What is a Full Node?

A full node is a client that fully validates transactions and blocks. Full nodes also help the network by accepting transactions and blocks from other full nodes, validating those transactions and blocks, and then relaying them to further full nodes.
Many people and organizations volunteer to run full nodes using spare computing and bandwidth resources.

What is a Bitcoind

bitcoind is a Bitcoin client under the MIT license in 32-bit and 64-bit versions for Windows, GNU/Linux-based OSes, Mac OS X, OpenBSD, and FreeBSD as well.

How To Start Bitcoind To Be Full Node

Install bitcoind by PKG:
# pkg install bitcoin-daemon
Install bitcoind by source:
# fetch https://github.com/UASF/bitcoin/archive/v0.14.2-uasfsegwit1.0.tar.gz
# tar xzvf v0.14.2-uasfsegwit1.0.tar.gz
# cd bitcoin-0.14.2-uasfsegwit1.0

Install dependencies

# pkg install autoconf automake libtool pkgconf boost-libs openssl libevent gmake
Then config builds and installs Bitcoind:

# ./autogen.sh
# configure –without-gui
Since we are on the command line, GUI is not required and –without-gui will disable it:

# gmake
# gmake install

Start Bitcoind client and wait for full-sync with other nodes:
# bitcoind -daemon
bitcoind will download a database that is about 150GB. You can check your node status by clicking on this URL:
https://bitnodes.earn.com

You can get full edition at:
https://contents.meetbsd.ir/ebook/bitcoin_bsdmag.pdf
Or:
https://bsdmag.org/download/celebrating-100th-issue/