Flash image to SD card with bmaptool

NOTE 1: in following examples we assume that SD card is present as linux device /dev/sdX, so you need to edit provided commands according to your setup.

NOTE 2: Be careful with following commands. Using one incorrect symbol MAY ERASE your working disk!

In case you need to write image to SD card, you always can use dd like this

sudo dd if=img.img of=/dev/sdX bs=1M status=progress

This works always but takes quite long time up to 20 minutes depending on SD card.

In order to speed up writing to SD we can use bmaptool. Main idea implemented by this utility - write only non-zero blocks. So, depending on image file this can be few faster.

Install it.

sudo apt install bmap-tools

And use like this

bmaptool create -o img.img.bmap ./img.img
sudo bmaptool copy --bmap img.img.bmap ./img.img /dev/sdX

Pay attention that you need to use create only if image is changed. And you have to use 'create' if image is changed. When you create, utility scans image and generate a map of empty blocks. It's just xml so you can check it. Also you can use --nobmap option like this

sudo bmaptool copy --nobmap ./img.img /dev/sdX

but I found that it takes longer than two above mentioned commands create+copy. I don't know why, just trust me - I'm an engineer.