SSH connection without password

Title is a little bit wrong, the password must entered once per session

Procedure found here : ssh configuration (in french)

1) On lheppc56 :

ssh-keygen -t dsa -b 1024           (enter a password)

chmod 600 ~/.ssh/id_dsa.pub ~/.ssh/id_dsa

scp ~/.ssh/id_dsa.pub scanner@lheppc57:~/.ssh/authorized_keys

2) On lheppc57 :

chmod 400 ~/.ssh/authorized_keys

home directory (/home/scanner on lheppc57) must have permission 755 otherwise does not work !

3) On lheppc56 :

ssh-agent /bin/bash
ssh-add    (enter password given in part 1)

4) No more password is needed to connect on lheppc57 till ssh-agent is running