Résumé
DIRAC [DIRAC] [TSA-08] is a software framework for building distributed computing systems. It was primarily designed forthe needs of the LHCb [LHCb] Collaboration, and is now used by many other communities within EGI [EGI] as a primary wayof accessing grid resources. In France, dedicated instances of the service have been deployed in different locations toanswer specific needs. Building upon this existing expertise, France Grilles [FG] initiated last year a project to deploy anational, multi-community instance in order to share expertise and provide a consistent high-quality service. After describingDIRAC main aims and functionalities, this paper presents the motivations for such a project, as well as the wholeorganizational and technical process that led to the establishment of a production instance that already serves 13communities: astro.vo.eu-egee.org, biomed, esr, euasia, gilda, glast.org, prod.vo.eu-eela.eu, superbvo.org,vo.formation.idgrilles.fr, vo.france-asia.org, vo.france-grilles.fr, vo.msfg.fr and vo.mcia.fr.