superflash

README

Superflash

Superflash is a tool for creating images of large disks but only storing the used blocks. When you then flash those disks, it happens a lot faster than the old dd method (flashing a 64GB Raspberry Pi image, for example is 50x faster)

Example

First use superflash to create a blank image:

superflash blank 31000 mydisk.img

Then mount it as a loop device

2040  sudo losetup /dev/loop0 mydisk.img

Then format it and mount it. You need to pass nodiscard to ensure that mkfs doesn't zero out the whole image

sudo mkfs.ext4 -E nodiscard /dev/loop0
mkdir mnt
sudo mount /dev/loop0 mnt

Lets create an example file:

sudo chmod 777 mnt
head -c 400M /dev/urandom  > mnt/afile.file

Now lets unmount the filesystem and create the superflash map (sfmap)

sudo umount mnt
superflash encode mydisk.img

You should get output like this:

end
done. Image was total 32505856000 bytes of which 31438340096 were trimmed

The resulting sfmap is far smaller than the img:

michael@pandora$ ls -hal
-rw-r--r-- 1 michael michael  31G Jan 16 12:53 mydisk.img
-rw-r--r-- 1 michael michael 430M Jan 16 12:55 mydisk.img.sfmap

Instead of doing dd you can now flash it like this:

superflash flash mydisk.img.sfmap /dev/sdc