FreeBSD Virtual Machines on Microsoft Hyper-v

Hyper-V supports both emulated and Hyper-V-specific devices for FreeBSD virtual machines. When running with emulated devices, no additional software is required to be installed. However emulated devices do not provide high performance and cannot leverage the rich virtual machine management infrastructure that the Hyper-V technology offers. In order to make full use of all benefits that Hyper-V provides, it is best to use Hyper-V-specific devices for FreeBSD. The collection of drivers that are required to run Hyper-V-specific devices are known as FreeBSD Integration Services (BIS).

It contains the installable BIS drivers and corresponding daemons for FreeBSD virtual machines.

For newer FreeBSD releases, BIS is built in to the FreeBSD operating system, and no separate download or installation is required except for a Hyper-V KVP (Key-Value Pair) ports download that is needed for FreeBSD 10.0.

BIS provide Core, Networking, Storage, Memory, Video and other functionalities. For feature availability in each FreeBSD version, it is published here:

https://technet.microsoft.com/en-us/library/dn848318.aspx.

And it will be updated for upcoming FreeBSD releases. You also could learn best practices for running FreeBSD on Hyper-v and get detailed feature description.

• Hyper-V drivers are included since FreeBSD 10.0
• Ports were available for unsupported FreeBSD 8.4, 9.1~9.3 and 10.0 (KVP) releases.

FreeBSD 10.1 and 10.2 users should refer to the below 2 errata to update the kernels. FreeBSD 10.3 has included the fixes.

• “Hyper-V KVP (Key-Value Pair) daemon indefinite sleep (When FreeBSD 10.1 and 10.2 virtual machines run on Hyper-V, the host may not get the expected response of a KVP query. When such a virtual machine runs on Azure, the host may try to recover the “irresponsive” virtual machine by killing it and starting it later, causing unnecessary virtual machine downtime.)”:

https://www.freebsd.org/security/advisories/FreeBSD-EN-16:04.hyperv.asc (This applies to FreeBSD 10.1 and 10.2. )

• “hv_netvsc(4) incorrect TCP/IP checksums(If the guest running on Hyper-V is configured as a gateway, the host will silently drop certain packets from the guest.)”:

https://www.freebsd.org/security/advisories/FreeBSD-EN-16:05.hv_netvsc.asc (This applies to FreeBSD 10.2.)

FreeBSD 11 users should refer to the below 1 errata to update the kernels.

• “There are some compatibility issues with the FreeBSD Hyper-V driver, which will cause the OS disk to be detached if August 2016 update rollup is applied on Windows host (KB3172614 or KB3179574).”

https://www.freebsd.org/security/advisories/FreeBSD-EN-17%3A03.hyperv.asc

Jails may not be able to properly access the network unless “Enable MAC address Spoofing” is enabled in the virtual machine's network adapter. This can be enabled by accessing the VM in question's settings and then expanding the desired network adapter's “Advanced Features” area and checking the box to enable MAC address spoofing. This issue affects both Shared IP and VIMAGE/VNET jails.

1. During startup, device nodes are created as new devices are discovered. This can mean that device names can change when new devices are added. If you get a ROOT MOUNT ERROR during startup, you should create labels for each IDE partition to avoid conflicts and changes. As for how, refer to https://www.freebsd.org/doc/handbook/geom-glabel.html.

1. If the virtual switch on the host is based on wireless network adapter, reduce the ARP expiration time to 60 seconds by “sysctl net.link.ether.inet.max_age=60”. Otherwise the networking of the VM may stop working after a while.

1. How to connect to Virtual Machine on Hyper-V through virtual serial? For Generation 1 Virtual Machine, it is straightforward to add hardware – COM. For Generation 2 Virtual Machine, follow below steps.

1. On the host, run below PowerShell command Set-VMComPort to add a virtual serial for the VM. Please run PowerShell as administrator.

Set-VMComPort -VMName <vm_name> -number 1 -path \\.\pipe\Testpipe

1. Enable the serial in the VM. Below is the example of FreeBSD VM.

echo 'console="comconsole"' >> /boot/loader.conf

1. Use putty to connect to the named pipe which is \\.\pipe\Testpipe in above example.

• Microsoft announces Hyper-V support for FreeBSD, August 9, 2012
• FreeBSD Testimonials from Microsoft, December, 2015

• freebsd-virtualization@freebsd.org

• FreeBSD Integration Services Team, bsdic@microsoft.com
• FreeBSD Virtual Machines on Hyper-v Tech Forum

• Hyper-V information on Wikipedia
• FreeBSD Virtual Machines on Hyper-v
• Create and Upload a FreeBSD VHD to Microsoft Azure
• FreeBSD 11.3 on the Azure Marketplace
• FreeBSD 12.1 on the Azure Marketplace
• Introduction to FreeBSD on Azure
• Connect to Virtual Machine on Hyper-V through Virtual Serial - Generation 2