Bootstrap XEN/PVH FreeBSD/ZFS from GNU/Linux

tested on a Slackware current dom0 (Sep 2020)

Introduction

We are considering FOUR way to deploy FreeBSD as a XEN/PVH guest:

install on UFS using installer
install on ZFS using installer (need special kernel)
use out-of-the-box and ready to use VM IMAGE
bootstrap like a brute on ZFS from within a Lignux dom0 (need special kernel)

Warning

The current guide is about for forth and brutal way. First, we need a kernel with ZFS built-in because we don’t have a loader here and we cannot load deliver the zfs and opensolaris modules. We then bootstrap the guest system from the XEN host/dom0, similarly to what we did with NetBSD and Slackware.

OpenZFS

on the Lignux dom0

See Setup ZFS on GNU/Linux

Requirements

mkdir -p /data/kernels/freebsd-current/
cd /data/kernels/freebsd-current/
wget http://ftp.free.fr/mirrors/ftp.freebsd.org/snapshots/amd64/13.0-CURRENT/kernel.txz
wget http://ftp.free.fr/mirrors/ftp.freebsd.org/snapshots/amd64/13.0-CURRENT/base.txz
rm -rf boot/ usr/
tar xJf kernel.txz

Skeleton

on the Lignux dom0

ls -lhF /data/kernels/kernel-zfs
vi freebsdzfs

kernel = "/data/kernels/kernel-zfs"
extra = "vfs.root.mountfrom=zfs:tank/root"
memory = 7168
name = "freebsdzfs"
vcpus = 3
maxvcpus = 8
disk = ['tap:tapdisk:aio:/root/guests/freebsdzfs/freebsdzfs.zfs,xvda,w']
vif = [ 'bridge=br0, vifname=freebsdzfs.0',
    'bridge=br0, vifname=freebsdzfs.1' ]
type = "pvh"

raw sparse file virtual disk

mkdir -p /root/guests/freebsdzfs/lala/
cd /root/guests/freebsdzfs/

dd if=/dev/zero of=freebsdzfs.zfs bs=1G count=0 seek=10

File-system

the kernel wants a GPT partition (GUID a504)

cgdisk freebsdzfs.zfs

Part. #     Size        Partition Type            Partition Name
----------------------------------------------------------------
        1007.0 KiB  free space
   1        10.0 GiB    FreeBSD ZFS               zfs0

losetup -a
losetup --find --partscan --show freebsdzfs.zfs

#cannot work - kernel won't find it
#zpool create tank `pwd`/freebsdzfs.zfs

ls -lF /dev/loop*
zpool create tank /dev/loop0p1
zpool list
zpool status

zfs get compression
zfs set compression=lz4 tank
zfs create -o mountpoint=`pwd`/lala/ tank/root
zfs list
zfs mount

System

slackpkg install libarchive
bsdtar -xJ --numeric-owner -f /data/kernels/freebsd-current/base.txz -C lala/

no need for a valid file-system table unless you have swap, but still it’s good to have one, even empty, to avoid complains at system startup

vi lala/etc/fstab

# Device                Mountpoint      FStype  Options         Dump    Pass#
#/dev/xbd0p2        none        swap    sw              0       0

vi lala/etc/ttys

#ttyv0  "/usr/libexec/getty Pc"         xterm   onifexists secure
xc0     "/usr/libexec/getty Pc"         xterm   onifexists secure

zfs unmount `pwd`/lala/
zfs unmount /tank/
zfs mount
rmdir lala/

zpool export tank
zpool list

losetup -a
losetup -d /dev/loop0

Ready to go

Now that you got fstab and ttys alright

xl create freebsdzfs -c

Timezone & network

ls -lF /etc/localtime
ln -s ../usr/share/zoneinfo/Europe/Moscow /etc/localtime
ln -s ../usr/share/zoneinfo/Europe/Paris /etc/localtime

vi /etc/rc.conf

ifconfig_xn0="inet 10.3.3.9 netmask 255.255.255.0 up"
defaultrouter="10.3.3.1"
hostname="freebsdzfs.localdomain"

mv /etc/hosts /etc/hosts.dist
vi /etc/hosts

::1                     localhost localhost.localdomain
127.0.0.1               localhost localhost.localdomain

# happy happy sendmail
10.3.3.9                freebsdzfs.localdomain freebsdzfs
10.3.3.1                gw
62.210.16.6             dns1
62.210.16.7             dns2

vi /etc/resolv.conf

nameserver 62.210.16.6
nameserver 62.210.16.7

shutdown -r now

Acceptance

hostname
ping -c1 opendns.com

/usr/libexec/locate.updatedb
date
sync
history -c
rm -f .history
shutdown -p now
^]
xl des freebsdzfs

Template

cd /root/guests/freebsdzfs/
mount -o remount,rw /data/
tar cSf /data/templates/freebsdzfs.zfs.tar freebsdzfs.zfs
mount -o remount,ro /data/
cd ../
rm -rf freebsdzfs/