bmaptool

bmaptool command [options] [arguments]

bmaptool is a utility for creating block maps (bmap) and copying images to block devices efficiently. It only writes data blocks, skipping empty or zero-filled areas, making it significantly faster than dd for sparse images.The tool provides integrity verification using SHA256 checksums and includes safety features to prevent accidental writes to mounted devices. It supports compressed images and can decompress on-the-fly during copy operations.

--bmap file

Path to the bmap file (auto-detected if not specified)

Copy without using bmap (entire image is written)

Output file for create command

Skip SHA256 checksum verification

Skip OpenPGP signature verification

copy

Copy an image file to a block device using bmap

Generate a bmap file for an image

Requires root privileges for writing to block devices. The bmap file must match the image file; mismatches cause verification failures. Protection mechanisms prevent writing to mounted devices. Without a bmap file, the tool falls back to copying the entire image like dd.

bmaptool was originally developed by Intel for efficient embedded Linux image deployment, addressing the slow and unsafe nature of using dd for flashing large disk images, particularly those with significant empty space. The project moved to the Yocto Project in 2024; the original Intel repository is now archived.

dd(1), pv(1), xzcat(1)

Source code