Google has published 4.4.3 update for its Nexus devices without telling us anything about it. There is no official announcement or blog about it. The reports are coming in that OTA updates are also being pushed. If you can’t wait for OTA, then you can upgarde your Nexus device manually. Just take back-up of data such as images or downloaded files. Once done, follow these steps (courtesy: Ubuntu Wiki)
First download the appropriate image for your device from this link.
How to update?
If you are using any Ubuntu-based system install fastboot by running this command:
sudo add-apt-repository ppa:phablet-team/tools
sudo apt-get update sudo apt-get install ubuntu-device-flash
If your Nexus device is unlocked then you can skip this step and move to next one, if not then continue:
1. Boot into the bootloader (power off the device and then power it on by holding the power button + volume up + volume down)
2. When you see the bootloader, connect the device to the PC
3. Open the terminal and run
sudo fastboot oem unlock
Now Nexus screen will show whether you want to unlock or now and also tell you which hardware keys to use to select ‘yes’. Use volume key to select the option you want and power key to select it.
Note: If unlocking fails, you may have to enable the USB debugging. Reboot the Nexus in Android. Enable the developer mode of your device by tapping seven times on the ‘Build number’. Then go to Developer option and select USB debugging. Now repeat the above steps.
Once you have unlocked the device, Nexus will take some time to reboot into unlocked system. In my case I had to once again enable the developer mode, and USB debugging so if that be the case you can checn under settings if the USB debugging is still enabled.
Insatll new Android updates
Now extract the Nexus image that you have downloaded on your PC, cd to the extracted folder and as run the following command:
run adb reboot-bootloader
Once your Nexus boots in to the boot loader, run the following command:
Wait for it to complete and once done your Nexus will boot into the brand new Android.
Please keep in mind, don’t disconnect the USB during any of the above opearations.