rsync +ssh

http://download.ithome.com.tw/article/index/id/1722

http://www.davidpai.tw/ubuntu/2011/rsync_backup/#comment-23526

http://ithelp.ithome.com.tw/questions/10184135

https://www.digitalocean.com/community/tutorials/how-to-copy-files-with-rsync-over-ssh

modify permission setting for establish: http://wallyjue.blogspot.tw/2008/08/ssh-unprotected-private-key-file.html