AFS, Backup and Archiving
Homedirectories
I told you above that it is possible to "mount" file systems from other machines via network (NFS). You can imagine that these pairwise mounts become a nightmare for administrators in a network of several hundred hosts. Besides that NFS is slow and has some problems with security.
AFS (Andrew-File-System) takes a different approach: The AFS filesystem is distributed across several servers; special "location servers" keep track where the files are located. Important files may reside on several servers. AFS-clients keep files that were transferred from a server in a cache on a local disk. So it's fast.
As a user, you can access AFS (almost) like any other file system using the path:
/afs/ipp-garching.mpg.de/... /afs/ipp/...Since AFS is a world wide file system the name of our "cell" appears in the path. You may access other AFS cells in the world just by specifying the appropriate cell name in the path (like /afs/mit.edu/). As a local user, you may use the short form to access the local cell.
The possibility of world wide access implies that the standard unix file permissions cannot be used. First, you need a "token" that is used by AFS to prove your identity. Such a token is automatically obtained for you when you log in so normally you don't have to care about it, but in some circumstances you have to get one manually by using the kinit command.
In AFS, access rights apply to directories, not single files. You can control them with subcommands of fs, try
fs listacl help fs setacl help
for more information.
Backup and Archiving
RZG hosts a large tape-robot. The archive data is mirrored using the tape archive facilities at the neighbouring LRZ.
