First Cluster Terminal Session

Suppose you are logged at login2.acf.ku.edu. If you are logged in on NoMachine, you need to  open a Terminal in order to follow along.  If you are logged in via a Terminal Emulator in your computer, you are ready to go.

You are looking at a shell prompt, which will probably be $. Type this command at the prompt:

$ qxlogin

That should transport you onto a randomly chosen compute node.

We suggest qxlogin because it creates a "graphical transport layer" between the compute node and the login2 system.  It may be that the compute node can relay images and such to your desktop. If your desktop happens to be incapable of receiving those X11 signals, we believe this is a "harmless", but excessive request.  A purely minimalistic request would be just "qlogin".

qxlogin is just a short script that asks the que system for a login on a compute node. While you are in a qxlogin session, you have access a piece of a node.  That session can be used to write programs or interact with them.

Type some commands to get a "feel" for your situation. The command "pwd" is short for "print working directory"

$ pwd

The "working directory" (WD) is sometimes called the "current working directory," it is the collection of files that are most immediately available.  Some programs we run will automatically look in the WD for data files and they will write output into the WD as well.

If you are trained on a Macintosh or Windows computer, you might not have noticed the fact that everything you do in your computer is governed by an environment, a collection of user account settings that define how the operating system interacts with you.  You can view the environment as currently configured by running this command.

$ env

If you are a Macintosh user, run the program Terminal (from the Utilities) and type "env". Similar. In Windows, open the Accessories and as for a "DOS Command box" and run "set".  Similar. It is important to realize that you do have an environment and when things go wrong, it may be that you need to check on those settings in order to fix a problem.  It is almost certain that when there is some nonsense in your account and something unexpected happens, we will ask "what is your SHELL?"  That's listed at the top of the environment.

Now understand this next thing. There are files in your current working directory. Probably.

The ls function is a workhorse. It has a lot of options.

$ ls -la

lists files with all (-a) files in long (-l) format. The important element here is that we asked to see all the files, even the "hidden" ones ("hidden" = the first letter in a file name begins is a period).

We encourage users to keep their files organized into separate directories.  The term "folder" is a more common name for a directory. Certainly folder is more likely to sound familiar to the modern Macintosh and Windows users.  You can create a directory, er, folder, with the mkdir command:

$ mkdir MyFirstDirectory

Make sure that directory was created by typing

$ ls -la

Change the WD into that new directory

$ cd MyFirstDirectory

Check where you are now:

$ pwd

Go back up one level

$ cd ..

When you are done, type

$ exit

That should bump you back to login2.acf.ku.edu.

Now, prepare to be amazed. While on login2, type

$ ls -la

You should see "MyFirstDirectory" that you created during the previous login session.

Then Run

$ qlogin

and the que system will randomly select another compute node for you. And when you get there, run this:

$ ls -la

You should see "MyFirstDirectory" there too.

How can it be there, when you are logged into a different compute node? That is the magic of NFS, the Network File System. All those separate computers are sharing your home directory. For more information, see our page on Cluster Storage.

The summary is this: Anything you save in your home account on any login2.acf.ku.edu will be available to any other system you are using within ACF at KU.

We are building up a more comprehensive list of Linux commands, please see http://crmda.ku.edu/linux-commands.


CRMDA Calendar

Like us on Facebook
One of 34 U.S. public institutions in the prestigious Association of American Universities
44 nationally ranked graduate programs.
—U.S. News & World Report
Top 50 nationwide for size of library collection.
—ALA
23rd nationwide for service to veterans —"Best for Vets," Military Times
Equity & Diversity Calendar

KU Today