15-410 AFS space
Beforehand
If you are getting AFS permission errors before
your personal volume has been created, try this:
% afslog cs.cmu.edu
% pts createuser $USER@andrew.cmu.edu -cell cs.cmu.edu
% afslog cs.cmu.edu
Location
Your AFS volume for 15-410 is located at /afs/cs.cmu.edu/academic/class/15410-f08/usr/$USER.
Since this volume is in the CS cell, you will need to use cross-cell authentication.
Luckily, this is easy.
Whenever you log in to an Andrew machine, or use kinit to get new tickets,
run afslog cs.cmu.edu. You may wish to arrange that this command is executed
each time you log in.
I deleted my files--Help!!
Your backup AFS volume is a snapshot of your live volume,
taken some time around midnight. So if it's noon and you just deleted
an important file, you might be in luck. If it's Fall of 2006 and
your username is xyzzy, then:
- The true name of your regular AFS volume is /afs/cs.cmu.edu/academic/class/15410-f06-users/xyzzy
- Your backup AFS volume is therefore /afs/.cs.cmu.edu/.BACKUP/academic/class/15410-f06-users/xyzzy
You will need to edit the pathname as appropriate...note that the backup pathname contains two more dots than the pathname of your regular volume.
Also note that symbolic links in your backup volume point to live volumes,
so the mygroup/ symbolic link in your backup volume will point to your
group's live volume (the one you just deleted the file from) and
you will need to manually construct the pathname to your group's backup
volume.
AFS problems
If you have permission problems with your AFS space,
please try the program we have developed to diagnose them:
% /afs/cs.cmu.edu/academic/class/15410-f08/pub/access_scratch
DO NOT SEND US MAIL saying "I am having trouble accessing my AFS space".
You must always provide us with a detailed explanation of the
problem, such as a transcript of your session showing what you tried. Of course, you
should not mail us the transcript; as with anything else, you should
place it in a location where we can access it and tell us where that is.
If access_scratch does fix things for you, its output should
give you a clue as to what you could do in the future to avoid the trouble.
Please note that AFS, like anything else, may break from time to time. If you
receive errors such as Connection timed out or No such device,
please wait at least one hour before contacting course staff--these outages frequently
resolve themselves (or are resolved by elves). In the other direction, once two to four
hours have gone by, please send us mail (and post to the .qa bboard so fellow
students know mail has been sent).
AFS layout
Inside your volume you will see multiple directories. With a few exceptions,
these are your hand-in directories (p0, p1, ... are for projects; hw0, hw1, etc.
are for homeworks). We have provided two directories for you
to use while you are preparing your assignments:
- REPOSITORY
- You may place a CVS or PRCS repository here for Project 0 and/or Project 1 if you wish.
- scratch
- You may organize this directory tree any way you find convenient.
You should probably not prepare your work in your hand-in directories, since
that would preclude you having a "safe" turned-in version while making changes to a version
under (perish the thought!) last-minute development.
Avoid non-Unix File-Transfer Tools
Any time you move 410-related files around with non-Unix
utilities such as WinSCP or SFTP
you will probably regret it. Here are two reasons why.
- AFS authentication probably won't work right. WinSCP
on your machine will be able to authenticate you to your Andrew
home directory but not to your 15-410 AFS volume in the Computer
Science AFS cell. The result will be mysterious "permission
denied" errors when you try to move files around, or folders you
can't look inside.
- If you use a non-Unix file-transfer tool to copy a file
from one part of your AFS space to another, any time you copy
an executable program file it will probably stop being
executable. This is because on Windows files are considered
executable when the file's name ends in .EXE,
but on Unix any file of any name is executable as a function of
its permission bits. If you drag a file from a window
showing part of your AFS space to another window showing a different
part of your AFS space, the file will flow onto your Windows machine,
merrily losing its executable bits, and then flow back into your AFS
space a pale shadow of its former self.
How should you move files around? The best way is probably
to use standard Unix
shell-prompt commands (cp, tar, etc.).
Using your CS AFS space as a remote repository
Some students
doing development on a non-Andrew machine (which we cannot
in general support) have reported permission problems when
they try to use ssh to access revision-control repositories
contained in their 410 AFS space. The problem is that the
ssh server on the Andrew Linux machine you contact gets
AFS tokens for the Andrew AFS cell before executing the
command you specify, but it doesn't know you will need
tokens for the CS AFS cell.
We have received a report that the following will
enable CVS over ssh.
export CVS_SERVER='afslog cs.cmu.edu;cvs'
This instructs CVS client programs (on your personal machine)
to request the Andrew Linux machine providing access to
your repository to run the indicated sequence of commands;
the first will acquire CS AFS tokens and the second will
run the CVS protocol.
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