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There was a nice thorough discussion of backups for non-rooted (and maybe also locked) devices here. Most of that covered Android 4.x+ because of the use of adb backup, which apparently doesn't exist in prior versions. A second question on backing up 2.3.x under the same conditions, found no answers.

I'm am dealing with Honeycomb 3.2.6, which I have not yet unlocked, and I am considering the last answer at the first link. I am considering if there is a way to, possibly temporarily, boot a recovery to do the backup. I can see three possibilities:

(1) That answer suggests connecting via USB with Debugging enabled and then:

abd reboot bootloader
fastboot boot twrp.img
fastboot reboot

As opposed to fastboot flash recovery twrp.img, that should temporarily boot the twrp.img without changing/wiping /data. From there it should be possible to do a nandroid backup to an SDCard. The author of that idea didn't seem to have tried it themselves. I wonder if anyone has, and if it's likely to work as described.

(2) According to the TWRP website for this device, if I fastboot flash recovery twrp.img and then on reboot press the proper key combination to enter the recovery (in this case power+volume-down), then

Note many devices will replace your custom recovery automatically during first boot. To prevent this, ... find the proper key combo to enter recovery. After typing fastboot reboot, hold the key combo and boot to TWRP. Once TWRP is booted, TWRP will patch the stock ROM to prevent the stock ROM from replacing TWRP. If you don't follow this step, you will have to repeat the install.

Is this true for TWRP on all/most/many devices?

(3) Another approach to temporarily booting a recovery, mentioned in one of the comments at that first link, is to boot one off of an SDCard. I found one example in another device I have. I'm wondering under what conditions that might work and how to arrange it? If anyone has any insight, I would also appreciate them.

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    you can safely try fastboot, if bootloader is locked it will just deny. for old devices cf-auto-root or other one-click-routing apps will work. for some older devices cwm or philz-touch recovery is signed and flashable from stock recovery
    – alecxs
    Dec 16, 2020 at 11:01
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    For Honeycomb devices the kernel should be new enough to contain the DirtyCow vulnerability (kernel after 2.6.22). Therefore temporary rooting using an app that uses the DirtyCow exploit should be possible. As alecxs said this exploit is typically contained in on-click-root-apps.
    – Robert
    Dec 16, 2020 at 11:55
  • also worth mention you can flash modified boot or system with proper flash tool according to your chipset android.stackexchange.com/q/213116
    – alecxs
    Dec 16, 2020 at 13:45

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