Extra space with extroot for LEDE

27 November 2016
necessary package
opkg update
opkg install block-mount
mount device
mkdir /mnt/sda1
mount /dev/sda2 /mnt/sda1
copy root directory content
mkdir -p /tmp/cproot
mount --bind / /tmp/cproot
tar -C /tmp/cproot -cvf - . | tar -C /mnt/sda1 -xf -
umount /tmp/cproot
configure /etc/config/fstab
block detect  > /etc/config/fstab

vi /etc/config/fstab
config global
        option anon_swap '0'
        option anon_mount '1'
        option auto_swap '1'
        option auto_mount '1'
        option delay_root '5'
        option check_fs '0'
        option from_fstab '1'

config mount
        option uuid 'some-uuid'
        option enabled '1'
        option target '/'
        option 'options' 'rw,sync'
        option fstype 'ext4'
        option enabled_fsck '0'

Reboot and Check
mount