To get add-apt-repository, which we will use later to add the bitcoin PPA:
sudo add-apt-repository ppa:bitcoin/bitcoin
sudo apt-get update
sudo apt-get install bitcoind
Before starting bitcointd you'll want to create directory and the bitcoin.conf configuration file:
vim bitcoin.conf or ...
There is a guide in the docs of the bitcoin source code that goes over how to build bitcoin as well as the dependencies needed. Within that same directory of the source (doc/) there are various other guides and explanations that you may find useful as well.
Linux build doc
There are multiple ways in which you can update Bitcoin Core to the latest version. Each one has its own advantages and disadvantages:
Build from source code: You can always update your software by cloning the git repository. This way you can verify the code and build the binary yourself. However, it is a resource intensive task and you will need to ...
useradd bitcoin and passwd bitcoin`
link /home/bitcoin/.bitcoin to external HDD with chown -R bitcoin:bitcoin
git clone bitcoin core in /home/USER/GitStuff
add bitcoin ppa repository
sudo apt install libdb4.8-dev && sudo apt install libdb4.8++-dev
/autogen.sh in /home/USER/GitStuff/bitcoin
/configure --withoug gui
10 su ...