Booting FreeBSD from ZFS

Here are my notes on how to configure a full ZFS-based FreeBSD system. In this particular case, the system is “FreeBSD 9.0-CURRENT #0: Thu May 12 15:34:46 UTC 2011” and it runs on a Dell Inspiron Mini 1012 (Intel Atom N450) with 1GB of RAM. This is just a P.O.C. as it is said that ZFS would required at least 2GB of RAM to perform nicely.

Get the media

I grabbed the FreeBSD-9.0-CURRENT-201105-amd64-memstick.img image from my nearest mirror and burned it onto an USB stick:

# sudo dd if=FreeBSD-9.0-CURRENT-201105-amd64-memstick.img of=/dev/rdisk2 bs=1m

Stick the USB pen into the laptop and boot from it. When asked the task to perform, just select “<Live CD>”.

Raise the devil

Log in as “root”. On the Live CD, there is no password set.

Run the sysinstall command and configure your keyboard layout ; then exit. Should you ask yourself, I used “Keymap” / “French ISO (accent)”, then “X Exit Install”.

Find the name of your disks. I only have one local:

# sysctl kern.disks kern.disks: da1 da0 ada0 # gpart list | egrep "Geom|Mediasize" Geom name: ada0 Mediasize: 200038809600 (186G) Geom name: da0 Mediasize: 65536 (64k) Mediasize: 735173120 (701M) Mediasize: 1025506304 (978M)

According to the reported sizes, my local disk is “ada0”. Clean the disk:

# gpart destroy ada0 ada0 destroyed

In my case, the disk contained previous partition layout from various testings and the gpart destroy command didn’t work. I had to wipe the disk out first:

# dd if=/dev/zero of=/dev/ada0 count=64 # gpart destroy ada0 ada0 destroyed

Create the partition table and the slices:

# gpart create -s gpt ada0 # gpart add -s 128K -t freebsd-boot -l boot ada0 ada0p1 added # gpart add -s 2G -t freebsd-swap -l swap ada0 ada0p2 added # gpart add -t freebsd-zfs -l tank ada0 ada0p3 added

Install the boot code to be able to actually boot from the ZFS root:

# gpart bootcode -b /boot/pmbr -p /boot/gptzfsboot -i 1 ada0 bootcode written to ada0

Load the ZFS modules to be able to create and populate the filesystems:

# kldload opensolaris.ko # kldload zfs.ko (...) ZFS filesystem version 5 ZFS storage pool version 28

Create the ZFS pool using the single disk:

# zpool create tank /dev/gpt/tank # zpool set bootfs=tank tank

Create the FreeBSD tree:

# zfs set checksum=fletcher4 tank # zfs create -o compression=on -o exec=on -o setuid=off tank/tmp # chmod 1777 /tank/tmp # zfs create -o compression=gzip -o dedup=on tank/usr # zfs create tank/usr/home # cd /tank; ln -s /usr/home home # mkdir /tank/var # cd /tank/var; ln -s /tmp tmp

Have a look at the “source” link below to get smarter directory layout.

Install the FreeBSD content:

# cd /usr/freebsd-dist # sh -c 'for FIC in *txz; do cat ${FIC} | tar --unlink -xpJf - -C /tank/; done'

Configure FreeBSD:

# chroot /tank # echo 'zfs_enable="YES"' > /etc/rc.conf # cat > /boot/loader.conf vfs.zfs.prefetch_disable="1" vfs.root.mountfrom="zfs:tank" zfs_load="YES" ^D # echo "/dev/gpt/swap none swap sw 0 0" >> /etc/fstab # passwd root # tzsetup # cd /etc/mail; make aliases # exit

Save the ZFS cache-file:

# cd /boot/zfs # zpool export tank && zpool import tank # cp /boot/zfs/zpool.cache /tank/boot/zfs/

Configure the filesystem mount points:

# zfs unmount -a # zfs set mountpoint=legacy tank # zfs set mountpoint=/tmp tank/tmp # zfs set mountpoint=/usr tank/usr # zfs set mountpoint=/usr/home tank/usr/home

Reboot into FreeBSD and enjoy:

# reboot

Note that the keyboard layout is configured as US on reboot…
Use “sysinstall” to configure the rest of the system.

BTW, the ZFS system goes like this:

# zpool list NAME SIZE ALLOC FREE CAP DEDUP HEALTH ALTROOT tank 184G 1.03G 183G 0% 1.14x ONLINE - # zfs list -r -o name,used,avail,refer,mountpoint,compressratio NAME USED AVAIL REFER MOUNTPOINT RATIO tank 1.10G 180G 324M legacy 2.02x tank/tmp 35K 180G 35K /tmp 1.00x tank/usr 735M 180G 735M /usr 2.57x tank/usr/home 38.5K 180G 38.5K /usr/home 1.04x

That’s All Folks!


  • Booting from ZFS RAID0/1/5/6 in FreeBSD 8.x/9.x
  • The Z File System (ZFS)

Author: Joel Carnat

@work Technical Architect and SysAdmin ; @home OpenBSD and FOSS, Karate, Kobudō, Jōdō, Bodyweight workout, Photography & Music

2 thoughts on “Booting FreeBSD from ZFS”

Leave a Reply

Your email address will not be published. Required fields are marked *


This site uses Akismet to reduce spam. Learn how your comment data is processed.