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The FreeBSD operating system contains innumerable powerful features. One of these features is bhyve, its native type 2 (OS-level) hypervisor, which can host virtual machines running multiple different OSes, including Linux.

This post will walk you through creating a Linux virtual machine on FreeBSD using the CBSD tool, which greatly simplifies creating and managing bhyve VMs.

Note: This tutorial is meant for a learning experiment only. It is not meant for use setting up production systems. It skips most security features and sets up no fault tolerance.


This tutorial assumes you have basic FreeBSD or Linux command-line or system administration skills and have gone through the process of installing FreeBSD.

FreeBSD Tips for Linux People

Software installation

FreeBSD has a very mature and reliable software package management system and a library of third-party packages similar to most Linux distributions. You can install pre-compiled binary packages using pkg or you can compile from source code using the ports collection.

I generally compile from ports, which allows custom compile-time options and can sometimes be more up-to-date, but pkg should be fine and definitely much faster.

Text-based User Interfaces

FreeBSD uses a very distinctive style of interactive menus. If you compile from ports, you will see it a lot. CBSD also uses it.

Screenshot of an example of the FreeBSD user interface, with its light blue background, checkboxes, and Ok and Cancel buttons
The distinctive FreeBSD interactive interface with its shadow box menu and its light blue background

  • To navigate the menu: use the <up/down> arrow keys
  • To change an option: navigate to that line, press the spacebar.
    • If the item is a checkbox, it will toggle the selection
    • A pop-up will appear if the option is a multi-choice or a text box entry

When you have finished the configuration, use the <left>/<right> arrow keys to navigate the options below the menu. Select <Ok> to confirm and hit enter.


  • Your favorite Linux command-line tools like grep, sed, awk, and find are all here but they sometimes behave a little differently than on GNU/Linux.
  • If you absolutely need the GNU versions, you can usually install them via packages or ports, with g or gnu prefixed to the name (gnugrep, gsed, etc.)
  • bash is also not installed by default. You can install it via pkg or ports

Root access

sudo access is not set up automatically, unlike many Linux distributions. In the default installation, FreeBSD expects users needing root access to be added to the wheel group (in /etc/group) and to su to root, using the root password to authenticate. If this is an important or shared host, you can configure sudo

The root user also defaults to csh as its login shell. You probably want to install bash and use that instead.

Setup and configuration

Host (FreeBSD Hypervisor) Requirements

  • CPUs must support FreeBSD bhyve virtualization (see the FreeBSD Handbook page on bhyve for compatible CPUs)
  • FreeBSD: At least 13.0-CURRENT. I tested this on 13.1-RELEASE
  • File system for VM storage: ZFS
    • If you don’t want to install root on ZFS, that’s fine. You can create a ZFS pool on another disk or disk partition.
    • I installed 13.1-RELEASE as ZFS-on-root and let the installer use its default partitions. Previous FreeBSD installers may require additional ZFS configuration
      • Static IP. If your host’s IP address changes, you may have to reconfigure CBSD later.

VNC Client

To connect to the console of the new VM during the installation phase, you will need a VNC (Virtual Network Computing) client on a graphics-based host (for example, Windows or a Linux desktop). When connecting from a Linux host, I like the TigerVNC client, which is available as a pre-built package for many Linux distros.

ZFS Storage

These instructions assume you have a ZFS pool of reasonable size and it’s named zpool. “Reasonable size” depends on how many VMs you want to create, but let’s assume a bare minimum of 10-20Gb per VM.

Install and Configure Tools


You will need to install the following via the pkg command or by compiling the port. The port group is in parentheses.

  • git (devel)
  • CBSD (sysutils)
  • nsd (dns)
  • tmux (sysutils)

Initialize CBSD

Before we run CBSD the first time, we need to initialize its configuration. You can find the default values in /usr/local/cbsd/share/initenv.conf but we’re going to change a few of those.

In addition to populating /usr/cbsd (the “workdir”) and writing configuration files, the initenv subcommand given the above values will also append boot-time CBSD options to /etc/rc.conf and /boot/loader.conf.

You can run the initenv subcommand one of two ways:

  1. Interactively. This is long and rather confusing if you don’t know what you’re doing.
  2. Using a seed file with the values pre-set.

Important: all CBSD commands need to be run as root


  • My host has the hostname nucklehead and the IP address You should use your own host’s values for those options.
  • For the RSYNC and RACCT questions, because this is a non-production system, you probably want to answer disable them to save resources
  • CBSD version 13.1.13 seems to ignore the racct=0 option (don’t enable accounting). After initialization is done, you can remove the line kern.racct.enable=1 from /boot/loader.conf
  • initenv may offer different configuration questions depending on answers to previous questions

Initialize CBSD the Quick Way

Configure CBSD from the command line
  1. Save the following to a file called initenv.conf
    # cbsd initenv preseed file for nucklehead host
    # refer to the /usr/local/cbsd/share/initenv.conf
    # for description.
  2. Edit nodeip to you FreeBSD’s IP address and nodename to the hostname
  3. Run
    env workdir=/usr/cbsd /usr/local/cbsd/sudoexec/initenv inter=0 `pwd`/initenv.conf

Initialize CBSD the Long Way

Configure CBSD interactively

This example shows a run-through of an interactive configuration, using the command

env workdir=/usr/cbsd /usr/local/cbsd/sudoexec/initenv

Enable pf Networking

The pf firewall needs some additional setup.

# Create the configuration file
cp /usr/local/examples/pf.conf /etc/pf.conf
# Enable the NAT gateway
echo 'gateway_enable="YES"' >> /etc/rc.conf
# Start
service start

Load kernel modules

We need to set up several kernel modules. We load them now then add them to /boot/loader.conf so they will load automatically at boot time.

for module in vmm if_tuntap if_bridge nmdm; do
    kldload "$module"
    echo "${module}_load=\"YES\"" >> /boot/loader.conf

Create our Linux Virtual Machine

We’re finally ready to create our VM.

We’re going to select the latest available supported version of Ubuntu. Note that this may not be the current Ubuntu release. We’ll cover how to configure releases with no CBSD support in a later post.


  • In this example, we are going to use Ubuntu Server 22.04.
  • Your menu options may differ if you’re using a different version of CBSD.
  • We will configure the VM manually through the UI. A later post will show how to configure from a template file instead.

Configure the VM

Run cbsd bconstruct-tui to start the VM configuration.

Screenshot of a menu to cover a VM in CBSD. The available options include OS type, hostname, and network options
This menu shows my configuration. You may want to tweak `jname` (the VM's identifying name), `host_hostname`, or network options.

We also want to set up our VNC endpoint so we can connect to the VM after it boots.

Navigate to the bhyve_vnc_options option and press enter to bring up the sub-menu.

Screenshot of the bconstruct-tui sub-menu for configuring the VNC endpoint
VNC configuration sub-menu

VNC options:

  • If you connect to your hypervisor via SSH, you want to change the bind IP (bhyve_vnc_tcp_bind) to that host’s IP address. You can also set it to to bind it to all the network interfaces on the host hypervisor.
  • If the vm_vnc_port is set to 0, a random port number will be assigned. We’ll set it here to 5901. Be careful of port collisions if you have more than one VM on the host. They each need a unique VNC port.
  • Be sure to set the password!
  • Select Save when done to go back to the main menu.

Once you’ve finished the configuration, select Ok in the main menu. You will then be asked if you want to create the vm immediately. We’ll select yes here.

Start the VM

Our VM still hasn’t started running, but CBSD has created its configuration. We can start the VM by running one more command.

cbsd bstart mylinuxvm

The first time you start an image with a specific operating system, you will need to wait as the image is pulled from the internet, which can take take several minutes or more, depending on the speed of your internet connection. CBSD will try to find the fastest mirror for you. Once the image for a specific Linux version has been downloaded, though, you can re-use it for more VMs with the same version, which will speed up the process greatly.

[root@nucklehead ~]# cbsd bstart mylinuxvm
init_systap: waiting for link: em0
Looks like /usr/cbsd/vm/mylinuxvm/dsk1.vhd is empty.
May be you want to boot from CD?
[yes(1) or no(0)]
Temporary boot device: cd
vm_iso_path: iso-Ubuntu-Server-22.04-amd64
No such media: /usr/cbsd/src/iso/cbsd-iso-ubuntu-22.04-live-server-amd64.iso in /usr/cbsd/src/iso
Shall i download it from: ?
[yes(1) or no(0)]
Download to: /usr/cbsd/src/iso/cbsd-iso-ubuntu-22.04-live-server-amd64.iso
Scanning for fastest mirror...
             Mirror source:                       bytes/sec:
 * [ 1/17  ]          0
 * [ 2/17  ]   failed (
 * [ 3/17  ]        failed (
 * [ 4/17  ]       failed (
 * [ 5/17  ]         failed (
 * [ 6/17  ]        failed (
 * [ 7/17  ]           failed (
 * [ 8/17  ]          failed (
 * [ 9/17  ]   failed (
 * [ 10/17 ]            failed (
 * [ 11/17 ]       failed (
 * [ 12/17 ]     593920
 * [ 13/17 ]     643072
 * [ 14/17 ]       0
 * [ 15/17 ]          0
 * [ 16/17 ]         0
 * [ 17/17 ] 8125098
retrieve ubuntu-22.04-live-server-amd64.iso from, size: 1g
/usr/cbsd/src/iso/cbsd-iso-ubuntu-22.04-live-s        1398 MB   10 MBps 02m08s
Checking CRC sum: 84aeaf7823c8c61baa0ae862d0a06b03409394800000b3235854a6b38eb4856f...Passed
Automatically register iso as: cbsd-iso-ubuntu-22.04-live-server-amd64.iso
Path already exist for: iso-Ubuntu-Server-22.04-amd64
VRDP is enabled. VNC bind/port:
For attach VM console, use: vncviewer
Resolution: 1024x768.
VNC pass: vncpass

Warning!!! You are running a system with open VNC port to the world wich is not secure
Please use IP filter or balancer with password to restrict VNC port access
Or change vnc_bind params to and reboot VM after maintenance work

bhyve renice: 1
Waiting for PID.
PID: 75699
bstart done in 4 minutes and 16 seconds
[root@nucklehead ~]#

We can check the status of our vm:

cbsd bls mylinuxvm

[root@nucklehead ~]# cbsd bls mylinuxvm
mylinuxvm  75699  2048    0          2        0     linux       DHCP      On

Once it starts, we can open our VNC client. For the VNC server, you need to enter the IP address of your FreeBSD host and the port that you assigned during configuration, e.g.

Install Ubuntu

A window should open showing the the Linux boot. Depending on how long it takes you to connect, you may see the grub boot menu or the Ubuntu installer may have already started. Go through the installation process.

Screenshot of a VNC client showing the console of a booting Linux server
Success! We're booting!

Screenshot of Ubuntu text installer completing the installation process
And installing!

Rebooting will usually close the VNC client, forcing reconnection. The host should boot to console, allowing you to log in with the username and password you chose during installation.

Screenshot of a VNC client showing a Linux console at the text login prompt!

Clean up

Once you’re done with the VM, you can run the following to stop and free the resources.

# Stop the VM
cbsd bstop jname=mylinuxvm
# Delete the VM configuration and ZFS volume
cbsd bdestroy jname=mylinuxvm
  • CBSD added some configuration options to the files to /etc/rc.conf and /boot/loader.conf that you will want to remove.

You can reboot your system to clear the following two changes, or manually revert them. Leaving them in place until the next reboot is probably harmless, though.

  • Unload the kernel modules you added via kldload above
  • Remove the VM’s network interfaces, probably named bridge1 and tap1, depending how many VMs you created. You can remove these with the command for each interface. (DO NOT try to destroy any other interfaces! Leave lo0 and em0 alone!)
    ifconfig tap1 down
    ifconfig tap1 destroy

And that’s it! Now you know how to create a basic Linux VM on FreeBSD bhyve!

If you have questions or comments, you can @ me on Twitter.