Getting Started

Obtain the code

The ALICE O² Software is hosted on GitHub under the AliceO2Group organization. The core package is AliceO2.

This means you can obtain the source code by cloning the repository:

git clone

There is no need for you to clone the repository manually, this part is covered in our build instructions.


In order to build the ALICE O² software we use aliBuild. Check out our build instructions.


The simplest way to run AliceO2 is by using directly our nightly builds from CVMFS. If you have a CERN account, you can connect via SSH to first to have CVMFS available.

This is how you list all available builds:

/cvmfs/ q | grep O2::nightly

And this is how you load one of them:

/cvmfs/ enter VO_ALICE@O2::nightly-20171130-1

Nightly builds are also available on selected Grid sites (the ones supporting the CVMFS repository), allowing for off-CERN testing.

Nightly builds are automatically announced on the mailing list. Read on the Get support section to know how to subscribe.


Since O² uses the Git version control system it is recommended you follow our AliPhysics Git tutorial to learn its rudiments.

Remember to fork the AliceO2 project on GitHub and please follow the coding guidelines, given that most of them are enforced by automatic checks.

Get support

For simple support questions please use our Discourse forum.

The first time you connect, you will need to hit the Sign up button and use your CERN credentials to register. It is easy to browse existing topics in Discourse, and mark the relevant reply as a solution. When you create a new discussion topic, Discourse suggests similar topics that might be duplicates to your issue. Once a topic has been opened from the web interface, every registered user gets an email notification. It is possible to reply to such emails directly from your email client if you wish.

If you think you have found a bug in our software, report it here. Change the issue type from Bug to something else if appropriate.