OpenSSH Commands

ssh, scp, sftp and ssh-keygen.All OpenSSH pages

ssh-keygen -lf: show the fingerprint of an SSH keyssh-keygen -lf key.pub prints the SHA256 fingerprint of an SSH key, as GitHub and ssh show it. -E md5 gives the old colon format; -lF checks known_hosts.
ssh-keygen -R hostname: remove a host from known_hostsssh-keygen -R hostname deletes a host's keys from known_hosts and keeps known_hosts.old. Ports as [host]:2222, hashed files, and checking the new key safely.
ssh-keygen -t ed25519: generate an SSH keyssh-keygen -t ed25519 -C email creates an Ed25519 key pair in ~/.ssh. Non-interactive options for scripts, installing the public key, and passphrase advice.
ssh-keygen -y -f id_ed25519: get the public key from a private keyssh-keygen -y -f ~/.ssh/id_ed25519 prints the public key of a private key, to recreate a lost .pub file or check a pair. Errors like invalid format explained.