Default [Q] Nandroid backup without app

I've got a tab lc7. I don't know the manufacturer. I bought on internet.
Some specifications :
build id : JDQ39
Android release: 4.2.2
model : 7LC
cpu_abi: armeabi-v7a
cpu.abi2=armeabi
manufacturer=unknown

My actual version of android is 4.2.2. I want to ugrade it to a more recent version of android, at least 4.3 to have restrict profils to let my kids use it.

Before trying to install any new ROM I want to make nandroid backup but unfortunaltely that device is not reconize by cwm nor twrp.
My computer is a debian and I can access my device with adb. I can be root on it and I try to make it permanent by installing busybox and SuperApp but even if my su binary is suid app complains my device is not rooted.

Anyway I search a way to make a nandroid manually. Is it possible ?

I found the special block device for boot, system, misc :
# 0 /tmp ramdisk (null) (null) 0
# 1 /bootloader vfat /dev/block/nanda (null) 0
# 2 /env emmc /dev/block/nandb (null) 0
# 3 /boot emmc /dev/block/nandc (null) 0
# 4 /system ext4 /dev/block/nandd (null) 0
# 5 /data ext4 /dev/block/nande (null) 0
# 6 /misc emmc /dev/block/nandf (null) 0
# 7 /recovery ext4 /dev/block/nandg (null) 0
# 8 /cache ext4 /dev/block/nandh (null) 0
# 9 /sdcard vfat /dev/block/mmcblk0p1 /dev/block/nandj 0

If you want more information, just tell me.

I search in the forum but all threads give information for nandroid but using an application.
Thanks in advance for any help.