Bitcoin ABC Ubuntu repo has been updated to provide the latest stable version 0.1.4.2.

Repo home page:

https://launchpad.net/~bitcoin-abc/ archive/ubuntu/ppa

If you are installing for the first time just execute these commands(*):

sudo apt-get install software-properties-common
sudo add-apt-repository ppa:bitcoin-abc/ppa
sudo apt-get update
sudo apt-get install bitcoind bitcoin-qt

if you already have a prev version of Bitcoin ABC just run:

sudo apt-get update
sudo apt-get upgrade

(*) If you have a previous version of bitcoind installed please remove it and remove also all the PPA repos who is going to provide alternative implementation of Bitcoin client. E.g. if you have Bitcoin Core installed via PPA this what you need to do:

sudo apt-get remove bitcoin*
sudo apt-add-repository --remove ppa:bitcoin/bitcoin