A contrived freebsd install script

freebsd9-zfs-install.sh

#!/bin/sh
zpool destroy zroot

for disk in 0 1 2 3 4 5; do
  gpart destroy -F ada${disk}
  gpart create -s gpt ada${disk}
  gpart add -b 34 -s 94 -t freebsd-boot ada${disk}
  gpart add -b 2048 -t freebsd-zfs -l disk${disk} ada${disk}
  gpart bootcode -b /boot/pmbr -p /boot/gptzfsboot -i 1 ada${disk}
  gnop create -S 4096 /dev/gpt/disk${disk}
done

zpool create -f -o altroot=/mnt -o cachefile=/var/tmp/zpool.cache zroot raidz2 gpt/disk0 gpt/disk1 gpt/disk2 gpt/disk3 gpt/disk4 gpt/disk5

zpool create -f -o altroot=/mnt -o cachefile=/var/tmp/zpool.cache zroot raidz2 gpt/disk0.nop gpt/disk1.nop gpt/disk2.nop gpt/disk3.nop gpt/disk4.nop gpt/disk5.nop
zpool export zroot
for disk in 0 1 2 3 4 5; do
  gnop destroy /dev/gpt/disk${disk}.nop
done
zpool import -o altroot=/mnt -o cachefile=/var/tmp/zpool.cache zroot

zpool set bootfs=zroot zroot
zfs set checksum=fletcher4 zroot

zfs create zroot/usr
zfs create zroot/usr/home
zfs create zroot/var

zfs create -o compression=off -o exec=on -o setuid=off zroot/tmp
zfs create -o compression=gzip-1 -o setuid=off zroot/usr/ports
zfs create -o compression=lzjb -o exec=off -o setuid=off zroot/usr/src
zfs create -o compression=lzjb -o exec=off -o setuid=off zroot/var/crash
zfs create -o exec=off -o setuid=off zroot/var/db
zfs create -o compression=lzjb -o exec=on -o setuid=off zroot/var/db/pkg
zfs create -o exec=off -o setuid=off zroot/var/empty
zfs create -o compression=gzip-9 -o exec=off -o setuid=off zroot/var/log
zfs create -o exec=off -o setuid=off zroot/var/run
zfs create -o compression=lzjb -o exec=on -o setuid=off zroot/var/tmp

zfs create -V 4G zroot/swap
zfs set org.freebsd:swap=on zroot/swap
zfs set checksum=off zroot/swap

chmod 1777 /mnt/tmp
cd /mnt ; ln -s usr/home home
chmod 1777 /mnt/var/tmp

cd /usr/freebsd-dist
export DESTDIR=/mnt
for file in base.txz lib32.txz kernel.txz doc.txz ports.txz src.txz;
do (cat $file | tar --unlink -xpJf - -C ${DESTDIR:-/}); done

cp /var/tmp/zpool.cache /mnt/boot/zfs/zpool.cache

cat << 'FIN' >> /mnt/etc/rc.conf
# all zfs, all the time
zfs_enable="YES"

# Network configuration
hostname="bsd"
ifconfig_em0="DHCP"
defaultrouter="10.0.0.1"
nameserver="10.0.0.1"

# need a mouse to get the bios to allow keyboard input, not to use
moused_enable="NO"

# ssh is useful
sshd_enable="YES"

# lets save some power
powerd_enable="YES"

# up to turning clocks on idle, but not disconnect/power off from bus like C3 does
performance_cx_lowest="C2"
economy_cx_lowest="C2"

# use ntpdate to set the time at the start, then slew with ntp
ntpdate_enable="YES"
ntpd_enable="YES"
ntpdate_hosts="0.freebsd.pool.ntp.org 1.freebsd.pool.ntp.org 2.freebsd.pool.ntp.org"

# disable Sendmail
sendmail_enable="NO"
sendmail_submit_enable="NO"
sendmail_outbound_enable="NO"
sendmail_msp_queue_enable="NO"
FIN

cat << 'FIN' >> /mnt/boot/loader.conf
zfs_load="YES"
vfs.root.mountfrom="zfs:zroot"
# default 30, reduces bursty io patterns
vfs.zfs.txg.timeout="5"
# for power savings
ahci_load="YES"
# disable p state throttling, we'll use c states instead
hint.p4tcc.0.disabled=1
hint.acpi_throttle.0.disabled=1
FIN

cat << 'FIN' >> /mnt/etc/resolv.conf
nameserver 10.0.0.1
FIN

touch /mnt/etc/fstab
zfs set readonly=on zroot/var/empty

zfs umount -af

zfs set mountpoint=legacy zroot
zfs set mountpoint=/tmp zroot/tmp
zfs set mountpoint=/usr zroot/usr
zfs set mountpoint=/var zroot/var