NSD
NSD is "an authoritative only, high performance, simple and open source name server."
Installation
Migration to nsd for bind users
Once the package is installed there are useful migration notes for users who currently run bind as their dns server in the file:
/usr/share/doc/nsd/NSD-FOR-BIND-USERS
Many users will wish to run nsd as their authoritative dns server concurrently with unbound as the validating, recursive, caching dns server on a single machine. It may be useful to refer to the wiki page for unbound.
Initial setup
Most likely you will run nsd with a DNS caching servers such as Unbound. So, to avoid void conflicts, this configuration use port 53530 for nsd, since port 53 is used by the DNS caching server. nsd will listen for requests on localhost. Additionally, the only firewall port that then needs to be open for dns queries coming from external machines (or other machines on the same local network) is port 53.
When installed, a commented sample configuration file is placed at /etc/nsd/nsd.conf.sample. Below is a minimal working example:
/etc/nsd/nsd.conf
server:
server-count: 1
ip-address: 127.0.0.1
port: 53530
do-ip4: yes
hide-version: yes
identity: "Home network authoritative DNS"
zonesdir: "//etc/nsd"
key:
name: "keyname"
algorithm: hmac-md5
secret: "secretkey"
zone:
name: "example.com"
zonefile: "example.com.zone"
See [1] for more examples.
Note that when running version 4.3.5 there will be a benign message in the status referring to "unable to initgroups nsd: Operation not permitted". This can be avoided by adding the following line to /etc/nsd/nsd.conf
username: ""
and the unit status will no longer have the initgroups message.
Starting and running nsd
Before starting up nsd you can check the zone files using the nsd-checkconf command with the zone file name as a parameter.
In order to build the zone database that makes nsd run exceptionally quickly the database file must be rebuilt each time a zone or configuration file is changed, and the following command is executed:
# nsd-control reload
In order to start nsd, start/enable the nsd.service systemd service.
Testing nsd
nsd can be run concurrently with bind during the testing phase. You can check forward and reverse local lookups on the port at 53530 using:
drill @127.0.0.1 -p 53530 mylocalmachine1.myhomenet.com drill @127.0.0.1 -p 53530 -x w.x.y.z
where w.x.y.z is a local address within the LAN.
Configuring unbound
Once this is working then if you are running unbound as the caching recursive server then you can switch the unbound configuration to forward queries from local machines on the same network to query nsd by using the following structure in unbound.conf (and see unbound), where it is assumed that nsd is listening to port 53530:
do-not-query-localhost: no local-zone: "example.com" nodefault domain-insecure: "example.com"
stub-zone:
name: "example.com"
stub-addr: 127.0.0.1@53530
Once the unbound.conf contains the above then restart unbound and check that local queries for the nsd zone entries works. Once it is all tested then you can switch unbound to listen on both 127.0.0.1 as well as on the external interface for the local network by having the lines in unbound.conf including:
interface: 127.0.0.1 interface: 10.0.0.1
where 10.0.0.1 is the ip address of the dns server running both nsd and unbound and providing local dns for other machines on the 10.x.x.x network.
The examples here all assume that only ipv4 is being used. Corresponding configurations for ipv6 should be included where necessary, and further details on the parameters for that can be found in the man files for the two packages as well as examples that can be found with web searches.
WAN facing dns
It is also possible to change the configuration files and interfaces on which the server is listening so that dns queries from machines outside of the local network can access specific machines within the LAN. This is useful for web and mail servers which are accessible from anywhere, and the same techniques can be employed as has been achieved using bind for many years, in combination with appropriate port forwarding in the network firewall machines, to allow incoming requests to access the correct machine.