text: Q:
  
  Working Rpi Hotspot but can't get ethernet/internet to work
  
  I've set up my pi as a wireless hotspot and am trying to share my Mac's internet via ethernet.
  The hotspot side of things works ok and if I have my mac's wifi (or even internet sharing) turned off I can ping and ssh with the Pi via ethernet.
  As soon as I enable internet sharing on the mac, I lose the ethernet connection.
  Anyone any ideas?
  
  A:
  
  If you have internet sharing turned off, and things work, that implies that either you have set up static IPs, or you are running a DHCP server on the pi side of the ethernet. I'm guessing the latter. If you share your mac's wifi connection over ethernet, the mac will be expecting to act as a DHCP server, not a client.
  Either way, your pi is now sitting there as either a static IP or a DHCP server, but definitely not a DHCP client, which is why it's not working. You need to reconfigure your eth0 to be a DHCP client. You need
  iface eth0 inet dhcp
  
  in /etc/network/interfaces
  You likely have 
  iface eth0 inet static
  
  which won't work in this case.
  
  