Option to verify written image after copy

[zhovner]

Sometimes an image is written successfully with no errors, but it is actually corrupted on some SD cards when read back.

Currently I verify the image with an extra command:

# Write image to disk
bmaptool copy image.img.gz /dev/sdisk

# Read from disk and verify with the bmap file
bmaptool copy --bmap image.img.bmap /dev/sdisk /dev/null

We need an option to perform the same verification with a single command.

Something like:

bmaptool -v copy — could be misread as the version option
bmaptool -p copy — "protective copy"?
bmaptool -s copy — "secure copy"?

or only full name:

• --verify
• --verify-write
• --readback-verify

This is how tools like rpi-imager, etcher etc. conceptually describe this feature.

[zhovner]

It might make sense to add something like a --checksum-retry option.

For example: after writing each block, read it back and verify the checksum. If the checksum does not match, retry writing that block again (either once or up to N times, where N is provided as an argument to --checksum-retry).

If all retry attempts fail, the process should fail immediately instead of continuing to write the rest of the image, since there is no point proceeding if the data is already corrupted.