Divertissement

After reading tons of things on the intarwebs, i wasn’t able to find anything specific on running TinyDNS on an EC2 instance. after getting it configured and working. I decided to blog my steps victory. This write up assumes that you have a basic understanding of TinyDNS, Ubuntu and EC2. If you do not, there are plenty of docs out there. just use google

After creating the EC2 instance with port 22 open to all and port 53 open to your private network (10.0.0.0/24,) you will need to download daemontools and djbdns, compile and config them, and lastly test to make sure they are working.

First off we will need to download and install daemon tools.

cd /usr/local/src
wget http://cr.yp.to/daemontools/daemontools-0.76.tar.gz
tar -xzvf daemontools-0.76.tar.gz
mv admin daemontools
cd daemontools/daemontools-0.76
sed -i 's/^gcc.*/& -include \/usr\/include\/errno.h/' src/conf-cc
./package/install

Most of this is self explanatory, except for the second to last line which uses sed to append a path to the header file. after the install is complete, we will remove the tarball to clean up.

rm –f /usr/local/src/daemontools-0.76.tar.gz

and we have to add a start up script to /etc/init/ so that svscanboot actually starts on boot. please create the file ‘/etc/init/svscanboot.conf’ and add the below entries to it.

#svscanboot - daemontools
description     "regular background program processing daemon"

start on runlevel [2345]
stop on runlevel [!2345]

respawn

exec /usr/local/bin/svscanboot

Next we will download and compile djbdns, as well as create users for the software to run as.

to create the users for tinydns / dnscache run:

useradd -d /var/tinydns -s /bin/false tinydns
useradd -d /var/tinydns -s /bin/false dnslog
/usr/local/bin/tinydns-conf tinydns dnslog /var/tinydns 127.0.0.1

useradd -d /var/dnscache -s /bin/false dnscache
useradd -d /var/dnscache -s /bin/false dnslog
/usr/local/bin/dnscache-conf dnscache dnslog /var/dnscache/tinydns YOUR_EC2_Internal_IP

Now we will download and compile the source.

cd /usr/local/src
wget http://cr.yp.to/djbdns/djbdns-1.05.tar.gz
tar -xzvf djbdns-1.05.tar.gz
cd djbdns-1.05
sed -i 's/^gcc.*/& -include \/usr\/include\/errno.h/' conf-cc
make && make setup check

and then remove the tarball / source.

rm –f /usr/local/src/djbdns-1.05.tar.gz
rm –rf /usr/local/src/djbdns-1.05

Now we will touch and edit some files in the /var/dnscache directory so that other computers can make requests to the host. the first file is ‘/var/dnscache/env/IP’

this should have your ip address already in it, please append ‘,127.0.0.1′ to this file so that dnscache will answer queries to both addresses. after that we will touch some files to grant access from specific IP address ranges.

echo ',127.0.0.1' > /var/dnscache/env/IP

touch /var/dnscache/root/ip/10
touch /var/dnscache/root/ip/127

Now we will need to add in specific entries so that your dnscache can query your tinydns service. The first entry is a reverse lookup entry while the last two are for the domain and TLD internal.

echo '127.0.0.1' > /var/dnscache/root/servers/10.in-addr.arpa
echo '127.0.0.1' > /var/dnscache/root/servers/example.internal
echo '127.0.0.1' > /var/dnscache/root/servers/internal

Now we will create some basic entries for our new TinyDNS service. our data file lives in ‘/var/tinydns/root/data’ after you make any modifications to this file, you must run make in this directory to compile the data and make your changes live.

cd /var/tinydns/root/
vi data

here is an example data file to get you started. just replace the 10.0.0.0 with your EC2 internal address and the domain example.internal with your domain name of choice

# default nameserver and domain lookup for example.internal and the TLD .internal
..:10.0.0.0:a:259200
.example.internal::ns.example.internal
.internal:10.0.0.0:a:259200

#
# REVERSE ZONE
#
# (reverse) dns servers: primary just add a second entry for a secondary server
Z0.0.10.in-addr.arpa:ns.example.internal:hostmaster.example.internal::::::::

# NS records
&0.0.10.in-addr.arpa::ns.example.internal:::

# MX handlers
@0.0.10.in-addr.arpa::relay.example.internal:10

#
# FORWARD ZONE:
#
# SOA record: primary nameserver is ns.example.internal and hostmaster
#             mail address is hostmaster@example.internal
Zexample.internal:ns.example.internal:hostmaster.example.internal::::::::

# NS records: primary
&example.internal::ns.example.internal:::

# MX records: relay.example.internal, distance = 10
@example.internal::relay.example.internal:10

# A records: ns.example.internal
=ns.example.internal:10.0.0.0:::

# PTR records: relays are in the same hosts as dns servers
+relay.example.internal:10.0.0.0:::

# more A records: gateway.example.internal
=gateway.example.internal:10.0.0.1:::
=www.example.internal:10.0.0.2:::
=db.example.internal:10.0.0.3:::

Now save the data file and run make:

cd /var/tinydns/root/ && make

now that we have a compiled data file, we can symlink tinydns and dnscache to the /service directory so that daemontools can supervise these processes.

ln -sf /var/tinydns /service
ln -sf /var/dnscache /service

So now that you have a running set of DNS services, we want to have our EC2 clients use these services.

For all client machines and the DNS host itself, you just need to modify your DHClient scripts to prepend your new domain and its related nameserver(s). In /etc/dhcp3/dhclient.conf will will be adding 3 lines above the ‘request’ entry. please replace 10.0.0.0 with your new Nameserver’s internal ec2 address, also replace the example.internal with your domain name.

prepend domain-name-servers 10.0.0.0;
prepend domain-name "example.internal";
prepend domain-search "example.internal";

You should be setup correctly now. to confirm and test perform the below:

dig ns.example.internal

if this worked you should see that the server returning the results is the 127.0.0.1 loopback address.
e.g.:
;; SERVER: 127.0.0.1#53(127.0.0.1)

you can also use nslookup to confirm the server is working. (anything prefixed with ‘>’ is to represent the nslookup prompt.)

nslookup

> server _TinyDNS_EC2_internal_address_
> ns.example.internal

if all is working you will recieve output like this:

> ns.example.internal
Server:		10.0.0.0
Address:	10.0.0.0#53

Non-authoritative answer:
Name:	ns.external.internal
Address: 10.0.0.0
>

if you receive any other messages you more than likely have a configuration issue. Check your TinyDNS and DNScache configs first, then check your networking config. Make sure that your DNScache is replying to queries via the internal interface, while TinyDNS replies via 127.0.0.1.

thats all for now.
Enjoy.
-Austin