SSH public key authentication: Difference between revisions

@@ Line 33: / Line 33: @@
    IdentityFile ~/.ssh/another-machine
 </syntaxhighlight>
+== SSH agent ==
+A ssh private key, for which a phrase is defined, can be clumsy if you use it multiple times. It is possible to store the private key identity in a ssh-agent. The ssh-agent uses the ssh private key identity when you issue a ssh command, for instance when using ssh to connect.
+To define NixOS to setup a ssh-agent, add this to your configuration:
+<syntaxhighlight lang="nix">
+programs.ssh.startAgent = true;
+</syntaxhighlight>
+NixOS will starta user systemd service with the ssh-agent at login. You can see the service with the command <code>systemctl --user status ssh-agent</code>.
+It provides also the environment variable $SSH_AUTH_SOCK which refers to <code>/run/user/1000/ssh-agent</code> , in this case for user id 1000.
+If you want to use a ssh key pair for authenticating, you can add this to the ssh-agent using the command ssh-add entering the phrase only once.
+<syntaxhighlight lang="console">
+[user@your-machine] $ ssh-add .ssh/id_rsa
+Enter passphrase for .ssh/id_rsa:
+Identity added: .ssh/id_rsa (myaccounts@mymachine)
+</syntaxhighlight>
+If you store the ssh public key with the command ssh-copy-id on <code>another-machine</code> as shown above, you can logon without giving a password or phrase.
 == SSH server config ==