Linux Server Security, Second Edition

This is the Title of the Book, eMatter Edition

Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.

Intermediate and Advanced SSH

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Note that such a cut and paste will work in any xterm, but for it to work at a tty

(text) console, gpm will need to be running. An alternative approach is to redirect

ssh-agent’s output to a file, make the file executable, and execute the file within your

current shell’s context (Example 4-6).

Once ssh-agent is running and

SSH_AUTH_SOCK and SSH_AGENT_PID have been declared

and exported, it’s time to load your private key. Simply type ssh-add, followed by a

space and the name (with full path) of the private key you wish to load.

You can use ssh-add as many times (to load as many keys) as you like. This is useful

if you have both an RSA and a DSA key pair and access different remote hosts run-

ning different versions of SSH (i.e., some that support only RSA keys and others that

accept DSA keys).

Passphrase-Less Keys for Maximum Scriptability

ssh-agent is useful if you run scripts from a logon session or if you need to run ssh

and/or scp repeatedly in a single session. But what about cron jobs? Obviously, cron

can’t perform username/password or enter a passphrase for PK authentication.

This is the place to use a passphrase-less key pair. Simply run ssh-keygen as described

earlier, but instead of entering a passphrase when prompted, press Enter. You’ll proba- ...