When you need to get your key onto another machine, and you don't want the silly login-logout-copy-paste nonsense. Do this:
$ cat ~/.ssh/id_rsa.pub | ssh firstname.lastname@example.org bash -c "mkdir -p .ssh && cat >> .ssh/authorized_keys"
Don't have a key? Here's how to make one
ssh-keygen # smash the enter button Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /Users/tonymet/tmp/kaka. Your public key has been saved in /Users/tonymet/tmp/kaka.pub. The key fingerprint is: SHA256:WXXXXX The key's randomart image is: +---[RSA 3072]----+ |o.+++=+*Bo=. | | . xxxxxxxxx . . | | xxxxxxxxx+ + .| | xxxxxxxxxx = . | | = .S . = | | B o . | | + . | | . | | | +----[SHA256]-----+