Downloaded and installed bitcoind--bandwidth usage gone through the roof I downloaded the Bitcoin Core daemon on a Ubuntu 16.04 platform from the bitcoin PPA.

sudo apt-get install software-properties-common
sudo apt-add-repository ppa:bitcoin/bitcoin
Press ENTER to continue

sudo apt-get update
sudo apt-get install bitcoind


Set up the Bitcoin daemon to auto-run.

nano /etc/systemd/system/multi-user.target.wants/bitcoind.service


Entered these instructions to the file:

[Unit]
Description=Bitcoin Server
After=network.target
After=syslog.target
[Install]
WantedBy=multi-user.target
Alias=bitcoind.service
[Service]
User=bitcoin
Group=bitcoin
Start=main service   (was a missing = in the original script)
ExecStart=/usr/bin/bitcoind
ExecStop=/usr/bin/bitcoin-cli stop
Restart=always
PrivateTmp=false


Looks as if the program has been installedd since I get this output from the following command line:

snerx@snerx:~$ systemctl status bitcoind
● bitcoind.service - Bitcoin Server
   Loaded: loaded (/etc/systemd/system/multi-user.target.wants/bitcoind.service; bad; vendor preset: enabled)
   Active: active (running) since Wed 2018-04-18 12:06:30 AEST; 17min ago
 Main PID: 4283 (bitcoind)
   CGroup: /system.slice/bitcoind.service
           └─4283 /usr/bin/bitcoind

Apr 18 12:06:30 snerx systemd[1]: Started Bitcoin Server.


That's all well and good. For the time being I'm not interested in downloading a full bitcoin blockchain but it appears that it must be doing so since after the install a full month's worth of bandwidth (200 GB) got eaten up in a 24 h period. And it looks as if something similar is going on still when I fire up my Ubuntu machine. Bandwidth usage has gone from KiB/s to MB/s and is going to drain the household internet budget very rapidly. 

What is this Frankenstein monster I have installed? 



I have since got an unlimited download internet account and have got a blockchain node up and running. I used the following command to install Bitcoin Core v0.16.0:

$ curl https://bitnodes.earn.com/install-full-node.sh | sh


Downloading the full node using the Bitcoin Core GUI was quite an epic, taking 9 days in total to catch up with 9 years and 18 weeks of blockchains (180GB)--much downtime from internet connection shutting down overnight. At a mere 13.6GB, downloading the full testnet blockchain with the bitcoind -testnet -daemon command was a much less time consuming proposition.
Bitcoin Core is full node software. This means that it will download, validate, and keep up with every transaction made in Bitcoin's history and future. Its goal is independence: if you run a node, you know that everything you see adds up (no theft, no money created out of nothing, ...), without relying on anyway else's judgement. However, it comes at the cost of high resources.

This is one of the ways of interacting with bitcoin-the-currency, but certainly not the only one. A good resource for finding wallet software is here: https://bitcoin.org/en/choose-your-wallet