[Beowulf] nfs pivot was: statless compute nodes

[Michael Di Domenico]

On Wed, May 27, 2015 at 9:56 PM, Joe Landman
<landman at scalableinformatics.com> wrote:
>
> There are some oddities, not the least of which most distributions are
> decidedly not built for this.  But if you get them to a point where they
> think they have a  /dev/root and they mount it, life generally gets much
> easier rather quickly.
>
> One of the other cool aspects of our mechanism is that we can pivot to a
> hybrid or NFS after fully booting.  And if the NFS pivot fails, we can fall
> back to our ramboot without a reboot.  Its a thing of beauty ... truly ...

Can you explain this in more detail?  I currently pxe boot into
busybox and then pivot_root to boot up RHEL.  it works well, but if it
fails, it gets all screwed up and i have to reboot.  i'd like to know
more about how boot the os and recover back to the pxe image if it
fails, that sounds really handy... :)