Flashing a custom image on an Android mobile could be just fun. But if you don't know why you want to do it, or do it just because it's a challenge. Then don't!
The bad and the good
I'm only pointing out some of the cons and the pros here.
- An OS image could contain malware; only use community trusted images.
- If you don't pay attention you can get malware running as root. That's B A D !
- May not have all the phones vendor functionality.
- The image may be buggy.
Consequences of a buggy image
- Lock up your phone when you least expect it.
- Drain the battery quicker.
- Suddenly reboot.
- You can get a newer more secure operating system.
- Use less battery.
- No crapware.
- Extra security functions.
sudo apt-get install android-tools-adb android-tools-fastboot
Download custom a recovery image. Personally I prefer ClockworkMod and the touch recovery. Note, this image is compiled for the Nexus 4 phone. Other phones use other images.
And to be on the safe side. Download the origian Nexus 4 firmware from Googles page Factory Images for Nexus Devices. Just in case... And if it is the case, untar the file and read the included instructions.
Doing the deed
This is notes for my personal use. If you decide to go through with this I don't take any responsibility for any bricked or damaged devices.
1. Enable USB debugging on Android
Settings → About phone.
Press repeatedly on Build number until you become a developer.
Settings → Developer options.
Check USB debugging.
2. Unlock bootloader
Connect phone to computer with USB cable.
Check that the cable is usable by listing devices with adb. If you don't get any response. Change the cable and try again. The last cable could be a cheep charger cable without data wires.
Reboot phone into bootloader.
adb reboot bootloader
Check that you get connection with fastboot.
Unlock your bootloader. This takes some time while the phone is erasing all data.
fastboot oem unlock
Choose Yes on phone by pressing Volume up, and then accept by pressing Power.
3. Flash and enter recovery
Flash recovery image.
fastboot flash recovery recovery-clockwork-touch-188.8.131.52-mako.img
Enter recovery image by pressing Volume up until Recovery mode is shown on top of screen. Press Power to enter the recovery image.
4. Prepare and install CyanogenMod
In ClockworkMod Recovery enter mounts and storage → format /system. Yes - Format.
In ClockworkMod Recovery enter mounts and storage → format /data and /data/media (/sdcard). Yes - Format.
Check the partitions is OK by going back to main menu and choose wipe data/factory reset and Yes - Wipe all user data. Check that you don't get any errors on formatting /data.
Choose install zip → choose zip from sideload and sideload CyanogenMod.
adb sideload cm-11-20140504-SNAPSHOT-M6-mako.zip
Then sideload gapps. Select again choose zip from sideload.
adb sideload gapps-kk-20140105-signed.zip
Just be on the safe side, go back and choose wipe data/factory reset and Yes - Wipe all user data.
reboot system now. First boot takes some time, be patient.
If you get problems booting into a clean system, I've read that another factory reset could do the trick.
5. Encrypt or not
After installing the phone you can choose to encrypt it or not. I like to encrypt my device with a passphrase. It's my data so why give it away if the phone get stolen; encryption makes it a bit harder for the bad guys.