[19606] in Athena Bugs
Re: New athena release 9.0
daemon@ATHENA.MIT.EDU (Jonathon Weiss)
Mon Aug 13 09:26:36 2001
Date: Mon, 13 Aug 2001 09:26:34 -0400
Message-Id: <200108131326.JAA01685@attraction.mit.edu>
To: "David M. Collins" <dmcollin@mit.edu>
CC: bugs@mit.edu
In-reply-to: "[19573] in Athena Bugs"
From: Jonathon Weiss <jweiss@MIT.EDU>
> I have a few comments about the current athena release. I was following
> the instructions to make a local account on an athena-linux machine at:
>
> http://web.mit.edu/olh/Private/Private.html
>
> I followed the instructions and succeeded in nuking my /etc/passwd file
> so I no longer had root access. Are the instructions up to date? In
Yes, they appear to be up-to-date. One thing yo watch out for is to
make sure that you use >> and not > when trying to add a user to the
passwd file. The latter will overwrite the existing contents of the
file.
> particular, what are the differences between passwd, passwd-,
> passwd.fallback, and passwd.local?
passwd is the file that the system uses from moment to moment. People
will get added to and removed from this file when they log in and out.
passwd.local is considered the "master" file, and private workstations
will replace passwd with it when they reboot or reactivate, in order
to insure consistancy. passwd- and passwd.fallback are not
particularly rellevant in our environment.
> Should the local directory be /home/user or /var/user?
The fact of the matter is that this doesn't matter too much.
> The instruction cp -r /usr/prototype_user /var/user copies the
> directory across, but it seems like it should just be the dotfiles
> that are copied.
The only files in this directory that aren't dotfiles are files that
may be significantly useful to new users (and there are only 2 of
them)
> When I rebooted in single user mode, I entered the root password
> but no longer had write priviledges. What is the point of single
> user mode if I cannot repair any files?
This is probably because the root filesystem was mounted readonly.
Linux does this so that you can boot to single user mode even if there
is some filesystem corruption that can't be corrected automatically.
On linux, the following command will generally give you write access
to the filesystem from single user mode:
mount -o remount /
> Furthermore, athena had automagically copied a version of /etc/passwd
> over /etc/fstab, so I had difficulty in mounting the files systems!!
> (This definitely seems like a bug.)
Athena wouldn't do this. It is almost certainly due to filesystem
corruption from shutting your machine down with the power button, and
you noted below.
> All of this time I could no longer
> run shutdown, so I was power cycling the machine. The inevitable
> happened and the hard drive was corrupted beyond repair with fsck. Not
> very surprising with ext2. Would it be possible to allow a single user
> mode with write access to the disk? (I can hardly see this is too much
> of a security risk when you must enter the root password.)
As I've noted above, the inaccessibility is not meant as a security
measure, but rather to assist in certain recovery situations.
Since this is not actually a bug (beyond the filesystem corruption
with we're unlikely to be able to correct on our own) I'm going to
close your bug report now, but please feel free to let us (or OLC)
know if you have additional problems.
Jonathon Weiss
jweiss@mit.edu
MIT/IS Athena Server Operations
