sshcopyid

ssh-copy-id is a utility that ships with the OpenSSH suite and is used to install a local public key on a remote system’s authorized_keys file. By placing your public key on the remote host, you can enable passwordless SSH login for that account, provided the remote server is configured to allow public key authentication.

How it works: ssh-copy-id connects to the remote host via SSH, creates the remote .ssh directory if needed, and appends the specified public key to ~/.ssh/authorized_keys with the correct permissions (typically 700 for .ssh and 600 for authorized_keys). It can handle multiple key files if invoked with multiple -i options, and it avoids duplicating keys that are already present. The command relies on being able to authenticate to the remote account for the initial installation.

Typical usage: ssh-copy-id [options] [user@]host. By default it copies the user’s default public key (for example ~/.ssh/id_rsa.pub). Common options include -i to specify a key file, -p to set a nonstandard port, and -o to pass ssh options. Example: ssh-copy-id -i ~/.ssh/id_rsa.pub [email protected], followed by a regular ssh login: ssh [email protected].

Notes: The remote account must permit key-based authentication, and file permissions on the remote side must be properly restricted. If the host requires a password for the initial login, you will be prompted. ssh-copy-id is a convenience wrapper around standard SSH and the remote authorization process; it does not replace the need for secure key management.