Google Glass, rooted. Hard-earned notes on upgrading the system.
There are so many pitfalls, it's hard to count them. Two major parts here.
Assuming you're able to get the device into fastboot and recognized by `fastboot devices`, here's what to do.
If your device isn't booting and you need to get it into fastboot mode
Here's what worked for me on OS X just now, documenting just the right thing to do, and none of the million other things I tried. I was updating to XE12, so I downloaded `glass_1-img-947604.zip` from the Glass Developer site. Unzip that into a directory of the same name. Then from your current directory, which now contains a directory called `glass_1-img-947604`, run
export ANDROID_PRODUCT_OUT=glass_1-img-947604 && fastboot flashall -w
For me the output was http://pastebin.com/hNiXs1mj
Getting the device into fastboot mode
I probably don't need to tell you here that the standard way to get into fastboot mode is to run `adb reboot bootloader`. If, however, you're in a state where you can't turn adb on because the system is not booting at all, this doesn't help you. So you need the hardware technique for getting into fastboot.
Start from the device being off, unplugged, and not totally dead. If it's not responding to the power button, you can hold it down for 10-15 seconds until it turns off.
Press and hold the camera button.
Keeping the camera button pressed, give the power button a single press.
Within two seconds the power light will come on. Keep the camera button pressed for another 2 seconds, then release.
The power light will stay on for something like 5 to 10 seconds, and then it will go off and enter a mode where it flashes briefly every 3 seconds or so. It's now in fastboot mode.
Plug it into your computer, and if that is setup right, Glass will now show up in `fastboot devices`.
The bolded instruction is missing from the authoritative post on this subject, Jenny Murphy's answer to this question on StackOverflow
