root@OpenWrt:~# sysupgrade -b /mnt/back.tar.gz
Saving config files...
root@OpenWrt:~# dd if=/dev/mtd0 of=/mnt/cfe.bin
dd: can't open '/mnt/cfe.bin': No space left on device
root@OpenWrt:~# dd if=/dev/mtd3 of=/mnt/overlay.bin
dd: can't open '/mnt/overlay.bin': No space left on device
root@OpenWrt:~#