BHYVE(8) Maintenance Procedures BHYVE(8)


bhyve - run a guest operating system inside a virtual machine


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


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

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.


-a 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.

-B type,[key=value][,key=value]...
Configure smbios data. type must be set to 1. Supported keys
are: manufacturer, product, version, serial, sku, family and

-c [[cpus=]numcpus][,sockets=n][,cores=n][,threads=n]
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

-C Include guest memory in core file.

-D Destroy the VM on guest initiated power-off.

-d Suspend CPUs at boot.

-e Force bhyve to exit when a guest issues an access to an I/O
port that is not emulated. This is intended for debug

-G [w][bind_address:]port
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 bind_address and port to listen for debugger
connections. Only a single debugger may be attached to the
debug server at a time. If the option begins with `w', bhyve
will pause execution at the first instruction waiting for a
debugger to attach.

-H 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.

-h Print help message and exit.

-k config_file
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.
See bhyve_config(5) for more details.

-l help Print a list of supported LPC devices.

-l lpcdev[,conf]
Allow devices behind the LPC PCI-ISA bridge to be configured.
The only supported devices are the TTY-class devices com1,
com2, com3 and com4, the boot ROM device bootrom, and the
debug/test device pc-testdev.

The possible values for the conf argument are listed in the -s
flag description.

-m memsize[K|k|M|m|G|g|T|t]
Set the 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.

The default is 256MiB.

-o var=value
Set the configuration variable var to value.

-P Force the guest virtual CPU to exit when a PAUSE instruction is

-S Wire guest memory.

-s help Print a list of supported PCI devices.

-s slot,emulation[,conf]
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.

The slot can be specified in one of the following formats:

+o pcislot
+o pcislot:function
+o 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.

The emulation argument can be one of the following:

hostbridge A simple host bridge. This is usually
configured at slot 0, and is required by most
guest operating systems.

amd_hostbridge Emulation identical to hostbridge but using a
PCI vendor ID of AMD.

passthru PCI pass-through device.

Accelerated Virtio network interface.

virtio-net Legacy Virtio network interface.

virtio-blk Virtio block storage interface.

virtio-9p Virtio 9p (VirtFS) interface.

virtio-rnd Virtio random number generator interface.

virtio-console 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 AHCI controller attached to arbitrary devices.

ahci-cd AHCI controller attached to an ATAPI CD/DVD.

ahci-hd AHCI controller attached to a SATA hard drive.

e1000 Intel e82545 network interface.

uart PCI 16550 serial device.

lpc LPC PCI-ISA bridge with COM1, COM2, COM3, and
COM4 16550 serial ports, a boot ROM, and,
optionally, the debug/test device. The LPC
bridge emulation can only be configured on bus

fbuf Raw framebuffer device attached to VNC server.

xhci eXtensible Host Controller Interface (xHCI) USB

nvme NVM Express (NVMe) controller.

The optional parameter conf 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

Other Network Backends:


vnic is the name of a configured virtual NIC on the

The network-backend-options are:

Enable promiscuous mode at the physical level
(default: false)

Enable promiscuous mode at the SAP level (default:

Enable promiscuous mode for all multicast addresses
(default: true)

The selected promiscuous modes are only enabled for
received traffic (default: true).

Block storage device backends:

+o /filename[,block-device-options]

+o /dev/xxx[,block-device-options]

The block-device-options are:

nocache Open the file with O_DIRECT.

direct Open the file using O_SYNC.

ro 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.

nodelete Disable emulation of guest trim requests via

9P device backends:

+o sharename=/path/to/share[,9p-device-options]

The 9p-device-options are:

ro Expose the share in read-only mode.

TTY device backends:

stdio Connect the serial port to the standard input and
output of the bhyve process.

/dev/xxx Use the host TTY device for serial port I/O.

Boot ROM device backends:

Map romfile in the guest address space reserved for
boot firmware. If varfile is provided, that file
is also mapped in the boot firmware guest address
space, and any modifications the guest makes will
be saved to that file.

Pass-through device backends:

/dev/pptN Connect to a PCI device on the host identified by
the specified 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

Virtio console device backends:

+o port1=/path/to/port1.sock[,portN=/path/to/port2.sock ...]

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.


+o Due to lack of destructors in bhyve, sockets on the
filesystem must be cleaned up manually after bhyve exits.

+o There is no way to use the "console port" feature, nor the
console port resize at present.

+o Emergency write is advertised, but no-op at present.

Framebuffer device backends:

+o [rfb=ip-and-port][,w=width][,h=height][,vga=vgaconf][,wait][,password=password]

Configuration options are defined as follows:

rfb=ip-and-port (or tcp=ip-and-port)
An IP address and a port VNC should listen on.
There are two formats:

+o [IPv4:]port
+o [IPv6]:port

The default is to listen on localhost IPv4 address
and default VNC port 5900. An IPv6 address must be
enclosed in square brackets.

unix=path The path to a UNIX socket which will be created and
where bhyve will accept VNC connections.

w=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.

wait 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

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 device backends:

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

NVMe device backends:

+o devpath[,maxq=#][,qsz=#][,ioslots=#][,sectsz=#][,ser=#][,eui64=#][,dsm=opt]

Configuration options are defined as follows:

devpath Accepted device paths are: /dev/blockdev or
/path/to/image or ram=size_in_MiB.

maxq Max number of queues.

qsz Max elements in each queue.

ioslots Max number of concurrent I/O requests.

sectsz Sector size (defaults to blockif sector size).

ser Serial number with maximum 20 characters.

eui64 IEEE Extended Unique Identifier (8 byte value).

dsm DataSet Management support. Supported values are:
auto, enable, and disable.

AHCI device backends:

+o [[hd:|cd:]path][,nmrr=nmrr][,ser=#][,rev=#][,model=#]

Configuration options are defined as follows:

nmrr Nominal Media Rotation Rate, known as RPM. Value 1
will indicate device as Solid State Disk. Default
value is 0, not report.

ser Serial Number with maximum 20 characters.

rev Revision Number with maximum 8 characters.

model Model Number with maximum 40 characters.

-U uuid 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

-u RTC keeps UTC time.

-W Force virtio PCI device emulations to use MSI interrupts
instead of MSI-X interrupts.

-w Ignore accesses to unimplemented Model Specific Registers
(MSRs). This is intended for debug purposes.

-x The guest's local APIC is configured in x2APIC mode.

-Y Disable MPtable generation.

vmname 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(5).


bhyve deals with the following signals:

SIGTERM Trigger ACPI poweroff for a VM


Exit status indicates how the VM was terminated:

0 rebooted
1 powered off
2 halted
3 triple fault
4 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 -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 \
-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 \
-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,vga=off,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 \

Run a UEFI virtual machine with a VARS file to save EFI variables. Note
that bhyve will write guest modifications to the given VARS file. Be sure
to create a per-guest copy of the template VARS file from

bhyve -c 2 -m 4g -w -H \
-s 0,hostbridge \
-s 31,lpc -p com1,stdio \
-l bootrom,/usr/share/bhyve/firmware/BHYVE_UEFI.fd,BHYVE_UEFI_VARS.fd \


bhyve_config(5), bhyvectl(8)

Intel, 64 and IA-32 Architectures Software Developers' Manual, Volume 3.

OmniOS February 26, 2022 OmniOS