MariaDB is an amazing replacement for the previous mysql, abducted by their new "owners", Oracle.
MariaDB is in direct competition with Percona and they both fully support all applications that run with the old mysql backend.
Here are the commands to run to add MariaDB to your Ubuntu 12 (precise) system:
sudo apt-get install python-software-properties
sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 0xcbcb082a1bb943db
sudo add-apt-repository 'deb http://mirror2.hs-esslingen.de/mariadb/repo/5.5/ubuntu precise main'
Once the key is imported and the repository added you can install MariaDB with:
sudo apt-get update
sudo apt-get install mariadb-server
See Installing MariaDB .deb Files for more information.
You can also create a custom MariaDB sources.list file. To do so, copy and paste the following into a file under /etc/apt/sources.list.d/(we suggest naming the file MariaDB.list or something similar), or add it to the bottom of your /etc/apt/sources.list file.
# MariaDB 5.5 repository list - created 2013-08-28 08:53 UTC
deb http://mirror2.hs-esslingen.de/mariadb/repo/5.5/ubuntu precise main
deb-src http://mirror2.hs-esslingen.de/mariadb/repo/5.5/ubuntu precise main
More information here: https://downloads.mariadb.org/