Using Jenkins agents with docker

** Generating an SSH key pair

    ssh-keygen    -t dsa -f ~/.ssh/jenkins_agent_key                                 

*** Create a Jenkins SSH credential

                                                                                     
         Go to your Jenkins dashboard;                                                
                                                                                      
         Go to Manage Jenkins option in main menu and click on credentials button;    
         select the drop option Add Credentials from the global item;                 
                                                                                      
     Fill the form:                                                                   
                                                                                      
         Kind: SSH Username with private key;                                         
                                                                                      
         id: jenkins                                                                  
                                                                                      
         description: The jenkins ssh key                                             
                                                                                      
         username: jenkins                                                            
                                                                                      
         Private Key: select Enter directly and press the Add button to insert your   
         private key from ~/.ssh/jenkins_agent_key                                    
                                                                                      
         Passphrase: fill your passphrase used to generate the SSH key pair and then  
         press OK