Priyanga wrote:

How to extract the boot image using flash tool.small explanation might be sufficient.thanks

+1. I can try to use a Windows VM. 
If you could post a little bullet pointed list of steps, I would be most grateful. And instead of paying a OneClick root, you'd want to assist via VNC, I'd be happy to compensate you for the time. I'm not a big fan of Windows, and specially not with the built-in screen reader for the blind.

In flash tool

Extract boot image
In the Download tab chose the scatter file (see my first post)
In the Readback tab, click add
Double click on the created entry
Choose where you want to put the boot.img and click save
Select :
Type Hex
region: EMMC_USER
Start Address: 0xAE00000
Length: 0x1000000
Click Ok
Shutdown your phone
Click on Read Back
Plug in your phone
Boot.img is extracted

Flash boot image
In the Download tab chose the scatter file (see my first post)
Make sure Download Only is selected in the dropdown list
Unckeck all entry but boot.
Click in the Location column of the boot entry
Choose the pached boot.img and click open
Shutdown your phone
Click on Download
Plug in your phone
Wait for the green check.
Done.

This is a simplified tutorial. There are plenty of guides, tutorials and videos all over the internet about this. If something don't work, use those guides.
This is ONLY for the BV6800 Pro. Remember you do this at your own risk, save your data before !

Thanks i will try.did you rooted your 6800?

Sams, thanks for tutorializing. Hard to follow from Mac.

In order to setup Magisk and backup the boot image from mac (ADB), I had to unlock the boot loader.
However, it looks like there is no TWRP recovery IMG for Blackview, and I don't want to flash anything onto my phone.
So, I'm stuck and cannot extract my boot.img for patching.

In other words, the boot partition is on /dev/block/mmcblk0p20, but I don't have read permissions.

My build is [color=#000000][size=85][font=Helvetica]BV6800Pro_Blackview-V1.4_20180920_20181130-1918[/size][/font][/color]

[color=#000000][size=85][font=Helvetica]Can somebody clearly answer, once and for all, where to download the official roms for that particular build? If I cannot extract my own boot image, I'd like to at least use the official one instead.[/size][/font][/color]

Priyanga wrote:

Thanks i will try.did you rooted your 6800?

That's the second thing I did when I received it, just after extracting the full stock ROM.

Ekavun, you don't need to unlock the bootloader and you don't need TWRP.
You only need to use flash tool to extract and flash back your boot partition. You can't use adb to do that.
I asked blackview 4 months ago to publish the stock ROM. They never did.
I extracted the stock ROM myself and saved all update.zip as they came.
I can provide the original boot image for your ROM version (or even the Magisk patched one if you want), but you will still need to flash back the patched image with flash tool.

I tryed.no success.i have knowledge in flashing rom in mtk devices.as you instructed i did everything correct .no chance to root.

What do you mean by
that

Priyanga wrote:

I tryed.no success.i have knowledge in flashing rom in mtk devices.as you instructed i did everything correct  .no chance to root.

Did you patched the boot image successfully with Magisk Manager before flashing it back ?

Yes i patched the boot image with magix.when i try to flash the patch error PMT changed it must be downloaded.please selectgormat all *download scene and try again