15. FAQ: Problems? Look here first

Contents:

• When I telnet to Eric why can't I get a login prompt?
• I'm using SSH, but I can't login/authenticate! Why?
• I'm using SSH, but I can't display Eric applications on my screen anymore --- why? (And it used to work with Telnet!)
• I'm using SSH and with an Xclient I get xserver killed messages...

When I telnet to Eric why can't I get a login prompt?

I telnet to Eric and see either this...

    telnet eric
    Trying 130.88.97.1...
    Connected to eric.
    Escape character is '^]'.
    Connection closed by foreign host.

...or this

    telnet eric
    Trying 130.88.97.1...
    telnet: connect to address 130.88.97.1: Connection timed out

What's wrong?

Telnet and FTP access to Eric have been blocked for some time now. You must use SSH login (and SCP or SFTP to transfer files). SSH and friends are described above.

I'm using SSH, but I can't login/authenticate! Why?

When I try to login/authenticate using SSH I am repeatedly asked for my password, but I still can't get in. I see this...

    mpciish2's password: 
    mpciish2's password: 
    mpciish2's password: 
    warning: Authentication failed.
    Disconnected; no more authentication methods available (No further 
    authentication methods available.).

...or this...

    Keyboard-interactive:
    PAM authentication
    Password: 
    Keyboard-interactive:
    PAM authentication
    LDAP Password: 
    simonh's password: 
    .
    .
    warning: Authentication failed.
    Disconnected; no more authentication methods available (No further 
    authentication methods available.).

In the first case, the most likely explanation is that your SSH client is either too old to support keyboard-interactive authentication or has not been configured to use this method. Keyboard-interactive authentication is described above. When logging in via the keyboard-interactive method you should see something like this (note the two lines "Keyboard-interactive" and "PAM authentication") :

    ssh eric -l mpciish2
    ---------------------------------------------------------------------------

    UMIST IT Regulations
    .
    .
    ---------------------------------------------------------------------------

    Keyboard-interactive:
    PAM authentication
    Password: 
    Authentication successful.
    .
    .

In the second case it is likely that you are using an incorrect user name. Remember that to login to a host via SSH, you need to specify the username: ssh [email protected] or ssh eric.umist.ac.uk -l mpciish2. If you do not explicitly state the username on the remote machine then the local username is assumed.

I'm using SSH, but I can't display Eric applications on my screen anymore --- why?

With Telnet, X11 connections are made separately (usually on port 6000); this is facilitated by setting the DISPLAY environment variable on the remote machine (this may be done automatically) and giving the remote machine permission to access you local screen (usually via the xhost command --- this may also be done automatically). One can do the same thing with SSH, though it is not recommended as this defeats the security offered by the encrypted (SSH) connection. Instead one should "tunnel" the X11 connection through the SSH connection. This procedure is detailed above

I'm using SSH and with an Xclient I get Xserver killed messages

When using SSH with X-tunnelling, X-clients (e.g., those launched from Cosmos or Eric) get permission to display on an X-server's screen (e.g., the screen in front of you) via the MIT-cookie/xauth mechanism (rather than using host-based authentication --- "xhost"). If this mechanism fails you will see "X-server killed" messages.

There are at least two possible causes of this. First, the cookie is not getting set on the remote machine (e.g., Cosmos or Eric). Check the date-stamp on your .Xauthority (in your home directory on the remote machine) --- it should have a date-stamp which reflects when you logged in. If it does not, then no cookie has been added; the file should also have a suitable cookie in it --- you can check this by using the xauth list command.

Possible solutions/causes: check your SSH configuration (X11 port forwarding should be enabled); check the permissions of .Xauthority (which should be rw-------); ensure you have the disk-space to write content to .Xauthority.