ssh: added ssh key login

wiki/linux/ssh.md

@@ -6,3 +6,9 @@ SSH is a network protocoll to securely connect to a computer.
 
 Edit the `/etc/ssh/sshd_config` and change the line containing `PermitRootLogin`
 to `PermitRootLogin yes`.
+
+## Add login via SSH public key
+
+To enable easy login without password you can add the contents of the file
+`~/.ssh/id_rsa.pub` from your local machine to the file `~/.ssh/authorized_keys`
+on the machine you want to log into.