Add distbuild-trove-nfsboot.write

The nfsboot.write deployment extension has been deprecated for a while
because it's not generally useful. It's only used for deploying
distbuild nodes to a Trove, as far as I know.

We still need to support setting up a bunch of machines that boot over
NFS from a Trove. But we can do this in a special-purpose .write
extension.

The new distbuild-trove-nfsboot.write is much more efficient than
the more generic nfsboot.write: instead of treating each system
individually (thus copying an almost identical ~2GB rootfs to the Trove
once per node) it copies the system image to the Trove once, and /then/
sets up a rootfs per node.

Upgrades are now supported, although the code assumes distbuild nodes
are stateless (as they should be) so nothing special is done for
upgrades, other than checking that there is already a version of the
given system in existance. The new extension does not create an
orig/ and run/ version of each system, because there is no need when the
deployed system is stateless.

There could be further gains in efficiency, but I don't have time to do
them right now. This write extension is full of compromises, its goal is
to better support the existing users who have a Trove and a distbuild
network deployed via NFS. It is specifically not intended to be useful
for other purposes.

Change-Id: I9a50c58b714ed272212d1d6c55b289aaa96051b1

0 files changed, 0 insertions, 0 deletions