Beam: A Tool for Complex Update Operations on File Trees

Beam is a program that synthesizes file trees from one or more source file trees. An instruction file contains the synthesis rules. The simplest form of a synthesis is making the destination tree an exact copy of a single source tree. If the destination tree already exists, it is verified for consistency with the sources and the synthesis rules. Updates occur when inconsistencies are detected. We present a concept for automated updates of heterogeneous workstation clusters using beam’s powerful synthesis facilities. A decomposition of a UNIX installation into separately maintainable file trees is proposed. Beam then recomposes these file trees to synthesize individual UNIX installations for each workstation. Another decomposition concept of beam are packs. A file tree can be grouped into packs of files. Usually, files of one pack are related to some common functionality of the software. Customizing a software package to individual needs is reduced to the selection of an appropriate set of packs. Thus, files not needed or seldomly used are not copied to the local disk. Instead, a symbolic link to the corresponding file on the server is created. The software package is complete without wasting too much space. The limited disk space of workstations is optimally used. The automated update concept of beam allows central maintenance and control of the updates without preventing arbitrary n–to–m relationships between servers and workstations. This centralism has the disadvantage that updates do not take place if the beam server is down. But this deficiency can be turned into a more graceful degradation if the beam installation itself is propagated and updated by each workstation. What software is updated, in which configuration and when updates occur can be controlled individually per workstation.