SSH Multiplexing

If you use a Linux or MacOS computer and your workflow involves making a lot of connections to HiPerGator you may want to use SSH Multiplexing to avoid having to go through MFA for every connection. Again, this does not work for Windows computers natively! The BitVise and Tabby clients are the only SFTP/ssh client we are aware of that support ssh multiplexing.

In a nutshell, ssh multiplexing works by creating a TCP socket the first time a connection is made. That socket can be used by subsequent connections within the idle timeout period to create new connections without triggering MFA.

See Using SSH Multiplexing for reference.

Multiplexing with username and password

To use SSH multiplexing with your username and password (without SSH key authentication). edit the ssh configuration file on your local computer (typically ~/.ssh/config) and add or modify the following entry. Be sure to change the 'albertgator' User to your username:

Host hpg
    User albertgator
    HostName hpg.rc.ufl.edu
    ControlPath ~/.ssh/cm-%r@%l-%h:%p
    ControlMaster auto
    ControlPersist 8h

Note: On a MacOS system, if you see a 'unix listener too long' error, you may have to create a ~/.ssh/control directory and use

  ControlPath ~/.ssh/control/%C

in the ~/.ssh/config

After the ~/.ssh/config changes, use this ssh command:

$ ssh hpg

NOTE: The "hpg" hostname is not a real hostname, instead it's a virtual hostname that you defined in the above configuration.

Multiplexing with SSH keys

See also Using SSH Keys To Access HPG.

Never share your private ssh keys even with Support staff. Your private ssh key works as your password and it must be kept in a non-shareable space with r/w permissions at the owner level (-rw------- or 600).

If you are using SSH key-based authentication, add this block instead. This configures the connection to go to a different port (2222) which is expecting ssh keys:

Host hpg
    User albertgator
    HostName hpg.rc.ufl.edu
    Port 2222
    ControlPath ~/.ssh/cm-%r@%l-%h:%p
    ControlMaster auto
    ControlPersist 8h