BHYVE(1M) Maintenance Commands BHYVE(1M)

run a guest operating system inside a virtual machine

bhyve [-aCDdeHhPSuWwxY] [-c  [[cpus=]numcpus][,sockets=n][,cores=n][,threads=n]] [-G port] [-B type,[key=value][,key=value]...] [-k file] [-l help|lpcdev [,conf]] [-m memsize[K|k|M|m|G|g|T|t]] [-o var=value] [-r file] [-s help|slot , emulation[,conf]] [-U uuid] vmname

bhyve is a hypervisor that runs guest operating systems inside a virtual machine.

Parameters such as the number of virtual CPUs, amount of guest memory, and I/O connectivity can be specified with command-line parameters.

bhyve runs until the guest operating system reboots or an unhandled hypervisor exit is detected.

The guest's local APIC is configured in xAPIC mode. The xAPIC mode is the default setting so this option is redundant. It will be deprecated in a future version.
Configure smbios data. type must be set to 1. Supported keys are: manufacturer, product, version, serial, sku, family and uuid.
Number of guest virtual CPUs and/or the CPU topology. The default value for each of numcpus, sockets, cores, and threads is 1. The current maximum number of guest virtual CPUs is 32. If numcpus is not specified then it will be calculated from the other arguments. The topology must be consistent in that the numcpus must equal the product of sockets, cores, and threads. If a setting is specified more than once the last one has precedence.
Include guest memory in core file.
Suspend CPUs at boot.
Destroy the VM on guest initiated power-off.
Force bhyve to exit when a guest issues an access to an I/O port that is not emulated. This is intended for debug purposes.
Start a debug server that uses the GDB protocol to export guest state to a debugger. An IPv4 TCP socket will be bound to the supplied port to listen for debugger connections. Only a single debugger may be attached to the debug server at a time. If port begins with ‘w’, bhyve will pause execution at the first instruction waiting for a debugger to attach.
Print help message and exit.
Yield the virtual CPU thread when a HLT instruction is detected. If this option is not specified, virtual CPUs will use 100% of a host CPU.
Set configuration variables from a simple, key-value config file. Each line of the config file is expected to consist of a config variable name, an equals sign (‘=’), and a value. No spaces are permitted between the variable name, equals sign, or value. Blank lines and lines starting with ‘#’ are ignored.
Allow devices behind the LPC PCI-ISA bridge to be configured. The only supported devices are the TTY-class devices com1 through com4, the boot ROM device bootrom, and the debug/test device pc-testdev.

help print a list of supported LPC devices.

Guest physical memory size. The size argument may be suffixed with one of K, M, G or T (either upper or lower case) to indicate a multiple of kibibytes, mebibytes, gibibytes, or tebibytes. If no suffix is given, the value is assumed to be in mebibytes.

memsize defaults to 256MiB.

Set the configuration variable var to value.
Force the guest virtual CPU to exit when a PAUSE instruction is detected.
Configure a virtual PCI slot and function.

bhyve provides PCI bus emulation and virtual devices that can be attached to slots on the bus. There are 32 available slots, with the option of providing up to 8 functions per slot.

print a list of supported PCI devices.
pcislot[:function] bus:pcislot:function

The pcislot value is 0 to 31. The optional function value is 0 to 7. The optional bus value is 0 to 255. If not specified, the function value defaults to 0. If not specified, the bus value defaults to 0.


Provide a simple host bridge. This is usually configured at slot 0, and is required by most guest operating systems. The amd_hostbridge emulation is identical but uses a PCI vendor ID of AMD.

PCI pass-through device.
Accelerated Virtio network interface.
Legacy Virtio network interface.
Virtio block storage interface.
Virtio 9p (VirtFS) interface.
Virtio random number generator interface.
Virtio console interface, which exposes multiple ports to the guest in the form of simple char devices for simple IO between the guest and host userspaces.
AHCI controller attached to arbitrary devices.
AHCI controller attached to an ATAPI CD/DVD.
AHCI controller attached to a SATA hard-drive.
Intel e82545 network interface.
PCI 16550 serial device.
LPC PCI-ISA bridge with COM1 to COM4 16550 serial ports, a boot ROM, and, optionally, the debug/test device. The LPC bridge emulation can only be configured on bus 0.
Raw framebuffer device attached to VNC server.
eXtensible Host Controller Interface (xHCI) USB controller.
NVM Express (NVMe) controller.
This optional parameter describes the backend for device emulations. If conf is not specified, the device emulation has no backend and can be considered unconnected.

Host Bridge Devices

Specify a hostbridge model to emulate. Valid model strings, and their associated vendor and device IDs are: amd (0x1022/0x7432), netapp (0x1275/0x1275), i440fx (0x8086/0x1237) and q35 (0x8086/0x29b0). The default value of model is netapp.
PCI vendor ID.
PCI device ID.

Providing extra configuration parameters for a host bridge is optional, but if parameters are provided then either model by itself, or both of vendor and devid must be specified.

Accelerated Virtio Network Backends:


vnic is the name of a configured virtual NIC on the system. mask is applied to the virtio feature flags which are advertised to the guest. Bits set in the mask value are removed from the advertised features.

Other Network Backends:


vnic is the name of a configured virtual NIC on the system.

The network-backend-options are:

Enable promiscuous mode at the physical level (default: false)
Enable promiscuous mode at the SAP level (default: true)
Enable promiscuous mode for all multicast addresses (default: true)
The selected promiscuous modes are only enabled for received traffic (default: true).

Block storage devices:


The block-device-options are:

Open the file with O_DIRECT.
Open the file using O_SYNC.
Force the file to be opened read-only.
Specify the logical and physical sector sizes of the emulated disk. The physical sector size is optional and is equal to the logical sector size if not explicitly specified.
Disable emulation of guest trim requests via DIOCGDELETE requests.

9P devices:


The 9p-device-options are:

Expose the share in read-only mode.

TTY devices:

Connect the serial port to the standard input and output of the bhyve process.
Use the host TTY device for serial port I/O.

Boot ROM device:

Map romfile in the guest address space reserved for boot firmware.

Pass-through devices:

Connect to a PCI device on the host identified by the specificed path.

Guest memory must be wired using the -S option when a pass-through device is configured.

The host device must have been previously attached to the ppt driver.

Virtio console devices:

A maximum of 16 ports per device can be created. Every port is named and corresponds to a UNIX domain socket created by bhyve. bhyve accepts at most one connection per port at a time.


  • Due to lack of destructors in bhyve, sockets on the filesystem must be cleaned up manually after bhyve exits.
  • There is no way to use the "console port" feature, nor the console port resize at present.
  • Emergency write is advertised, but no-op at present.

Framebuffer devices:

The path to a UNIX socket which will be created and where bhyve will accept VNC connections.
=IPv4:port or [IPv6%zone]:port
An IP address and a port VNC should listen on. The default is to listen on localhost IPv4 address and default VNC port 5900. An IPv6 address must be enclosed in square brackets and may contain an optional zone identifier.
=width and h=height
A display resolution, width and height, respectively. If not specified, a default resolution of 1024x768 pixels will be used. Minimal supported resolution is 640x480 pixels, and maximum is 1920x1200 pixels.
Possible values for this option are “io” (default), “on” , and “off”. PCI graphics cards have a dual personality in that they are standard PCI devices with BAR addressing, but may also implicitly decode legacy VGA I/O space (0x3c0-3df) and memory space (64KB at 0xA0000). The default “io” option should be used for guests that attempt to issue BIOS calls which result in I/O port queries, and fail to boot if I/O decode is disabled.

The “on” option should be used along with the CSM BIOS capability in UEFI to boot traditional BIOS guests that require the legacy VGA I/O and memory regions to be available.

The “off” option should be used for the UEFI guests that assume that VGA adapter is present if they detect the I/O ports. An example of such a guest is OpenBSD in UEFI mode.

Instruct bhyve to only boot upon the initiation of a VNC connection, simplifying the installation of operating systems that require immediate keyboard input. This can be removed for post-installation use.
This type of authentication is known to be cryptographically weak and is not intended for use on untrusted networks. Many implementations will want to use stronger security, such as running the session over an encrypted channel provided by IPsec or SSH.

xHCI USB devices:

A USB tablet device which provides precise cursor synchronization when using VNC.

NVMe devices:

Accepted device paths are: /dev/blockdev or /path/to/image or ram=size_in_MiB.
Max number of queues.
Max elements in each queue.
Max number of concurrent I/O requests.
Sector size (defaults to blockif sector size).
Serial number with maximum 20 characters.

AHCI devices:

Nominal Media Rotation Rate, known as RPM. value 1 will indicate device as Solid State Disk. default value is 0, not report.
Serial Number with maximum 20 characters.
Revision Number with maximum 8 characters.
Model Number with maximum 40 characters.
Wire guest memory.
RTC keeps UTC time.
Set the universally unique identifier (UUID) in the guest's System Management BIOS System Information structure. By default a UUID is generated from the host's hostname and vmname.
Ignore accesses to unimplemented Model Specific Registers (MSRs). This is intended for debug purposes.
Force virtio PCI device emulations to use MSI interrupts instead of MSI-X interrupts.
The guest's local APIC is configured in x2APIC mode.
Disable MPtable generation.
Alphanumeric name of the guest.

bhyve uses an internal tree of configuration variables to describe global and per-device settings. When bhyve starts, it parses command line options (including config files) in the order given on the command line. Each command line option sets one or more configuration variables. For example, the -s option creates a new tree node for a PCI device and sets one or more variables under that node including the device model and device model-specific variables. Variables may be set multiple times during this parsing stage with the final value overriding previous values.

Once all of the command line options have been processed, the configuration values are frozen. bhyve then uses the value of configuration values to initialize device models and global settings.

More details on configuration variables can be found in bhyve_config(4).

bhyve deals with the following signals:

Trigger ACPI poweroff for a VM

Exit status indicates how the VM was terminated:

powered off
triple fault
exited due to an error

To run a virtual machine with 1GB of memory, two virtual CPUs, a virtio block device backed by the /my/image filesystem image, and a serial port for the console:
bhyve -c 2 -s 0,hostbridge -s 1,lpc -s 2,virtio-blk,/my/image \
  -l com1,stdio -A -H -P -m 1G vm1

Run a 24GB single-CPU virtual machine with three network ports.

bhyve -s 0,hostbridge -s 1,lpc -s 2:0,virtio-net-viona,vmvnic0 \
  -s 2:1,virtio-net-viona,vmvnic1 -s 2:2,virtio-net-viona,vmvnic2 \
  -s 3,virtio-blk,/my/image -l com1,stdio \
  -A -H -P -m 24G bigvm

Run an 8GB virtual machine with 2 quad core CPUs, 2 NVMe disks and one other disk attached as a Virtio block device, an AHCI ATAPI CD-ROM, a single viona network port, an i440fx hostbridge, and the console port connected to a socket.

bhyve -c sockets=2,cores=4,threads=2 \
  -s 0,hostbridge,model=i440fx -s 1,lpc \
  -s 1:0,nvme,/dev/zvol/rdsk/tank/hdd0 \
  -s 1:1,nvme,/dev/zvol/rdsk/tank/hdd1 \
  -s 1:2,virtio-blk,/dev/zvol/rdsk/tank/hdd1 \
  -s 2:0,ahci,cd:/images/install.iso \
  -s 3,virtio-net-viona,vnic=vmvnic0 \
  -l com1,socket,/tmp/vm.com1,wait \
  -A -H -P -m 8G

Run a UEFI virtual machine with a display resolution of 800 by 600 pixels that can be accessed via VNC at:

bhyve -c 2 -m 4G -w -H \
  -s 0,hostbridge \
  -s 3,ahci-cd,/path/to/uefi-OS-install.iso \
  -s 4,nvme,/dev/zvol/rdsk/tank/hdd0 \
  -s 5,virtio-net-viona,vnic=vnmic0 \
  -s 29,fbuf,rfb=,w=800,h=600,wait \
  -s 30,xhci,tablet \
  -s 31,lpc -l com1,stdio \
  -l bootrom,/usr/share/bhyve/firmware/BHYVE_UEFI.fd \

bhyvectl(1M), bhyve_config(4),

Intel, 64 and IA-32 Architectures Software Developer’s Manual, Volume 3.

April 20, 2021 OmniOS