TweetFollow Us on Twitter

DIY: BIND DNS Server

Volume Number: 23 (2007)
Issue Number: 07
Column Tag: Networking

DIY: BIND DNS Server

How to turn OS X client into a full-featured DNS server

by Ben Greisler

DNS is important!

To paraphrase Steve Ballmer, "DNS! DNS! DNS!"

What is the "DNS" and why is it so danged important? DNS stands for Domain Name Service and it is the method of translating domain names to IP addresses. Almost every aspect of network usage involves some level of name services and without it problems will pop up, sometimes in ugly ways.

In this article, we will assume that you know that you need to provide DNS services for your network. There are a number of ways you can do this including using OS X Server which has BIND (Berkeley Internet Name Domain) built in, but say you don't want to spend the $500 to $1000 that OS X Server will cost? Is there a lower cost way of doing this? If you have a spare OS X client machine hanging around, the answer is yes. With just a little bit of time and some low-key effort, you can get BIND running on almost any OS X client machine.

DNS Server Basics

A common scenario is that you just bought a shiny new Xserve and in the process of setting it up you turn on DNS services and pop in a few machines that you need records for. Nice and simple. Apple has done a reasonable job of giving administrators an easy method to get DNS up and running. Some people will argue that it is too simple and basic, but it is enough for Open Directory to be happy if you are setting up an OD master and clients trying to authenticate against it. An issue comes up when you realize that best practice states that you should have two DNS servers to provide some redundancy.

The basic steps we will take are to provide a method of starting up the BIND DNS server already in OS X, provide it with the proper configuration and give it some records to work with. There are a number of files involved:

/System/Library/StartupItems/BIND/BIND
/System/Library/StartupItems/BIND/StartupParameters.plist
/etc/rndc.key
/etc/named.conf
/etc/hostconfig
/var/named/named.local
/var/named/named.ca
/var/named/localhost.zone
/var/named/db.192.168.254 (this is an example)
/var/named/greisler.org.zone (this is an example)

Some of these files exist and will need modification; others will need to be built from scratch. None of it is hard, and following the steps below will get you a running DNS server faster and easier than you would expect.

Getting Started

In this article, we will be using a machine with OS X 10.4.9 installed on it. The test domain is greisler.org. Since OS X client has BIND already installed, all we need to do is get it running; it is really straightforward. The following steps will allow BIND to start every time the machine starts using a StartupItem. We will then provide a way to control the server.

Creating the StartupItem

Open up Terminal or ssh into the machine. I know some people will be unhappy with this, but I find that logging in as root makes things a bit easier while setting up the DNS server.

Create a folder named BIND within /System/Library/StartupItems and navigate to it:

mkdir  /System/Library/StartupItems/BIND
cd  /System/Library/StartupItems/BIND

Create two files within the BIND folder:

touch BIND
touch StartupParameters.plist

Open up the BIND file in your favorite editor and drop in the following text:

#!/bin/sh
. /etc/rc.common
if [ "${DNSSERVER}" = "-YES-" ]; then
  ConsoleMessage "Starting Cheap BIND DNS Server"
  /usr/sbin/named
fi

Make BIND executable:

chmod +x BIND

Open up the StartupParameters.plist file in your favorite editor and drop in the following text:

{
  Description = "Cheap DNS Server";
  Provides = ("DNS Server");
  OrderPreference = "None";
  Messages =
  {
  start = "Starting Cheap BIND DNS Server";
  stop = "Stopping Cheap BIND DNS Server";
  };
}

Allow BIND to be controlled:

We now need to make the RNDC (Remote Name Daemon Controller) configuration files:

rndc-confgen -a

Letting OS X know that we want a DNS server to run:

Open up /etc/hostconfig in your favorite editor and drop in the following text:

DNSSERVER=-YES-

DNS Zone Files

With those steps, we have made ourselves a functional DNS server all ready to go, but now we need to give it some information on what to serve. If you have access to OS X Server, it is an easy job of setting up your configurations and copying over the various zone files. If you don't, you can use the following examples as a template and just modify them with the appropriate data for your environment. In this article, we are using greisler.org in the 192.168.254.x range as the example.

In a nutshell, we need to build a forward zone file that converts names to IP addresses, a reverse zone file that converts IP addresses to names and then we need to tell the named.conf file that they exist for usage.

Forward Zone File:

To build the forward zone file, navigate to /var/named and make a file that will contain the forward zone information:

cd /var/named
touch greisler.org.zone

Inside the file build out the zone information you need, such as:

$TTL 86400
greisler.org.   IN      SOA     nameserver.greisler.org. admin.greisler.org. (
                        2007010201
                        3h
                        1h
                        1w
                        1h )
greisler.org.              IN      NS  nameserver.greisler.org.        
greisler.org.              IN      A   192.168.254.240  
nameserver.greisler.org.   IN      A   192.168.254.240  
test.greisler.org.         IN      A   192.168.254.22  
dnsiscool.greisler.org.    IN      A   192.168.254.23  
bubba.greisler.org.        IN      A   192.168.254.24

Reverse Zone File:

To build the reverse zone file, navigate to /var/named and make a file that will contain the forward zone information:

cd /var/named
touch db.192.168.254

Inside the file build out the zone information you need, such as:

$TTL 86400
254.168.192.in-addr.arpa. IN SOA nameserver.greisler.org. admin.greisler.org. (
                        2007010203
                        3h
                        1h
                        1w
                        1h )
254.168.192.in-addr.arpa.   IN   NS   nameserver.greisler.org.        
240.254.168.192.in-addr.arpa.   IN    PTR   nameserver.greisler.org.        
22.254.168.192.in-addr.arpa.   IN   PTR    test.greisler.org.      
23.254.168.192.in-addr.arpa.   IN   PTR   dnsiscool.greisler.org. 
24.254.168.192.in-addr.arpa.   IN   PTR   bubba.greisler.org.

Modifying named.conf

To allow the DNS to recognize those zones, we need to tell /etc/named.conf about the zone files by editing /etc/named.conf and placing the following text within it:

zone "greisler.org" {
        type master;
        file "/var/named/greisler.org.zone";
        };
         
zone "254.168.192.in-addr.arpa" IN {
        file "db.192.168.254";
        type master;
};

Testing the DNS Server:

Restart the computer and test the DNS server:

nameserver:~ backup$ host -a dnsiscool
Trying "dnsiscool.greisler.org"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 32764
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 1
;; QUESTION SECTION:
;dnsiscool.greisler.org.      IN   ANY
;; ANSWER SECTION:
dnsiscool.greisler.org. 86400   IN      A   192.168.254.23
;; AUTHORITY SECTION:
greisler.org.          86400   IN      NS nameserver.greisler.org.
;; ADDITIONAL SECTION:
nameserver.greisler.org.86400   IN      A   192.168.254.240
Received 97 bytes from 192.168.254.240#53 in 18 ms

We can see from this example we have asked for the A records for dnsiscool.greisler.org and it returned in the answer section that its IP address is 192.168.254.23, which is what we expected. We can try this for the PTR or reverse look up records:

nameserver:~ backup$ host -a 192.168.254.23
Trying "23.254.168.192.in-addr.arpa"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 21546
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 1
;; QUESTION SECTION:
;23.254.168.192.in-addr.arpa.   IN   PTR
;; ANSWER SECTION:
23.254.168.192.in-addr.arpa.   86400 IN    PTR  dnsiscool.greisler.org.
;; AUTHORITY SECTION:
254.168.192.in-addr.arpa.   86400   IN   NS   nameserver.greisler.org.
;; ADDITIONAL SECTION:
nameserver.greisler.org.   86400   IN   A      192.168.254.240
Received 122 bytes from 192.168.254.240#53 in 2 ms

We asked for the PTR record for 192.168.254.23 and it returned in the answer section, dnsiscool.greisler.org. Success!

Understanding Zone Files

There are many good references on how to build a zone file, but I find that the easiest way to get started is to look at an existing file and to understand what is in it. We have the sample zone files earlier in the article, so let's dissect them and see what we find.

Forward Zone:

A forward DNS record is called an "A" record. This is the type of record that might get used when you enter a URL into a browser and the DNS system needs to find its associated IP address. Our sample forward zone file is located in /var/named and looks like this:

$TTL 86400
greisler.org.   IN      SOA     nameserver.greisler.org. admin.greisler.org. (
                        2007010201   ; serial
                        3h            ; refresh
                        1h            ; retry
                        1w            ; expiry
                        1h )         ; minimum
greisler.org.   IN      NS         nameserver.greisler.org.        
greisler.org.   IN      A          192.168.254.240  
nameserver.greisler.org.   IN      A   192.168.254.240  
test.greisler.org.   IN      A       192.168.254.22  
dnsiscool.greisler.org.   IN      A   192.168.254.23  bubba.greisler.org.   IN      A       192.168.254.24

The first line gives us the TTL or Time To Live. This is how long cached data will live on your DNS server.

The second line includes the SOA or Start Of Authority. This tells us that this 'nameserver' is authoritative for this domain. The portion that has admin.greisler.org declares the email address of the zone contact. Notice it doesn't use the standard email format we are normally used to (admin@greisler.org); It simply replaces "@" with a dot.

The following section is slightly modified from the earlier examples as I have added notations for the definitions of each line. The data in this section is mostly for use with slave DNS servers and doesn't impact us at the moment. The serial number is exactly that; it allows us to serialize the zone file for whatever usage we may want. In this case, it is the date the zone was made.

The 8th line tells us which DNS server is authoritative for the zone. We only have one listed in this example, but we typically would list two or more depending on the size of the environment.

The following lines include the actual information regarding the records we want to resolve. For example if the server "bubba.greisler.org" had the IP of 192.168.254.24, we write it out as:

bubba.greisler.org.   IN      A       192.168.254.24

Note that there is a trailing dot after the server name. Be careful with your dots and make sure they are in the right places. FYI: "IN" means Internet and is the class of record. The "A" means address.

Reverse Zone:

The reverse zone allows the DNS server to resolve IP addresses into host names. In the OS X server world, without reverse lookups many things will fail badly, such as a login to Open Directory. A reverse record is known as a pointer record or PTR. Let's look at our example:

$TTL 86400
254.168.192.in-addr.arpa. IN SOA nameserver.greisler.org. admin.greisler.org. (
                        2007010203
                        3h
                        1h
                        1w
                        1h )
254.168.192.in-addr.arpa.        IN      NS      nameserver.greisler.org.        
240.254.168.192.in-addr.arpa.    IN      PTR     nameserver.greisler.org.        
22.254.168.192.in-addr.arpa.     IN      PTR     test.greisler.org.      
23.254.168.192.in-addr.arpa.     IN      PTR     dnsiscool.greisler.org. 
24.254.168.192.in-addr.arpa.     IN      PTR     bubba.greisler.org.

Most of the information from the forward zone is the same or similar to the reverse zone except that we define the IP address first. You might have noticed that the IP addresses are listed in reverse order and have ".in-addr.arpa." tagged onto them; this is the correct formatting. Also, note the trailing dot after each host name.

The /etc/named.conf file:

The /etc/named.conf file contains the configuration information for the 'named' daemon. What was important to us was to enter the information for the new zones, forward and reverse, that we made and make 'named' aware of them. In the example below you will see the entries that begin with "zone" and how they point at the "zone file" files in /var/named.

You will see zone file entries for named.ca, localhost.zone and named.local. The named.ca file holds the DNS root server information. These are the official top-level DNS servers of the hierarchical DNS search process. The other two files provide local information, which is consistent on all machines. Basically, it defines what "localhost" and "127.0.0.1" are.

The file also contains information regarding what gets logged and where it gets logged. This may be important if you have a non-standard place you like to have the logs located. You can choose different levels of logging including: info, debug, notice, warning, error, critical, alert and emerg.

//
// Include keys file
//
include "/etc/rndc.key";
// Declares control channels to be used by the rndc utility.
//
// It is recommended that 127.0.0.1 be the only address used.
// This also allows non-privileged users on the local host to manage
// your name server.
//
// Default controls
//
controls {
        inet 127.0.0.1 port 54 allow {any;}
        keys { "rndc-key"; };
};
options {
        directory "/var/named";
        /*
         * If there is a firewall between you and nameservers you want
         * to talk to, you might need to uncomment the query-source
         * directive below.  Previous versions of BIND always asked
         * questions using port 53, but BIND 8.1 uses an unprivileged
         * port by default.
         */
        // query-source address * port 53;
};
// 
// a caching only nameserver config
// 
zone "." IN {
        type hint;
        file "named.ca";
};
zone "localhost" IN {
        type master;
        file "localhost.zone";
        allow-update { none; };
};
zone "0.0.127.in-addr.arpa" IN {
        type master;
        file "named.local";
        allow-update { none; };
};
zone "greisler.org" {
        type master;
        file "/var/named/greisler.org.zone";
        };
         
zone "254.168.192.in-addr.arpa" IN {
        file "db.192.168.254";
        type master;
};
logging {
        category default {
                _default_log;
        };
        channel _default_log  {
                file "/Library/Logs/named.log";
                severity info;
                print-time yes;
        };
};

Conclusion

There is much more to utilizing DNS itself, but we have given you the tools to build a DNS server. You can now use this server as a spare, a test bed for configurations or anything else you can think of.

A common use of DNS within a network is to refer to devices specific to our network, such as file servers. We can also put in entries for IP printers, individual workstations or anything that has an IP address. It is a lot easier to remember "3rdfloorprinter" than "172.16.23.192." It is also handy to have people hitting your email server by its internal address rather than having to go outside the network only for it to come back in.

There are many references to use when dealing with DNS. The standard reference seems to be the Liu and Albitz book, DNS and BIND. It is a great book that requires some effort to get through, but seems to do its best answering specific questions. It isn't something that you would sit down and read from front page to back at one shot, but it's content is top notch.

When doing web searches for information on BIND, it is good to know what version you are running. The latest version of OS X at the time this article was written was 9.3.2. You can check yours by typing in command line "named -v" and it will return the version:

nameserver:~ backup$ named -v  
BIND 9.3.2
Make sure you peruse the man pages for the following:
named
named.conf
rndc
rndc.conf
rndc-confgen

Gather your resources and newly minted DNS server and have at it. DNS server management is a skill that is rewarded with smoothly running systems.


Ben has been everything from a Mac user to CTO of one of the leading Macintosh professional services firms. Besides writing an occasional article for MacTech, you can find him presenting at Macworld (including a session called "DNS: Demystified, co-presented with Doug Hanley) or consulting with clients around the world. You can reach him at ben@greisler.org.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

VLC Media Player 2.2.0 - Popular multime...
VLC Media Player is a highly portable multimedia player for various audio and video formats (MPEG-1, MPEG-2, MPEG-4, DivX, MP3, OGG, ...) as well as DVDs, VCDs, and various streaming protocols. It... Read more
Sound Studio 4.7.8 - Robust audio record...
Sound Studio lets you easily record and professionally edit audio on your Mac. Easily rip vinyls and digitize cassette tapes, or record lectures and voice memos. Prepare for live shows with live... Read more
LibreOffice 4.4.1.2 - Free, open-source...
LibreOffice is an office suite (word processor, spreadsheet, presentations, drawing tool) compatible with other major office suites. The Document Foundation is coordinating development and... Read more
Freeway Pro 7.0.3 - Drag-and-drop Web de...
Freeway Pro lets you build websites with speed and precision... without writing a line of code! With its user-oriented drag-and-drop interface, Freeway Pro helps you piece together the website of... Read more
Cloud 3.3.0 - File sharing from your men...
Cloud is simple file sharing for the Mac. Drag a file from your Mac to the CloudApp icon in the menubar and we take care of the rest. A link to the file will automatically be copied to your clipboard... Read more
Cyberduck 4.6.5 - FTP and SFTP browser....
Cyberduck is a robust FTP/FTP-TLS/SFTP browser for the Mac whose lack of visual clutter and cleverly intuitive features make it easy to use. Support for external editors and system technologies such... Read more
Firefox 36.0 - Fast, safe Web browser. (...
Firefox for Mac offers a fast, safe Web browsing experience. Browse quickly, securely, and effortlessly. With its industry-leading features, Firefox is the choice of Web development professionals and... Read more
Thunderbird 31.5.0 - Email client from M...
As of July 2012, Thunderbird has transitioned to a new governance model, with new features being developed by the broader free software and open source community, and security fixes and improvements... Read more
VOX 2.4 - Music player that supports man...
VoxIt just sounds better! The beauty is in its simplicity, yet behind the minimal exterior lies a powerful music player with a ton of features & support for all audio formats you should ever need... Read more
A Better Finder Rename 9.46 - File, phot...
A Better Finder Rename is the most complete renaming solution available on the market today. That's why, since 1996, tens of thousands of hobbyists, professionals and businesses depend on A Better... Read more

Get The Whole Story – Lone Wolf Complete...
Get The Whole Story – Lone Wolf Complete is Now Available and On Sale Posted by Jessica Fisher on February 27th, 2015 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Check Out the Trailer for the Upcoming F...
Check Out the Trailer for the Upcoming FINAL FANTASY: Record Keeper Posted by Jessica Fisher on February 26th, 2015 [ permalink ] DeNA and Square Enix have announced that | Read more »
Legacy Quest is an Upcoming Rouge-like T...
Legacy Quest is an Upcoming Rouge-like That’ll Kill the Whole Family Posted by Jessica Fisher on February 26th, 2015 [ permalink ] Nexon Co. | Read more »
Grudgeball: Enter the Chaosphere Review
Grudgeball: Enter the Chaosphere Review By Jordan Minor on February 26th, 2015 Our Rating: :: MUSCLE MENUniversal App - Designed for iPhone and iPad Regular Show gets an above average game.   | Read more »
Action RPG League of Angels – Fire Raide...
Gaia is being invaded by the Devil Prince and the demonic Devil Army at his disposal, and it’s up to you and your avatar to defeat him in League of Angels – Fire Raiders. Raise a mighty army from hundreds of recruitable angel heroes and take the... | Read more »
Burn Rubber on the Ice With a New Cars:...
Burn Rubber on the Ice With a New Cars: Fast as Lightning Update Posted by Jessica Fisher on February 26th, 2015 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
AdVenture Capitalist Review
AdVenture Capitalist Review By Jordan Minor on February 26th, 2015 Our Rating: :: DAS KAPITALUniversal App - Designed for iPhone and iPad An inadvertent Marxist manifesto.   | Read more »
Monster vs Sheep Review
Monster vs Sheep Review By Jennifer Allen on February 25th, 2015 Our Rating: :: SAMEY FUNUniversal App - Designed for iPhone and iPad What Monster vs Sheep lacks in variety it makes up for with stress relieving fun. At least, for a... | Read more »
Is Your Face Ready for the New Outwitter...
Is Your Face Ready for the New Outwitters 2.0 Trailer? Posted by Jessica Fisher on February 25th, 2015 [ permalink ] One Man Left Studios has announced that their turn-based strategy game, | Read more »
HowToFormat Review
HowToFormat Review By Jennifer Allen on February 25th, 2015 Our Rating: :: USEFUL TIPSiPhone App - Designed for the iPhone, compatible with the iPad Making a presentation and want to get it just right? HowToFormat teaches you how... | Read more »

Price Scanner via MacPrices.net

Apple restocks refurbished Mac minis for up t...
The Apple Store has restocked Apple Certified Refurbished 2014 Mac minis, with models available starting at $419. Apple’s one-year warranty is included with each mini, and shipping is free: - 1.4GHz... Read more
Save up to $50 on iPad Air 2s, NY tax only, f...
 B&H Photo has iPad Air 2s on sale for $50 off MSRP including free shipping plus NY sales tax only: - 16GB iPad Air 2 WiFi: $469.99 $30 off - 64GB iPad Air 2 WiFi: $549 $50 off - 128GB iPad Air 2... Read more
16GB iPad Air 2 on sale for $447, save $52
Walmart has the 16GB iPad Air 2 WiFi on sale for $446.99 on their online store for a limited time. Choose free shipping or free local store pickup (if available). Sale price for online orders only,... Read more
iMacs on sale for up to $205 off MSRP
B&H Photo has 21″ and 27″ iMacs on sale for up to $205 off MSRP including free shipping plus NY sales tax only: - 21″ 1.4GHz iMac: $1029 $70 off - 21″ 2.7GHz iMac: $1199 $100 off - 21″ 2.9GHz... Read more
Apple Takes 89 Percent Share of Global Smartp...
According to the latest research from Strategy Analytics, global smartphone operating profit reached US$21 billion in Q4 2014. The Android operating system captured a record-low 11 percent global... Read more
New Travel Health App “My Travel Health” iOS...
Rochester, Minnesota based Travel Health and Wellness LLC has announced that its new iOS app help safeguard the user’s health when traveling abroad — “My Travel Health” is now available on the Apple... Read more
Sale! MacBook Airs for up to $115 off MSRP
B&H Photo has MacBook Airs on sale for up to $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 11″ 128GB MacBook Air: $799 100 off MSRP - 11″ 256GB MacBook Air: $999 $100... Read more
15-inch 2.0GHz Retina MacBook Pro (refurbishe...
The Apple Store has Apple Certified Refurbished previous-generation 15″ 2.0GHz Retina MacBook Pros available for $1489 including free shipping plus Apple’s standard one-year warranty. Their price is... Read more
Wither The iPad mini? End Of The Road Imminen...
AppleDailyReport’s Dennis Sellers predicts that the iPad mini is going to be left to wither on the vine, as it were, and then just allowed to fade away — a casualty of the IPhone 6 Plus and other... Read more
Android and iOS Duopoly Owns 96.3% of Smartph...
IDC reports that Android and iOS inched closer to total domination of the worldwide smartphone market in both the fourth quarter (4Q14) and the calendar year 2014 (CY14). According to data from the... Read more

Jobs Board

Sr. Technical Services Consultant, *Apple*...
**Job Summary** Apple Professional Services (APS) has an opening for a senior technical position that contributes to Apple 's efforts for strategic and transactional Read more
Event Director, *Apple* Retail Marketing -...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global engagement strategy and team. Delivering an overarching brand Read more
*Apple* Pay - Site Reliability Engineer - Ap...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
*Apple* Solutions Consultant - Retail Sales...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
*Apple* Solutions Consultant - Retail Sales...
**Job Summary** As an Apple Solutions Consultant (ASC) you are the link between our customers and our products. Your role is to drive the Apple business in a retail Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.