How to boot thinkpad X1 from USB.

1. Format USB stick so it has a bootable ISO image (linux has various ways to do this; I used usb-creator-gtk for no particular reason other than it was already on my machine).
2. Power cycle.
3. Hold down F12.  The initial screen says to hold down the "blue botton" which doesn't exist.
4. Select the USB stick from the bootable options.
5. Press return.

Of course, like many things to do w/ linux and installation these days, this just doesn't work (at least for me).  I keep hitting "(initramfs) Unable to find a medium containing a live file system" which is a known bug.  

So, now the google searching begins.  


Looks like it's a USB 3.0 issue.  The most expedient fix is to check for other USB connections on the laptop.  The one on the left side of the x1 seems to do the trick.