When a host rebuilds, its SSH key changes
A fresh install or a system rebuild swaps the host’s RSA/ED25519 key pair.
If you still have the old key in ~/.ssh/known_hosts, the next SSH connection will
trigger a “WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!” message.
That warning is a safety feature, but it also blocks automation and forces users
to manually edit the file.
The quickest, safest way to clean up stale entries is to let OpenSSH do the work
with ssh-keygen -R. The command removes every key that matches the supplied
hostname or IP, regardless of whether the entry is hashed or plain.