Without getting into too many technicalities, the bootloader is essentially the program that gets loaded first when starting your device, and it is responsible for booting the Android kernel. Think of the bootloader as the BIOS of a computer.

Most (if not all) devices are shipped from the manufacturer with locked bootloaders. This is for security reasons. A locked bootloader does not allow easy flashing of images, which means that it is difficult to change or modify the operating system. Unlocking a bootloader (using fastboot) on most Nexus devices results in a complete loss of all personal data from the device. Having a locked or unlocked bootloader has no bearing on the functioning of the device. Unlocking it gives you more options to play around with the OS. Additionally, an unlocked bootloader means that you can easily root your device no matter what -- unlike most non-Nexus devices, if you lose root, it is trivial to get it back.

Root essentially means that you have root (or superuser) access to the file system on Android. It is similar to being “administrator” on a Windows PC. It has nothing to do with your device or the bootloader, it has to do with the Android OS (i.e., you cannot “root” your device – you root the Andoid build that you are running). To have root, you need to be booted into the Android OS that you have rooted. If you are in fastboot mode, root is irrelevant. In order to perform root, you will most likely have to unlock your bootloader first (see above)

Recovery is like a mini OS, which allows you to perform various functions, usually related to flashing files to your device, or updating files, or backing things up, etc. The stock image has a recovery included, but its functionality is very limited. There are a number of custom recoveries available, but the two most popular for the Nexus 4 are CWM and TWRP. There are various versions of each. More details to come in this section.

A ROM is slang for an mobile OS build.

A stock ROM is a ROM that is built by Google and is signed by Google’s platform keys. Everything else is a custom ROM.

No, as was mentioned above, unlocking the bootloader allows you to (among a few other things) flash images easily to the device when not booted into the Android OS. Root allows you access to manipulate the files WITHIN the Android OS.

Yes. Because you will have to flash custom recovery in order to flash a file which grants you root access. For more information on rooting, refer to following points in spoilers within this post.

No.

No.

No, but it is recommended as some custom ROMs will have additional features which require root access.

While these steps might not be definite; these are however common approaches used by fellow owners.

1. Unlocking the bootloader
2. Flashing Custom Recovery (Either temporary or permanently)
3. Rooting (via Recovery)
4. Flashing Custom Kernel
5. Flashing Custom ROM

As shown above, the common process flow for unleashing our device. Step 1 is easily reversible via fastboot commands (or BootUnlocker apps via PlayStore which requires Root); whereby Step 2 - 4 can be reversed by flashing stock images via fastboot.

Head over to this link to read on what steps are required to revert to stock:

http://forum.xda-developers.com/showthread.php?t=2010312

Ensure that you install Universal Naked Drivers instead of the default LG / Nexus drivers.

Head over to the link above to download the drivers, and then use google's instructions to install the driver and browse for the folder extracted from the .zip file you downloaded (instead of Google's driver).

Read section C > Manual ways of doing it for a detailed instructions / guides

In order to check your CPU bins, you must be rooted and have Android Terminal Emulator installed, then follow the steps below:
1. Launch the 'Terminal Emulator' application.
2. Type 'su' and hit Enter.
3. If there are any pop-up prompts requesting for SuperUser access, GRANT it.
3. Type 'dmesg | grep PVS' and hit Enter.
4. It should return a line and show you whether if yours are SLOW, NOMINAL, FAST or FASTER. If it does not return these values, try rebooting your device and try again.

Note: This might not work on custom kernels as kernel developers might have changed the return value.
Credits to XDA Community for the original thread.

(Originally posted by cowithgun)

Kraits and bionic optimization speed up 2 things in your phone:

1. string / memory operation. these operation including string copy, memory copy, compare, etc. even a simply file copy uses these operation. all these implemented in a library known as bionic library in android. it's similar to libc in pc. this is the bionic optimization.

2. after Qualcomm introduce krait core (since S4), they release new code that allow you to use extended instructions that can only be found in Krait core to do some math operation. by implementing these new code, some math function such as sin(), cos(), etc will be faster. Many heavy graphic app uses math functions.

What custom ROM/kernel developer do is to get these code from Code Aurora, and implement in their ROM/kernel then recompile it. You may not notice performance improvement if you just swipe homescreen, etc but if you do benchmark, you will see a huge improvement.

For example, before any optimization, most N4 getting like 17k Antutu score. After Bionic optimization around you will get around 19k. You should see huge improvement in the RAM score, in this case 3274. Also check out the CPU floating point score, 2139, in this case, not optimized yet.



Now, if you optimize the math library with Krais extended instruction, you should see huge improvement in CPU floating point score, in this case 4182. With both optimized, you see a jump from 17k Antutu score to 21k, around 30% improvement at the same CPU speed.

(Originally posted by cowithgun)
WARNING: A word of caution, proceed only if you're clear of what you are doing. No one should be held responsible for any mishaps that happened for following this tutorial.

1) Download and install VMware player (or any VM you like)
- http://www.vmware.com/products/player/

2) Install Ubuntu 12/13 as long as it is 64 bit. To compile JellyBean you need 64 bit OS.
- http://www.ubuntu.com/

3) Setup the VM
- http://source.android.com/source/initializing.html

4) Download the source
- http://source.android.com/source/downloading.html
- get mako-kernel android-4.2.2_r1.2 (latest, newer than OTA 4.2.2)
- leave it overnight

5) Build it.
- make -j4
- leave it for an hour or so
- If you wanna use Linaro compiler, get this: http://www.linaro.org/

6) You will get a working zImage if compiled without error

7) Unpack the ori boot.img using this: http://forum.xda-developers.com/showthread.php?t=915808

8) Replace the zImage and pack it back.

9) Make sure you have backup your phone

10) Flash into your phone:
dd if=newboot.422.oc.img of=/dev/block/platform/msm_sdcc.1/by-name/boot

11) reboot, voila!

12) Once you successfully compiled your own kernel, make the appropriate changes, depending on feature you want:

- To calibrate the color, change file /arch/arm/mach-msm/lge/devices_lge.c accordingly:
https://github.com/franciscofranco/mako/com...0f931085952bfd2

- To overclock/undervolt, change file /msm/arch/arm/mach-msm/acpuclock-8064.c

My freq table:
http://forum.lowyat.net/index.php?showtopi...&#entry59139540

Note that, i have "Faster" CPU binding.

13) Bionic / Krait optimization required you to recompile libc.so and libmath.so using code from Code Aurora.

14) Linaro gcc optimization, change make file to use -O3 and you need to fix a few compiler errors.

It's do-able, not rocket science and the experience will make you know your phone even more.

Good luck!

ps: standard disclaimer; i m not responsible for sh1t...

Wug's Nexus Root Toolkit
http://forum.xda-developers.com/showthread.php?t=2015469
Video tutorial:


OR..

mskip's Nexus 4 Toolkit
http://forum.xda-developers.com/showthread.php?t=1995688

View simplified / summarised guide written by polarzbearz here.

For original guide on XDA, refer to this link: here

Head over to Nexus 4 @ XDA-Developers and have glimpse at all the available custom ROMs, kernels, customisations, themes, applications and etc.