Pi-hole

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Pi-hole is a light weight application that configures a DNS and DHCP server for the purpose of blocking advertisements. It comes with an optional control panel written in PHP. As the name suggests, it is designed to run on a Raspberry Pi, although it can also be installed on anything that runs a supported version of Linux.

Running Pi-hole on the original Raspberry Pi 1 works, though the web interface might be somewhat sluggish. I am using Pi-hole as an alternative to OpenWRT as a local DNS/DHCP server and it is working fine. Drawbacks with Pi-hole compared to OpenWRT is that the system needs to be updated independently unlike OpenWRT and the initial boot time is definitely longer. However, the Pi-hole user interface has a lot more information and the ability to see DNS queries in real time is a bonus.

Installation

Pi-hole can be installed on a clean install of Raspbian (Raspberry Pi OS), Ubuntu, Debian, Fedora, or CentOS. The installation process can be started by running their install script with alternative methods listed on their installation page. 

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

Follow the installation steps and make a note of the admin password that is generated. If you did not see the admin password or if you've forgotten it, you can reset it with pihole -a -p.

If you intend to use their block page feature, you will need to block port 443 so that secure requests are dropped rather than have a security warning show. 

# iptables -A INPUT -p tcp --dport 443 -j REJECT --reject-with tcp-reset
# iptables -A INPUT -p udp --dport 443 -j REJECT --reject-with icmp-port-unreachable
# ip6tables -A INPUT -p tcp --dport 443 -j REJECT --reject-with tcp-reset
# ip6tables -A INPUT -p udp --dport 443 -j REJECT --reject-with icmp6-port-unreachable

Edit /etc/pihole/pihole-FTL.conf, and set BLOCKINGMODE=IP. If you are using IPv6 on your network, ensure that the IPV6_ADDRESS value in setupVars.conf is correct. Apply your changes by restarting pihole-FTL or with killall -SIGHUP pihole-FTL. If this works correctly, going to a blacklisted host will show a blocked page and going to the secured version of the blacklisted host will immediately result in a connection refused error.

To make these IPtable rules persistent, install the iptables-persistent package and save the rules with the following commands. 

# apt-get install iptables-persistent
# iptables-save > /etc/iptables/rules.v4
# ip6tables-save > /etc/iptables/rules.v6

Administration

TFTP / PXE Boot Support

OpenWRT TFTP Settings

Unlike in OpenWRT where you can define the TFTP settings for dnsmasq directly in Luci, with Pi-hole, you will need to define the dnsmasq DHCP options configuration in a configuration file manually.

Create a dnsmasq configuration file at /etc/dnsmasq.d/02-tftp.conf with the following lines to define the next server and next file. These are the same values that you would have entered in OpenWRT via Luci. Ensure that the TFTP root exists and contains your PXE boot files. 

# Defined within /etc/dnsmasq.d/02-tftp.conf
tftp-root=/tftpboot
dhcp-boot=pxelinux.0,10.1.2.54,10.1.2.54


Restart dnsmasq (via systemd or the Pi-hole control panel) to apply.

Updating

Updating Pi-hole is as simple as running: 

# pihole -up


Troubleshooting

Pi-hole is blocking itself when accessing pihole URL

When navigating to http://pihole/, you may see an error "Access to the following website has been denied:" and that "This is primarily due to being flagged as: Not found on any Blacklist". This is a red herring since lighttpd will serve the website blocked page for any domains it does not recognize.

You can still navigate to http://pihole/admin to view the dashboard.

See Also