What is SSH?

Secure Shell, or SSH, is a cryptographic (encrypted) network protocol to allow remote login, file transfer and other network services over a secure channel. SSH replaces telnet, rlogin, rsh and rexec, which are less secure because they operate in plaintext that can be inspected by other users on the same networks. SSH also sets up X11 connections, so the DISPLAY environment variable does not have to be set on remote machines. For file transfer, SSH implementations typically provide scp and sftp commands to securely copy files from one host to another, and rsync supports transfers via SSH by default.

How do I use SSH?

The simplest way to use SSH on Linux, UNIX or OS X is on the command line. In your terminal session, type:

ssh username@eniac.seas.upenn.edu

Where username is your SEAS account name (typically the same as your PennName) or the name of an activity account you manage.

The first time you connect to a host, you will be asked to verify its authenticity:

The authenticity of host 'eniac.seas.upenn.edu (2607:f470:8:64:5ea5::14)' can't be established.
ECDSA key fingerprint is 3a:ea:ab:7d:d1:65:21:7d:66:88:28:a4:c6:40:92:97 [MD5].
Are you sure you want to continue connecting (yes/no)?

Type yes and press the Enter key. That host will be remembered by its fingerprint from now on in the account on the machine you are currently using (including other machines that mount your home directory). The list of verified hosts is kept in ~/.ssh/known_hosts.

To complete your login, enter your password at the prompt (your PennKey password will work, as will your SEAS password if you have set one):

username@eniac.seas.upenn.edu's password:

Where username is the name of the account you are connecting to.

You will now begin a session on the remote computer using your default shell (typically bash), where you can type commands.

To end your session, type:

exit

Ending your session this way will preserve your command history and perform other housekeeping tasks that might not occur if you simply close quit your terminal on your local computer, put it to sleep, or shut it down.

For additional information about the ssh command, please check the man page:

% man ssh

How do I SSH from a Windows Computer?

The supported SSH client for Windows at Penn is Van Dyke Technologies' SecureCRT, provided for free to all Penn staff, students and faculty at: http://www.upenn.edu/computing/product/specs/securecrt.html.

After installing the client, follow these steps to connect:

  1. Double-click on the SecureCRT icon on the desktop.
  2. When the program opens, a list of hosts will be presented. Double-click on "eniac.seas.upenn.edu".
  3. The first time you connect to a server, a dialogue box will appear asking whether or not you would like to accept the new host key. Click on the button marked "Accept & Save".
  4. Enter your user name and password when prompted. Your username is the first part of your email address, i.e. username@eniac.seas.upenn.edu.

These instructions will place you at the unix command prompt. When you're finished, you can exit SecureCRT by simply typing "exit".

WARNING: Closing the session while a program is running in the unix environment can lead to lost data. Try to use "exit" whenever possible.

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