Backup rootfs partition to work with eFlasher...

[vveljk]

What I did:
I flashed Ubuntu Core with Qt-Embedded to emmc.
I have installed all needed applications and made complete configuration of system.

What I would like to do:
Now I would like to backup this "rootfs" partition so I can simply overwrite the rootfs.img file in Ubuntu Core with Qt-Embedded with my new rootfs.img and be able to reproduce this same image to my new NanoPC-T2

I allready made image with dd, but this image is 8GB big.
I know that dd copies also free space, but I also tried with writing zeros to unlocated space and put conv=sparse in dd command, but I still get 8GB image.

What is the way to make rootfs.img file only with usable data?

Thank you.

[vveljk]

Just wanted to post that I allready solved the issue.

I installed VM ubuntu on my computer and used make_ext4fs tool from https://github.com/friendlyarm/debian_nanopi2.git
Tool is for 32-bit enviroment so I had to install also lib32c-dev

From NanoPC-T2 I made image of rootfs with dd and then mounted that image in ubuntu.

The syntax for make_ext4fs is in build.sh which is included in debian_nanopi2.git package.