.tar.gz archive.boot.img file exactly 512 bytes in size.boot.img back to a test drive using dd results in a bootable partition table matching the source.Always check the checksum if provided. Look for a corresponding .md5 , .sha256 , or .asc file.
sudo ./install-mbr /dev/sda
Since the primary OS likely cannot boot, you must move the .tar.gz file to a live USB environment (such as Ubuntu Live or SystemRescue). Once booted into the live environment, you can access the local terminal. Extraction and Installation mbr support.tar.gz download