PiHole - PiHole Recursive DNS

Last edited: August 30, 2022 - 6 minutes read


How to setup your own recursive dns.


Pi-hole is a Linux network-level advertisement and Internet tracker blocking application which acts as a DNS sinkhole intended for use on a private network. It can also be extended to be it’s own recursive DNS server.

Let’s start by installing PiHole. Simply run the following command and follow it’s instructions:

$ curl -sSL https://install.pi-hole.net | bash

PiHole should now be installed. Make sure to configure your own router settings so that your system serves as the default DNS server for the network.

1. Unbound

Now let’s turn our PiHole instalation into it’s own recursive DNS server.

Start by installing unbound through your favorite package manager. Possibly by running:

$ sudo apt install unbound

Once you have unbound installed, run the following command to make sure you have the root.hints file properly installed:

$ wget https://www.internic.net/domain/named.root -qO- | sudo tee /var/lib/unbound/root.hints

Now let’s configure unbound. Run the next three commands.

Edit unbound configuration.

$ cat << EOF > /etc/unbound/unbound.conf.d/pi-hole.conf

    # The  verbosity  number, level 0 means no verbosity, only errors.
    # Level 1 gives operational information. Level  2  gives  detailed
    # operational  information. Level 3 gives query level information,
    # output per query.  Level 4 gives  algorithm  level  information.
    # Level 5 logs client identification for cache misses.  Default is
    # level 1.
    verbosity: 0

    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!
    # Read  the  root  hints from this file. Make sure to
    # update root.hints evry 5-6 months.
    root-hints: "/var/lib/unbound/root.hints"

    # Trust glue only if it is within the servers authority
    harden-glue: yes

    # Ignore very large queries.
    harden-large-queries: yes

    # Require DNSSEC data for trust-anchored zones, if such data is absent, the zone becomes BOGUS
    # If you want to disable DNSSEC, set harden-dnssec stripped: no
    harden-dnssec-stripped: yes

    # Number of bytes size to advertise as the EDNS reassembly buffer
    # size. This is the value put into  datagrams over UDP towards
    # peers. The actual buffer size is determined by msg-buffer-size
    # (both for TCP and UDP).
    edns-buffer-size: 1232

    # Rotates RRSet order in response (the pseudo-random
    # number is taken from Ensure privacy of local IP
    # ranges the query ID, for speed and thread safety).
    # private-address:
    rrset-roundrobin: yes

    # Time to live minimum for RRsets and messages in the cache. If the minimum
    # kicks in, the data is cached for longer than the domain owner intended,
    # and thus less queries are made to look up the data. Zero makes sure the
    # data in the cache is as the domain owner intended, higher values,
    # especially more than an hour or so, can lead to trouble as the data in
    # the cache does not match up with the actual data anymore
    cache-min-ttl: 300
    cache-max-ttl: 86400

    # Have unbound attempt to serve old responses from cache with a TTL of 0 in
    # the response without waiting for the actual resolution to finish. The
    # actual resolution answer ends up in the cache later on.
    serve-expired: yes

    # Harden against algorithm downgrade when multiple algorithms are
    # advertised in the DS record.
    harden-algo-downgrade: yes

    # Ignore very small EDNS buffer sizes from queries.
    harden-short-bufsize: yes

    # Refuse id.server and hostname.bind queries
    hide-identity: yes

    # Report this identity rather than the hostname of the server.
    identity: "Server"

    # Refuse version.server and version.bind queries
    hide-version: yes

    # Prevent the unbound server from forking into the background as a daemon
    do-daemonize: no

    # Number  of  bytes size of the aggressive negative cache.
    neg-cache-size: 4m

    # Send minimum amount of information to upstream servers to enhance privacy
    qname-minimisation: yes

    # Deny queries of type ANY with an empty response.
    # Works only on version 1.8 and above
    deny-any: yes

    # Do no insert authority/additional sections into response messages when
    # those sections are not required. This reduces response size
    # significantly, and may avoid TCP fallback for some responses. This may
    # cause a slight speedup
    minimal-responses: yes

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

    # Fetch the DNSKEYs earlier in the validation process, when a DS record is
    # encountered. This lowers the latency of requests at the expense of little
    # more CPU usage.
    prefetch-key: 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

    # more cache memory. rrset-cache-size should twice what msg-cache-size is.
    msg-cache-size: 50m
    rrset-cache-size: 100m

    # Faster UDP with multithreading (only on Linux).
    so-reuseport: yes

    # Ensure kernel buffer is large enough to not lose messages in traffix spikes
    so-rcvbuf: 4m
    so-sndbuf: 4m

    # Set the total number of unwanted replies to keep track of in every thread.
    # When it reaches the threshold, a defensive action of clearing the rrset
    # and message caches is taken, hopefully flushing away any poison.
    # Unbound suggests a value of 10 million.
    unwanted-reply-threshold: 100000

    # Minimize logs
    # Do not print one line per query to the log
    log-queries: no
    # Do not print one line per reply to the log
    log-replies: no
    # Do not print log lines that say why queries return SERVFAIL to clients
    log-servfail: no
    # Do not print log lines to inform about local zone actions
    log-local-actions: no
    # Do not print log lines that say why queries return SERVFAIL to clients
    logfile: /dev/null

    # Ensure privacy of local IP ranges
    private-address: fd00::/8
    private-address: fe80::/10

Remove unbound configuration from resolvconf.

$ cat << EOF > /etc/resolvconf.conf
# Configuration for resolvconf(8)
# See resolvconf.conf(5) for details

# If you run a local name server, you should uncomment the below line and
# configure your subscribers configuration files below.

# Mirror the Debian package defaults for the below resolvers
# so that resolvconf integrates seemlessly.

Remove unbound resolvconf file.

$ sudo rm /etc/unbound/unbound.conf.d/resolvconf_resolvers.conf

Finally restart your unbound service.

$ sudo systemctl restart unbound.service

2. Configuring PiHole

Set a new password for PiHole admin console:

$ pihole -a -p

Go to pi.hole/admin on your browser and log in.

Update your DNS settings and make sure to desellect all upstream DNS servers and add localhost#5335 as a custom DNS.

PiHole DNS Settings

You now have a privacy preserving recursive DNS server.

3. (Bonus) PiVPN

Now that you’ve configured your own privacy preserving recursive dns, you might want to use it even when outside your own network.

Let’s create a vpn by installing PiVPN. Once more run the following command and follow it’s instructions:

$ curl -L https://install.pivpn.io | bash

PiVPN should now be installed. Make sure to configure your router’s port forwarding settings so that port 1194 is redirected to your system.

You can create client interfaces by running:

$ pivpn add

Once your client interface is created, you can generate a qr code for it by running:

$ pivpn -qr
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