Fulcrum on a RaspiBlitz

This is a rough overview, the guide is a work in progress.

Tested environments:

  • Raspberry Pi4 8GB 64bit RaspberryOS with SSD and ZRAM
    First sync took 48h. Can expect 2 - 2.5 days.

  • Raspberry Pi4 4GB 64bit RaspberryOS with SSD and 10GB ZRAM
    First sync took 3 days.

  • See RPi-specific settings under heading “Create a config file”.


    Do I need to stop Electrs?

  • Don’t really need to, Electrs (and also Fulcrum) are very light once synched. Chugging through the 450GB transaction history poses the challenge for the RPi. Best is to stop all services you don’t use, but testing is valuable in any circumstance.

    Database corrupted

  • Received an error like:
    FATAL: Caught exception: It appears that Fulcrum was forcefully killed in the middle of committing a block to the db.
    We cannot figure out where exactly in the update process Fulcrum was killed, so we cannot undo the inconsistent state caused by the unexpected shutdown. Sorry!
    The database has been corrupted. Please delete the datadir and resynch to bitcoind.
  • Delete the database and restart Fulcrum to start the sync from scratch
    sudo rm -rf /mnt/hdd/app-storage/fulcrum/db
    sudo systemctl restart fulcrum

Automated setup

  • Issue: https://github.com/rootzoll/raspiblitz/issues/2924
  • PR: https://github.com/rootzoll/raspiblitz/pull/2966


    cat bonus.fulcrum.sh

    run with debug

    bash -x bonus.fulcrum.sh on ```

  • if running RaspiBlitz v1.7.2 and above the script is part of the image:
    config.scripts/bonus.fulcrum.sh on

    Display the Tor address

  • sudo cat /mnt/hdd/tor/fulcrum/hostname


  • TCP port 50021
  • SSL 50022
  • the IP address is your Raspiblitz IP
  • consider using Zerotier or Tailscale for remote connection though clearnet


  • sudo journalctl -fu fulcrum


    sudo systemctl restart fulcrum

Edit the config

  • sudo nano /home/fulcrum/.fulcrum/fulcrum.conf

Manual setup

Prepare bitcoind

  • To avoid errors like
    503 (content): Work queue depth exceeded

    set in the /mnt/hdd/bitcoin/bitcoin.conf:

  • Restart bitcoind
    sudo systemctl bitcoind restart
  • If the txindex was not built before WAIT until it finishes (takes ~7 hours).
    Monitor the bitcoin debug.log).
    sudo tail -n 100 -f /mnt/hdd/bitcoin/debug.log | grep txindex

Prepare the system and directories

  • # Create a dedicated user
    sudo adduser --disabled-password --gecos "" fulcrum
    cd /home/fulcrum
    # sudo -u fulcrum git clone https://github.com/cculianu/Fulcrum
    # cd fulcrum
    # Install dependencies
    # sudo apt install -y libzmq3-dev
    sudo apt install -y libssl-dev # was needed on Debian Bullseye
    # Set the platform
    if [ $(uname -m) = "aarch64" ]; then
    elif [ $(uname -m) = "x86_64" ]; then
    # Download the prebuilt binary
    sudo -u fulcrum wget https://github.com/cculianu/Fulcrum/releases/download/v1.7.0/Fulcrum-1.7.0-${build}.tar.gz
    sudo -u fulcrum  wget https://github.com/cculianu/Fulcrum/releases/download/v1.7.0/Fulcrum-1.7.0-${build}.tar.gz.asc
    sudo -u fulcrum  wget https://github.com/cculianu/Fulcrum/releases/download/v1.7.0/Fulcrum-1.7.0-${build}.tar.gz.sha256sum
    # Verify
    # Get the PGP key
    curl https://raw.githubusercontent.com/Electron-Cash/keys-n-hashes/master/pubkeys/calinkey.txt | sudo -u fulcrum gpg --import
    # Look for 'Good signature'
    sudo -u fulcrum  gpg --verify Fulcrum-1.7.0-${build}.tar.gz.asc
    # Look for 'OK'
    sudo -u fulcrum sha256sum -c Fulcrum-1.7.0-${build}.tar.gz.sha256sum
    # Decompress
    sudo -u fulcrum tar -xvf Fulcrum-1.7.0-${build}.tar.gz
    # Create the database directory in /mnt/hdd/app-storage (on the disk)
    sudo mkdir -p /mnt/hdd/app-storage/fulcrum/db
    sudo chown -R fulcrum:fulcrum /mnt/hdd/app-storage/fulcrum
    # Create a symlink to /home/fulcrum/.fulcrum
    sudo ln -s /mnt/hdd/app-storage/fulcrum /home/fulcrum/.fulcrum
    sudo chown -R fulcrum:fulcrum /home/fulcrum/.fulcrum

Create a config file

  • https://github.com/cculianu/Fulcrum/blob/master/doc/fulcrum-example-config.conf
  • Can paste the this as a block to create the config file, but fill in the PASSWORD_B (Bitcoin Core RPC password):
    echo "\
    datadir = /home/fulcrum/.fulcrum/db
    bitcoind =
    rpcuser = ${RPC_USER}
    rpcpassword = ${PASSWORD_B}
    # RPi optimizations
    # avoid 'bitcoind request timed out'
    bitcoind_timeout = 300
    # reduce load (4 cores only)
    bitcoind_clients = 1
    worker_threads = 1
    # for 4GB RAM
    fast-sync = 1024
    # server connections
    # disable peer discovery and public server options
    peering = false
    announce = false
    tcp =
    # ssl via nginx
    " | sudo -u fulcrum tee /home/fulcrum/.fulcrum/fulcrum.conf
  • The ports 50021 and 50022 are used to not interfere with a possible Electrs or ElectrumX instance.
  • Note the different settings for 4 and 8 GB RAM
  • Edit afterwards with sudo nano /home/fulcrum/.fulcrum/fulcrum.conf

Create a systemd service

  • Can paste this as a block to create the fulcrum.service file:
    echo "\
    After=network.target bitcoind.service
    ExecStart=/home/fulcrum/Fulcrum-1.7.0-${build}/Fulcrum /home/fulcrum/.fulcrum/fulcrum.conf
    " | sudo tee /etc/systemd/system/fulcrum.service



  • sudo journalctl -fu fulcrum
    sudo systemctl status fulcrum

Open the firewall

  • sudo ufw allow 50021 comment 'Fulcrum TCP'
    sudo ufw allow 50022 comment 'Fulcrum SSL'

Set up SSL

  • Paste this code as a block to make Fulcrum available on the port 50022 with SSL ncryption through Nginx
    cd /home/fulcrum/.fulcrum
    # Create a self signed SSL certificate
    sudo -u fulcrum openssl genrsa -out selfsigned.key 2048
    echo "\
    prompt             = no
    default_bits       = 2048
    default_keyfile    = selfsigned.key
    distinguished_name = req_distinguished_name
    req_extensions     = req_ext
    x509_extensions    = v3_ca
    C = US
    ST = Texas
    L = Fulcrum
    O = RaspiBlitz
    CN = RaspiBlitz
    subjectAltName = @alt_names
    subjectAltName = @alt_names
    DNS.1   = localhost
    DNS.2   =
    " | sudo -u fulcrum tee localhost.conf
    sudo -u fulcrum openssl req -new -x509 -sha256 -key selfsigned.key \
        -out selfsigned.cert -days 3650 -config localhost.conf
    # Setting up the nginx.conf
        isConfigured=$(sudo cat /etc/nginx/nginx.conf 2>/dev/null | grep -c 'upstream fulcrum')
        if [ ${isConfigured} -gt 0 ]; then
                echo "fulcrum is already configured with Nginx. To edit manually run \`sudo nano /etc/nginx/nginx.conf\`"
        elif [ ${isConfigured} -eq 0 ]; then
                isStream=$(sudo cat /etc/nginx/nginx.conf 2>/dev/null | grep -c 'stream {')
                if [ ${isStream} -eq 0 ]; then
                echo "
    stream {
            upstream fulcrum {
            server {
                    listen 50022 ssl;
                    proxy_pass fulcrum;
                    ssl_certificate /home/fulcrum/.fulcrum/selfsigned.cert;
                    ssl_certificate_key /home/fulcrum/.fulcrum/selfsigned.key;
                    ssl_session_cache shared:SSL-fulcrum:1m;
                    ssl_session_timeout 4h;
                    ssl_protocols TLSv1 TLSv1.1 TLSv1.2 TLSv1.3;
                    ssl_prefer_server_ciphers on;
    }" | sudo tee -a /etc/nginx/nginx.conf
                elif [ ${isStream} -eq 1 ]; then
                        sudo truncate -s-2 /etc/nginx/nginx.conf
                        echo "
            upstream fulcrum {
            server {
                    listen 50022 ssl;
                    proxy_pass fulcrum;
                    ssl_certificate /home/fulcrum/.fulcrum/selfsigned.cert;
                    ssl_certificate_key /home/fulcrum/.fulcrum/selfsigned.key;
                    ssl_session_cache shared:SSL-fulcrum:1m;
                    ssl_session_timeout 4h;
                    ssl_protocols TLSv1 TLSv1.1 TLSv1.2 TLSv1.3;
                    ssl_prefer_server_ciphers on;
    }" | sudo tee -a /etc/nginx/nginx.conf
                elif [ ${isStream} -gt 1 ]; then
                        echo " Too many \`stream\` commands in nginx.conf. Please edit manually: \`sudo nano /etc/nginx/nginx.conf\` and retry"
                        exit 1
    # Test nginx
    sudo nginx -t
    # Restart nginx
    sudo systemctl restart nginx

    Create a Tor .onion service

    • On RaspiBlitz v1.7.2 run:
      /home/admin/config.scripts/tor.onion-service.sh fulcrum 50021 50021 50022 50022
    • Previous versions:
      /home/admin/config.scripts/network.hiddenservice.sh fulcrum 50021 50021 50022 50022
    • To set up manually see the guide here.

    Remove the Fulcrum user and installation (not the database)

    sudo systemctl disable fulcrum
    sudo systemctl stop fulcrum
    sudo userdel -rf fulcrum
    # Remove Tor service
    /home/admin/config.scripts/tor.onion-service.sh off electrs
    # Close ports on firewall
    sudo ufw deny 50021
    sudo ufw deny 50022
    # To remove the database directory
    # sudo rm -rf /mnt/hdd/app-storage/fulcrum/db

    Docker setup

    The database persisted and serving on ports tcp: 50025, ssl: 50027.

    Will mount the existing database from (can be any directory to sync new in < 10h on an SSD):


    bitcoind is running on the localhost.

    Adapted config in the ./fulcrum.conf

    bitcoind =
    rpcuser = RPCUSER
    rpcpassword = RPCPASSWORD
    bitcoind_timeout = 600
    bitcoind_clients = 1
    worker_threads = 1
    fast-sync = 1024
    peering = false
    announce = false
    tcp =
    ssl =

Generate TLS credentials

  • openssl req -newkey rsa:2048 -sha256 -nodes -x509 -days 3650 -subj "/O=Fulcrum" -keyout "tls.key" -out "tls.cert"

Start the image

  • adapt the values as needed
    docker image pull cculianu/fulcrum:latest
    docker run \
    --network="host" \
    -p 50025:50025 \
    -p 50027:50027 \
    -v "$(pwd)"/fulcrum.conf:/fulcrum.conf \
    -v "$(pwd)"/tls.key:/tls.key \
    -v "$(pwd)"/tls.cert:/tls.cert \
    -v /mnt/hdd/hdd-snapshot-clone/app-storage/fulcrum/db:/db \
    -e DATA_DIR=/db \
    -e SSL_CERTFILE=/tls.cert \
    -e SSL_KEYFILE=/tls.key \
    openoms/fulcrum \
    Fulcrum /fulcrum.conf

    Docker compose snippet

  •   fulcrum:
        image: cculianu/fulcrum:latest
        depends_on: [bitcoind]
          - ${PWD}/fulcrum.conf:/fulcrum.conf
          - ${PWD}/tls.key:/tls.key
          - ${PWD}/tls.cert:/tls.cert
          - DATA_DIR=/db
          - SSL_CERTFILE=/tls.cert
          - SSL_KEYFILE=/tls.key
        command: [ "Fulcrum", "/fulcrum.conf" ]


  • https://github.com/cculianu/Fulcrum
  • https://sparrowwallet.com/docs/server-performance.html