Booted up my computer this morning and went to load a local Magento 2 site, got an error message
Service Temporarily Unavailable.
Turns out it was as simple as mysql server not running.
Confusing, since Magento 1 gave you a more helpful
MYSQL server has gone away message.
Anyways, the solution was simply to start it.
1. Start MYSQL server.
Open a terminal and run:
.maintenance.flag, if it exists.
Check in your root M2 directory, for a file
var/.maintenance.flag. This file is created when there are errors and the site should not be shown. Simply delete the file.
rm -f var/.maintenance.flag