How can I use passwordless logins, if I have a passphrase set? Every time I try to login to my remote machine, I get prompted for a password.

Use ssh-agent and ssh-add.

What is ssh-agent?

ssh-agent is a program to hold private keys used for public key authentication (RSA, DSA). The idea is that ssh-agent is started in the beginning of an X-session or a login session, and all other windows or programs are started as clients to the ssh-agent program. The agent initially does not have any private keys. Keys are added using ssh-add.

What does ssh-add do?

When executed without arguments, ssh-add adds the files $HOME/.ssh/id_rsa, $HOME/.ssh/id_dsa and $HOME/.ssh/identity. If the identity has a passphrase, ssh-add asks for the passphrase (using a small X11 application if running under X11, or from the terminal if running without X). It then sends the identity to the agent. Several identities can be stored in the agent; the agent can automatically use any of these identities.

ssh-add -l displays the identities currently held by the agent."''

How can I start ssh-agent automatically?

There are several ways to start it. I use an alias in $HOME/.bashrc, because I startup in Red Hat runlevel 3 alias startx'ssh-agent startx'

Is there any tutorial about ssh, key management, passwordless login ?

Yes, Daniel Robbins, CEO of Gentoo Linux has written a series of great tutorials on the IBM developers page: http://www-106.ibm.com/developerworks/library/l-keyc.html talks about RSA/DSA authentication. http://www-106.ibm.com/developerworks/library/l-keyc2/] talks about ssh-agent and a easy to use tool called keychain to manage a single ssh-agent session shared between different windows. * http://www-106.ibm.com/developerworks/linux/library/l-keyc3/] talks about advanced topics like agent forwarding.

Added by AmitChakradeo

Back to SSH FAQ