ubuntu ssh keygen

username@ubuntu:~$ ssh-keygen -t dsa
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/username/.ssh/id_dsa
Your public key has been saved in /home/username/.ssh/id_dsa.pub

username@ubuntu:~$ cd .ssh/
This moves you into .ssh directory where the keys were saved. Now to copy the public key to the server.
username@ubuntu:~$ scp id_dsa.pub id@serverIP:./id_dsa.pub

Logging server
username@server:~$ cd .ssh
serverusername@server:~$ touch authorized_keys2
serverusername@server:~$ chmod 600 authorized_keys2
serverusername@server:~$ cat ../id_dsa.pub >> authorized_keys2
serverusername@server:~$ rm ../id_dsa.pub