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Manual Pages  — BHYVE


bhyve – run a guest operating system inside a virtual machine



bhyve [-abehuwxACHPSWY] [-c numcpus] [-g gdbport] [-l lpcdev[,conf]] [-m memsize[K|k|M|m|G|g|T|t]] [-p vcpu:hostcpu] [-s 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.

If not using a boot ROM, the guest operating system must be loaded with bhyveload(8) or a similar boot loader before running bhyve, otherwise, it is enough to run bhyve with a boot ROM of choice.

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.
  Generate ACPI tables. Required for FreeBSD Ns /amd64 guests.
  Enable a low-level console device supported by FreeBSD kernels compiled with device bvmconsole . This option will be deprecated in a future version.
-c numcpus
  Number of guest virtual CPUs. The default is 1 and the maximum is 16.
  Include guest memory in core file.
  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.
-g gdbport
  For FreeBSD kernels compiled with device bvmdebug, allow a remote kernel kgdb to be relayed to the guest kernel gdb stub via a local IPv4 address and this port. This option will be deprecated in a future version.
  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.
-l lpcdev[,conf]
  Allow devices behind the LPC PCI-ISA bridge to be configured. The only supported devices are the TTY-class devices com1 and com2 and the boot ROM device bootrom.
-m memsize[K|k|M|m|G|g|T|t]
  Guest physical memory size in bytes. This must be the same size that was given to bhyveload(8).

The size argument may be suffixed with one of K, M, G or T (either upper or lower case) to indicate a multiple of kilobytes, megabytes, gigabytes, or terabytes. If no suffix is given, the value is assumed to be in megabytes.

memsize defaults to 256M.

-p vcpu:hostcpu
  Pin guest's virtual CPU vcpu to hostcpu.
  Force the guest virtual CPU to exit when a PAUSE instruction is detected.
-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.

slot 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.

hostbridge |amd_hostbridge

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.
  Virtio network interface.
  Virtio block storage interface.
  Virtio RNG 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 AHCI controller attached to arbitrary devices.
  AHCI controller attached to an ATAPI CD/DVD.
  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 and COM2 16550 serial ports and a boot ROM. The LPC bridge emulation can only be configured on bus 0.
fbuf Raw framebuffer device attached to VNC server.
xhci eXtensible Host Controller Interface (xHCI) USB 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.

Network devices:


If mac is not specified, the MAC address is derived from a fixed OUI and the remaining bytes from an MD5 hash of the slot and function numbers and the device name.

The MAC address is an ASCII string in ethers(5) format.

Block storage devices:
/filename[,block-device-options ]
/dev/xxx[,block-device-options ]

The block-device-options are:
  Open the file with O_DIRECT.
direct Open the file using O_SYNC.
ro Force the file to be opened read-only.
sectorsize=logical[/physical ]
  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.

TTY devices:
stdio 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 at the selector described by slot, bus, and function numbers.

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

The host device must have been reserved at boot-time using the pptdev loader variable as described in vmm(4).

Virtio console devices:
port1= /path/to/port1.sock,anotherport= ...
  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:
[rfb=[IP: ]port ][,w=width ][,h=height ][,vga=vgaconf ][,wait ][,password=password ]
  An IP address and a port VNC should listen on. The default is to listen on localhost IPv4 address and default VNC port 5900. Listening on an IPv6 address is not supported.
width and 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.

Please refer to the bhyve FreeBSD wiki page (Lk https://wiki.freebsd.org/bhyve) for configuration notes of particular guests.

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 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:
tablet A USB tablet device which provides precise cursor synchronization when using VNC.
  Wire guest memory.
  RTC keeps UTC time.
-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 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. This should be the same as that created by bhyveload(8).


bhyve deals with the following signals:

  Trigger ACPI poweroff for a VM


Exit status indicates how the VM was terminated:

0 rebooted
1 powered off
2 halted
3 triple fault


If not using a boot ROM, the guest operating system must have been loaded with bhyveload(8) or a similar boot loader before bhyve(4) can be run. Otherwise, the boot loader is not needed.

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, one of which has a MAC address specified:

bhyve -s 0,hostbridge -s 1,lpc -s 2:0,virtio-net,tap0 \
  -s 2:1,virtio-net,tap1 \
  -s 2:2,virtio-net,tap2,mac=00:be:fa:76:45:00 \
  -s 3,virtio-blk,/my/image -l com1,stdio \
  -A -H -P -m 24G bigvm

Run an 8GB quad-CPU virtual machine with 8 AHCI SATA disks, an AHCI ATAPI CD-ROM, a single virtio network port, an AMD hostbridge, and the console port connected to an nmdm(4) null-modem device.

bhyve -c 4 \
  -s 0,amd_hostbridge -s 1,lpc \
  -s 1:0,ahci,hd:/images/disk.1,hd:/images/disk.2,\
cd:/images/install.iso \
  -s 3,virtio-net,tap0 \
  -l com1,/dev/nmdm0A \
  -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,ahci-hd,disk.img \
  -s 5,virtio-net,tap0 \
  -s 29,fbuf,tcp=,w=800,h=600,wait \
  -s 30,xhci,tablet \
  -s 31,lpc -l com1,stdio \
  -l bootrom,/usr/local/share/uefi-firmware/BHYVE_UEFI.fd \


bhyve(4), nmdm(4), vmm(4), ethers(5), bhyvectl(8), bhyveload(8)


bhyve first appeared in FreeBSD 10.0 .


Neel Natu <Mt neel@freebsd.org> Peter Grehan <Mt grehan@freebsd.org>

BHYVE (8) June 2, 2017

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