MLG Software : Password file and user accounts

General

The Machine Listening Group runs a Yellow Pages / Network Information Services (YP/NIS) `cell' whose sole function is to distribute central information about the password file i.e. who the users are. Thus MLG users do not normally have entries in the /etc/passwd file of individual machines, but only exist in the YP maps. See the man pages on, e.g., ypserv, for more information on how this works.

KEW.MEDIA.MIT.EDU is the master server for our domain, "bhg". FINCHLEY and SOUND are slave servers (meaning that users can continue to log in even if KEW is down, otherwise a nasty vulnerability). The master password file is kew:/etc/passwd.yp, but normally you wouldn't have to touch it. You should be able to change your password on any machine using the command 'yppasswd'.

The one time you do need to work on the master passwd file directly is when you are setting up accounts for new users. There are instructions on how to do that here.

Root access

All members of the group should be able to run commands as root on all our workstations using the sudo(8) command (see the man page). The ability to run sudo is determined by the /etc/sudoers file, which exists as an independent file on each machine, but should probably be the same across all machines. To add or remove users from the sudoers file, simply edit it in a text editor, or use /usr/local/etc/visudo which is actually a shell around emacs. The syntax (at least for simple access methods) should be obvious.

Once you have edited sudoers, you need to copy it to all the other machines. Note that sudoers is normally mode 004, meaning that it is only readable by root. To distribute, I normally make a copy of it, e.g. in /net/sound/usr/tmp/sudoers, then make that world readable. Then I run, as root, a script of the following form:

% foreach f (`cat ~dpwe/.bvg-hosts`)    # /net/kew/usr/people/dpwe/.bvg-hosts
					# is a list of our machines
> echo $f
> rsh $f "cp /net/sound/usr/tmp/sudoers /etc; chmod 004 /etc/sudoers"
> end

Actually, that doesn't work on about half the machines (their /.rhosts, /etc/hosts and /etc/hosts.equiv do not all contain KEW, so I cannot rsh root commands onto them) but you get the idea.

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DAn Ellis <dpwe@media.mit.edu>
MIT Media Lab Perceptual Computing