I have a proof of concept system doing this. I started with a 7.2
install on zfs root, compiled world and kernel from 8, took a snapshot
and made a clone for the 7.2 install, and proceeded to upgrade the
current fs to 8.0. After updating the loader.conf in the 7.2 zfs to
point to its own cloned fs, I can pick which one to boot with a simple
"zpool set bootfs=z/ROOT/7.2" or "zpool set bootfs=z/ROOT/8.0" before
rebooting. I also tried rsyncing from a FFS based system into a new ZFS
in that same zpool, used DESTDIR with installkernel and installworld to
update the imported OS to support zfs, setup its boot loader and misc
config files, and was able to boot from it using zpool to set it as the
bootfs. Somewhat like shifting around OS images in a virtualization
environment except its easy to reach inside the "image" to
upgrade/modify it, copy them between systems, and no execution overhead
while running one since its still on bare metal (but only one running OS
per server of course). This makes it very easy to swap an OS onto
another server if you need better/lesser hardware or just want to test.
Dan Naumov wrote:
This reminds me. I was reading the release and upgrade notes of OpenSolaris
2009.6 and noted one thing about upgrading from a previous version to the
new one::
When you pick the "upgrade OS" option in the OpenSolaris installer, it will
check if you are using a ZFS root partition and if you do, it intelligently
suggests to take a current snapshot of the root filesystem. After you finish
the upgrade and do a reboot, the boot menu offers you the option of booting
the new upgraded version of the OS or alternatively _booting from the
snapshot taken by the upgrade installation procedure_.
Reading that made me pause for a second and made me go "WOW", this is how
UNIX system upgrades should be done. Any hope of us lowly users ever seeing
something like this implemented in FreeBSD? :)
- Dan Naumov
On Tue, Jun 2, 2009 at 9:47 PM, Zaphod Beeblebrox <zbee...@gmail.com> wrote:
The system boots from a pair of drives in a gmirror. Mot because you can't
boot from ZFS, but because it's just so darn stable (and it predates the use
of ZFS).
Really there are two camps here --- booting from ZFS is the use of ZFS as
the machine's own filesystem. This is one goal of ZFS that is somewhat
imperfect on FreeBSD at the momment. ZFS file servers are another goal
where booting from ZFS is not really required and only marginally
beneficial.
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