ssh-keyscan

Scan host for keys

$ ssh-keyscan [hostname]

$ ssh-keyscan -p [port] [hostname]

$ ssh-keyscan -t ed25519 [hostname]

$ ssh-keyscan -f [hosts_file]

$ ssh-keyscan [hostname] >> ~/.ssh/known_hosts

ssh-keyscan [options] [host...]

ssh-keyscan is a utility for gathering SSH public host keys from remote servers. It connects to each specified host and retrieves the server's public keys, outputting them in a format suitable for appending to ~/.ssh/known_hosts or /etc/ssh/ssh_known_hosts files.
The tool is primarily used for automating host key distribution in environments where manually accepting host keys during first connection is impractical. It can scan multiple hosts in parallel, read host lists from files, and filter by key type (RSA, Ed25519, ECDSA). The -H option hashes hostnames in the output for additional privacy.

-t type

Key type (rsa, ed25519, ecdsa).

SSH port.

Read hosts from file.

Hash hostnames in output.

Connection timeout.

ssh(1), ssh-keygen(1)