Update won't install. How to fix (or should I bother)?

Question

I got a tablet from a friend. It's a Nexus 7 running Android 6.0.1. The first thing I did was reset to factory settings. After setting up, I saw there was an update to install. But it won't install.

Currently going to "System Updates" in settings shows "Android System Update Downloaded and verified..." and states, "This software update will improve the security of your Nexus 7 with the February 2016 patches. Downloading updates over a mobile network or while roaming may cause additional charges." And also, "Update size: 1.5 MB".

When I tap "RESTART & INSTALL", that button changes to "CANCEL INSTALL" and I see "Rebooting to install in 10 seconds..." which counts down. Then it shows, "Rebooting now..." but nothing happens.

If I wait for the screen to turn off, and press the lock button to light up the screen, I see it hasn't shut down. Unlocking it I find the screen with the "RESTART & INSTALL" button just as if I didn't tap it already.

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I'm completely new to Android (though I am a Linux sysadmin if that matters or helps).

How can I get the update installed? Alternatively, is this even something to worry about?

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Googling around turned up nothing useful, although I did find a forum thread from 2012 showing a similar issue with 4.2.1—but no solution.

(Note that as I'm completely new to Android, if there is some "default" advice I should know about such as there is for Mac, "if you can't figure it out take it to the Genius Bar," then please tell me as I don't know it.)

Answer 1

How can I get the update installed?

It is possible that the device has been rooted or tampered with by your friend, such that it no longer passes the integrity check before OTA updates. Whether this is the case is trivial; if you want the update regardless, you will have to resort to flashing a factory image which requires you to unlock your bootloader and lose data on the tablet in the process.

However...

Alternatively, is this even something to worry about?

Nexus 7, even the 2013-released version you have, is long obsolete as seen by Google, and therefore misses out on a large amount of security patches since its last official update in 2016. Updating it to a Feb. 2016 patch will not change how vulnerable it is by much.

To get an up-to-date security patch, unlock your bootloader, flash a custom recovery then a recent custom ROM such as LineageOS, which would bring you to both a newer Android version and security patch at the same time (Android 7.1.2 and patch set Oct. 2017 at time of writing).