Secure Shell (SSH)

Users must use SSH for connecting to NERSC computers. Telnet access to NERSC resources was disabled on December 8, 1999.

All NERSC computers accept connections via SSH protocol version 2 protocol. Protocol version 1 was disabled on October 1, 2003. There is no SSH access to the mass storage system at NERSC. See the HPSS pages for more information about connecting to HPSS.

What is SSH?

SSH (Secure Shell) is a program to log into another computer over a network, execute commands on a remote machine, and move files from one machine to another. It provides strong authentication and secure communications over unsecure channels. It is intended as a replacement for rlogin, telnet, rsh, and rcp.

SSH provides a much higher level of security than telnet. All communications are automatically and transparently encrypted, including passwords. This prevents "password sniffing", one of the most common means by which computer system security is compromised. The UNIX version of SSH also provides a remote copy operation (scp). Another utility for secure file transfer is available with many SSH implementations is known as sftp, which replaces the insecure ftp protocol. Additionally, SSH allows secure X Window connections.

Similar to many other communications packages, SSH is implemented with a server "daemon" (sshd) to handle inbound connections, and a client (ssh) to handle outbound connections. NERSC is running an SSH daemon for the version 2.0 and 1.5 SSH protocols on its machines.

ssh and slogin

The ssh and slogin are the standard UNIX command names for interactive login from a shell or terminal window. They are secure replacements for the older remote connection commands, "telnet", "rlogin", and "rsh".

sftp

The sftp utility is a secure replacement for the standard file transfer utility, "ftp".

scp

The scp command is a secure replacement for the Unix remote file copy command, "rcp".

Both sftp and scp allow secure file transfers between machines.

SSH Information

• SSH Home Page (Information about the SSH 2.0 protocol that is undergoing standardization in the IETF and elsewhere)
• The OpenSSH Home Page