Ask SIPB - April 20, 2007

Ever wondered how you can get to your files from any Athena computer? How lockers work? How you can share files with your friends? In today's issue of Ask SIPB, we'll cover these questions and more.

What is AFS?

AFS, the Andrew File System (a CMU development, named after Andrew Carnegie and Andrew Mellon), is a networked, distributed filesystem with several convenient features. It's available for most platforms used today, including Windows, Mac OS X, Linux, and Solaris. AFS allows you to access your files from anywhere in the world, on any computer with AFS installed, with just a single, unique AFS path - somewhat like a URL on the web. It also lets you easily allow other people to have limited or full access to your files.

How do I use AFS on my computer?

There are several reasons to want AFS on your computer. One common use is to store your classwork directly in your Athena home directory, so that you can access it from your own computer as well as from all Athena workstations. Another advantage is that you don't have to worry about the overhead of FTP when editing your website; you can save your files to what appears to be a local directory, and it will save automatically to AFS.

OpenAFS, the most popular AFS client, is installed on all Athena workstations, including the Windows and Macintosh computers. Since AFS uses Kerberos for authentication and encryption, you will need to download and install Kerberos first (if you're on Windows or Linux; Kerberos is included with Mac OS X, so you just need to download the MIT Kerberos Extras). After installing Kerberos and restarting, you can download the appropriate version from OpenAFS.org and set it up — or, if you're on Linux, just install both Kerberos and OpenAFS with your distribution's package manager.

Once you have Kerberos and OpenAFS set up on your own computer, you can start using it. Acquire Kerberos tokens, either via the graphical client (Leash on Windows, Kerberos.app on Mac), or by typing "kinit username" at a command prompt. Then type the command "aklog athena", which authenticates you to Athena's AFS servers and gives you tokens for the Athena cell. Now you can access your, which authenticates you to Athena's AFS servers and gives you tokens for the Athena cell. Your home directory is under /afs/athena.mit.edu/user, in subdirectories based on the first two letters of your username.

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To ask us a question, send email to sipb@mit.edu. We'll try to answer you quickly, and we can address your question in our next column. You can also stop by our office in W20-557 or call us at x3-7788 if you need help. Copies of each column and pointers to additional information are posted on our website: http://www.mit.edu/~asksipb/