UNIX for Dummies Questions & Answers

we have a file particular group(say abc) and we have a user(say def) in that group.I created file ram.txt it looked like this..
-rwxr--r-- 1 def abc 10 Oct 16 03:54 ram.txt

I changed the owner and group of the file as below
-rwxr--r-- 1 kriz test 10 Oct 16 03:58 ram.txt

when I log in as def to the machine and try to edit the file it says "read only" but when I save the file using wq!, it saves the contents and all the perm changes we did are lost and it agian goes to original settings..

Any Idea why it is happening? How to make a file readonly by chown option..

Since you changed owner from def to kriz, why should def be able to write anything? It is normal behaviour that your changes are lost. Even if def was in group abc - abc has no permission to write to this file. So I guess def is counted as "other" and so the last parts of the the permissions count for def which are only "r" = read.
I don't see the problem, sorry.

That's just normal. I doubt it saves the contents - it keeps the file as is cause of lacking permissions to def. It will be just updating the inode.

The idea behind doing this we have a user called as 'def" and we a file created using def. The passwd for def is known to many people. In order to restrict the acess of the file we could like to change it to someother owner,so that everyone has only read perm on that file.

Is there anyoher way to acheive it...

Having 1 user which many people use might be no good idea. To have a bit more of control, I suggest you create a group and put all those users that should have access to that file into that group and just assign that group to that file with chgrp.
The user which this file belongs can be for example the user "nobody" so no user owns that file, but all in the group can use it with the rights you've set.