Backup/dump kernel image without root or twrp/cwm Is there any way to backup/dump kernel image without root or twrp/cwm ?
It is possible to dump device partitions without root or custom recovery - if your device has "fastboot" mode and is boot unlocked. I'm not going to describe unlocking the boot loader, but with a fastboot device it is usually pretty easy - search the internet for instructions for your specific device.

You will need a TWRP recovery image for your device, but you don't need to actually install it on the device - we'd just temporarily boot into it to get access to the raw boot partition. Look at https://twrp.me/Devices/ and download the image for your device.

Preparations:

You need to find out which partition you want to backup from the device's storage. Usually there is a by-name directory somewhere under the devices tree that lists all the operating system's partitions with names and physical partition identifiers.


Install ADB and Fastbook command line tools.
On your device, enable "Developer Mode" and then go into the developer settings and enable "USB debugging".
Connect your device to your computer.
On your computer run adb devices and verify your device is listed. You may need to authorize access on the device itself in a popup that will appear.
Run adb shell to go into the device's command line shell
Run find /dev -name 'by-name' 2&gt;/dev/null to find the by-name directory. It should list one, though if there are a couple, it shouldn't be a problem and both should work.
Take the directory name and run ls -la &lt;by-name-directory&gt; (replacing the place holder with the actual directory name)
Find the name of the partition you are interested in - if you want just the kernel, the name is boot, or if your device has multiple slots, it is probably boot_a - and record the physical partition path listed for it. It should be something like /dev/block/mmcblk0p22 (this is on my Mi A1 device - if you have a different one, the number after "p" will be different and possibly even the number before "p").


If you do not have a by-name directory on your device, you might want to search the internet for the correct device name, though there are ways to detect the correct partition from within the device - comment if you need help.

Steps to Backup


Reboot your device to the fastboot boot loader. There's usually a boot time key combination for this, on my Xiaomi Mi A1 its POWER + VOLUME-DOWN, but you can also use ADB to do that: execute adb reboot-bootloader to go directly to fastboot mode.
Use fastboot to boot into the TWRP image you downloaded, without installing it on the device: fastboot boot recovery-3.2.1-1.img . It will take a couple of minutes for the device to boot into TWRP, so be patient.
On your computer, run adb pull /dev/block/mmcblk0p22 boot.img, replacing "mmcblk0p22" with the correct boot device path you found in the preparations stage, and "boot.img" with where you actually want to save the kernel boot image.


If your device has multiple boot slots, its probably a good idea to backup both (on my device, for some reason, after a clean install and update, they are not identical).

Good luck.