Ether is a super potent "starting fluid" that works in gas and diesel engines that can get your truck started in a pinch.  However, starting a gas engine cold is a lot easier than a diesel engine as the diesel engine requires heat to combust the fuel while gassers can rely on their spark plugs. 

Some diesels actually have no glow plugs and actually have a system where you can pump ether into the truck for easier winter starting.  Unimogs actually have this setup as do some Cummins models.  But other diesels can be damaged if you use ether so it's important to read you're truck's manual before you make a mistake that could greatly reduce your diesel engine's life and/or possibly cause it to blow up.  This happened to the fellow who sold me my HJ60.  His wife was in a car accident and his diesel Chevy pickup truck would not start so he had to use either.  2,000 miles later it blew up.

To me this reminds me of one thing which is that Japanese diesels seem to start a lot easier than American and European diesels.  I'm not sure what this will do but typically American and European diesels are fine with while many Japanese diesels will be damaged.
 

You might also want to check out About Glow Plugs