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Yes, yes I know there are no real passwords or even hashes in that file on modern systems. However, I am quite curious if this is a good, easy way to totally lock down a system from everyone and what would break first. I don't have a spare system, but it sure sounds like a fun experiment. Has anyone tried this?

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This is pretty interesting from the point of view where you might want to build a system where your users are unable to lookup the usernames of other users. – pacey Nov 9 '10 at 17:44
And according to pacey (below) also unable to lookup their own names as well! – Allen Nov 9 '10 at 19:48
up vote 5 down vote accepted

Just for you I tried it :-)

Any user will be able to login like normal. This is because login runs with root privileges. After being logged in the user won't have access to /etc/passwd which might cause problems with userland applications.

The first thing you might notice is that the shell cannot read your username which produce a prompt like

I have no name!@vs245042:~$
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+1 just for trying it for me. I'm surprised that your system wasn't totally borked. Does it really say "I have no name!" or are you just paraphrasing? Which distro/version did you try? – User1 Nov 9 '10 at 19:47
I tried this on a Debian 4.0 machine with bash as login shell. It is not paraphrased it's copied from terminal. – pacey Nov 9 '10 at 20:27
Also, ls will only show UID and GID in numeric form. ~<username> won't expand either. – Slartibartfast Nov 10 '10 at 3:11
Wow. If you didn't know that someone did a chmod, how would you ever figure out what happened? – User1 Nov 10 '10 at 15:49

Setup an auditctl on /etc/passwd and see what tries to access it:
auditctl -w /etc/passwd -p war

Then afterwards analyse the output of:
ausearch -f /etc/passwd

See what's trying to access it, if it's all root processes then you're fine.

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That's a cool idea. Is there a way to config auditctl to only log non-root users? – User1 Nov 9 '10 at 21:07

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