Pablo Saiz (CERN)
AliEn is the GRID interface that ALICE has developed to be able to do its distributed computing. AliEn provides all the components needed to build a distributed environment, including a file and metadata catalogue, a priority-based job execution model and a file replication system. Another of the components provided by AliEn is an automatic software package installation service, PackMan. PackMan allows having multiple versions of each package, dependencies, support for different platforms, post installation methods and package setup and configuration. The rest of this paper will describe how the PackMan works, starting with how the packages are created and registered in the AliEn file catalogue, how the users specify the packages that they need, and finally how the packages are installed and configured before the jobs are executed.