Howto force ssh to use a specific private key?

With ssh -i <private key filename> you can instruct ssh to use an extra private key to try authentication.

The documentation is not clear on how to explicitly use only that key.

Solution 1:

You can use the IdentitiesOnly option:

ssh -o "IdentitiesOnly=yes" -i <private key filename> <hostname>

Solution 2:

An alternative could be to generate a pair of keys using

ssh-keygen

and create a special configuration for the specified host and corresponding private key

Edit ~/.ssh/config

Host handy_server
    HostName x.y.z.w
    IdentityFile ~/.ssh/handy.pub
    IdentitiesOnly yes
    User userk
    Port 22