OpenSSH Configuration on Windows

There are certain tasks that I do every couple of months or even only every couple of years. One of those is setting up a new computer for development work. Then I struggle with some basic setup again as I have forgotten how I did it last time. One of those tasks is setting up OpenSSH.

Configure Hosts

In the folder %USERPROFILE%/.ssh create the config file for OpenSSH and add the configuration for commonly used hosts.

For example:

Host github.com
    User git
    IdentityFile ~/.ssh/my_github_identity.key
    IdentitiesOnly yes

This associates the my_github_identity.key private key file with the user git when accessing github repositories through OpenSSH.

I also add hosts as needed. For example, development machines on the local network, accessed through SSH.

Host raspberrypi
    User martin
    IdentityFile ~/.ssh/local_machines_identity.key
    IdentitiesOnly yes

SSH Authentication Agent

To avoid being asked the passphrase for the private key every time it is used we can add that key to the ssh authentication agent.

The ssh agent is available as a Windows service that needs to be enabled. Go to Services and find “OpenSSH Authentication Agent” and set its startup type to “Automatic”. Also manually start it for the first time.

Now we can add the private key to the agent:

ssh-add my_github_identity

This should ask for the passphrase of the private key again. From now on, the agent will take care of authentication when the key is used. This is convenient when working with Git CLI or any Git GUI that uses OpenSSH.