[Question] Can we use a partition as a seed to create an img file?

[Peirl]

I read that we can use old containers/file systems as seeds to speed up the download of files, eg:casync extract http://example.com/myimage.caibx --seed=/dev/sda1 /dev/sda2.

Is it possible for me to use a partition as a seed file to download an image file?
For example, I have two ubuntu iso images, ubuntu_v1.iso and ubuntu_v2.iso and I have partition 1, /dev/sda1 burnt using ubuntu_v1.

Can I use the partition 1 as a seed to download ubuntu_v2.iso?
i.e. casync extract http://example.com/ubuntu_v2.caibx --seed=/dev/sda1 ubuntu_v2.iso

[Peirl]

Oh, it works.