$ sudo apt-get install docker-compose
{
"data-root": "/your_external_disk_mount_point"
}
Save & exit sudo systemctl daemon-reload
sudo systemctl start docker
sudo docker info | grep "Docker Root Dir:"
Note for future bitcoin upgrades: Here we're basically changing the bitcoin Dockerfile to use the bitcoin image compatible with Raspberry Pi 4 instead of the Desktop compatible version in the default Dockerfile. The above is for Bitcoin v0.18.1For future bitcoin upgrades, here's how you can find which filename & hash to put in there:For BITCOIN URL go to https://bitcoincore.org/en/download/ , right-click on ARM Linux (the header or 32-bit, NOT 64-bit - Raspbian as of this writing is 32-bit only even if the processor is 64-bit), select "Copy link location" and paste it into the BITCOIN_URL line.For BITCOIN_SHA256 on that same page click the "Verify release signatures" link and open the file with a text editor. This link is the same one as in the Dockerfile we're editing, specified in BITCOIN_ASC_URL. You will see the hashes for the sha256 signatures for various platforms. The one we're looking for is "bitcoin-version-arm-linux-gnueabihf.tar.gz". Copy the long string of letters & numbers across it and paste it into the BITCOIN_SHA256 line.
sudo ./dojo.sh install
sudo docker ps -a