On the S9, Samsung introduced (security) and AVB (Android Verified Boot 2.0) with dm-verity on the system partition, but boot.img itself is signed with a Samsung OEM key. 2. Location and extraction The boot.img is stored in the boot partition , not inside the super partition (system/vendor).
dd if=/dev/block/by-name/boot of=/sdcard/boot.img On a rooted S9, you can pull it via adb pull /sdcard/boot.img . Use bootimg-tools or magiskboot (from Magisk) to unpack: samsung s9 boot.img
Check partitions on S9:
A typical boot.img contains: