If you are rocking a Nexus device, then it's that time of the month again - the latest security update releases are now available. You can either wait for the OTA to appear or manually install the factory images from the Google Developer site. But what if you don't want to wipe your device? You can still use the images... here's how.
To use a factory image, first locate your device in the list and download the latest image from the link. Here is the list for the Nexus 9 for example.
Next, extract the tgz file to view the image and script files. You don't want to use 'flash-all', because this can also wipe the device. What you want to do is reboot your device to the bootloader ('adb reboot bootloader'), then use the 'flash-base' script. This just updates your bootloader and radio (if required).
After this is done, and your device has rebooted back to the bootloader, find the images zip file in the directory and unzip it. In here you will find the various component images. Simply flash them in turn, excluding userdata if it is present. When that is complete, use 'fastboot reboot' and you'll be back up and running with the latest release! Simple!
No more waiting for OTAs ever again... :)