In article <7oep3l$2jo6@enews1.newsguy.com>,
"Waif" <waif@ods.ods.net> wrote:

>I posted previously and was told this was more than likely an issue with DNS
>being improperly set up, which is highly believable.

>From memory (and I stand to be corrected), the default timeout for DNS
queries is about 90s, so if your PCs are trying DNS queries and failing it
would appear that they (or your SCO box) are trying 4 times.

Literally as I typed this I had a thought ...

The default configuration for SCO DNS servers includes a list of root
servers for the internet (with comments to change these to current values
as they could be wrong). If your system is not connected to the net, and is
mis-configured, it could be trying to contact some other server to get an
address.

In all the stuff below, where I have used <yourdomain.com> you should use
your own domain name (without the < & >). If you do not have a domain name
registered, then you can effectively use whatever you like as you are not
connected to the outside world - but if you use a non registered name and
later connect then your are likely to have problems.

As a starting point, look at your /etc/named.conf file. You should have
entries like :
  zone "<yourdomain.com>" {
          type master;
          file "hosts";
  };
  
  zone "nnn.nnn.nnn.in-addr.arpa" {
          type master;
          file "rev";
  };

These tell named about your local network.

At the bottom, you will probably have an entry like :
  zone "." {
          type hint;
          file "root.cache";
  };

This tells named what servers to go to if asked for an address NOT in
<yourdomain.com>.

You need to be logged in as root for the following steps, so be VERY
careful.
Check the file root.cache (in /etc/named.d by default) and comment out any
servers listed (putting a ";" at the front of every line should do it).
Then tell named to reload it's database :

Get the process ID of named, either by "cat /etc/named.pid" or by "ps
-ef|grep named". Tell named to reload it's database by "kill -HUP <pid>"
where <pid> is the number found in step 1.

If this is the problem, when first connecting from the PCs, one of three
things will happen :
1) The delay will be gone
2) You will get an error message about not being able to resolve a host
name
3) There will be no change, in which case I don't think it is likely to be
a DNS problem.


On the PCs, chack that in the DNS tab of TCP/IP properties :
  A hostname is entered in the hostname box.
  <yourdomain.com> is entered in the domain box.
  Only the IP address of the unix system is listed under servers.
  <yourdomain.com> is listed in the search domains box.


As far as system loading is concerned, I wouldn't worry. Our network makes
extensive use of DNS (around 140 nodes over 4 sites, all using one DNS
server), and our DNS server has to handle our internet access as well.
Quickly checking I see that in nearly 8 days uptime, the DNS server has
consumed a total of under 3 1/2 hours of CPU - this works out (allowing for
quiet times etc) as only a couple of percent of our capcity. On a small
network like yours I doubt if you will see anything like that loading. We
have an Acer server with dual Pentium II 200's, 1G ram, and about 56G disk.

Hope this is some help, Simon

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