Advanced SSH Configuration
Example SSH config
The following configuration is an example ssh client configuration file specific to our clusters. You can use it on Linux, Windows Subsystem for Linux (WSL), and macOS. It allows you to use tab completion of the clusters, without the .ycrc.yale.edu
suffixes (i.e. ssh grace
or scp ~/my_file grace:my_file
should work). It will also allow you to re-use and multiplex authenticated sessions. This means clusters that require Duo MFA will not force you to re-authenticate, as you use the same ssh connection to host multiple sessions. If you attempt to close your first connection with others running, it will wait until all others are closed.
Save the text below to ~/.ssh/config
and replace NETID
with your Yale netid. Lines that begin with #
will be ignored.
# If you use a ssh key that is named something other than id_rsa,
# you can specify your private key like this:
# IdentityFile ~/.ssh/other_key_rsa
# Uncomment the ForwardX11 options line to enable X11 Forwarding by default (no -Y necessary)
# On a Mac you still need xquartz installed
Host *.ycrc.yale.edu mccleary grace milgram
User NETID
#ForwardX11 yes
# To re-use your connections with multi-factor authentication
# Uncomment the two lines below
#ControlMaster auto
#ControlPath ~/.ssh/tmp/%h_%p_%r
Host mccleary grace milgram
HostName %h.ycrc.yale.edu
Warning
For multiplexing to work, the ~/.ssh/tmp
directory must exist. Create it with mkdir -p ~/.ssh/tmp
For more info on ssh configuration, run:
man ssh_config
Store Passphrase and Use SSH Agent on macOS
By default, macOS won't always remember your ssh key passphrase and keep your ssh key in the agent for SSH agent forwarding. In order to not repeatedly enter your passphrase and instead store it in your keychain, enter the following command on your Mac (just once):
ssh-add -K ~/.ssh/id_rsa
Or whatever your private key file is named.
Note
If you use homebrew your default OpenSSH may have changed. To add your key(s) to the system ssh agent, use the absolute path: /usr/bin/ssh-add
Then and add the following to your ~/.ssh/config
file (create this file if it doesn't exist, or add these settings to the Host *.ycrc.yale.edu ...
rule if it does).
Host *.ycrc.yale.edu mccleary grace milgram
UseKeychain yes
AddKeystoAgent yes
You can view a list of the keys currently in your agent with:
ssh-add -L