Generating an SSH key without a password. For example, for passphraseless old school Hadoop clusters. This is generally done from within a users home directory such as /Users/username on Mac.

ssh-keygen -t rsa -P ""

Generating an SSH key with a password. This is generally done from within a users home directory such as /User/username on Mac.

ssh-keygen -t rsa

How to copy a generated SSH key to the Mac clipboard. This is arguably better than manually copying and pasting.

cat ~/.ssh/id_rsa.pub | pbcopy