[Android Central Question]

I have a tablet (thousands, actually) and we have a custom Android build running on it. We can't get a hold of the team that made the Android image (they are in China). We need to make some changes to the device.

What we want to do is make the changes on one device, make an image of that device, then push it on all the others.

The model number is bt1078

I can boot into recovery by holding down the volume buttons and power. There are options for "apply update", but none for "make backup".

If I boot into bootloader (one of the options), it just hangs during boot. Same thing if I use adb reboot bootloader.

If I power off then on, the device starts up just fine.

It seems that I need to install a custom recovery for bt1078, but none can be found.

Also, while the device is running, I do not have the ability to install anything. All settings have been disabled. So I can't install the TWRP app or any other app. Everything needs to be done via adb.

Also, if I run adb devices, I do get 00000000000000000000 recovery.
If I run fastboot devices I get nothing.
I've tried "fastboot flash recovery twrp-3.2.1-0.img" and it hands with "< waiting for any device >"

Any recommendations on what I could try?

[Rukbat]

You have very few options. About the best (from years of experience outsourcing software, which is what you did) is to have a local company write a version of Android for you that they can get running on the device - and that will accept TWRP. (And that you can put on all the other devices.)

Then you spend the time to put that system on all your tablets, and use TWRP to create and restore backups. You can make changes to one, back it up, and restore it to all the rest.

It's going to cost, but amortize that over the thousands of devices and it's probably only a few dollars per device.

A local company so that a) they have the threat of a major lawsuit hanging over them if they don't supply what you contract for (make sure you have a signed [preferably notarized] contract before you pay anything) and b) so they're available when you decide to update to a later version of Android. (They can start with AOSP, so the source is always available.)

There are other methods, but most of them are cheaper but won't be as good (like a foreign company, a high school kid who knows Android well, etc.)

With thousands of devices to offer them as "customers", it's a large enough project even for a company that won't start talking to you unless the opening shot of "well, for $1,000" doesn't frighten you off, and for you that's just a few cents a device.