How to back up NAND from linux

Hi,
I want to back up my board's NAND flash to my host. I have a Ubuntu box and
I have installed picocom on it. I am able to communicate with picocom and
the supervivi menu is accessible. Whe I select u for backing up the kernel,
it asks me to use DNW. I don't know how to go further. I don't have a
windows computer. I have installed usbpush in /usr/bin.

Also does the NAND backup include everything in the NAND? I mean if I
install a new kernel, and it doesn't work well, can I revert to the old
configuration by restoring the NAND?

Thanks.

I would expect if usbpush can put stuff into NAND it should be able to get
it as well.

DNW backups the whole image, everything.  DNW allows you to restore
previously saved images.

Have a look here:

http://groups.google.com/group/mini2440/browse_thread/thread/39fffdba68f...

Well, it seems there's no way to do it in Linux, need to use windows... :(

I did something crazy. I installed virtualbox and created a win XP VM. Next
I used picocom in linux to send the command [u] to supervivi and I used DNW
in the VM to receive the backup. It worked!.....for a while. After about
93% transfer, I got err:31>>cancelled by host.
It was painfully slow....450kbps I think, and I am stuck with 1 GB NAND!!!