How to Download and Manually Install on Google Nexus 4, Nexus 5, and Other Devices

Google has announced the rollout of Android 5.0 Lollipop for its Nexus series of smartphones and tablets. Many Nexus users bought the devices because Google said these devices would be the first to get Android updates. While that may not have been the case with Android 5.0 Lollipop, but the Nexus series is still part of the first wave of devices to get a taste of the latest dessert. The update will show up soon and in the meantime you can refresh your memory by reading about the best new features in Android 5.0 Lollipop.
For those who can't wait, there's a quicker way to get Android 5.0 Lollipop on Google Nexus 4, Google Nexus 5, Google Nexus 7 (Wi-Fi), Google Nexus 7 (2013) Wi-Fi, Google Nexus 9 (Wi-Fi), and Google Nexus 10, amongst other devices. You can flash the latest Android OS to your Nexus device using a factory image.

Here's how to manually download Android 5.0 Lollipop and force install it on your Google Nexus devices.
1. Download and install the latest Android SDK on your Windows computer. This installs two programs, ADB, and Fastboot, which can be accessed through the command terminal on your PC, as a part of the software development kit.
2. Add the SDK folder to the PATH by following these steps:

• Right click My Computer and click on Properties.
• Click on Advanced System Settings.
• Click on System Properties > Advanced > Environment Variables.
• In the Window, select Path, then click on Edit, and then type in the name of the directory where you installed the SDK, and remember that each entry is separated by a semi-colon.

3. Enable USB debugging on your device. First, go to Settings > About Phone > Software information.
4. Tap Build number seven times.
5. Go to Settings > Developer options. Tick USB debugging.
6. Download the correct factory image for your device.

• Android 5.0 Lollipop for Nexus 4
• Android 5.0 Lollipop for Nexus 5
• Android 5.0 Lollipop for Nexus 7 (Wi-Fi)
• Android 5.0 Lollipop for Nexus 7 (2013) Wi-Fi
• Android 5.0 Lollipop for Nexus 9 (Wi-Fi)
• Android 5.0 Lollipop for Nexus 10

7. Extract the image on your computer.
8. Connect your device to your computer over USB.
9. Start the device in fastboot mode.
The easiest way to do this is to hold a key combination while powering up the device. For Nexus 5, hold the volume up, volume down and power buttons while powering on the device. The full list of key combinations for different devices is here.
You can also boot into fastboot mode using the ADB tool: With the device powered on, go to the command terminal and execute the following: adb reboot bootloader
If needed, unlock the device's bootloader through your computer using the command terminal and executing: fastboot oem unlock
1. Open a command terminal and navigate to the unzipped system image directory.
2. Execute flash-all.bat, which was a part of the unzipped image file. This script installs the necessary bootloader, baseband firmware(s), and operating system. For this to work, you need to have added the folder where ADB and Fastboot are installed to the system's path as described in step 2.
3. When this is done, Google recommends that you lock the bootloader for security. You can do that by booting the device in fastboot mode while still connected via USB, and using the command terminal to execute: fastboot oem lock.