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Bitcoin
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Bitcoin

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Table of contents

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The base of the Lightning node is a fully trustless Bitcoin Core node. It keeps a complete copy of the blockchain and validates all transactions and blocks. By doing all this work ourselves, nobody else needs to be trusted.

In the beginning, we will use the Bitcoin testnet to familiarize ourselves with its operations. This sync is handled directly by the Pi and should not take longer than a few hours. Just let it sync overnight.

Installation

We will download the software directly from bitcoin.org, verify its signature to make sure that we use an official release and install it.

  • Login as "admin" and create a download folder
    $ mkdir /home/admin/download
    $ cd /home/admin/download
  • If you upgrade and have previously downloaded files, delete them first
    $ rm *

We download the latest Bitcoin Core binaries (the application) and compare the file with the signed checksum. This is a precaution to make sure that this is an official release and not a malicious version trying to steal our money.

  • Get the latest download links at bitcoincore.org/en/download (ARM Linux 32 bit), they change with each update. Then run the following commands (with adjusted filenames) and check the output where indicated:
# download Bitcoin Core binary
$ wget https://bitcoincore.org/bin/bitcoin-core-0.18.0/bitcoin-0.18.0-arm-linux-gnueabihf.tar.gz
$ wget https://bitcoincore.org/bin/bitcoin-core-0.18.0/SHA256SUMS.asc
$ wget https://bitcoin.org/laanwj-releases.asc

# check that the reference checksum matches the real checksum
# (ignore the "lines are improperly formatted" warning)
$ sha256sum --check SHA256SUMS.asc --ignore-missing
> bitcoin-0.18.0-arm-linux-gnueabihf.tar.gz: OK

# import the public key of Wladimir van der Laan, verify the signed  checksum file
# and check the fingerprint again in case of malicious keys
$ gpg --import ./laanwj-releases.asc
$ gpg --refresh-keys
$ gpg --verify SHA256SUMS.asc
> gpg: Good signature from "Wladimir J. van der Laan ..."
> Primary key fingerprint: 01EA 5486 DE18 A882 D4C2 6845 90C8 019E 36C2 E964

commands to check bitcoind signature

  • Now we know that the keys from bitcoin.org are valid, so we can also verify the Windows binary checksums. Compare the following output with the checksum of your Windows Bitcoin Core download.
$ cat /home/admin/download/SHA256SUMS.asc | grep win

e2478cd7955c36a5b0d31133d876cc602fb47142e65ca367c0cf21ea6dce04db  bitcoin-0.18.0-win64-setup.exe
29f449e2d1986a924b512e043893f932170830a45981323d8943ba6410848153  bitcoin-0.18.0-win64.zip
  • Extract the Bitcoin Core binaries, install them and check the version.
$ tar -xvf bitcoin-0.18.0-arm-linux-gnueabihf.tar.gz
$ sudo install -m 0755 -o root -g root -t /usr/local/bin bitcoin-0.18.0/bin/*
$ bitcoind --version
> Bitcoin Core Daemon version v0.18.0

Prepare Bitcoin Core directory

We use the Bitcoin daemon, called “bitcoind”, that runs in the background without user interface and stores all data in a the directory /home/bitcoin/.bitcoin. Instead of creating a real directory, we create a link that points to a directory on the external hard disk.

  • While logged in with user "admin", change to user “bitcoin”
    $ sudo su - bitcoin

  • We add a symbolic link that points to the external hard disk.
    $ ln -s /mnt/hdd/bitcoin /home/bitcoin/.bitcoin

  • Navigate to the home directory an d check the symbolic link (the target must not be red). The content of this directory will actually be on the external hard disk.
    $ ls -la

verify .bitcoin symlink

Configuration

Now, the configuration file for bitcoind needs to be created. Open it with Nano and paste the configuration below. Save and exit.
$ nano /home/bitcoin/.bitcoin/bitcoin.conf

# RaspiBolt: bitcoind configuration
# /home/bitcoin/.bitcoin/bitcoin.conf

# remove the following line to enable Bitcoin mainnet
testnet=1

# Bitcoind options
server=1
daemon=1

# Connection settings
rpcuser=raspibolt
rpcpassword=PASSWORD_[B]

onlynet=ipv4
zmqpubrawblock=tcp://127.0.0.1:28332
zmqpubrawtx=tcp://127.0.0.1:28333

# Raspberry Pi optimizations
dbcache=100
maxorphantx=10
maxmempool=50
maxconnections=40
maxuploadtarget=5000

⚠️ Change rpcpassword to your secure password [B], otherwise your funds might get stolen.

👉 additional information: configuration options in Bitcoin Wiki

Start bitcoind

Still logged in as user "bitcoin", let's start "bitcoind" manually. Monitor the log file a few minutes to see if it works fine (it may stop at "dnsseed thread exit", that's ok). Exit the logfile monitoring with Ctrl-C, check the blockchain info and, if there are no errors, stop "bitcoind" again.

$ bitcoind
$ tail -f /home/bitcoin/.bitcoin/testnet3/debug.log
$ bitcoin-cli getblockchaininfo
$ bitcoin-cli stop

Autostart bitcoind

The system needs to run the bitcoin daemon automatically in the background, even when nobody is logged in. We use “systemd“, a daemon that controls the startup process using configuration files.

  • Exit the “bitcoin” user session back to user “admin”
    $ exit

  • Create the configuration file in the Nano text editor and copy the following paragraph.
    $ sudo nano /etc/systemd/system/bitcoind.service

# RaspiBolt: systemd unit for bitcoind
# /etc/systemd/system/bitcoind.service

[Unit]
Description=Bitcoin daemon
After=network.target

[Service]
ExecStartPre=/bin/sh -c 'sleep 30'
ExecStart=/usr/local/bin/bitcoind -daemon -conf=/home/bitcoin/.bitcoin/bitcoin.conf -pid=/home/bitcoin/.bitcoin/bitcoind.pid
PIDFile=/home/bitcoin/.bitcoin/bitcoind.pid
User=bitcoin
Group=bitcoin
Type=forking
KillMode=process
Restart=always
TimeoutSec=120
RestartSec=30

[Install]
WantedBy=multi-user.target
  • Save and exit
  • Enable the configuration file
    $ sudo systemctl enable bitcoind.service
  • Copy bitcoin.conf to user "admin" home directory for RPC credentials
    $ mkdir /home/admin/.bitcoin
    $ sudo cp /home/bitcoin/.bitcoin/bitcoin.conf /home/admin/.bitcoin/
  • Restart the Raspberry Pi
    $ sudo shutdown -r now

Verification of bitcoind operations

After rebooting, the bitcoind should start and begin to sync and validate the Bitcoin blockchain.

  • Wait a bit, reconnect via SSH and login with the user “admin”.

  • Check the status of the bitcoin daemon that was started by systemd (exit with Ctrl-C)

    $ systemctl status bitcoind.service

Bitcoind status

  • See bitcoind in action by monitoring its log file (exit with Ctrl-C)
    $ sudo tail -f /home/bitcoin/.bitcoin/testnet3/debug.log

  • Use the Bitcoin Core client bitcoin-cli to get information about the current blockchain
    $ bitcoin-cli getblockchaininfo

  • Please note:

    • When “bitcoind” is still starting, you may get an error message like “verifying blocks”. That’s normal, just give it a few minutes.
    • Among other infos, the “verificationprogress” is shown. Once this value reaches almost 1 (0.999…), the blockchain is up-to-date and fully validated.

Explore bitcoin-cli

If everything is running smoothly, this is the perfect time to familiarize yourself with Bitcoin Core and play around with bitcoin-cli until the blockchain is up-to-date.

  • A great point to start is the book Mastering Bitcoin by Andreas Antonopoulos - which is open source - and in this regard especially chapter 3 (ignore the first part how to compile from source code):
    • you definitely need to have a real copy of this book!
    • read it online on Github

Mastering Bitcoin

👉 additional information: bitcoin-cli reference

Once the blockchain is synced on testnet, the Lightning node can be set up.

Bitcoin Core upgrade

If you want to upgrade to a new release of Bitcoin Core in the future, check out the FAQ section:
How to upgrade Bitcoin Core

Next: Lightning >>