Centralised authentication using NIS
On the client side, users will have to use the utility 'yppasswd' to
change their passwords instead of passwd.
On the client side, open /etc/yp.conf. This file should contain a list of
the NIS servers for your domain. Multiple NIS servers can be specified
here so if one goes down, the NIS client will try the other. Hostnames are
also allowed here but make sure that the host's IP address is present in
/etc/hosts because NIS does not use DNS.
ypserver 192.168.0.100
ypserver nisbackup.freeos.com
Open /etc/passwd and remove the entries for all users that are to be
authenticated off the NIS master server. Also remove their shadow password
entries from /etc/shadow. At the bottom of /etc/passwd add this entry --
'+::::::'. Do the same for /etc/group but add the entry '+:::' here.
Start ypbind.
/etc/rc.d/init.d/ypbind start
Now try to login to your machine using a login/password pair that does not
exist on your machine. If the login is successful then your NIS setup is
working correctly.
The above '+' entries means that anyone who is in the NIS password database
will be able to login to this machine. You might not want that. You would
like only a few users or specific group of users access to a machine.
Edit /etc/nsswitch.conf and put in the following entries, if not already
there. Comment out any other passwd and group entries.
passwd: compat
group: compat
Some distributions like Red Hat use "passwd: files nisplus nis" here. That
will also work fine. In fact, with this entry in nsswitch.conf, you do not
require the '+' entries in /etc/passwd. What you lose is the ability to
selectively disallow certain users or netgroups, as we're trying to do below.
Now edit your passwd file and replace the '+::::::' entry with the name of
the user you want to allow, prefixed with a '+' and followed by
'::::::'.
+mayank::::::
+foo::::::/bin/false
+@nisgrp::::::
Here user mayank has access to the machine. User foo is also allowed but
the shell is set to /bin/false. Finally the netgroup nisgrp is also
allowed access. Here you see that you can also modify user date for the
client machine. You could also specify a different home directory path here.
To disallow access to few users/netgroups prefix the username with a '-'
instead. Also make sure that '+::::::' is a the bottom of the file and
this entry appears above it.
-mayank::::::
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