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SSH Connection to Unix Computers

SSH or a secure shell connection to a computer is one where the account name and password are sent across the network in an encrypted format. This make it harder for someone listening on the network to catch your information and enable that person to log into your account.

When computers make an SSH connection, they exchange "secret" keys so that they can identify themselves at a later time. This helps prevent another computer to use the ip address of one of the machine and fake that computer's network identity.

There are times when a computer will change its SSH key, such as when the SSH program is upgraded or the system on one of the computers is changed. When a connection is attempted after such a change or when a third computer is spoofing one of the addresses, the SSH login will send the user a notice that the keys do not match. If this is a harmless situation due to a system change, you will be given the file to change and the line number to delete from that file. Delete the line and issue the ssh command again.

You will be then asked if you want to exchange keys. Say yes.

For Windows XP or Vista 32 bit, download Putty to your desktop by following the links on

Click on putty which is now on your desktop.

Click on Run on the first pop-up window.

Fill in the fully qualified host name in the slot Host name. For the print/file server in Chemistry this would be; for Geological Sciences this would be

The Port should be set to 22 and the type of connection set to ssh.

For a first time connection you will receive a "Putty Security Alert." See above under the discussion of ssh. Answer Yes to exchange keys.

Login as: youraccount
youraccount's password:

For Macs running OS X or other unix computers, start up a terminal window. For Macs find the Terminal program by going to the Finder Menu by clicking on the desktop background. On the Finder menu, slide down under GO to Utilities or Applications if Utilities is not listed. You will find the Utilities folder in the Applications folder. Double click on the Terminal program in the Utilities folder.

In the terminal window, type

ssh youraccountname@unixcomputername

where youraccountname is the account on the unix computer and unixcomputername is the name of the computer to which you want to connect. If your account name on the unix computer is the same as the account name on the system you are currently using, you may omit the youraccountname@ from the line above. Depending upon whether your Mac or unix system is setup to search first on its own subnet to resolve a computers full name, the unixcomputername may be the a simple one word name such as chemps or geops. If your computer is not set up to do the subnet search first, you will have to use a fully qualified name in the unixcomputername portion of the command. A fully qualified name for chemps is; for geops it is

When the connection is made, you will asked for the password for youraccountname on the computer to which you are making the connection.

Last update 10-26-2007 - Margaret Doll