Start/stop the linux half

I have a remote sensing application where power use is an issue (has to be solar)

The nature of the beast is that I have to read some data loggers every 30 minutes - some of the data (pics) has to be stored on an SD and other stuff has to be ftp'd (cellular) off to the world. There is a bit of data bashing to do as well - read emails and take actions about sending stuff.

All in all, moderately heavy lifting. Too much for an Arduino alone.

Is it feasible to use the Arduino as a supervisor that turns on (powers up) the Linux bit - then based on some sort of message - powers it off Linux half off.

I was going to do all this with a Pi and a product called "Sleepy Pi" - I still could - but the Yun looks like a nice way of doing it.