Credit goes to them, blame goes to him.
= What is AFS? =
-The '''Andrew File System''' or '''AFS''', is a distributed network file system invented at [http://www.cmu.edu/index.shtml Carnegie Mellon University] as part of Project Andrew (approximately their equivalent of MIT's Project Athena). More importantly, it is the file system used to store most files on Athena today. This includes your personal home directory, your dorm site, and probably some of the software you run, if you ever use clusters. (Though all user directories were migrated from NFS in the summer of 1992, some files probably still remain on NFS and, of course, various file systems are used on personal computers and servers).
+The '''Andrew File System''' or '''AFS''' is a distributed network file system invented at [http://www.cmu.edu/index.shtml Carnegie Mellon University] as part of Project Andrew (approximately their equivalent of MIT's Project Athena). More importantly, it is the file system used to store most files on Athena today. This includes your personal home directory, the data and websites of many living groups and student groups on campus, and probably some of the software you run (if you ever use Athena clusters). (Though all user directories were migrated from NFS in the summer of 1992, some files probably still remain on NFS and, of course, various file systems are used on personal computers and servers.)
'''''In Short: AFS is probably where some of the files you care about live'''''
-For the most part using AFS, particularly at MIT, is well-hidden and can be used like any other UNIX file system. For some things, you will need to know a bit more
+For the most part, using AFS, particularly at MIT, is well-hidden and can be used like any other UNIX file system. For some things, you will need to know a bit more. Let's start by defining some terms.
= Some MIT/AFS terminology =
'''locker'''::
- For practical purposes, a folder. Probably the what you'll care about most of the time. Technically any directory mountable under /mit, regardless of how its stored. Today, most lockers (possibly all) lockers are stored in AFS.
+ For practical purposes, a folder. Probably the what you'll care about most of the time. Technically any directory mountable under /mit, regardless of how its stored. Today, most lockers lockers are stored in AFS.
'''tokens'''::
Essentially proof to the AFS servers that you are who you say you are, thus allowing you to access files you are supposed to. Analogous to Kerberos tickets.
'''cell'''::
- AFS concept of an "administrative domain of authority." Each cell has its own set of users, groups, and administrators. Analogous to a Kerberos realm. Each top-level directory in /afs corresponds to a cell. The cells you are most likely to care about are athena.mit.edu and sipb.mit.edu
+ AFS concept of an "administrative domain of authority." Each cell has its own set of users, groups, and administrators. Analogous to a Kerberos realm. Each top-level directory in /afs corresponds to a cell. The cells you are most likely to care about are {{athena.mit.edu}} and {{sipb.mit.edu}}.
= The Basics =
== The Layout of a Typical MIT Locker ==
-Every Athena user has a locker (their home directory) which mounts at {{{/mit/<username>}}} From a technical standpoint, its stored in the volume {{{user.<username>}}} which is located at {{{/afs/athena.mit.edu/user/<first letter>/<second letter>/<user name>}}} For example, the user {{{sipbtest}}} has a home directory that mounts at {{{/mit/sipbtest}}}, is volume {{{user.sipbtest}}}, and is accessible at {{{/afs/user/s/i/sipbtest}}}. Projects, Dorms, Classes, etc. are all mounted at {{{/mit/<lockername>}}} and stored at various places in AFS
+Every Athena user has a locker (their home directory), which mounts at {{{/mit/<username>}}}. From a technical standpoint, it is stored in the volume {{{user.<username>}}} which is located at {{{/afs/athena.mit.edu/user/<first letter>/<second letter>/<user name>}}}. For example, the user {{{joeuser}}} has a home directory that mounts at {{{/mit/joeuser}}}, is volume {{{user.joeuser}}}, and is accessible at {{{/afs/user/j/o/joeuser}}}. Lockers for projects, software, classes, living groups, and student groups are all mounted at {{{/mit/<lockername>}}} and stored at various places in AFS.
-Within this folder there are 4 special subdirectories you want to care about
+Within each locker, there are (by default) 4 special subdirectories you want to care about.
'''{{{Public}}}'''::
By default, this directory can be read by everyone (and I do mean EVERYONE!), so put files here you want to share with the entire world.
'''{{{Private}}}'''::
By default, this directory can only be read and can only be ''listed'' by you (from AFS, not from web) whereas the files in other directories can (by default) only be read by you, but can be listed by anyone. This means that other people can't see the contents of your files, but they can see what files you have outside of {{{Private}}}
'''{{{OldFiles}}}'''::
- This folder is a link to a read-only copy of a backup of your files (created nightly at 3 a.m.) This copy can not be edited and does not count towards your quota. (From a technical standpoint, this is a separate volume, user.<username>.backup and is stored only as changes against the current copy).
+ This folder is a link to a read-only copy of a backup of your files (created nightly at 3 a.m.). This copy cannot be edited and does not count towards the locker's quota. (From a technical standpoint, this is a separate volume, user.<username>.backup and is stored only as changes against the current copy.)
'''{{{www}}}'''::
- Where you should put a website, if you want one. There is very little special about this directory from an AFS standpoint, but it is world readable (like Public) and is linked directly if someone goes to {{{http://www.mit.edu/~<username>}}}
+ Where you should put a website, if you want one. There is very little special about this directory from an AFS standpoint, but it is world-readable (like Public) and is linked directly to {{{http://www.mit.edu/~<lockername>}}} as well as {{{http://web.mit.edu/<lockername>}}}.
== Accessing Lockers ==
=== From Athena ===
-On Athena you can access a locker either as its full AFS path, if you know it ( e.g. /afs/athena.mit.edu/course/6/6.01 ) or under {{{/mit}}} if it is "attached." Yet a third way is to use tilde expansion and simply {{{ cd ~<locker> }}} (e.g. {{{cd ~6.01}}}) which will take you to the full path. Often, however, you want to attach lockers because it is easier to refer to them outside of the shell (in a script, for example) and software is set-up to run with a path under {{{/mit}}}. There are a few ways to attach a locker:
+On Athena, you can access a locker either as its full AFS path, if you know it (e.g. {{{/afs/athena.mit.edu/course/6/6.01}}}), or under {{{/mit}}} if it is "attached." Yet a third way is to use tilde expansion and simply {{{ cd ~~<locker> }}} (e.g. {{{cd ~~6.01}}}) which will take you to the full path. Often, however, you want to attach lockers because it is easier to refer to them outside of the shell (in a script, for example) and software is set up to run with a path under {{{/mit}}}. There are a few ways to attach a locker:
* If you are running on a [http://debathena.mit.edu Debathena] machine, such as [http://linerva.mit.edu linerva.mit.edu], then simply {{{cd /mit/<locker>}}} and it will be auto-attached.
* If you are on another Athena machine and don't want to run software out of the locker, than simply type {{{attach <locker>}}} and then `cd` to it.
- * If, however, you want to use software in the locker, you will be better served by running {{{add <locker>}}} (e.g. {{{add ruby-lang}}}). This will attach the locker at {{{/mit/<locker>}}} and will add the `bin` directory (for your architecture) of that locker to your PATH. What this means is that you should be able to run any software thereafter by simply typing the name of the program at the command line.
-
+ * If, however, you want to use software in the locker, you will be better served by running {{{add <locker>}}} (e.g. {{{add ruby-lang}}}). This will attach the locker at {{{/mit/<locker>}}} and will add the `bin` directory (for your architecture) of that locker to your PATH. What this means is that you should be able to run any program located in that locker by simply typing the name of the program at the command line.
+ * If you frequently use the same locker, it may be helpful for you to add the {{{add <locker>}}} command to your {{{.environment}}} file. To do this simply from the Athena command line, type {{{echo "add lockername" > ~/.environment}}} or {{{echo "add lockername >> ~/.environment}}}.
=== From the Web ===
-Generally any locker that you would access on Athena as {{{/mit/<locker>}}} is accessible on the web as {{{{http://web.mit.edu/<locker>}}}. For example, the barnowl locker is at [http://web.mit.edu/barnowl]. As you can see, if there is no index.html (see below), the files in the directory are listed. By default, however, none of the contents are readable except in the `www` and `Public` folders.
+Generally any locker that you would access on Athena as {{{/mit/<locker>}}} is accessible on the web as {{{http://web.mit.edu/<locker>}}}. For example, the barnowl locker is at [http://web.mit.edu/barnowl]. As you can see, if there is no index.html (see below), the files in the directory are listed. By default, however, none of the contents are readable except in the `www` and `Public` folders.
Also, you may access something in one of the MIT AFS cells by taking its full AFS path after web.mit.edu ([http://web.mit.edu/afs/athena.mit.edu/activity/c/chess-club]). (That link also shows that if you have a text file named README readable, as a link to Public/README for example, its contents will be displayed below the directory listing).
= Troubleshooting =
=== I'm trying to access my files, {{{fs la}}} says I should have permissions here, but it still says {{{: Permission denied}}} ===
-There are two likely possibilities. First, its likely that your tokens may have expired. To get new tokens, make sure you have valid kerberos tickets and then run {{{aklog}}}. Another possibility is that you have tokens but not for the correct cell. {{{tokens}}} will tell you what tokens you already have. In all likelihood, if you are reading this, you probably want {{{aklog athena sipb}}}
+There are two likely possibilities. First, its likely that your tokens may have expired. To get new tokens, make sure you have valid kerberos tickets and then run {{{aklog}}}. Another possibility is that you have tokens but not for the correct cell. {{{tokens}}} will tell you what tokens you already have. In all likelihood, if you are reading this, you probably want {{{aklog athena sipb}}}. Finally, a third possibility is that your group membership has changed since you acquired tokens. Try running {{{aklog -force}}}
=== I'd really prefer that not everyone could list my files, how should I stop this? ===
What you '''don't''' want to do is take away the l permission from {{{system:anyuser}}} because then no one will be able to get to your `Public` or `www` which you probably don't want. All told, there is no way to stop people on Athena from listing your files (unless you keep everything under `Private` or a similarly restricted directory). It is rather trivial to stop web users, however. A solution I recommend, if you have a website in `www`, is to make a page `redirect.html` (or similar) with the contents like:
and then doing a {{{ln -s www/redirect.html index.html}}} in the top level of the locker. Alternatively you can link index.html to a blank file in your `Public` or `www` (you can't simply it in the top level because its not readable there, this will result in a 403 Forbidden error).
=== It was around 6am on a Sunday morning and suddenly I couldn't access my files ===
-Yea, IS&T restarts the AFS servers weekly around 6am.
+Yeah, most AFS servers restart weekly at 6 AM on Sunday.
=== It isn't Sunday and I can't get to my files ===
There may be a non-scheduled AFS outage. Check [http://3down.mit.edu 3down], hopefully it will be back up soon :-(.
sipb-www / wiki.git / blobdiff