Accessing HPC2N¶

This section provides information on how to login/access the HPC2N systems, and how to change a password after logging in the first time. You will also find information on what to do if you have forgotten your password, as well as information on X11 and shells.

Login nodes¶

Kebnekaise login node¶

The domain name for the main login node of Kebnekaise is:

kebnekaise.hpc2n.umu.se

ThinLinc login node¶

The ThinLinc login node for Kebnekaise is:

kebnekaise-tl.hpc2n.umu.se

For more information about using ThinLinc to access Kebnekaise, see our ThinLinc documentation. If you need a graphical interface for your work, then it is recommended to use ThinLinc.

For a more detailed list of our available systems, as well as more information about the hardware of Kebnekaise, please refer to our hardware pages.

Login and File Transfer¶

To be able to access HPC2N clusters from a remote computer using your HPC2N login name and password, you need to use a secure shell (optionally with GSSAPI for passwordless login). On GNU/Linux, OS X, and other Unix-like operating systems we recommend using OpenSSH’s ssh (secure shell) for login and scp (secure copy) for file transfer.

ThinLinc is an option for all major platforms, and the recommended way of accessing HPC2N if you are on Windows and/or need to use any graphical functions.

The following table shows recommended SSH and file transfer clients for all major platforms:

Documentation can be found on the above sites or by typing man ssh or man scp if you are using a terminal emulator. You can also get more information in the section below on SSH X11 forwarding.

user@localhost:~$ ssh yourusername@kebnekaise.hpc2n.umu.se
user@localhost:~$ scp yourusername@kebnekaise.hpc2n.umu.se:file /tmp

Also note that the HPC2N and SUPR accounts are separate!

Passwordless login

GSSAPI with ssh and PuTTY clients

For the ssh client, enable the following configuration options in $HOME/.ssh/config:

Host *.hpc2n.umu.se
 GSSAPIAuthentication       yes
 GSSAPIDelegateCredentials  yes
 PreferredAuthentications   gssapi-keyx,gssapi-with-mic,password

Before running the ssh command make sure you have a valid Kerberos ticket (klist command) or obtain one by running the kinit command:

kinit $USER@HPC2N.UMU.SE

On Windows users can use PuTTY. In PuTTY configuration menu Connection –> Auth make sure that both of the Kerberos 5 GSSAPI boxes are checked, to attempt GSSAPI authentication and to allow GSSAPI credential delegation.

SSH X11 forwarding¶

This section is about how to enable SSH X11 forwarding on other SSH clients.

In order to enable this, you must login with

ssh -X <username>@hpc2n.umu.se

where you change to your own HPC2N username in the above.

SSH supports tunneling of X11 (X-Windows). This is also very useful if you want to open graphical displays from the remote machine on your local computer. To achieve this, an X11 server must be running on your local machine. The X11 connections are then tunneled and automatically encrypted by your SSH client.

For some types of graphical software this does not work correctly (if they need input from keystrokes). In those cases you must use

ssh -Y <username>@hpc2n.umu.se

This is not recommended otherwise, as a program then potentially has access to do things like keylogging.

Installing an X11 Server

In order to use X11, you need to have an X11 server running on your local machine. There are both free and commercial X11 servers available for the various operating systems.

GNU/Linux

• If you are logged in to a graphical environment (like X), an X11 server is most likely already running.

OS X

• XQuartz - X11 used to be available as an optional package on the install disc, but is now maintained in the XQuartz project.

Windows

There are several X11 servers available, here are three that are free:

• Xming - available for all versions of Windows. Very easy to install and use. May sometimes hang and need restarting.
• MobaXterm - SSH client with X11 included. Also includes file browser.

• Cygwin - available for all versions of Windows. Note that this is a full “Linux-like” environment, not just an X11 server.

  • Download setup.exe and make sure you select the following packages (from the ‘Select Package’ screen - should be available after the initial file downloads):

  • Go to “xorg-X11-base” and click on it to open it and select these files (or just change “skip” to “install”): Under the Graphics group, also select opengl, if you want OpenGL support.

    X-startup-scripts
    XFree86-lib-compat
    xorg-*
    xterm
    xwinwm
    lib-glitz-glx1
    

  • Then when the Cygwin X server is installed, start an xterm and type XWin -multiwindow in it and then enter.

  • You can now run your SSH client.

Enabling X11 Forwarding in your SSH Client¶

Once you are running an X11 server, you will need to enable X11 forwarding/tunneling in your SSH client.

The descriptions will be for a few select - but common - ones.

• “ssh”: X11 tunneling should be enabled by default. To be certain it is enabled, you may use ssh -X or ssh -Y.
• PuTTY: Prior to connection, in your connection’s options, under “Tunnels”, check “Enable X11 forwarding”, and save your connection.
• MobaXterm: X11 is automatically enabled.
• Secure CRT: Right-click a saved connection, and select “Properties”. Expand the “Connection” settings, then go to “Port Forwarding” -> “Remote/X11”. Check “Forward X11 packets” and click “OK”.

SSH will set the remote environment variable $DISPLAY to “localhost:XX.YY” when this is working correctly. If you had previously set your $DISPLAY environment variable to your local IP or hostname, you must remove any set/export/setenv of this variable from your login scripts. The environment variable $DISPLAY must be left as SSH sets it, which is to a random local port address. Setting $DISPLAY to an IP or hostname will not work.

Note: If you are logging in with GSSAPI, you must forward your credentials (Kerberos ticket) in order to be able to login. There is a little about logging in with GSSAPI in that section further up on this page.

First time login, password change¶

The first time you log in to any HPC2N system (see the first section on the page on how to log in) you must change your password. This is done using the passwd command:

passwd

Use a good password that combines letters of different case. Do not use dictionary words. Avoid using the same password that you also use in other places.

• It will first ask for your current password. The first time you login, that will be the temporary password you created with the HPC2N password reset service.
• Type in that and press enter.
• Then type in the new password you want, enter, and repeat.
• You have changed the password.

You get your initial password from the Password restore service, as mentioned in the welcome mail you received when your HPC2N account was created.

Forgotten Password¶

If you forget your password it can be restored the same way you set your initial password; using the Password restore service. It requires that you have a SUPR id and that your account at HPC2N is connected to your SUPR id.

Remember to change your password when you have logged in again with the new, temporary password.

Shells¶

When your account is activated, your default shell will be set to bash - the GNU Bourne-Again SHell (bash), which is completely compatible with the Bourne shell (sh). For more details on bash, enter “man bash” while logged in.

Another popular shell is tcsh - an enhanced version of the Berkeley UNIX C shell (csh). The tcsh shell is completely compatible with the standard csh, and all csh commands and scripts work unedited with tcsh. For more details on tcsh, enter “man tcsh” while logged in.

To change your shell temporarily, type the shell name as a command (“bash“, “tcsh“). This will run the new shell as a subshell. To return to your original shell, simple type

exit

To permanently change your login shell, use the command chsh:

chsh

You will then be given a list of shells to chose from.

$ chsh
Current shell is ‘/bin/bash’ for user username.
Valid shells are:
    /bin/bash
    /bin/tcsh
Enter new shell [/bin/bash]:    
 
Choose a shell and hit enter.

The next time you log on, you will start in the new shell. However, you may switch back at any time.