Setup Pi-Hole as a Recursive DNS Server with Unbound

Installing and Configuring Unbound

1. Run the following commands in a terminal window:
   # install unbound
   sudo apt install unbound
   # update root hints file
   wget https://www.internic.net/domain/named.root -qO- | sudo tee /var/lib/unbound/root.hints
   # edit unbound configuration
   sudo nano /etc/unbound/unbound.conf.d/pi-hole.conf
2. Paste the following configuration into pi-hole.conf

   server:
       # If no logfile is specified, syslog is used
       # logfile: "/var/log/unbound/unbound.log"
       verbosity: 0

       interface: 127.0.0.1
       port: 5335
       do-ip4: yes
       do-udp: yes
       do-tcp: yes

       # May be set to yes if you have IPv6 connectivity
       do-ip6: no

       # You want to leave this to no unless you have *native* IPv6. With 6to4 and
       # Terredo tunnels your web browser should favor IPv4 for the same reasons
       prefer-ip6: no

       # Use this only when you downloaded the list of primary root servers!
       # If you use the default dns-root-data package, unbound will find it automatically
       #root-hints: "/var/lib/unbound/root.hints"

       # Trust glue only if it is within the server's authority
       harden-glue: yes

       # Require DNSSEC data for trust-anchored zones, if such data is absent, the zone becomes BOGUS
       harden-dnssec-stripped: yes

       # Don't use Capitalization randomization as it known to cause DNSSEC issues sometimes
       # see https://discourse.pi-hole.net/t/unbound-stubby-or-dnscrypt-proxy/9378 for further details
       use-caps-for-id: no

       # Reduce EDNS reassembly buffer size.
       # Suggested by the unbound man page to reduce fragmentation reassembly problems
       edns-buffer-size: 1472

       # Perform prefetching of close to expired message cache entries
       # This only applies to domains that have been frequently queried
       prefetch: yes

       # One thread should be sufficient, can be increased on beefy machines. In reality for most users running on small networks or on a single machine, it should be unnecessary to seek performance enhancement by increasing num-threads above 1.
       num-threads: 1

       # Ensure kernel buffer is large enough to not lose messages in traffic spikes
       so-rcvbuf: 1m

       # Ensure privacy of local IP ranges
       private-address: 192.168.0.0/16
       private-address: 169.254.0.0/16
       private-address: 172.16.0.0/12
       private-address: 10.0.0.0/8
       private-address: fd00::/8
       private-address: fe80::/10

3. Press CTRL+O, Enter, CTRL+X to write the changes to pi-hole.conf
4. Continue with the following commands in terminal
   # restart the unbound service
   sudo service unbound restart
   # test a DNS lookup via unbound
   dig github.io @127.0.0.1 -p 5335
5. Back in the web browser, navigate back to the Pi-Hole web interface
6. Log in if you are not already
7. Select Settings > DNS
8. Uncheck any of the previously selected upstream DNS servers
9. Check the box next to Custom 1 (IPv4)
10. Enter 127.0.0.1#5335 as the address
11. Scroll down and click the Save button

Testing the Changes

1. Open a new tab in the web browser and navigate to https://yahoo.com
2. Go back into Pi-Hole and select Query Log from the left navigation
3. Filter the results on www.yahoo.com
4. You should see entries showing the DNS requests forwarding to localhost#5335