[Nexus 9 Q&A, Help & Troubleshooting] GedBlake:
Hi, albsat...

Apologies it's taken me so long to respond, but with Christmas coming up, and helping out with family related stuff, I've not had much chance this past week to post stuff.

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Anyhow, to try to answer to your question...

Having thought long and hard about this problem... the problem isn't so much re-locking the bootloader with fastboot oem lock. I suspect this alone, shouldn't cause any problems.

It's the **Enable OEM unlock** setting in Developer Options, that is potentially dangerous.

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If Android (for whatever reason) won't boot, (bootlooping, for example), and if all other possible remedies fail... you would normally just (re)unlock the bootloader with fastboot oem unlock, and fastboot flash a factory image.

BUT THIS WILL NOT WORK

, if the **Enable OEM unlock** setting in Developer Options has also been disabled.

If the device is soft-bricked at this point, and Android won't boot such that you cannot gain access to Developer Options (in order to re-enable that setting), then the device is permanently soft-bricked.

And there is nothing that can be done to rescue the device:(. And this was my earlier prediciment, as previously described.

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Let me see of if I can explain why I think this...

In a previous post on this thread, I wrote the following...

This was largely just desperate optimism on my part, in the hope that somebody might know of some ADB or terminal command... but having recently read the OP

in this thread

, I now know that my attempts to unbrick my previous Nexus 9, was likely a hopeless cause:(.

If, and as I suspect, the **Enable OEM unlock** setting in Developer Options, is an additional layer of security, then it probably CANNOT be circumvented by some ADB or terminal command.

It wouldn't be much of a security measure if it was that easy!!

Consider the following hypothetical scenario...

"Let's suppose a guy, a regular non-techy kind of guy, buys a brand new Nexus 9 tomorrow. Now, this guy knows nothing about fastboot or factory stock images or any of that stuff. Developer Options, by default, is hidden to him, 'cos he doesn't know you need to tap 7 times on the build number... And so, consequently also, the **Enable OEM unlock** setting is also hidden and by default, it's disabled.

He doesn't know this, and from his point of view, he doesn't want or need to know this. He just wants a nice tablet for browsing the web, checking his emails, posting on Twitter or Facebook, and maybe playing the occasional game. So he takes his new purchase home, and sets it up... with WiFi key and Google Account details, etc. He installs some apps from PlayStore, and copies over his music/pics/documents and other stuff from his laptop.

**But he's a security minded guy, so he decides to set a LOCK PATTERN or PIN NUMBER on his lock screen.**

One day, whilst going to work, he absent mindedly leaves his Nexus 9 on the train... which is then subsequently found by somebody who is not entirely honest. Instead of turning it into the police or the train stations lost property office, this scurrilous individual decides to keep the tablet for himself. He sees the device is PIN or PATTERN locked, but being a bit of an Android expert, he's non too worried about this. All he has to do, is unlock the bootloader and fastboot flash a factory stock image, and the stolen device will be his...

...Or so he thinks!!!

His first stumbling block (and upon which successfully flashing a factory stock image depends), is first unlocking the bootloader... and which of course will fail, because the lawful owner NEVER enabled **Enable OEM unlock** in Developer Options. Indeed, he wasn't even aware that such a setting existed. And our opportunist thief cannot boot Android in order to enable this setting, because he is not in possession of the LOCK PATTERN or PIN CODE required to get past the lock screen.

He is in possession of a useless tablet."

So, in this scenario... the setting **Enable OEM unlock** in Developer Options, has served it's purpose, in rendering the Nexus 9 useless to somebody who has no lawful right to it, and why I think that there was no possible way of salvaging my original Nexus 9. Any such method would undermine the whole point of it.

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So, in conclusion...

Re-locking the bootloader is probably safe... The danger is ALSO, AND AT THE SAME TIME disabling the **Enable OEM unlock** option in Developer Options... and is risky, as you're potentially disallowing the bootloader from EVER being unlocked again.

And if Android won't boot... FOR WHATEVER REASON, there is NO WAY of re-enabling that setting:(.

So, once you've enabled it, my advice is to NEVER disable it... regardless of what you do with the bootloader lock state.

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Anyhow, I hope my lengthy post sheds some light on all of this... And is of assistence to whomever has the patience to read the whole damn thing:).

Sorry, but I do tend to waffle on at times:).

Kind Rgrds,

Ged.