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
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
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:
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)?
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
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):
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:
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
How do I SSH from a Windows Computer?
The supported SSH client for Windows at Penn is SecureCRT by Van Dyke Technologies, which may be downloaded for free by all Penn staff, students and faculty. It is already installed on all CETS lab Windows computers.
With SecureCRT installed, follow these steps to connect:
- Double-click on the SecureCRT icon on the desktop.
- When the program opens, a list of hosts will be presented. Double-click
- 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 the Accept & Save button.
- Enter your user name and password when prompted. Your username is the first part of your email address, i.e. email@example.com.
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.