Using scp or rsync within a script can be difficult  because
the  script  will suddenly ask for a password or passphrase,
and a background script (perhaps run by cron) might not have
a  "user"  who  can answer.  The solution is the no-password
approach based on public/private keys.  This is one  of  the
useful answers given at

http://askubuntu.com/questions/159925/how-to-read-the-password-from-variable


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You  don't  need  to  worry about passwords when you can use
something called Public Key Infrastructure.

This is a  method  of  using  public  and  private  keys  to
authenticate  a user.  You store a copy of your private key,
and the other server has a copy of your public key. When you
log  in,  they  have  a  little conversation with each other
which confirms the public and private keys match so you  can
log in without entering a password.

This  is  as  secure  as anything as long as you don't share
your private key with anyone!

To set this up is really simple.

On source machine, run ssh-keygen.  You can accept  all  the
defaults, that'll be enough for this purpose. It'll generate
your private (id_rsa) and public(id_rsa.pub)  keys  in  your
~/.ssh folder.

Now  you  want to get the public key on the server, which is
easy too.

From the source pc, run ssh-copy-id username@servername.

This will place  a  copy  of  id_rsa.pub's  content  in  the
server's ~/.ssh/authorized_keys.

Now  if  you ssh from the source to the destination you will
get in without requiring a password.

How does this affect rsync I hear you ask?  Rsync uses ssh!

Please remember: NEVER GIVE OUT YOUR PRIVATE KEY (id_rsa) or
someone can pretend to be you.
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If anyone has additional useful info, please email me at:
   jc1742@gmail.com