BHYVE(8)                FreeBSD System Manager's Manual               BHYVE(8)

     bhyve â<“ run a guest operating system inside a virtual machine

     bhyve [-AaCDeHhPSuWwxY]
           [-c  [[cpus=]numcpus][,sockets=n][,cores=n][,threads=n]] [-G port]
           [-l help|lpcdev[,conf]] [-m memsize[K|k|M|m|G|g|T|t]]
           [-p vcpu:hostcpu] [-r file] [-s help|slot,emulation[,conf]]
           [-U uuid] vmname

     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.

     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.

     -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.

     -A          Generate ACPI tables.  Required for FreeBSD/amd64 guests.

     -c [setting ...]
                 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 16.  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.

     -C          Include guest memory in core file.

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

     -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 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 port to listen for debugger connections.
                 Only a single debugger may be attached to the debug server at
                 a time.  If port begins with â<˜wâ<™, bhyve will pause execution
                 at the first instruction waiting for a debugger to attach.

     -h          Print help message and exit.

     -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.

     -l [help|lpcdev[,conf]]
                 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.

     -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.

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

     -r file     Resume a guest from a snapshot.  The guest memory contents
                 are restored from file, and the guest device and vCPU state
                 are restored from the file â<œfile.kernâ<.

                 Note that the current snapshot file format requires that the
                 configuration of devices in the new VM match the VM from
                 which the snapshot was taken by specifying the same [-s] and
                 [-l] options.  The count of vCPUs and memory configuration
                 are read from the snapshot.

     -s [help|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

                 help        print a list of supported PCI devices.

                 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.

                             passthru    PCI pass-through device.

                             virtio-net  Virtio network interface.

                             virtio-blk  Virtio block storage interface.

                                         Virtio SCSI interface.

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

                             virtio-rnd  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

                             ahci-cd     AHCI controller attached to an ATAPI

                             ahci-hd     AHCI controller attached to a SATA

                             e1000       Intel e82545 network interface.

                             uart        PCI 16550 serial device.

                             lpc         LPC PCI-ISA bridge with COM1 and COM2
                                         16550 serial ports, a boot ROM, and,
                                         optionally, the debug/test device.
                                         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.

                             nvme        NVM Express (NVMe) controller.

                             hda         High Definition Audio Controller.

                 [conf]      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 backends:




                                         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.

                                         With virtio-net devices, the mtu
                                         parameter can be specified to inform
                                         the guest about the largest MTU that
                                         should be allowed, expressed in

                                         With netgraph backend, the path and
                                         peerhook parameters must be specified
                                         to set the destination node and
                                         corresponding hook.  The optional
                                         parameters socket and hook may be
                                         used to set the ng_socket(4) node
                                         name and source hook.  The ADDRESS,
                                         HOOK and NAME must comply with
                                         netgraph(4) addressing rules.

                             Block storage devices:



                             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 DIOCGDELETE requests.

                             SCSI devices:


                             The scsi-device-options are:

                             iid=IID     Initiator ID to use when sending
                                         requests to specified CTL port.  The
                                         default value is 0.

                             9P devices:


                             The 9p-device-options are:

                             ro          Expose the share in read-only mode.

                             TTY devices:

                             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:

                             romfile     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 pptdevs loader variable as
                             described in vmm(4).

                             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


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

                                           â<¢<¢   There is no way to use the
                                               "console port" feature, nor the
                                               console port resize at present.

                                           â<¢<¢   Emergency write is advertised,
                                               but no-op at present.

                             Framebuffer devices:


                                         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 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.

                                         vgaconf   Possible values for this
                                                   option are â<œioâ< (default),
                                                   â<œonâ< , and â<œoffâ<.  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 â<œioâ< 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

                                                   The â<œonâ< 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 â<œoffâ< 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
                                                   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.

                                         password  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.

                             NVMe devices:

                             devpath     Accepted device paths are:
                                         /dev/blockdev or /path/to/image or

                             maxq        Max number of queues.

                             qsz         Max elements in each queue.

                             ioslots     Max number of concurrent I/O

                             sectsz      Sector size (defaults to blockif
                                         sector size).

                             ser         Serial number with maximum 20

                             AHCI devices:

                             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

                             rev         Revision Number with maximum 8

                             model       Model Number with maximum 40

                             HD Audio devices:

                             play        Playback device, typically /dev/dsp0.

                             rec         Recording device, typically

     -S          Wire guest memory.

     -u          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

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

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

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

     -Y          Disable MPtable generation.

     vmname      Alphanumeric name of the guest.  This should be the same as
                 that created by bhyveload(8).

     The current debug server provides limited support for debuggers.

     Each virtual CPU is exposed to the debugger as a thread.

     General purpose registers can be queried for each virtual CPU, but other
     registers such as floating-point and system registers cannot be queried.

     Memory (including memory mapped I/O regions) can be read and written by
     the debugger.  Memory operations use virtual addresses that are resolved
     to physical addresses via the current virtual CPU's active address

     The running guest can be interrupted by the debugger at any time (for
     example, by pressing Ctrl-C in the debugger).

     Single stepping is only supported on Intel CPUs supporting the MTRAP VM

     Breakpoints are supported on Intel CPUs that support single stepping.
     Note that continuing from a breakpoint while interrupts are enabled in
     the guest may not work as expected due to timer interrupts firing while
     single stepping over the breakpoint.

     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
     4       exited due to an error

     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 \

     Run a UEFI virtual machine with a VNC display that is bound to all IPv6
     addresses on port 5900.

           bhyve -c 2 -m 4G -w -H \
             -s 0,hostbridge \
             -s 4,ahci-hd,disk.img \
             -s 5,virtio-net,tap0 \
             -s 29,fbuf,tcp=[::]:5900,w=800,h=600 \
             -s 30,xhci,tablet \
             -s 31,lpc -l com1,stdio \
             -l bootrom,/usr/local/share/uefi-firmware/BHYVE_UEFI.fd \

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

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

     bhyve first appeared in FreeBSD 10.0.

     Neel Natu <>
     Peter Grehan <>

FreeBSD 13.0-RELEASE           January 18, 2021           FreeBSD 13.0-RELEASE