Can ZFS boot from other than the root of a pool?

[Karl Denninger]

For a number of reasons having to do with backup strategy I want to 
mount a ZFS root from "poolname/root" instead just "poolname."

That works ok; I can set in /boot/loader.conf:
vfs.root.mountfrom="zfs:zroot/root"

But -- I cannot actually boot from there.  Unless the /boot directory is 
in zfs:/zroot the system cannot find it, and I see no obvious way to 
"teach" the loader that I want it to look in the filesystem under the 
top level.

This isn't a terrible pain as I can simply mount zroot on /mnt and then 
copy zroot/root/boot over to zroot/boot whenever I make changes to the 
kernel or boot environment (which is infrequent) but I'm wondering if 
I'm missing something that would make booting directly from the 
filesystem where root is specified to be possible.

(Obviously until the loader.conf file is found the system doesn't know 
where root is either, so this does look at first blush to be a "chicken 
and egg" problem.)

-- 
-- Karl
karl at denninger.net


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