[NTLUG:Discuss] "You Don't Exist: Go Away!"

[George E. Lass]

Christopher Browne wrote:
> 
> I am having an unfortunate situation where a machine periodically gets
> somewhat 'wedged up' such that:
>   a) Port services that check for user IDs die;
>   b) Permissions on files apparently "disappear";
>   c) Pretty much anything that checks IDs against /etc/passwd gets
>      hosed.
> 
> This does _not_ appear to be the result of a hack; it seems moderately
> "time based," probably relating to some resource filling up thereby
> making {utmp|PAM} throw up.
> 
> Other interesting facts:
> - It seems to happen _around_ once a day.  But not greatly predictable.
>    Oct 27, 03:38
>    Oct 27, 21:32
>    Oct 30, 08:02
>    Oct 31, about 1:56am
>    Nov 1, between 9:00 and 9:02 pm.
> 
> - I don't need to reboot to get everything to "reset;" if I drop to
>   runlevel 1 via "init 1," and then head back to "init 3", this seems
>   to suffice to clear things up.
> 
> - Debian Unstable Pretty Much Up To Date.
>   Linux knuth 2.2.14 #5 Sat May 6 07:29:45 CDT 2000 i586 unknown
> 
> The two things I've seen looking on Google that match the symptoms are:
> 
> a) "Oops.  You deleted /etc/passwd."
> 
>    Not the case.
> 
> b) Something vague involving utmp being "somehow messed up."
> 
> Anyone run into this sort of thing before?

I did just last week, but it happened when I was in the process of
trying to build my own boot disk.  I *think* the problem had to do
either with some missing files in /etc/pam.d or with some missing
tty device nodes.  

In any event I found the following result doing a search for

"go away, you don't exist" on google/linux:

http://www.cs.unt.edu/~srt/linux/linux-faq.ascii

Question 9.21.  You don't exist. Go away.

This is not a viral infection :-).  It comes from various programs such
as
write, talk and wall, if your invoking uid doesn't correspond to a valid
user (probably due to /etc/passwd being corrupted), or if the session
(pseudoterminal, specifically) you're using isn't properly registered in
the utmp file (probably because you invoked it in a funny way).

Good Luck,

George