github.com/Pankov404/juju@v0.0.0-20150703034450-be266991dceb/doc/system-ssh-key.txt (about)

     1  The idea of having a system SSH key is to support a number of real and
     2  potential use-cases.
     3   * The system ssh key could be used to monitor the bootstrap process, and this
     4     would benefit the new users that don't have an existing SSH key
     5   * Allows the api server machines to ssh to other machines in the environment
     6     * could be used to set up ssh tunnels through a single public facing IP
     7       address on the server
     8     * allows juju-run commands to be run on remote machiens
     9  
    10  Juju already creates a private key for serving the mongo database. It was an
    11  option to also use this key, but in the end, having different keys for
    12  different purposes just seems like a more robust idea.
    13  
    14  A system key is generated when the environment is bootstrapped, and uploaded
    15  as part of the cloud-init machine creation process. The public key part is
    16  added to the authorized keys list.
    17  
    18  This means that we need to generate an identity file and the authorized key
    19  line prior to creating the new machine.
    20  
    21  If subsequent state server machines are created, they also need to have the
    22  system identity file on them. Actually, it is most likely the API server jobs
    23  that we really care about.
    24