ITS Linux Computing

lxcluster.tlt.psu.edu

If you need remote access to the CLC linux cluster, this is the place to find directions. Your first step is to get an SSH client. If you have linux on your machine, then you probably already have Openssh installed, but if not, and you have a recent version of linux, you can probably use up2date, yum, apt-get, yast, or any other updating software that comes with your distribution. If you have Windows on your computer, you can download SSH clients from http://downloads.its.psu.edu if you are a student, faculty or staff. Once you log in, go to the 'File Transfer' section and download the appropriate client. You can also download SSH clients for Mac OSX from this site, but the terminal applications is usually installed and can access a command line ssh client.

If you do not need to display any graphical applications, you can simply use any SSH client for your platform. Please follow the directions immediately below for instructions on this method. If you do need to run a graphical application, please skip to the next section. (What do we mean by graphical applications? We are referring to applications that open a window. Whether it be to interface with the application, or to display data, if a window opens when using the application, we call that a graphical application.)

NON-GRAPHICAL SSH

LINUX

If you are connecting to the cluster from Linux/Unix and are using a command line ssh client, just type "ssh lxcluster.tlt.psu.edu -l <PSUid>" where <PSUid> is your penn State User Id. If you have not ssh'ed to the cluster from that machine before you will get a message stating that the authenticity of the host cannot be established, it will give you an RSA key, and ask if you want to continue. Type 'yes' to continue, and then enter your password when it prompts you for it.

WINDOWS

If you are using Secure Shell for Windows, start the application, and to get started quickly, click the 'Quick Connect' button. Then enter the cluster name "lxcluster.tlt.psu.edu" and your username. Leave the port set to 22, hit Enter, and when it prompts you for your password, enter your Penn State password. There are several ssh clients for windows. Another one that is very popular (and also free) is cygwin, which is not only an ssh client, but a bash shell environment. We'll tell you more of what you can do with cygwin later.

MacOSX

If you are using Mac OSX, and are just using MacOSX's terminal application, start it by going to the Finder -> Applications -> Utilities -> Terminal. Once the terminal window comes up, type "ssh lxcluster.tlt.psu.edu -l <PSUid>" where <PSUid> is your Penn State User Id. If you have not ssh'ed to the cluster from that machine before you will get a message stating that the authenticity of the host cannot be established, it will give you an RSA key, and ask if you want to continue. Type 'yes' to continue, and then enter your password when it prompts you for it.

GRAPHICAL SSH

LINUX

If you are using a fairly recent version of a more popular distribution of linux (Red Hat, Fedora, Suse, Debian, etc.) then you shouldn't need any special software. Since you are using linux, you most llikely already have X windows running. If you don't have a graphical login then you'll need to start the X Windows system, but this is not the normal setup for a desktop linux machine. The only change you might have to make, is when connecting to the cluster, use the command "ssh -Y lxcluster.tlt.psu.edu -l <PSUid>". The -Y option enables trusted X11 forwarding. This means that X11 will be forwarded to your screen and not subjected to the X11 security extention controls. For more information type "man ssh" on your linux console.

WINDOWS

In order to display graphical applications from the cluster on a windows PC, you need to have an X windows environment. This is different that Microsoft's "Windows" Operating system. The most common way to do this, is to download and install X/cygwin. During the installation, follow all of the default prompts until you are prompted to install a selection of packages. The default is fine, but you will need two additional applications to follow along with this tutorial. In the 'Net' category, select the 'openssh' package. Selecting this will automatically select any dependencies it requires. You will also nee to click on the 'X11' category and choose 'xterm'. Again, selecting this will automatically select it's dependencies. Continue with the installation choosing the default prompts. Once you have installed everything, click on the cygwin icon on your desktop, and a window will appear.

This black window is your bash environment. You can use this similarly as though you were on a linux machine. You can run asn ssh client from this window, or view the files on your windows machine, but with typical bash commands, or use bash commands to run a script. Additional applications such as vi are installable through cygwin's installer program. If you've deleted it, you can just download the setup.exe file from cygwin's site and just run it again.

The next step is to start the windowing environment. In the bash command line window, type "startx" and hit "Enter" as shown below.

After you hit "Enter" a bunch of text will scroll up and off the screen of your bash shell window. Don't worry because after a second or two, another window should appear, this time it's white. This is your "xterm" window. See the example below:

Inside the xterm window is where you'll connect to the cluster. Type "ssh -Y lxcluster.tlt.psu.edu -l <userid>" where <userid> is your PSU ID. See below.

Once you've logged in, you should be able to access any application on the cluster, and even be able to use the graphical interface. In the following images, we started Maple, and you can see that it starts and works just like if it were on your own machine.

MacOSX

Macintosh computers running MacOSX already have a built in X11 windows system, and it's conveniently called X11. It is located under Applications -> Utilities -> X11. Start it up and it will open an xterm window for you.

Once you have the xterm window up, ssh to the cluster by typeing "ssh -Y lxcluster.tlt.psu.edu -l <userid>" where <userid> is your PSU ID. See the following image for an example:

Once you have logged in, running graphical applications is just as easy as being on a linux lab machine, just type your command and it should display. Here we show a Mac running Ansys from the cluster on MacOSX using X11:

Unfortunately we've seen problems trying to get X11 to work with the cluster. Fortunately, you can use the freely available OroborOSX, and it seems to work great. Once you've installed OroborOSX, using it is basically the same as using X11.

Connecting to the Cluster with VNC

If you are interested in working in a full linux environment, but don't want to install linux, run a live distribution, or need software that is available on PSU lab machines, then you can use VNC. A VNC client is available for all platforms with RealVNC being one of the most popular viewers. Go to http://realvnc.com/download.html to download a VNC viewer for Windows, Linux and Unix. MacOSX users can get OSXvnc, a free VNC viewer, from http://www.redstonesoftware.com/vnc.html. Please install this before continuing on to the next part.

In order to use the vnc software on the lxcluster, you will need an ssh client. Please see the top of this page for instructions to download an ssh client.

Now ssh to the lxcluster.tlt.psu.edu server using the command "ssh lxcluster.tlt.psu.edu -l <userid>". Once you have successfully logged into the cluster, run the command 'lxclustervnc' at the prompt. This will start a script that will make it easier to run the vnc server daemon. The first time you run this, you will be prompted to create a password (unless you have run the vnc server on the cluster before). This password is ONLY for logging into your vnc session. It does NOT change your PSU Access Account password, and should be different from your PSU Access Account. You will then see a message that states the default resolution for your vnc session. You can change this if you wish, or just press ENTER to continue with the default setting. (The resolution change is per session - It will go back to the default the next time you run 'lxclustervnc') After this the script will pause for a couple seconds while it starts the vnc daemon for your account. It will then tell you the server name and the port you will need to connect to. Once it displays this information, it will sit and wait for you to cancel the vnc session. Leave this prompt sit here in waiting until you are completely done with your vnc session. ***IMPORTANT*** You MUST leave this shell window as is, until you are done with your session. If you log out, or close the window, your vnc session will be terminated.

Now that you have your vnc session running, using the server name and display port shown in the ssh window, run the vnc viewer you downloaded and installed. Input the servername and display port as it was shown in the ssh window. It should follow the form "server:port" and look something like "lxcluster1.clc-labs.its.psu.edu:9". The vnc viewer will then ask you for the password you have made for your vnc session. If you have forgotten it, open a new ssh connection to lxcluster.tlt.psu.edu and run the command 'vncpasswd'. It will prompt for a new password, and then verify it.

When you are finished with your vnc session, close the vnc viewer window, do not go to logout on the menu. Then go back to your ssh window, which should still be running, and answer yes to the question of "Would you like to cancel your vnc session now? [yes/no]". This will properly terminate your vnc daemon for your account.

CONTACTS:

If you experience any problems in trying to access the cluster, please email CLC-LINUX@PSU.EDU.

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This page was last modified: 10/23/2006 3:06:14 PM.