Sync a bare metal Pi-Hole instance with a Pi-Hole docker container on another host

I've run Pi-Hole bare metal for years and recently decided to run a secondary instance of Pi-Hole on another machine as a Docker container. Gravity Sync keeps them updated with all the same DNS records, block lists, etc. Here's how I set it up.

I have a post explaining how to install and configure Pi-Hole. Here I will only be focusing on setting up Gravity Sync with the assumption that both instances of Pi-Hole are already up and running on their hosts.

In order for Gravity Sync to work with a Pi-Hole container, you need to use volumes to map the /etc/pihole and /etc/dnsmasq.d directories inside the container to local directories on your host, so that Gravity Sync can access and interact with the config files. This is demonstrated in my post linked above.

SSH into the host where you have the Pi-Hole container running, and use the following command to execute the Gravity Sync install script:

curl -sSL https://raw.githubusercontent.com/vmstan/gs-install/main/gs-install.sh | bash

Enter the information as prompted and once configuration is done you’ll see an explanation of additional steps. Next, SSH into the host running the bare metal Pi-Hole instance and use the same command to install Gravity Sync, follow the prompts, etc.

Once done, still on the bare metal host, edit the file at /etc/gravity-sync/gravity-sync.conf. Uncomment all the lines about the remote host and fill out the information. Here is mine as an example:

# REQUIRED SETTINGS ##########################

REMOTE_HOST='192.168.0.100'
REMOTE_USER='ariel'

# CUSTOM VARIABLES ###########################

# Pi-hole Folder/File Customization - Only need to be customized when using containers
# LOCAL_PIHOLE_DIRECTORY=''                         # Local Pi-hole data directory
REMOTE_PIHOLE_DIRECTORY='/home/ariel/docker/pihole/config'
# LOCAL_DNSMASQ_DIRECTORY=''                # Local DNSMASQ/FTL data directory
REMOTE_DNSMASQ_DIRECTORY='/home/ariel/docker/pihole/dnsmasq'
# LOCAL_FILE_OWNER=''                       # Local file owner for Pi-hole
REMOTE_FILE_OWNER='ariel'

# Pi-hole Docker/Podman container name - Docker will pattern match anything set below
# LOCAL_DOCKER_CONTAINER=''                                 # Local Pi-hole container name
REMOTE_DOCKER_CONTAINER='pihole'

# HIDDEN FIGURES #############################
# See https://github.com/vmstan/gravity-sync/wiki/Hidden-Figures

Now you should be all set. Go to whichever instance of Pi-Hole has all the DNS records and block lists that you want to sync between the two (for me that was the bare metal one) and use the command gravity-sync push to clone all the information to the other host. Once successful, use gravity-sync auto to enable regular syncs between both.