openWrt snapshot working on SD; now how do I flash it to NAND?

[lyzby]

I got a current snapshot of openWrt working on the Sheevaplug on an SD card (see http://plugcomputer.org/plugforum/index.php?topic=2057).  Now I'd like to be able to flash it to nand. 

One aspect I don't understand is how to get the root file system contained in the file, openwrt-kirkwood-rootfs.tar.gz into a form which may be flashed into the nand?

There also appears to be some magic in the naming of mtd partions as rootfs and rootfs_data, as used in this HOWTO for the dockstar:  https://forum.openwrt.org/viewtopic.php?id=25603

Finally, is there a good general explanation of the use of uBoot on the Sheevaplug with respect to NAND and RAM.  There seem to be certain magic values for addresses, but it's hard to tell whether they are required or conventional.