AFS (Andrew File System) A Distributed File System Zihou Wang
Contents • What is AFS • Benefits of AFS • How to use AFS • Summary
What is AFS • AFS is a distributed file system that enables file sharing across both local area and wide area networks. • AFS is marketed, maintained, and extended by Transarc Corporation. • AFS is originally developed at the Information Technology Center at Carnegie-Mellon University
Benefit of AFS • Cache Manager • Whenever a remote file is accessed a chunk of that file gets copied to local disk and so subsequent accesses (warm reads) are almost as fast as to local disk • Location independence • AFS does file mapping (file name to location) at the server
Benefit of AFS (continue) • Scalability • AFS cells can range from the small to the massive • Improved security • AFS makes use of Kerberos to authenticate users • AFS uses access control lists(ACL) to restrict access to file directories
Benefit of AFS (continue) • Single systems image • Every client and server in a network of systems use the same view of file store • Improved system management capability • Administrators are able to make configuration changes from any client in the AFS cell and no need to take systems off-line.
How to use AFS $ pwd /afs/nwstg/project/spot $ ls -l total 44 drwxrwxrwx 3 root system 2048 Aug 22 14:39 altmanb drwxr-xr-x 2 altmanb staff 2048 Jul 29 16:25 bin drwxrwxrwx 5 root system 2048 Mar 22 16:32 cgi-bin drwxrwxrwx 2 root system 2048 Apr 02 14:03 friedman drwxrwxrwx 2 root system 2048 May 23 13:19 murthyja drwxrwxrwx 3 root system 2048 Jul 18 13:24 porricelli drwxrwxrwx 2 altmanb staff 2048 Jul 30 13:47 release drwxrwxrwx 8 altmanb staff 2048 Jul 29 16:01 spotdata drwxrwxrwx 3 altmanb staff 2048 Mar 25 17:00 spottest drwxrwxrwx 4 root system 2048 Apr 30 14:43 wangz drwxrwxrwx 5 root system 2048 Mar 25 13:57 webdocs
How to use AFS (continue) $ cd altmanb ksh: altmanb: Permission denied. $ fs listacl altmanb fs: You don't have the required access rights on 'altmanb' $ fs listacl wangz Access list for wangz is Normal rights: system:administrators rlidwka wangz rlidwk
How to use AFS (continue) $ fs listacl cgi-bin Access list for cgi-bin is Normal rights: system:administrators rlidwka system:anyuser rl altmanb rlidwk wangz rlidwk friedman rlidwk porricel rlidwk murthyja rlidwk
How to use AFS (continue) $ fs listquota wangz Volume Name Quota Used %Used Partition project.spot.wangz 100000 12878 13% 42% $ fs help setacl fs setacl: set access control list aliases: sa Usage: fs setacl -dir <directory>+ -acl <access list entries>+ [-clear] [-negative] [-id] [-if] [-help] Where: -clear clear access list -negative apply to negative rights -id initial directory acl (DFS only) -if initial file acl (DFS only)
Summary Usually, AFS is used on UNIX workstation, such as HP, DEC, SUN, and SGI. Now more and more users like to use AFS and Transarc have made AFS available to PCs and Macs as well as Cray (IBM main frame).