Getting Started with Galileo A quick introduction Connecting: The preferred method of connecting to Galileo is "ssh" (Secure Shell). Ssh is available on most of the Unix machines around grounds, and several versions are available for PCs running Windows. (If you need ssh on a Unix computer and can't find it, please contact the computer's administrator and ask him or her to install it. It'll be well worth the adminstrator's time to do so.) Unlike telnet, rsh or rlogin, ssh encrypts data before sending it across the network. Many people aren't aware that everything they type during a telnet session is visible to anyone on the network, if they have the tools to look. These tools are available for many operating systems, including Windows95, and can be found for free at Web sites around the world. When you type your password or read a mail message during a telnet session, anyone with a Windows95 computer could potentially be listening in. Ssh protects your private communications by creating a secure connection between you and the remote computer. An excellent implementation of ssh for Windows95 or WindowsNT is "TTSSH" (TeraTerm SSH), which can be found at: http://www.zip.com.au/~roca/ttssh.html TTSSH is installed on the PCs in the physics department's computer lab (room 315). A pre-installed copy of TTSSH is also available on one of our NT servers, Curie. If you are working from a Windows95 or WindowsNT computer in the physics department, you can get TTSSH by temporarily mapping a drive to: \\curie\public and copying the file "SSH TeraTerm" from the directory: "apps\win32\TeraTerm SSH" onto your desktop. Double-clicking on the resulting icon will start up TTSSH. ITC has recently purchased a site license for another Windows-based SSH client, called SecureCRT. It can be found at: http://www.itc.virginia.edu/itcweb/networks/securecrt.html Another good implementation of ssh for Windows 95 and NT can be found at: ftp://ftp.ucsb.edu/.2/mirrors/security/ssh/contrib/ssh-1.2.14-win32bin.zip This is also locally available from \\curie\public. Look in the directory: "Kits\Win32\Ssh" This version of ssh is closer to the Unix version, modified to run under 95 and NT. Note that it won't work unless you define the "HOME" environment variable. Included with it are "scp" (a secure copy program, similar to rcp) and support for forwarding X connections. The latter may make it more convenient than TTSSH if you use X. Note that you'll need to define the DISPLAY environment variable on your PC before invoking ssh, to let it know you have an X server. Once installed, you can use it to pop up an xterm from galileo by issuing the following command: ssh galileo -l userid xterm -ls where "userid" is your user name on Galileo. Currently, you can still also use telnet, rsh and rlogin to connect to Galileo, but only from within the physics department. In the future, we expect to turn off all access except through ssh. Using more than one node: Galileo is a cluster of computers that behave, in some respects, like one machine. Each computer (or "node") in the cluster is individually quite fast, so even if you only use one node, you'll see good performance. When you ssh to galileo, a master node locates one of the other nodes that's currently least busy and connects you with it. Since our cluster has twelve nodes, the first twelve people using it could potentially each have an entire computer all to themselves. To find out who's logged on and what node they're using, type "show users". To see the status of each node, type "show cluster". You may want to use more than one node at a time, though. There are several ways of doing this. The simplest is just "ssh". The cluster is set up so that, once you're logged on, you can use ssh to go to any node without typing in a password. For example, if you wanted to go to node12, you'd just type "ssh node12" and you'd be there. If you just want to execute a command on node12, without logging in, you could type "ssh node12 command". Next, there's the "run" command. Run executes a command on a remote node in much the same way as ssh, but with a few differences: First, run doesn't give you a choice of node: it picks the currently least-busy node and runs your command there. Second, run preserves your current working directory, so that if you're in the directory "~/programs/goodstuff", run will automatically change to that directory on the remote machine before it executes your command. Finally, run preserves your environment variables. Any variables you set before invoking run are also set on the remote machine before your command is executed. For finer-grained parallelism, there are the packages PVM and MPI. These can be used to write parallel applications which make use of all or some of the cluster nodes at once. For information and tutorials see the PVM and MPI web sites. Scratch space: Each node in the cluster has a 4 GB scratch disk. These scratch areas are available from all nodes, and are called "/scratch1" through "/scratch11". The scratch space on the local node can also be referred to as "/s_local". (Using the local scratch space will always be faster than using scratch space from another computer.) To find out how much scratch space is available in the cluster, type "show scratch". NOTE: Beginning October 2000, files more than one month old in Galileo's scratch areas will automatically be deleted. Setting your environment: When you start using Galileo, avoid the temptation to copy your .login, .cshrc, .profile or other startup files from other computers. Galileo is a different sort of machine, and these files probably won't work properly there. Instead, try out the system-wide defaults, and take a look at the "preferences" command. Preferences lets you set several common environent variables in a way that doesn't depend on what shell you're using. Currently, these are: MAILER -- Preferred mail program (e.g., "pine") EDITOR -- Preferred editor (e.g., "emacs") PRINTER -- Preferred printer (e.g., "physics_315") We'll probably add more as time goes by. Suggestions are welcome! Migrating files from other computers: If you've been using another Unix machine and you decide you want to migrate all of your files from there to Galileo, consider the "migrate" command. When run, migrate will ask you a few questions, including the name of the computer you'd like to copy files from. It will then proceed to copy the files into your area on Galileo. Startup files like .login and .profile are treated specially. Since they're probably not appropriate for galileo, they're put into "dotfiles" directory under your home directory, so you have them for reference, but they won't effect your environment. Migrate does nothing to your files on the original computer other than copying them to Galileo. Your original files will still be there until you delete them yourself. Migrate WILL, however, overwrite any files you already have stored on Galileo. For this reason, it may not be appropriate for those who are already using Galileo extensively. Programming and applications: Finally, a word about compilers/interpreters and applications on Galileo. The best source of information about these is the software section of the galileo web page: http://galileo.phys.virginia.edu/software. This page has links to much documentation. Suggestions are welcome for new software and applications you'd like to see installed.     For More Information about Galileo, contact Bryan Wright.