Apple Xserve Up Mac OS X Server Specifications download pdf (Page 33)

Chapter 2 Connecting to Remote Computers 33

To generate the identity key pair:

1 Enter the following command on the local computer:

$ ssh-keygen -t dsa

2 When prompted, enter a filename in the user’s folder to save the keys in; then enter a

password followed by password verification (empty for no password).

For example:

Generating public/private dsa key pair.

Enter file in which to save the key (/Users/anne/.ssh/id_dsa):

frog

Enter passphrase (empty for no passphrase):

Enter same passphrase again:

Your identification has been saved in

frog

Your public key has been saved in

frog

.pub.

The key fingerprint is:

4a:5c:6e:9f:3e:35:8b:e5:c9:5a:ac:00:e6:b8:d7:96 [email protected]

This creates two files. Your identification or private key is saved in one file (frog in our

example) and your public key is saved in the other (frog.pub in our example).

The key fingerprint, which is derived cryptographically from the public key value, also

appears. This secures the public key, making it computationally infeasible for

duplication.

3 Copy the resulting public file, which contains the local computer’s public key, to the

.ssh/authorized_keys file in the user’s home folder on the remote computer (~/.ssh/

authorized_keys).

The next time you log in to the remote computer from the local computer you won’t

need to enter a password.

Note: If you are using an Open Directory user account and have logged in using the

account, you do not need to supply a password for SSH login. On Mac OS X Server

computers, SSH uses Kerberos for single sign-on authentication with any user account

that has an Open Directory password. (Kerberos must be running on the Open

Directory server.) For more information, see Open Directory Administration.

Updating SSH Key Fingerprints

The first time you connect to a remote computer using SSH, the local computer

prompts for permission to add the remote computer’s fingerprint (or encrypted public

key) to a list of known remote computers. You might see a message like this:

The authenticity of host "server1.example.com" can’t be established.

RSA key fingerprint is a8:0d:27:63:74:f1:ad:bd:6a:e4:0d:a3:47:a8:f7.

Are you sure you want to continue connecting (yes/no)?

The first time you connect, you have no way of knowing whether this is the correct

host key. Most people respond “yes.” The host key is then inserted into the ~/.ssh/

known_hosts file so it can be verified in later sessions.

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Apple Xserve Up Mac OS X Server Specifications Page 33

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