[Samsung Galaxy Nexus] oldblue910:
With the Galaxy Nexus, there are a LOT of different firmware variants, most of which are updated by Samsung, not Google. This guide attempts to sort all of this out for the beginner and help you make sense of it all.

WHAT IS ALL THIS TALK ABOUT FIRMWARE VARIATIONS?

With every Nexus phone, there has been a "master" firmware, plus other localized firmware variants for certain regions or carriers. Sometimes these variants will contain language packs, additional ringtones, slightly different baseband (radio) firmware to make it work better for a particular carrier's network, etc.

In the case of the Nexus S, Google maintained the master and all the local variants. On the Nexus One and the Xoom, Google only maintained the master firmware while carriers and/or OEMs maintained the local variants. In the case of the Galaxy Nexus, there are three Google-maintained master firmware variants, and many more Samsung-maintained local variants.

WHAT ARE THE DIFFERENT VARIANTS AND WHAT DO THEY MEAN?

Below is a definitive list of all known firmware variants for the Galaxy Nexus, and what models they shipped on:

GSM/HSPA+ Models

takju - USA region- and carrier-independent firmware released on models sold in the USA through the Google Play Store

yakju - International region- and carrier-independent firmware released on models sold throughout western Europe.

yakjudv - Variant for Australia

yakjujp - Variant for the Middle East

yakjujt - Variant for Turkey

yakjukr - Variant for South Korea

yakjusc - Variant for Japan

yakjuux - Variant for Canada

yakjuvs - Variant for Brazil

yakjuxe - Variant for Russia and the former Eastern Bloc

yakjuxw - Variant for certain carriers in Western Europe

yakjuzs - Variant for China and Hong Kong

CDMA/LTE Models

mysid - Variant for Verizon in the USA

mysidspr - Variant for Sprint in the USA

HOW CAN I TELL WHICH FIRMWARE I HAVE ON MY DEVICE

Using any file manager app, go into your /system folder and open the file called "build.prop". Find the line that starts with ro.product.name. Whatever comes after the equals sign (=), that's the firmware you have.

WHICH FIRMWARE IS UPDATED BY GOOGLE AS OPPOSED TO SAMSUNG?

Google updates the following firmware variants:

takju

yakju

mysid

Every other variant is updated and maintained by Samsung.

SO YOU'RE TELLING ME THAT THE SPRINT GALAXY NEXUS GETS UPDATES FROM SAMSUNG AND NOT GOOGLE?!?!

Yep.

WHY DOES IT MATTER WHERE MY UPDATES COME FROM ANYWAY?

For all practical purposes, it probably doesn't. However, this becomes an issue if you want timely updates. When Google drops a new OTA update for the Galaxy Nexus, they always announce it through official Android channels. When they announce a Galaxy Nexus OTA, they are only referring to devices running the firmware that they control.

This means that if you have a Sprint Galaxy Nexus, or a GSM model running one of the yakju(xx) firmware variants, your device is not included in the OTA rollout from Google. Your update will instead come from Samsung sometime in the future after they make whatever region- and/or carrier-specific changes they need to make for the firmware.

I HAVE A VERIZON GALAXY NEXUS. THE FIRMWARE IS UPDATED BY GOOGLE SO WHY DOES IT ALWAYS TAKE LONGER FOR UPDATES TO HIT MY DEVICE THAN THE GSM/HSPA+ DEVICE

Even though Google maintains and updates the mysid firmware on the Verizon Galaxy Nexus, Verizon must test and approve the updates before Google is allowed to roll them out. This introduces delays, sometimes lengthy ones. For instance, Android 4.0.4 began rolling out to the Galaxy Nexus GSM model on March 28, 2012. The Verizon device didn't get the update until two months later, on May 31, 2012 due to testing delays. That's not to say that all future OTAs will occur on a two month delay, but it's best to be prepared for the worst.

WHAT'S THIS I'VE HEARD ABOUT BEING ABLE TO FLASH YAKJU FIRMWARE ON A DEVICE RUNNING YAKJU(XX)? IF I DO THIS, WILL MY UPDATES COME FROM GOOGLE?

You can flash yakju firmware onto any Galaxy Nexus GSM device that's running a yakju(xx) variant. This is outside the scope of this guide, but instructions can be found here on XDA with a little searching. Once you're up and running on yakju, your updates will come from Google rather than Samsung.

DOES THE SAME THING GO FOR CDMA? COULD I FLASH THE VERIZON MYSID FIRMWARE TO MY SPRINT MODEL AND GET UPDATES FROM GOOGLE?

No, No, No and NO! If you tried this, you'd probably risk hard bricking your phone, and even if it did boot, you'd have no mobile data and probably wouldn't be able to make calls either.

WHAT IF I HAVE FIRMWARE-RELATED QUESTIONS THAT AREN'T ADDRESSED IN THIS GUIDE?

Post them here and I'm sure someone can answer it for you.