Ubuntu Wiki

If you have difficulty logging in on ubuntu/edubuntu LTSP5 thin clients, here are some tips on common problems and how to debug the situation.

Update SSH Keys

Try logging into the server and running:

• sudo ltsp-update-sshkeys

then for gutsy (7.10) and above, you need to update the image:

• sudo ltsp-update-image

or for a i386 image on a 64bit server . . .

• sudo ltsp-update-image --arch i386

When your thin client logs you into the server, it checks the server's identity by looking at its ssh key. Most often, if the server's IP address gets changed, the key no longer matches and logins fail. The above will update the list of keys and IP addresses.

Note that the recent (May 13, 2008) OpenSSL vulnerability fix updates the server keys and these steps will be required.

Sabayon?

Did you install Sabayon? If you install Sabayon, only those users for whom you have created a sabayon profile will be able to login. You can remove it again, or create profiles.

Is authentication working?

Log onto the server and look at the file /var/log/auth.log. You should be able to see a log where the user is being authenticated by the server:

Sep  6 08:50:00 brooks sshd[23377]: Accepted password for dave from 192.168.1.50 port 4982 ssh2
Sep  6 08:50:00 brooks sshd[23379]: (pam_unix) session opened for user dave by (uid=0)
Sep  6 08:59:14 brooks sshd[25169]: Accepted password for paul from 192.168.1.57 port 2413 ssh2
Sep  6 08:59:14 brooks sshd[25176]: (pam_unix) session opened for user paul by (uid=0)

If this is not working or there is some error, you have a problem here.

A user session problem?

If the user session itself dies quickly, it could look like a failed login. You can login to the server and look in the file .xsession-errors in the user's home directory to see all errors from the session. It's normal for there to be a bunch of warnings in this file, so you'll have to sift through it a bit and look for things which sound really terminal to the session.

Log files on the client

First you need to set the thin client root password. Once you've done that, you can login to the thin client text console (press <ctrl><alt><F1> to get a console) and type:

• less /var/log/ldm.log to look at the display manager logs, which often show login problems.

• less /var/log/Xorg.0.log to look at the X environment logs, which tend to show problems with the graphical environment itself.

Typing 'q' will quit less. Hitting <ctrl><alt><F7> should get you back to the graphical login screen on a thin client.