Dump Android Device image.

1. Preparation
The following preparations are required before creating a Fastboot ROM.
- Bootloader Unlocked device
- GSI with built-in SU (Phh-AOSP, LineageOS GSI, etc.) or boot.img with patched Magisk or KernelSU boot.img
- DSU Sideloader (GSI Only)
- adb and fastboot environment

2. Dump Image
You can pull files as img by running certain commands with root privileges. In other words, you are doing that and pulling out img's such as boot and vbmeta.
Let's do the necessary commands to save the img.

Note: boot GKI(⚠Don't use fastboot flash boot)
fastboot boot KSU_boot.img

## Dump Image Commands ##
# 1. Superuser

su

# 2. Go to the path where each image is located (or /dev/block/by-name/ for MediaTek, etc.)
↓ Copy
cd /dev/block/bootdevice/by-name/

# 3. Create backup directory
↓ Copy
mkdir /sdcard/backup_img

# 4. Backup everything except cache and userdata to /sdcard
↓ Copy
for file in *; do
    if [[ "${file}" = cache* || "${file}" = userdata* ]]; then continue ; else dd if=/dev/block/bootdevice/by-name/"${file}" of=/sdcard/backup_img/"${file}".img ; fi
done

# 5. MD5 check list
↓ Copy
echo "" > /sdcard/backup_img/md5.txt
for file in *; do
    if [[ "${file}" = cache* || "${file}" = userdata* ]]; then continue ; else
	echo "${file}" >> /sdcard/backup_img/md5.txt
	md5sum /dev/block/bootdevice/by-name/"${file}" >> /sdcard/backup_img/md5.txt
	md5sum /sdcard/backup_img/"${file}".img >> /sdcard/backup_img/md5.txt
	echo "" >> /sdcard/backup_img/md5.txt
    fi
done