Unable to install OTA update on a rooted device? Well, you just can’t. No matter what you try. The reason is — an OTA update doesn’t accepts a system that has been modified, and hence it refuses to install. The only way to get around this is getting the stock system back on your device and then install the OTA.
And when we say a stock system, that also includes the stock recovery. If you’re thinking unrooting the device via SuperSU would do, then that’s also not possible since there still will be some modified system files on the device that the OTA won’t accept.
So your only way to install an OTA update with Root is installing the full stock firmware back on the device.
Now installing stock firmware isn’t same for all devices. Every manufacturer has its own way of installing stock firmware on their devices, like Samsung uses its own proprietary software called Odin, LG has its own Flash Tool, Sony too has a FlashTool, Motorola has RSDLite, HTC has RUUs for each device and Nexus devices come with factory images flashable via Fastboot. And these are just the tools for the major Android manufacturers, but Android is a big world and there many more devices from various manufacturers with different solutions for installing stock firmwares . Any all MTK devices can be flashed with SP flash tool
Resources for Installing Stock Firmware
Below are some resources for the popular manufacturers/devices to install stock firmware, so that you can install an OTA update.
Google Nexus devices
Google Nexus devices are one of the easiest to install the stock firmware. Google provides fastboot flashable factory images for all of its Nexus devices and for all Android versions ever released for them. You can get these factory images at the link below, along with a detailed step-by-step flashing instructions:
Installing stock firmware on Samsung devices is easy as well. You just have to download an Odin flashable .tar file of stock firmware for your device model number and flash it using Odin.
Below are links to two site that have the largest database of stock firmwares for all Samsung devices. Download firmware for your device model number from these resources and then flash them using Odin
Firmware downloads: SamMobile | Samsung-Updates
Sony Xperia Devices
Installing stock firmware on Sony devices is easier too. A custom tool called FlashTool is available for Sony Xperia devices that lets you flash stock Xperia firmwares that come as a .ftf file. There’s a nice tool called XperiFirm to find and download .ftf firmware for Sony Xperia device. Below are links to both the tools:
Motorola has an architecture very close to Nexus devices for bootloader, and hence also has a very similar way for installing stock firmware. You’ve option to use either RSDLite, a Motorola-distributed software to flash stock firmware OR you could tear open a stock firmware, get the .img files for all system partitions and manually flash each partition via Fastboot (or mfastboot.exe) like Nexus devices.
HTC provides the easiest of all method to install stock firmwares. Stock firmware for HTC devices come as a RUU (Rom Upgrade Utility) which is a standalone click based installer with a firmware pre-packaged into it.
For HTC users from USA, HTC has a page to download latest available RUU for all the devices released in the country along with installation instructions.
We personally find LG devices hard to install a stock firmware, but maybe that’s because we’ve had less experience with LG devices. Anyway, LG stock firmware come as .kdz files and can be installed using LG Flash Tool. The resource for both firmware download and Installation instruction is the best you can find on the interwebs for LG devices.
All MTK devices have the same flash tool that’s the SP flash tool . If your device is MTK then you just need to search on google for the stock firmware of your device and download the SP flash tool from below . you will also require the MTK drivers .