Transcript AFS (Andrew File System)

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
drwxr-xr-x
2 altmanb
drwxrwxrwx
5 root
drwxrwxrwx
2 root
drwxrwxrwx
2 root
drwxrwxrwx
3 root
drwxrwxrwx
2 altmanb
drwxrwxrwx
8 altmanb
drwxrwxrwx
3 altmanb
drwxrwxrwx
4 root
drwxrwxrwx
5 root
system
staff
system
system
system
system
staff
staff
staff
system
system
2048
2048
2048
2048
2048
2048
2048
2048
2048
2048
2048
Aug
Jul
Mar
Apr
May
Jul
Jul
Jul
Mar
Apr
Mar
22
29
22
02
23
18
30
29
25
30
25
14:39
16:25
16:32
14:03
13:19
13:24
13:47
16:01
17:00
14:43
13:57
altmanb
bin
cgi-bin
friedman
murthyja
porricelli
release
spotdata
spottest
wangz
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
project.spot.wangz
Quota
100000
Used %Used
12878
13%
Partition
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).