Re: Installing a system onto ZFS

Aristedes Maniatis wrote:
> Yesterday I tried to install (using the August 2007 snapshot iso) a new
> FreeBSD system using ZFS. This is what I did:
> 
> * boot from CD
> * type "load ZFS" on the boot loader prompt (could this be made default
> for FreeBSD 7 release?)
> * drop into the live CD shell and use fdisk, disklabel and zfs to create
> the appropriate partitions (/boot which is UFS2 and /usr /tmp /var /
> which are ZFS). ZFS volumes are created inside ad4s1d.
> 
> A problem is then that the installer tries to mount the partitions and
> presumably knows nothing about the ZFS partitions I mounted within the
> live CD shell. Is there a way to do this, or am I expecting too much of
> the installer tool at this early stage of ZFS in FreeBSD?
> 
> It appears that the only alternative is to install a full system onto
> UFS2 partitions, install a second disk with ZFS volumes, copy across the
> data and set up the boot loader on the second drive, then discard the
> first drive. Is that what others are doing?

What I do is install a minimal system into the UFS root (ad4s1a or
whatever, to become the boot partition). Then I create the ZFS
volumes from within, mounted on a temporary mount-point and copy
over the whole contents of the minimum installation. After that, I
fix the fstab entry in ZFS and prepare mounting of the boot partition
on a directory in the ZFS root (fstab, mount point). Finally, I add
the boot_from entry to /boot/loader.conf (on the boot partition).

After booting for the first time with a ZFS root (the temporary
mount point where the ZFS file system have been initially mounted
after creation is ignored, if a ZFS file system is accepted as the
root file system), I clean up the UFS boot partition to only hold
/boot, rescue (and for the time being /bin, /lib and /etc, which
allows to override the root partition from the loader and instead
boot with a minimal UFS root again ...)


In short: Minimal install to (e.g.) ad4s1a (where ad4s1 also has a
reasonably sized SWAP and the rest as ad4s1d for ZFS). Just select
to create a 512MB root FS in the installer, the swap partition and
use the rest for an UFS partition to be mounted on a dummy mount
point (which you are going to unmount before you start creating
ZFS file systems in that space). Then proceed as normal with the
installation, boot to single user, create ZFS pool and file systems,
copy over the contents of the UFS file system, patch fstab and
loader.conf and create a mount point for /boot reboot and you are
running on a ZFS root without the need for a second disk drive.


This does not take half as long as the text may suggest, and the
minimal installation is small enough to fit into a reasonably sized
boot partition (I use 512MB, since I often keep multiple old kernels,
but 256 should be enough and you might even get along with 128MB,
but I never tried that since it is too small to keep my kernels).

Regards, STefan