FreeBSD Dom0
This guide explains how to setup a FreeBSD Dom0 for testing purposes. In order to set it up a box with an Intel CPU that supports EPT is needed. This guide assumes that the user has already installed a plain version of FreeBSD amd64 into the box (either a RELEASE or a snapshot of HEAD or STABLE branches). In my specific case I'm using a stable/10 snapshot and the install has been done using ZFS-on-Root.
Checking out the code and updating the system
FreeBSD Dom0 support is only available as a set of patches on top of the HEAD branch. The following is needed in order to check it out:
# pkg install git # git clone git://xenbits.xen.org/people/royger/freebsd.git # cd freebsd # git checkout pvh_dom0_v6
Now the normal update world procedure from The FreeBSD Handbook should be followed.
Installing Xen
Before installing Xen we need to install the following dependencies:
# pkg install mercurial git bash python bcc glib pkgconf yajl gmake pixman perl5 markdown bison gettext gawk gcc47
Then the Xen source should be fetched using git:
# git clone git://xenbits.xen.org/xen.git
And finally we compile the Xen hypervisor and install the toolstack:
# cd xen # ./configure HOSTCC=gcc47 CC=gcc47 # gmake -j8 xen HOSTCC=gcc47 CC=gcc47 # cp xen/xen /boot/ # gmake -j8 install-tools HOSTCC=gcc47 CC=gcc47
In order to have a working Xen host, the xencommons rc.d script has to be started, we are going to add it to /etc/rc.conf. We will also setup a bridge so our guests can have network and enable the Xen console in order to get a login prompt:
# echo 'xencommons_enable="YES"' >> /etc/rc.conf # echo 'cloned_interfaces="bridge0"' >> /etc/rc.conf # echo 'ifconfig_bridge0="addm bge0 SYNCDHCP"' >> /etc/rc.conf # echo 'ifconfig_bge0="up"' >> /etc/rc.conf # echo 'xc0 "/usr/libexec/getty Pc" xterm on secure' >> /etc/ttys # mkdir -p /var/lock # mkdir -p /var/run/xen
A new loader(8) option has been added in order to pass the boot parameters to the Xen kernel. In the following example Xen is setup to boot to the serial console, and Dom0 is limited to 4 vCPUs and 2G of RAM:
# echo 'xen_cmdline="dom0_mem=2048M dom0_max_vcpus=4 dom0pvh=1 com1=115200,8n1 guest_loglvl=all loglvl=all console=com1"' >> /boot/loader.conf
Now we are ready to boot into the newly installed FreeBSD Xen Dom0. In order to do this some manual interaction with the bootloader is needed. When the bootloader appears drop into the prompt and type the following:
OK unload OK load /boot/xen OK set module_path=/boot/kernel OK load kernel OK load zfs OK load ... OK boot
NOTE: in some cases (specially when using ZFS), it might be needed to increase the amount of allowed wired memory, this can be done by increasing the vm.max_wired sysctl tunable.
Creating your first PV guest
In this example we will show how to create a Debian PV guest, first we need to fetch the Debian kernel, initramfs and config file:
# fetch http://ftp.nl.debian.org/debian/dists/wheezy/main/installer-amd64/current/images/netboot/xen/initrd.gz > initrd.gz # fetch http://ftp.nl.debian.org/debian/dists/wheezy/main/installer-amd64/current/images/netboot/xen/vmlinuz > vmlinuz # fetch http://ftp.nl.debian.org/debian/dists/wheezy/main/installer-amd64/current/images/netboot/xen/debian.cfg > debian.cfg
For the disk we are going to use a ZFS ZVOL:
# zfs create -V 10g tank/debian
And the edited configuration file:
#============================================================================ # AT INSTALLATION TIME #============================================================================ kernel = "vmlinuz" ramdisk = "initrd.gz" #============================================================================ # TO BOOT INSTALLED SYSTEM # # Comment all of the above installation options and uncomment the # below instead #============================================================================ #bootloader="pygrub" #============================================================================ # STANDARD OPTIONS #============================================================================ # # The following options are common to both installation time and normal booting. # # Only a subset of the available options are included below. # See /usr/share/doc/xen-utils-common/examples for full examples. #---------------------------------------------------------------------------- # Initial memory allocation (in megabytes) for the new domain. memory = 512 # A name for your domain. All domains must have different names. name = "debian" # Number of Virtual CPUS to use, default is 1 vcpus = 2 #---------------------------------------------------------------------------- # Define network interfaces. vif = ['bridge=bridge0'] #---------------------------------------------------------------------------- # Define disks disk = ['phy:/dev/zvol/tank/debian,xvda,w']
Launch the guest and attach to the console:
# xl create -c debian.cfg
After the install has finished, destroy the guest:
# xl destroy debian
And edit the configuration file, so it looks like:
#============================================================================ # TO BOOT INSTALLED SYSTEM # # Comment all of the above installation options and uncomment the # below instead #============================================================================ bootloader="pygrub" #============================================================================ # STANDARD OPTIONS #============================================================================ # # The following options are common to both installation time and normal booting. # # Only a subset of the available options are included below. # See /usr/share/doc/xen-utils-common/examples for full examples. #---------------------------------------------------------------------------- # Initial memory allocation (in megabytes) for the new domain. memory = 512 # A name for your domain. All domains must have different names. name = "debian" # Number of Virtual CPUS to use, default is 1 vcpus = 2 #---------------------------------------------------------------------------- # Define network interfaces. vif = ['bridge=bridge0'] #---------------------------------------------------------------------------- # Define disks disk = ['phy:/dev/zvol/tank/debian,xvda,w']
