applications - Transfer root to SDcard with switch_root didn't work

I'm trying to install Debian on the Android 4.4 (modded with cyanogenmod) that's installed on my nexus 10 to one external sd card. I'm reading this tutorial :

http://whiteboard.ping.se/Android/Debian

I've attached the Leef microSD microUSB Connector with a 64GB sd card inside to the mini usb port of my nexus 10 as you can see here :

The tutorial talks about the The ASUS Transformer TF101 and the instructions are based on this tablet. Instead I have a tablet nexus 10,that's equipped with an internal sd card where I have installed android 4.4 + cyanogenmod. For this reason I need to know how to change some part of the tutorial to adapt it to my situation. Anyway on my desktop computer I have partitioned the sd card in this way :

Disk /dev/sdf: 64.0 GB, 64021856256 bytes
255 heads, 63 sectors/track, 7783 cylinders, total 125042688 sectors
Units = sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0004504c

   Device Boot      Start         End      Blocks   Id  System
/dev/sdf1            2048    32767999    16382976    b  W95 FAT32
/dev/sdf2        32768000   125042687    46137344   83  Linux

My nexus 10 recognizes the sd card as sda2. According with the tutorial I have issued the following commands,but something did not work :

mount -o rw,remount / 

mkdir /mnt/deb
mount -t ext4 /dev/block/sda2 /mnt/deb
/mnt/deb/busybox sh
/mnt/deb/busybox mount -t proc none /mnt/deb/proc
/mnt/deb/busybox mount -t sysfs none /mnt/deb/sys
/mnt/deb/busybox mount -t tmpfs none /mnt/deb/dev
/mnt/deb/busybox mdev -s
exec /mnt/deb/busybox switch_root /mnt/deb /init



BusyBox v1.21.1 (2013-07-08 10:07:37 CDT) multi-call binary.

Usage: switch_root [-c /dev/console] NEW_ROOT NEW_INIT [ARGS]

Free initramfs and switch to another root fs:
chroot to NEW_ROOT, delete all in /, move NEW_ROOT to /,
execute NEW_INIT. PID must be 1. NEW_ROOT must be a mountpoint.

        -c DEV  Reopen stdio to DEV after switch

but where is the mistake ?