How to Generate a Public/Private Key Pair for Use With Secure Shell

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Users must generate a public/private key pair when their site implements host-based authentication or user public-key authentication. For additional options, see the ssh-keygen(1) man page.

Before You Begin

Ask your system administrator whether host-based authentication is configured.

Start the key generation program.
```
mySystem$ ssh-keygen -t rsa
Generating public/private rsa key pair.
...
```
where –t is the type of algorithm, either rsa, dsa, or rsa1.
Specify the path to the file that will hold the key.
By default, the file name id_rsa, which represents an RSA v2 key, appears in parentheses. You can select this file by pressing the Return key or provide an alternative file name.
```
Enter file in which to save the key (/home/username/.ssh/id_rsa):<Press Return>
```
The file name of the public key is created automatically by appending the string .pub to the name of the private key file.
Type a passphrase for using your key.
This passphrase is used for encrypting your private key. A null entry is strongly discouraged. Note that the passphrase is not displayed when you type it in.
```
Enter passphrase (empty for no passphrase): passphrase
```

Retype the passphrase to confirm it.

Enter same passphrase again: passphrase
Your identification has been saved in /home/username/.ssh/id_rsa
Your public key has been saved in /home/username/.ssh/id_rsa.pub
The key fingerprint is:
0e:fb:3d:57:71:73:bf:58:b8:eb:f3:a3:aa:df:e0:d1 username@mySystem

Check that the path to the key file is correct.
```
$ ls ~/.ssh
id_rsa
id_rsa.pub
```
At this point, you have created a public/private key pair.
Log in to the remote host.
Choose one of the following login steps based on your site's authentication method.
- For host-based authentication, copy the local host's public key to the remote host.
  1. Type the following command on one line with no backslash.
```
$ cat /etc/ssh/ssh_host_rsa_key.pub | ssh RemoteSys \
'cat >> ~/.ssh/known_hosts && echo "Host key copied"'
```
  2. When you are prompted, supply your login password.
```
Enter password: password
Host key copied
$
```
    You can now log in to the remote host.
- For user authentication with public keys, populate your authorized_keys file on the remote host.
  1. Copy your public key to the remote host.
    Type the following command on one line with no backslash.
```
mySystem$ cat ~/.ssh/id_rsa.pub | ssh myRemoteSys \
'cat >> ~/.ssh/authorized_keys && echo "Key copied"'
```
  2. When you are prompted, supply your login password.
```
Enter password: password
Key copied
mySystem$
```
(Optional) Avoid future prompting for passphrases.
See the ssh-agent(1) and ssh-add(1) man pages.