Configuration File#

The ssh program receives its configuration from either the command line or from configuration files ~/.ssh/config and /etc/ssh/ssh_config. Command-line options take precedence over configuration files. The user-specific configuration file ~/.ssh/config is used next. Finally, the global /etc/ssh/ssh_config file is used.

Some commonly used configuration options:

X11 forwarding
port forwarding
configure public key authentication

For example, I have multiple supercomputer accounts and would like to configure my ssh login.

First, I made the file, config, in my ~/.ssh/ directory:

touch ~/.ssh/config

Next, edit the file with vi:

vi ~/.ssh/config

Finally, I added these configuration options and saved the file:

Host *                            # Apply these options to all hosts
ServerAliveInterval 90            # Keeps the server alive by sending null packet (90 seconds)
StrictHostKeyChecking no          # Automatically add new host keys to the known_hosts 

Host ou                           # Alias for OU supercomputer, Oscer/Schooner
  Hostname schooner.oscer.ou.edu  # IP address of Oscer/Schooner
  User van                        # My username
  
Host osu                          # Alias for OSU supercomputer, Pete
  Hostname pete.hpc.okstate.edu   # IP address of Pete
  User van                        # My username

Now to log into either supercomputers, I just type:

Oscer/Schooner

ssh ou

Pete

ssh osu