bhyve, the BSD Hypervisor

bhyve is a hypervisor/virtual machine manager for FreeBSD that was introduced in FreeBSD 10.0

bhyve Frequently Asked Questions

General Questions

Q: What hardware does it run on?

A: bhyve supports Intel processors with Extended Page Tables. Processor EPT compatibility can be determined at but most Atom C2000, Core i3, i5, i7 and related Xeon processors are supported. Presence of the "POPCNT" (POPulation Count) processor feature in dmesg(8) indicates EPT support.

AMD RVI (Rapid Virtualization Indexing, formerly Nested Page Tables) was merged into FreeBSD CURRENT on October 21st, 2014 with SVN release tag r273375

"Barcelona" class and newer AMD processors include the required RVI extension and as with Intel processors, presence of the "POPCNT" (POPulation Count) processor feature in dmesg(8) indicates RVI support. Note some processors such as Kuma core have POPCNT feature but lacks required "NRIPS" (Next RIP Save) feature.

Q: Does bhyve support ARM A15/v8 virtualization extensions?

A: Not yet but a GSoC project exists to add this.

Q: What versions of FreeBSD does bhvye support as a host?

A: bhyve is included in FreeBSD/amd64 10.0-RELEASE amd64, with development being done in CURRENT.

Q: Could bhyve be ported to other operating systems?

Yes. See the xhyve, Pluribus Netvisor efforts.

Q: Does bhyve support i386 VMs?

A: Yes, as of February 5th, 2014: r261504

Q: What VM operating systems does bhyve support?

A: bhyve supports any version of FreeBSD i386/amd64 with VirtIO support. OpenBSD, NetBSD and GNU/Linux are supported using the using the sysutils/grub2-bhyve port. UEFI support is available for FreeBSD, GNU/Linux, SmartOS and Windows:

Tested GNU/Linux distributions include:

See the grub2-bhyve page for detailed sysutils/grub2-bhyve instructions and for best results use FreeBSD CURRENT with the -w bhyve flag.

Q: What does bhyve "look" like?

To load a FreeBSD kernel from disk image vm0.img with 256M RAM and the name vm0:

/usr/sbin/bhyveload -m 256 -d ./vm0.img vm0

This will show the FreeBSD loader screen and you should see the device /dev/vmm/vm0

To boot the VM with 2 vCPUs, the same 256M RAM and the tap0 network interface:

/usr/sbin/bhyve -c 2 -m 256 -A -H -P \
-s 0:0,hostbridge \
-s 1:0,virtio-net,tap0 \
-s 2:0,ahci-hd,./vm0.img \
-s 31,lpc -l com1,stdio \

After the VM has been shutdown, its resources can be reclaimed with:

/usr/sbin/bhyvectl --destroy --vm=vm0

Q: What is the easiest way to try bhyve?

The included method booting FreeBSD virtual machines is the /usr/share/examples/bhyve/ script:


unxz FreeBSD-11.0-CURRENT-amd64.raw.xz

sudo sh /usr/share/examples/bhyve/ -d FreeBSD-11.0-CURRENT-amd64.raw vm0

Q: How do I configure bhyve and install a VM operating system?

A: Begin with the FreeBSD Handbook chapter and manual page.

Q: What is the string I need to add to "/etc/ttys" for older versions of FreeBSD?"

ttyu0 "/usr/libexec/getty 3wire.9600"   vt100   on secure

Q: Is this requirement scheduled to go away?

Yes. The r260913 patches lay the groundwork for auto-enabling the serial console and FreeBSD 9.3, 10.1 and 11-CURRENT all include the permanent fix. The same goes for the snapshot VM-IMAGES.

Q: Does libvirt support bhyve?

A: Yes

Q: Are there other frameworks for bhyve?

A: There is vmrc among others, a search of Github will reveal several.

Q: Can I run multiple bhyve hosts under VMware nested VT-x EPT?

A: Yes, but you must enable it: look for the GUI or vhv.allow or vhv.enable options, depending on your version of VMware. VMware Fusion: Processors & Memory: Advanced options: Enable hypervisor applications in this virtual machine

Confirmed with VMware Workstation, VMware Player, VMware Fusion and ESXi. Note that you must stop all running VMs before you can enable EPT pass-through.

Q: Can I run multiple bhyve hosts under Linux KVM with nested VT-x EPT?

A: Maybe. You must enable it and note the known limitations. Please let us know if you are successful.

Q: Can I run bhyve and VirtualBox on FreeBSD at the same time?

A: No. See this thread for more information.

Q: Does VirtualBox support nested VT-x EPT?

A: No.

Q: Does Hyper-V support nested VT-x EPT?

A: No.

Q: Does bhyve support nested VT-x EPT (bhyve under bhyve)?

A: Not yet. This is being investigated.

Q: Does Debian GNU/kFreeBSD support bhyve?

A: Good question!

Q: Can I use disk images from VirtualBox or other virtualization platforms on bhyve?

A: bhyve does not currently support reading foreign disk image formats directly, so one will have to convert existing disk images to a raw image using qemu-img. This can be accomplished by doing the following on a FreeBSD system:

$ pkg install qemu-devel
$ qemu-img convert -f vmdk -O raw virtual_box_image.vmdk bhyve_raw_image.img

VMDK, QCOW, QCOW2, VDI and more images can be converted to raw images using the qemu-img utility in the qemu-devel port.

Q: Is it "bhyve", "BHyVe" or BHyve?

A: The developers mercifully retired "BHyVe" and simply refer to it as "bhyve", after the utility.

Q: When was bhyve first released?

bhyve was officially released on January 20th, 2014 as part of FreeBSD 10.0.

Technical Questions

Q: What comprises bhyve?

A: The vmm.ko loadable kernel module, the libvmmapi library, the bhyve, bhyveload and bhyvectl utilities.

In total these binaries are under 500K in size.

Q: Does bhyve have any dependencies?

A: The bhyve kernel module requires CPU EPT support and bhyve VMs uses the VirtIO (MSI and MSI-X) set of devices for virtualized storage and network devices. The FreeBSD GENERIC kernel has included VirtIO drivers beginning with the 8.4, 9.2 and 10.0 amd64 releases and their equivalent STABLE branches.

Q: Does bhyve support VT-d PCI device pass-through?

A: Yes, on Intel CPUs. See

Q: Does bhyve support AHCI devices?

A: Yes, and they provide non-blocking I/O for higher performance. CD: -s 4,ahci-cd,/path/to/image.iso HD: -s 4,ahci-hd,/path/to/disk.img

Q: What boot media are supported?

A: Raw disk images and any block device such as ZFS zvols and iSCSI targets, plus ISOs using the AHCI driver.

Q: Does bhyve have its own MAC address allocation?

A: Yes, as of commit r258141 on November 14th, 2013, FreeBSD has its own allocation of IEEE Organizationally Unique Identifiers (hex: 58-9C-FC / base16: 589cfc) and bhyve will be allocated a sub-set of these.

Q: Does bhyve have an "out-of-band"/"lights-out management" serial console?

A: Yes, and it can be accessed several ways including as a nmdm nullmodem terminal or a pty. stdio output can also be sent to a terminal multiplexer like tmux or screen. Example nmdm syntax is:

-s 31,lpc -l com1,stdio Becomes: -s 31,lpc -l com1,nmdm0A Before starting the VM, run: kldload nmdm Start the VM but note that it will not display any output when booted. Connect to the serial interface with: cu -l /dev/nmdm0B -s 9600

Notes: A is connected to B nmdmN is a a 32 bit unsigned integer so you have plenty to use. ptys can be created with socat. This functionality is included in the FreeBSD 10.0 release.

Q: Does bhyve have ACPI support?

A: Yes, support for a proper "power down" at shutdown arrived with SVN commit r259826. Full suspend and resume is under development.

Q: Is there any way to determine if an OS is virtualized?

A: Yes, the kern.vm_guest sysctl will report if a FreeBSD guest is under KVM or bhyve.

Q: Where are the sources?

A: The source is in FreeBSD SVN source repository: sys/amd64/vmm/, usr.sbin/bhyve/, usr.sbin/bhyveload/, usr.sbin/bhyvectl/, and lib/libvmmapi/


Q: What will I see if my CPU does not support EPT?

# kldload vmm
vmx_init: processor does not support VMX operation
module_register_init: MOD_LOAD (vmm, 0xffffffff81e17169, 0) error 6

Q: What will I see if EPT is disabled in BIOS?

# sh /usr/share/examples/bhyve/ ...
Launching virtual machine "...
vm_create: Device not configured

Q: What will I see if a VM name is over 31 characters long?

vmcreate: Invalid argument

Q: Why does my system appear to stop booting just after "Starting background file system checks in 60 seconds."?

A: This indicates that your /etc/ttys is not properly configured for serial output for use with bhyve.

Q: Why is my VM only booting once I attach to the "nmdm" device?

A: This is a bug has been fixed with r262884.

Q: Why won't VMs archive with tar?

A: creates disk images using the truncate(1) command and as per the tar(1) manual page, "There is not yet any support for multi-volume archives or for archiving sparse files."

Q: Why can't I network VMs over a wireless host interface?

A: Access points cannot determine the destination VMs and only see the host. Consider a simple pf(4) pf.conf configuration:

nat on wlan0 from bridge0:network to any -> (bridge0)
pass out all
pass in all

Q: Why does mounting my FreeBSD with ZFS on root VM fail with "error 45" when "Mounting from zfs:" ?

A: You are probably attempting to boot an older version of FreeBSD on a zpool that you created with a newer version of FreeBSD and the available ZFS features are not available. A safe set of features to use with FreeBSD 9.2 and 10.0 are:

zpool create -d -o feature@async_destroy=enabled -o feature@empty_bpobj=enabled -o feature@lz4_compress=enabled -o ...

Q: Why does my VM fail with "vm_run error -1, errno 25" ?

A: This can happen if your kernel and world are out of sync.

Q: Are there any debugging options for bhyve?

A: Yes: The gdb interface.

Q: Why can't my nested VMs reach the network?

A: The bottom most hypervisor needs to run the virtual interface in promiscuous mode in order for packets destined for an ethernet address other than that of the first level guest to be received by the virtual interface.

Enabling Promiscuous mode in VMWare ESX

Q: Why can't my VM acquire an address via DHCP?

Q: Why is the host and VM unable to communicate across the network?

Q: Why is the VM and systems on the network unable to communicate with each other?

Q: Why are connections interrupted, seemingly at random?

A: It sounds like you are having more or less random routing issues. If your hosts IP is assigned to a member of a bridge (for example the NIC itself), try moving the IP to the bridge itself instead.

Future Directions

Q: What is needed to support additional VM operating systems?

All operating systems load and boot differently and a simple grub2 "chainload" is not possible. Source availability and modifiability are obviously important when addressing this issue on other operating systems. VirtIO drivers are also important for a meaningful bhyve experience. bhyve supports MSI-X and MSI interrupts although MSI interrupts are not part of the VirtIO specification. We appreciate your research into other operating systems!

Q: Does bhyve support UEFI/BIOS?

A: Yes, as of October 3rd, 2015 and SVN tags r288522 and r288524.

Required components:

FreeBSD HEAD as of SVN tag r288524

UEFI Binaries

Optional UEFI build instructions

Windows unattended build templates

User-provided Windows and valid license keys.

SmartOS 20151001 or newer

Detailed instructions to come.

Q: Could bhyve support VGA graphics?

A: Yes, this is closely related to UEFI/BIOS support.

Q: What is the largest-known bhyve deployment?

A: Over 1,000 nodes with over 7,000 virtual machines.


Q: Is there a mailing list or IRC channel?

A: The most popular places to discuss bhyve are the mailing list and the #bhyve channel on

Q: How can I help?

A: First and foremost, by testing bhyve on your unique hardware and in every configuration you can imagine. There could easily be remaining bugs and it is in everyone's best interests for these to be resolved ASAP.

If you think you have an issue, considering asking about it on IRC. If you know you have an issue, consider posting it on the FreeBSD Virtualization mailing list.

Testing ideas:

Q: How do I report a panic?

A: If your host or VM panics and enters the debugger, the information you provide can be very useful for revealing and reproducing bugs. Typing "bt" at the debugger will produce a backtrace and "show thread" on various hex strings may yield more. Please capture this information and use your best judgement in sending it to the bhyve developers or the freebsd-virtualization mailing list. If in doubt, I am happy to relay reports (address below).

Do consider using the sysutils/panicmail port with bhyve.

bhyve Presentations

bhyvecon Tokyo 2014 Presentations

bhyve Presentations


bhyve (last edited 2016-02-05 16:34:45 by MarieHeleneKvello-Aune)