Backup rootfs and create custom SD image (to burn your application into other boards)

Backup rootfs

Run the following commands on your target board. These commands will back up the entire root partition:

sudo passwd root
su root
cd /
tar --warning=no-file-changed -cvpzf /rootfs.tar.gz \
    --exclude=/rootfs.tar.gz --exclude=/var/lib/docker/runtimes \
    --exclude=/etc/firstuser --exclude=/etc/friendlyelec-release \
    --exclude=/usr/local/first_boot_flag --one-file-system /