Some notes on RootOnZFS article in wiki

Mel Flynn mel.flynn+fbsd.current at
Mon Dec 21 16:28:38 UTC 2009

On Monday 21 December 2009 07:03:52 krad wrote:
> 2009/12/21 Mel Flynn
> <mel.flynn+fbsd.current at<mel.flynn%2Bfbsd.current at maili
> > Hi,
> >
> > yesterday went through the RootOnZFS (gpt mirror version) and here's a
> > few notes:
> > 1) You cannot use the install CD. It doesn't have a livefs and so you can
> > never do the actual install in 2.2. The DVD will work and the USB image.
> > I ended up using the livefs CD and the USB image, cause I didn't want to
> > loose
> Maybe that procedure needs modifying a bit, but you can do its from disk1.
> As i have. Things are a bit clumsy but it does work.

- Using 8.0-RELEASE disc 1 amd64, 2 coasters burnt on two different machines 
with two different OS's, the Fixit option from CD/DVD kept asking for the 
livefs CD, so I assume it's not on there or two different coasters had the 
exact same errors.
- Livefs doesn't have /dist/8.0-RELEASE/*.
- Ejecting livefs won't work when mounted.
- umount is on CD.
- /rescue/umount is too big for space left on md0.
- is also too big for space left on md0.

So I'm curious how the 'clumsy' method works.

> > 3) By adding the swap partitions on the two mirrored disks to /etc/fstab
> > top
> > actually shows the sum of these as available swap. My expectation is/was
> > that
> > the swap would be mirrored and thus I'd have only the size of one swap
> > partition. If this isn't the case, can I get by with 1 of the two since
> > they're double the intended size or should one use 2 and thus create them
> > half
> > the intended size?
>  No as if you loose a disk you will only have 1/2 the swap you need.

Point taken.

> > 4) The given mount points have sane defaults, however, I use cvs to
> > checkout
> > the ports. It would be nice to have one example where data is already in
> > a directory tree and how one can promote it to a zfs filesystem with
> > special properties.
> You cant really promote something to a file system. The ideal situation is
> you create the fs before you unpack the ports tar ball (or cvs). Otherwise,
> rename /usr/ports (/usr/ports.old/, create the fs as desired, then rsync
>  the files there (or cp, or mv). Then delete the old tree.

Right, I was wondering if that would actually work. If I do for example:
zfs create -o compression=on zroot/usr/local/etc

with files in there, would this result in the files being 'below' the mount 
point or would they be forever lost?

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