The FreeBSD Diary

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uptime, w, and who show nobody logged in 2 November 2000

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I was working on a box for a client. They asked me to help. After fixing the problem, I checked to see if the client was still logged in. Here's what I saw:

[root@p100:/var/log] # who
[root@p100:/var/log] # w
9:21PM  up  5:18, 0 users, load averages: 0.08, 0.09, 0.03
 USER             TTY      FROM              LOGIN@  IDLE WHAT

That's wrong. You can't issue a who or a w and get no users. You're logged in. You should at least see you. uptime gave similar incorrect information.

Actually, you can be logged in and not seen. Here are the various things people have mentioned:

screen will let you do this, using the deflogin off option in your screen rc. add a chmod 711 ~; touch .nofinger and you're pratically invisible

My first thought was: someone has root'd this box.

So I asked on IRC and was told that it seems that my /var/log/wtmp is screwed. DOH!

So I logged out and back in again. Then everything worked:

[root@p100:/var/mail] # who
dan              ttyp1   Nov  1 21:24   (203.79.82.27)
[root@p100:/var/mail] # uptime
 9:50PM  up  5:47, 1 user, load averages: 0.00, 0.01, 0.00

Why?

The explanation is easy. The problem I was fixing was a full /var filesystem. That meant the contents of /var/log/wtmp was incorrect. It's updated each time someone logs in. By logging out and back in again, that file was updated correctly.

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