• General

  • Panic shutdown? - Hold Power and Volume-Up

I got to thinking about being able to lockdown the phone after reading someone mention volume-up and power puts an iPhone into lockdown mode, so I tried it on my Pixel 6. After about 10 seconds the screen shuts off, and evidently it's turned off as when I hit the power button it starts the boot process.

Am I doing a force shutdown, or?

Seems like this might be a good thing to keep in mind to get the phone into BFU with one hand, and a single action. Are there any issues, and is this reliable? It seems to work locked or unlocked.

    I am aware holding power button for over 30 seconds will do a hard reboot, bypassing the OS. Maybe you have found a way to do a hard power off bypassing the OS too.

    patienttruth99 Are there any issues, and is this reliable?

    One thing to keep in mind is that you would be bypassing the zero-on-free security feature that is supposed to clear most RAM memory during shutdown. Theoretically this might leave your phone RAM memory module susceptible to data extraction for up to a minute or something like that, if someone managed to disassemble your phone and connect wires to the RAM memory module fast enough. The RAM memory module should lose its content eventually though, if left powered off.

    Of course, it is still better than leaving the phone on completely, if swiping down to the power menu and selecting power off or reboot isn't practical to do. But hard power off and hard reboot are not designed to be security features, and is hard to do quick and bypasses some security features that would be done during a regular shutdown.

    If we want a way to quickly shut down the phone with zero-on-free activated, using only one hand and without having to see the screen, it would be better if GrapheneOS adds this as a feature, for example, quick double click on power button causes a regular power off to happen.

        GrapheneOS has an emergency mode that you can activate to call 112 when the power button is pressed five times (but that only works if you don't use the "press power button twice to activate camera from anywhere" shortcut).

        Unfortunately, it does not lock the phone down, which is a bummer.

        On my previous phone, emergency mode activated lockdown mode, preventing biometric login and notifications, which is a very useful thing for some threat scenarios - I had an involuntary interaction with law enforcement where I locked down the phone and then used a lockdown shortcut to run a voice recorder to have the entire interaction recorded, with biometric login disabled, on GOS you need to unlock the phone, activate the recorder, and then activate lockdown mode using touchscreen, much less convenient.

        (A lock screen shortcut for a voice recorder similar to a lock screen shortcut for camera would also be very useful)

          ryrona thanks, that makes sense.

          I think quick access to BFU makes a lot of sense, as does LeslieFH s suggestion of access to a recorder mode. Although camera access seems like a stop gap to that for now.

          Funny story about press 5 x for emergency... I tried it on an old Samsung I had, yet click 2x for camera was on. The fire department and police show up at my worksite. They're asking about an emergency in my line of work. I'm like, nope, we're all good. We haven't heard any of our profession working near by either. Police ask if I have an SOS mode. It hits me...🤦 He's like you better call your wife... Turns out my phone has sent her an audio clip and a photo of my frustratedly trying to turn the camera on. She'd left work and driven half way to the site by the time I got s hold of her. A very effective tool, but I think someone made the right call by not allowing it with the 2x for camera option. I turned mine off after that experience.

              ryrona I am aware holding power button for over 30 seconds will do a hard reboot, bypassing the OS

              When you say "bypassing the OS", you mean the Linux kernel isn't involved at all? As in, the hardware/firmware traps the super long keypress and hard resets the device (as if the battery was removed) or whether init does a immediate shutdown (bypassing system server / framework cleanup) straight up with reboot syscall?

              GrapheneOS Pixel fastboot mode clears memory

              On super long press of the power button, is fastboot involved with the reboot?

                    ignoramous When you say "bypassing the OS", you mean the Linux kernel isn't involved at all? As in, the hardware/firmware traps the super long keypress and hard resets the device (as if the battery was removed)

                    Yes, this is my understanding. All devices have some way to do a hard reboot or hard power off, as in bypassing all software, since the Linux kernel could theoretically freeze or hang, in a way where the watchdog isn't triggered, and it must be possible to recover from a state like that. On Pixel devices, I believe holding power button for 30 seconds is that hardware override, that simply flips power off and on again. But I am not certain. I haven't found any documentation that confirms this.

                    ignoramous On super long press of the power button, is fastboot involved with the reboot?

                    As I understand it, this is only if you enter fastboot by holding volume down during power on. If the bootloader always cleared all RAM memory, GrapheneOS wouldn't have needed to do it themselves too during early kernel boot.

                          ryrona On Pixel devices, I believe holding power button for 30 seconds is that hardware override, that simply flips power off and on again. But I am not certain. I haven't found any documentation that confirms this.

                          Yep, there's no mention of a hard power reset in the CDD (compatibility definition document) at least, though a Google Support answer mentions hard power reset may work on Android 8+.

                          DivestOS developer indicates on PrivacyGuides that the feature is ODM/OEM specific (possibly hinting at hardware/firmware level power reset, like you suspect).

                          For Pixels specifically, it'll be good for GrapheneOS to document just what happens.

                            What about the lockdown option in the powermenu? Isn't that doing what you want? Or does it not encrypt on enabling it?

                              spl4tt What about the lockdown option in the powermenu? Isn't that doing what you want? Or does it not encrypt on enabling it?

                              No, it does not bring back storage to an encrypted state. It does not even shut down running apps. It just forces you to enter primary credentials again, fingerprint won't work. I tried it just now.