Flashing a new kernel on the SheevaPlug

This is the last piece of the puzzle with regards to our using a customized Ubuntu on the internal Flash. After that, we'll switch to using ArmedSlack on the MMC (but we'll keep that rescue Ubuntu image on the internal Flash).
Because we've pretty much done that before, flashing the new kernel is very straightforward, so I'm going to comment a little bit about the U-Boot commands we use.

As you'd expect, the "fatload usb 0 0x00800000 uImage" just takes the uImage file from the USB and loads it in RAM @ address 0x00800000, and it's this RAM image that we are going to flash. Because of the

mtdparts=orion_nand:0x400000@0x100000(uImage),0x1fb00000@0x500000(rootfs)

option we pass to our U-Boot boot command (see what the command "printenv bootargs" reports in the Marvell>> prompt, or refer to the setenv we did previously), U-Boot expects the kernel uImage to be 0x400000 bytes in length (that's 4 MB) starting at address 0x100000 on the NAND Flash. Therefore, we will need to write the 4MB from our RAM containing the loaded uImage to 0x100000 on the Flash.
But before we can write the Flash we need to erase it.
Oh, and don't worry about our kernel image not being exactly 4 MB in length. As long as its size is less that 4 MB, you'll be fine.
If it's more though, then you will need to move the rootfs starting at 0x100000 + 4MB = 0x500000, and change your bootargs parameters accordingly.

All in all, to replace the existing kernel with a new

Marvell>> usb start
(Re)start USB...
USB:   scanning bus for devices... 2 USB Device(s) found
   scanning bus for storage devices... 1 Storage Device(s) found
Marvell>> fatload usb 0 0x00800000 uImage
reading uImage
...................................................................................................................................................................................................................................................................................................................

3152056 bytes read
Marvell>> nand erase clean 0x00100000 0x00400000

NAND erase: device 0 offset 0x100000, size 0x400000
Erasing at 0x4e0000 -- 100% complete. Cleanmarker written at 0x4e0000.
OK
Marvell>> nand write.e 0x00800000 0x00100000 0x00400000

NAND write: device 0 offset 0x100000, size 0x400000

Writing data at 0x4ff800 -- 100% complete.
4194304 bytes written: OK
Marvell>> reset

The bootup sequence shouldn't be that much different from the one you got when testing the new kernel in RAM