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> ssh-keygen -t ed25519 -C "your_email@example.com"

... see above link

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Adding your key to another machine 

In order to login to another machine over ssh without requiring a password, we can add the public ssh key to the server's list of authorized keys.

For each user:

• they should generate (on their local machine) their keypair using ssh-keygen -t rsa (the rsa can be replaced with dsa or rsa1 too, though those options are not recommended).
• they need to put the contents of their public key (id_rsa.pub) into ~/.ssh/authorized_keys on the server being logged into.

Adding your key to Github

Navigate to Settings → SSH and GPG keys. Click New

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