[TAG] PAM auth failure - can't login in.

[Benjamin A. Okopnik]

On Sat, Apr 16, 2005 at 08:12:37AM -0400, Radick, Don (IHG) wrote:
>  
> 
> ==========================================================
> strace testing method:
> 
> login to initial console as root.  ok.
> "strace -vfo login.root login root"
> switch to VTY 2 with "Alt-F2"

Ah - there's the problem. Well documented, Don!

(I'm not joking. Even though it didn't work for you, the way you've
descibed your process clearly pointed to what's wrong with it, so that
troubleshooting can continue pas this point. Kudos!)

You're not supposed to flip to a VT - you're supposed to do the login
right in the console or xterm where you executed it. Otherwise, you're
"strace"ing a process that never actually gets any user input, while
running a login that is not being "strace"d! Here's me, doing the login
tango:

----------------------------------------------------------------------
ben at Fenrir:~$ su -
Password: 
root at Fenrir:~# strace -s 1024 -vfFo login.ben login ben
Password: 
Last login: Sat Apr 16 08:00:00 2005 on tty1
You have mail.
ben at Fenrir:~$ exit
logout
root at Fenrir:~#
----------------------------------------------------------------------

That produces a log file, "login.ben", containing all the stuff I need.
If the process failed, the reason for the failure would usually be
contained in the last 10-20 lines.

Now, in theory, you _could_ attach "strace" to a running process by
using the "-p <PID>" option - start logging in at a console, flip
to another one, do "ps ax" to find the PID of the login process, attach
"strace", flip back, and finish logging in. I find my first version to
be less of a hassle, though. :)


* Ben Okopnik * Editor-in-Chief, Linux Gazette * http://linuxgazette.net *