Android is indeed a great operating system, but the manufacturer skinning makes it cumbersome to use. That is when the power users like us tend to experiment with the custom ROMs. Installing a ROM is a complicated procedure that needs a good level of technical expertise. We would simplify the process of installing a ROM for the benefit of novices in this field. Please follow the steps carefully.
The steps involved in the procedure can be broadly categorized as below. Before doing this, it's highly recommend to back up Android phone in case of data loss.
Before you can install ROM, you need to unlock the bootloader of your device and install a custom recovery. Since this is a generalized guide on custom ROM installation, we won't be able to go into finer details as it depends on the individual device. The most widely used custom recoveries are ClockWork Mod and TWRP.
We advise you to check the authority sites like XDA developers to find the proper guidelines on how to root your device and flash the custom recovery. Once you have rooted your phone and installed the custom recovery, you can come back to this article for the further steps.
Making a backup is essential to be safe. If the custom ROM installation goes wrong somewhere, you can always restore the stock ROM from backup. It would be preferable to take an NANDROID backup. The Nandroid backup backs up everything on your device, including your apps.
To make a Nandroid backup.
1) Boot into custom recovery. The method differs for each phone. The usual way is to press and hold Volume Up, Power and Home button together till you feel the vibration.
2) Browse through the menu and find the Backup or Nandroid backup. Label it with something identifiable.
3) Tap on the option to confirm and let it finish.
Once the backup is complete, transfer it to your desktop.
You can also use Titanium Backup to backup your apps and their settings. This procedure will ease you of installing all your apps once again. The difference between the two is while Nandroid backs up your entire system. Titanium can selectively backup your apps alone.
You have decided to install a custom ROM would mean you have already chosen a ROM to your liking. Download the ROM of your choice – preferably to your computer. Most of the ROMs do not come with Google apps. You will need to download the appropriate GApps package for the purpose.
The ROM and GApps package will be in Zipping format. Save them on your PC and transfer them to phone. The GApps package chosen should be compatible with your ROM. If you are using a ROM based on Android Lollipop, you will need to use the associated GApps. You can download GApps from opengapps.org.
Follow the steps below. Take care not to miss any action, lest your phone can get bricked.
• Boot into recovery.
• Browse to install on the menu. The correct option depends on your recovery.
• Locate the ROM you transferred in step Select it to flash.
• Let the process complete. It can take anywhere between 2 to 5 minutes.
• Now locate the GApps file you transferred to your phone and flash it the same as above.
• Once it is complete, choose Wipe cache and data. The options will depend on your recovery.
• Reboot system once all these steps are completed.
That is it – your phone now has the new ROM. You can now restore your data from Titanium Backup if you have it, or go about reinstalling your apps freshly. Please note that this is a generalized guide for installing custom ROMs. Exact guidelines will be entirely dependent on your device model. Happy Flashing!