Syntax
ssh-keygen [-q] [-b <bits>] -t <type> [-N <new_passphrase>] [-C <comment>]
[-f <output_keyfile>]
ssh-keygen -p [-P <old_passphrase>] [-N <new_passphrase>] [-f <keyfile>]
ssh-keygen -i [-f <input_keyfile>]
ssh-keygen -e [-f <input_keyfile>]
ssh-keygen -y [-f <input_keyfile>]
ssh-keygen -c [-P <passphrase>] [-C <comment>] [-f <keyfile>]
ssh-keygen -l [-f <input_keyfile>]
ssh-keygen -B [-f <input_keyfile>]
ssh-keygen -D <reader>
ssh-keygen -U <reader> [-f <input_keyfile>]
ssh-keygen -r <hostname> [-f <input_keyfile>] [-g]
ssh-keygen -G <output_file> [-v] [-b <bits>] [-M <memory>] [-S <start_point>]
ssh-keygen -T <output_file> -f <input_file> [-v] [-a <num_trials>]
[-W <generator>]
A detailed description of the operands is provided in the OpenSSH man pages.
Description
Each authentication algorithm requires its own key pair comprising a private and a public key. The ssh-keygen utility enables you to create such a key pair (RSA, DSA, ECDSA or Ed25519). You specify the authentication algorithm with the -t parameter.
ssh-keygen generates, administers and converts authentication keys for the OpenSSH client ssh. ssh-keygen can generate RSA or DSA keys.
Generally a user who wants to use OpenSSH with RSA or DSA authentication will start ssh-keygen in order to generate the authentication key in $HOME/.ssh/id_rsa, $HOME/.ssh/id_dsa, $HOME/.ssh/id_ecdsa oder $HOME/.ssh/id_ed25519. In addition, the system administrator can generate hot keys using ssh_keygen.
Private keys are saved under $HOME/.ssh/<identity>, public keys under $HOME/.ssh/<identity>.pub in the user’s directory. Here <identity> stands for
id_dsa ( -t dsa) for DSA and
id_rsa ( -t rsa) for RSA and
id_ecdsa (-t ecdsa) for ECDSA and
id_ed25519 (-t ed25519) for Ed25519
You can also give the file a different name:
When the keys are generated, ssh-keygen inquires the name of the file in which the private key is to be stored.
The file name for the public key is automatically adapted and given the extension “.pub”.
Further information on ssh-keygen can be found in the OpenSSH man pages.
Files
A description of the ssh-keygen files is provided in the OpenSSH man pages.