Nexus won't boot after update So I have a Nexus 7 2013 no root vanilla. I just recently flashed it with vanilla 6.0.1 since it could not update from 5.1.1. Then a few days ago an update came out and I updated. Now my nexus tries to boot goes to the colorful boot screen then the text comes up saying starting apps then shuts off and tries to boot once more. When ever I try to boot into boot loader with volume up and power button it says no command. Any idea on what I can do to fix this?
This most probably means that you are stuck in a device boot-loop. The easiest way to fix Nexus devices (in my opinion) is to use the Nexus Root Toolkit, which automatically fixes most problems with a click of a button. 

You'll need a machine running windows and a USB cable to make this work. First, install Nexus Root Toolkit on Windows. After the setup is completed, open the program and add the phone type in the popup box. Now you should see 2 windows (the toolkit and the log). Click on Soft-Bricked/Bootloop on the Restore/Upgrade/Downgrade section then click on Flash Stock + Unroot (this is for both root and non-root devices). From here, just follow the steps the guide tells you and your device should go back to normal. However, MAKE SURE that you click 'no-wipe mode' on the third slide if you want to keep all your data.

That is the easiest way I found for fixing bootloops on Nexus devices. There are plenty of other ways to do it manually though (especially if your device is not rooted). 
Here are some listed below:

http://xda-university.com/as-a-user/how-to-recover-from-a-bootloop

http://www.ibtimes.co.uk/fix-boot-loop-issues-stock-rooted-android-467411

http://smallbusiness.chron.com/fix-boot-loop-android-78426.html