The present invention relates to the operation and maintenance of radio base stations in mobile communication systems. An inventive radio base station, which can be upgraded remotely in a safe way. In one embodiment of the invention, the radio base station comprises a file system comprising different versions of files, so that an old version of a file can be reverted to should problems in the operation of the radio base station occur. In another embodiment of the invention, the radio base station comprises a back-up area in which a copy of the files of the file system are stored. The back-up area is independent of the file system, so that if problems with the files in the file system are detected, the contents of the back-up area can be stored in the file system.