[U-Boot] anyone implemented a failsafe upgrade involving two kernel/rootfs pairs?

[Robert P. J. Day]

  i want to do pretty much what's described here:

https://github.com/DFE/HidaV/wiki/Safe-Update-and-boot-fallbacks

that is, a single u-boot and config in flash, followed by a pair of
kernel/rootfs partitions, that is remotely upgradeable by, from
userspace, determining the "older" (backup) of the pairs, overwriting
that pair with a new pair, then flipping the switch in the u-boot
configuration to always boot the newer kernel and rootfs (with an
emergency revert to the backup pair under circumstances i haven't
imagined yet).

  it *looks* fairly straightforward, but while that's a nice write-up,
it does warn right up front that it hasn't been implemented so if
anyone has done something like this they care to share, that would be
delightful.

  FYI, i'm using this pdlogic zoom am1808 experimenter kit:

http://www.logicpd.com/products/system-on-modules/zoom-am1808/

for testing and, at the very end, the only change i would have to make
is modify the solution to handle NOR flash that will be on the
production board.

  if there's a writeup on this out there somewhere, that would be
great.  if not, if i can get this done, i'll be happy to write it up
and post it publicly on my wiki for others.

  at the moment, i'm using openembedded to build a bootable
kernel/rootfs pair for this board, and starting by adding the
u-boot-fw-utils package so i have fw_{printenv/setenv} onboard.
thanks for any pointers.

rday

p.s.  i do have the bootable SD card that came with the kit, it's
based on the arago project so i know i have something that boots to
userspace as a starting point -- always good to know.

-- 

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Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
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