Thanks for the help, sethlans & karurosu. Those two suggestions made it work.
The environment in u-boot was a little weird. When I reset and do a printenv inside u-boot, I get both:
bootargs=console=ttyS0,115200 mtdparts=nand_mtd:0x400000@0x100000(uImage),0x1fb00000@0x500000(rootfs) rw root=/dev/mtdblock1 rw ip=10.4.50.4:10.4.50.5:10.4.50.5:255.255.255.0:DB88FXX81:eth0:none
If I type "printenv bootargs", I just get the second, longer line. Note that it includes the "root=...". I found that I needed to re-enter that whole line, but with "mmcblk0p1" substituted for "mtdblock1".
I'm pretty sure I'm now running off the sd card, because "df" yields:
Filesystem 1K-blocks Used Available Use% Mounted on
rootfs 7707056 516540 6799016 8% /
tmpfs 257816 0 257816 0% /lib/init/rw
varrun 257816 232 257584 1% /var/run
varlock 257816 0 257816 0% /var/lock
udev 257816 12 257804 1% /dev
tmpfs 257816 0 257816 0% /dev/shm
tmpfs 257816 0 257816 0% /var/cache/apt
Since, rootfs is much bigger, it must be the sd card. Also, during boot, I get the messages "EXT3 FS on mmcblk0p1, internal journal", "EXT3-fs: mounted filesystem with ordered data mode.", "VFS: Mounted root (ext3 filesystem)." I'm not sure how else to tell, since "mount" just tells me "rootfs on / type rootfs (rw)", rather than telling me the actual device.
Two weird things that I'd still like help with.
- I tried to mount the built-in nand flash with the command "mount -r /dev/mtdblock1 /nandflash", but it gives me the error message "FAT: bogus number of reserved sectors", and crashes the system. No further response until I physically reset. Should it be possible to mount the internal flash, while running with the sd card as root?
- The file system seems MUCH bigger on the sd card than it was in the internal flash even though, I think, it is identical. As you can see above, df tells me that 516MB is used on the root file system. When running off the internal flash, df told me that ~185MB was used. I imaging that some of the difference is the journaling (the SD is formatted with ext3). Is there some other reason that the same data is using 2.5X the space?
Thanks again for all the help, past and future.