Ubuntu Manpage: qemu-doc - QEMU version 2.11.1 User Documentation

Provided by: qemu-system-common_2.11+dfsg-1ubuntu7.42_amd64

NAME

       qemu-doc - QEMU version 2.11.1 User Documentation

SYNOPSIS

       qemu-system-i386 [options] [disk_image]

DESCRIPTION

       The QEMU PC System emulator simulates the following peripherals:

       -   i440FX host PCI bridge and PIIX3 PCI to ISA bridge

       -   Cirrus CLGD 5446 PCI VGA card or dummy VGA card with Bochs VESA extensions (hardware level, including
           all non standard modes).

       -   PS/2 mouse and keyboard

       -   2 PCI IDE interfaces with hard disk and CD-ROM support

       -   Floppy disk

       -   PCI and ISA network adapters

       -   Serial ports

       -   IPMI BMC, either and internal or external one

       -   Creative SoundBlaster 16 sound card

       -   ENSONIQ AudioPCI ES1370 sound card

       -   Intel 82801AA AC97 Audio compatible sound card

       -   Intel HD Audio Controller and HDA codec

       -   Adlib (OPL2) - Yamaha YM3812 compatible chip

       -   Gravis Ultrasound GF1 sound card

       -   CS4231A compatible sound card

       -   PCI UHCI, OHCI, EHCI or XHCI USB controller and a virtual USB-1.1 hub.

       SMP is supported with up to 255 CPUs.

       QEMU uses the PC BIOS from the Seabios project and the Plex86/Bochs LGPL VGA BIOS.

       QEMU uses YM3812 emulation by Tatsuyuki Satoh.

       QEMU uses GUS emulation (GUSEMU32 <http://www.deinmeister.de/gusemu/>) by Tibor "TS" Schütz.

       Note  that,  by  default,  GUS  shares  IRQ(7)  with  parallel ports and so QEMU must be told to not have
       parallel ports to have working GUS.

               qemu-system-i386 dos.img -soundhw gus -parallel none

       Alternatively:

               qemu-system-i386 dos.img -device gus,irq=5

       Or some other unclaimed IRQ.

       CS4231A is the chip used in Windows Sound System and GUSMAX products

OPTIONS

disk_image is a raw hard disk image for IDE hard disk 0. Some targets do not need a disk image.

Standard options

-h Display help and exit

-version
Display version information and exit

-machine [type=]name[,prop=value[,...]]
Select the emulated machine by name. Use "-machine help" to list available machines.

For architectures which aim to support live migration compatibility across releases, each release
will introduce a new versioned machine type. For example, the 2.8.0 release introduced machine types
"pc-i440fx-2.8" and "pc-q35-2.8" for the x86_64/i686 architectures.

To allow live migration of guests from QEMU version 2.8.0, to QEMU version 2.9.0, the 2.9.0 version
must support the "pc-i440fx-2.8" and "pc-q35-2.8" machines too. To allow users live migrating VMs to
skip multiple intermediate releases when upgrading, new releases of QEMU will support machine types
from many previous versions.

Supported machine properties are:

accel=accels1[:accels2[:...]]
This is used to enable an accelerator. Depending on the target architecture, kvm, xen, hax or tcg
can be available. By default, tcg is used. If there is more than one accelerator specified, the
next one is used if the previous one fails to initialize.

kernel_irqchip=on|off
Controls in-kernel irqchip support for the chosen accelerator when available.

gfx_passthru=on|off
Enables IGD GFX passthrough support for the chosen machine when available.

vmport=on|off|auto
Enables emulation of VMWare IO port, for vmmouse etc. auto says to select the value based on
accel. For accel=xen the default is off otherwise the default is on.

kvm_shadow_mem=size
Defines the size of the KVM shadow MMU.

dump-guest-core=on|off
Include guest memory in a core dump. The default is on.

mem-merge=on|off
Enables or disables memory merge support. This feature, when supported by the host, de-duplicates
identical memory pages among VMs instances (enabled by default).

aes-key-wrap=on|off
Enables or disables AES key wrapping support on s390-ccw hosts. This feature controls whether AES
wrapping keys will be created to allow execution of AES cryptographic functions. The default is
on.

dea-key-wrap=on|off
Enables or disables DEA key wrapping support on s390-ccw hosts. This feature controls whether DEA
wrapping keys will be created to allow execution of DEA cryptographic functions. The default is
on.

nvdimm=on|off
Enables or disables NVDIMM support. The default is off.

s390-squash-mcss=on|off
Enables or disables squashing subchannels into the default css. The default is off.

enforce-config-section=on|off
If enforce-config-section is set to on, force migration code to send configuration section even
if the machine-type sets the migration.send-configuration property to off. NOTE: this parameter
is deprecated. Please use -global migration.send-configuration=on|off instead.

-cpu model
Select CPU model ("-cpu help" for list and additional feature selection)

-accel name[,prop=value[,...]]
This is used to enable an accelerator. Depending on the target architecture, kvm, xen, hax or tcg can
be available. By default, tcg is used. If there is more than one accelerator specified, the next one
is used if the previous one fails to initialize.

thread=single|multi
Controls number of TCG threads. When the TCG is multi-threaded there will be one thread per vCPU
therefor taking advantage of additional host cores. The default is to enable multi-threading
where both the back-end and front-ends support it and no incompatible TCG features have been
enabled (e.g. icount/replay).

-smp [cpus=]n[,cores=cores][,threads=threads][,sockets=sockets][,maxcpus=maxcpus]
Simulate an SMP system with n CPUs. On the PC target, up to 255 CPUs are supported. On Sparc32
target, Linux limits the number of usable CPUs to 4. For the PC target, the number of cores per
socket, the number of threads per cores and the total number of sockets can be specified. Missing
values will be computed. If any on the three values is given, the total number of CPUs n can be
omitted. maxcpus specifies the maximum number of hotpluggable CPUs.

-numa node[,mem=size][,cpus=firstcpu[-lastcpu]][,nodeid=node]
-numa node[,memdev=id][,cpus=firstcpu[-lastcpu]][,nodeid=node]
-numa dist,src=source,dst=destination,val=distance
-numa cpu,node-id=node[,socket-id=x][,core-id=y][,thread-id=z]
Define a NUMA node and assign RAM and VCPUs to it. Set the NUMA distance from a source node to a
destination node.

Legacy VCPU assignment uses cpus option where firstcpu and lastcpu are CPU indexes. Each cpus option
represent a contiguous range of CPU indexes (or a single VCPU if lastcpu is omitted). A non-
contiguous set of VCPUs can be represented by providing multiple cpus options. If cpus is omitted on
all nodes, VCPUs are automatically split between them.

For example, the following option assigns VCPUs 0, 1, 2 and 5 to a NUMA node:

-numa node,cpus=0-2,cpus=5

cpu option is a new alternative to cpus option which uses socket-id|core-id|thread-id properties to
assign CPU objects to a node using topology layout properties of CPU. The set of properties is
machine specific, and depends on used machine type/smp options. It could be queried with
hotpluggable-cpus monitor command. node-id property specifies node to which CPU object will be
assigned, it's required for node to be declared with node option before it's used with cpu option.

For example:

-M pc \
-smp 1,sockets=2,maxcpus=2 \
-numa node,nodeid=0 -numa node,nodeid=1 \
-numa cpu,node-id=0,socket-id=0 -numa cpu,node-id=1,socket-id=1

mem assigns a given RAM amount to a node. memdev assigns RAM from a given memory backend device to a
node. If mem and memdev are omitted in all nodes, RAM is split equally between them.

mem and memdev are mutually exclusive. Furthermore, if one node uses memdev, all of them have to use
it.

source and destination are NUMA node IDs. distance is the NUMA distance from source to destination.
The distance from a node to itself is always 10. If any pair of nodes is given a distance, then all
pairs must be given distances. Although, when distances are only given in one direction for each pair
of nodes, then the distances in the opposite directions are assumed to be the same. If, however, an
asymmetrical pair of distances is given for even one node pair, then all node pairs must be provided
distance values for both directions, even when they are symmetrical. When a node is unreachable from
another node, set the pair's distance to 255.

Note that the -numa option doesn't allocate any of the specified resources, it just assigns existing
resources to NUMA nodes. This means that one still has to use the -m, -smp options to allocate RAM
and VCPUs respectively.

-add-fd fd=fd,set=set[,opaque=opaque]
Add a file descriptor to an fd set. Valid options are:

fd=fd
This option defines the file descriptor of which a duplicate is added to fd set. The file
descriptor cannot be stdin, stdout, or stderr.

set=set
This option defines the ID of the fd set to add the file descriptor to.

opaque=opaque
This option defines a free-form string that can be used to describe fd.

You can open an image using pre-opened file descriptors from an fd set:

qemu-system-i386
-add-fd fd=3,set=2,opaque="rdwr:/path/to/file"
-add-fd fd=4,set=2,opaque="rdonly:/path/to/file"
-drive file=/dev/fdset/2,index=0,media=disk

-set group.id.arg=value
Set parameter arg for item id of type group

-global driver.prop=value
-global driver=driver,property=property,value=value
Set default value of driver's property prop to value, e.g.:

qemu-system-i386 -global ide-hd.physical_block_size=4096 disk-image.img

In particular, you can use this to set driver properties for devices which are created automatically
by the machine model. To create a device which is not created automatically and set properties on it,
use -device.

-global driver.prop=value is shorthand for -global driver=driver,property=prop,value=value. The
longhand syntax works even when driver contains a dot.

-boot
[order=drives][,once=drives][,menu=on|off][,splash=sp_name][,splash-time=sp_time][,reboot-timeout=rb_timeout][,strict=on|off]
Specify boot order drives as a string of drive letters. Valid drive letters depend on the target
architecture. The x86 PC uses: a, b (floppy 1 and 2), c (first hard disk), d (first CD-ROM), n-p
(Etherboot from network adapter 1-4), hard disk boot is the default. To apply a particular boot order
only on the first startup, specify it via once. Note that the order or once parameter should not be
used together with the bootindex property of devices, since the firmware implementations normally do
not support both at the same time.

Interactive boot menus/prompts can be enabled via menu=on as far as firmware/BIOS supports them. The
default is non-interactive boot.

A splash picture could be passed to bios, enabling user to show it as logo, when option
splash=sp_name is given and menu=on, If firmware/BIOS supports them. Currently Seabios for X86 system
support it. limitation: The splash file could be a jpeg file or a BMP file in 24 BPP format(true
color). The resolution should be supported by the SVGA mode, so the recommended is 320x240, 640x480,
800x640.

A timeout could be passed to bios, guest will pause for rb_timeout ms when boot failed, then reboot.
If rb_timeout is '-1', guest will not reboot, qemu passes '-1' to bios by default. Currently Seabios
for X86 system support it.

Do strict boot via strict=on as far as firmware/BIOS supports it. This only effects when boot
priority is changed by bootindex options. The default is non-strict boot.

# try to boot from network first, then from hard disk
qemu-system-i386 -boot order=nc
# boot from CD-ROM first, switch back to default order after reboot
qemu-system-i386 -boot once=d
# boot with a splash picture for 5 seconds.
qemu-system-i386 -boot menu=on,splash=/root/boot.bmp,splash-time=5000

Note: The legacy format '-boot drives' is still supported but its use is discouraged as it may be
removed from future versions.

-m [size=]megs[,slots=n,maxmem=size]
Sets guest startup RAM size to megs megabytes. Default is 128 MiB. Optionally, a suffix of "M" or
"G" can be used to signify a value in megabytes or gigabytes respectively. Optional pair slots,
maxmem could be used to set amount of hotpluggable memory slots and maximum amount of memory. Note
that maxmem must be aligned to the page size.

For example, the following command-line sets the guest startup RAM size to 1GB, creates 3 slots to
hotplug additional memory and sets the maximum memory the guest can reach to 4GB:

qemu-system-x86_64 -m 1G,slots=3,maxmem=4G

If slots and maxmem are not specified, memory hotplug won't be enabled and the guest startup RAM will
never increase.

-mem-path path
Allocate guest RAM from a temporarily created file in path.

-mem-prealloc
Preallocate memory when using -mem-path.

-k language
Use keyboard layout language (for example "fr" for French). This option is only needed where it is
not easy to get raw PC keycodes (e.g. on Macs, with some X11 servers or with a VNC or curses
display). You don't normally need to use it on PC/Linux or PC/Windows hosts.

The available layouts are:

ar de-ch es fo fr-ca hu ja mk no pt-br sv
da en-gb et fr fr-ch is lt nl pl ru th
de en-us fi fr-be hr it lv nl-be pt sl tr

The default is "en-us".

-audio-help
Will show the audio subsystem help: list of drivers, tunable parameters.

-soundhw card1[,card2,...] or -soundhw all
Enable audio and selected sound hardware. Use 'help' to print all available sound hardware.

qemu-system-i386 -soundhw sb16,adlib disk.img
qemu-system-i386 -soundhw es1370 disk.img
qemu-system-i386 -soundhw ac97 disk.img
qemu-system-i386 -soundhw hda disk.img
qemu-system-i386 -soundhw all disk.img
qemu-system-i386 -soundhw help

Note that Linux's i810_audio OSS kernel (for AC97) module might require manually specifying clocking.

modprobe i810_audio clocking=48000

-balloon none
Disable balloon device.

-balloon virtio[,addr=addr]
Enable virtio balloon device (default), optionally with PCI address addr.

-device driver[,prop[=value][,...]]
Add device driver. prop=value sets driver properties. Valid properties depend on the driver. To
get help on possible drivers and properties, use "-device help" and "-device driver,help".

Some drivers are:

-device ipmi-bmc-sim,id=id[,slave_addr=val][,sdrfile=file][,furareasize=val][,furdatafile=file]
Add an IPMI BMC. This is a simulation of a hardware management interface processor that normally
sits on a system. It provides a watchdog and the ability to reset and power control the system. You
need to connect this to an IPMI interface to make it useful

The IPMI slave address to use for the BMC. The default is 0x20. This address is the BMC's address
on the I2C network of management controllers. If you don't know what this means, it is safe to
ignore it.

bmc=id
The BMC to connect to, one of ipmi-bmc-sim or ipmi-bmc-extern above.

slave_addr=val
Define slave address to use for the BMC. The default is 0x20.

sdrfile=file
file containing raw Sensor Data Records (SDR) data. The default is none.

fruareasize=val
size of a Field Replaceable Unit (FRU) area. The default is 1024.

frudatafile=file
file containing raw Field Replaceable Unit (FRU) inventory data. The default is none.

-device ipmi-bmc-extern,id=id,chardev=id[,slave_addr=val]
Add a connection to an external IPMI BMC simulator. Instead of locally emulating the BMC like the
above item, instead connect to an external entity that provides the IPMI services.

A connection is made to an external BMC simulator. If you do this, it is strongly recommended that
you use the "reconnect=" chardev option to reconnect to the simulator if the connection is lost.
Note that if this is not used carefully, it can be a security issue, as the interface has the ability
to send resets, NMIs, and power off the VM. It's best if QEMU makes a connection to an external
simulator running on a secure port on localhost, so neither the simulator nor QEMU is exposed to any
outside network.

See the "lanserv/README.vm" file in the OpenIPMI library for more details on the external interface.

-device isa-ipmi-kcs,bmc=id[,ioport=val][,irq=val]
Add a KCS IPMI interafce on the ISA bus. This also adds a corresponding ACPI and SMBIOS entries, if
appropriate.

bmc=id
The BMC to connect to, one of ipmi-bmc-sim or ipmi-bmc-extern above.

ioport=val
Define the I/O address of the interface. The default is 0xca0 for KCS.

irq=val
Define the interrupt to use. The default is 5. To disable interrupts, set this to 0.

-device isa-ipmi-bt,bmc=id[,ioport=val][,irq=val]
Like the KCS interface, but defines a BT interface. The default port is 0xe4 and the default
interrupt is 5.

-name name
Sets the name of the guest. This name will be displayed in the SDL window caption. The name will
also be used for the VNC server. Also optionally set the top visible process name in Linux. Naming
of individual threads can also be enabled on Linux to aid debugging.

-uuid uuid
Set system UUID.

Block device options

-fda file
-fdb file
Use file as floppy disk 0/1 image.

-hda file
-hdb file
-hdc file
-hdd file
Use file as hard disk 0, 1, 2 or 3 image.

-cdrom file
Use file as CD-ROM image (you cannot use -hdc and -cdrom at the same time). You can use the host CD-
ROM by using /dev/cdrom as filename.

-blockdev option[,option[,option[,...]]]
Define a new block driver node. Some of the options apply to all block drivers, other options are
only accepted for a specific block driver. See below for a list of generic options and options for
the most common block drivers.

Options that expect a reference to another node (e.g. "file") can be given in two ways. Either you
specify the node name of an already existing node (file=node-name), or you define a new node inline,
adding options for the referenced node after a dot (file.filename=path,file.aio=native).

A block driver node created with -blockdev can be used for a guest device by specifying its node name
for the "drive" property in a -device argument that defines a block device.

Valid options for any block driver node:
"driver"
Specifies the block driver to use for the given node.

"node-name"
This defines the name of the block driver node by which it will be referenced later. The name
must be unique, i.e. it must not match the name of a different block driver node, or (if you
use -drive as well) the ID of a drive.

If no node name is specified, it is automatically generated. The generated node name is not
intended to be predictable and changes between QEMU invocations. For the top level, an
explicit node name must be specified.

"read-only"
Open the node read-only. Guest write attempts will fail.

"cache.direct"
The host page cache can be avoided with cache.direct=on. This will attempt to do disk IO
directly to the guest's memory. QEMU may still perform an internal copy of the data.

"cache.no-flush"
In case you don't care about data integrity over host failures, you can use
cache.no-flush=on. This option tells QEMU that it never needs to write any data to the disk
but can instead keep things in cache. If anything goes wrong, like your host losing power,
the disk storage getting disconnected accidentally, etc. your image will most probably be
rendered unusable.

"discard=discard"
discard is one of "ignore" (or "off") or "unmap" (or "on") and controls whether "discard"
(also known as "trim" or "unmap") requests are ignored or passed to the filesystem. Some
machine types may not support discard requests.

"detect-zeroes=detect-zeroes"
detect-zeroes is "off", "on" or "unmap" and enables the automatic conversion of plain zero
writes by the OS to driver specific optimized zero write commands. You may even choose
"unmap" if discard is set to "unmap" to allow a zero write to be converted to an "unmap"
operation.

Driver-specific options for "file"
This is the protocol-level block driver for accessing regular files.

"filename"
The path to the image file in the local filesystem

"aio"
Specifies the AIO backend (threads/native, default: threads)

"locking"
Specifies whether the image file is protected with Linux OFD / POSIX locks. The default is to
use the Linux Open File Descriptor API if available, otherwise no lock is applied.
(auto/on/off, default: auto)

Example:

-blockdev driver=file,node-name=disk,filename=disk.img

Driver-specific options for "raw"
This is the image format block driver for raw images. It is usually stacked on top of a protocol
level block driver such as "file".

"file"
Reference to or definition of the data source block driver node (e.g. a "file" driver node)

Example 1:

-blockdev driver=file,node-name=disk_file,filename=disk.img
-blockdev driver=raw,node-name=disk,file=disk_file

Example 2:

-blockdev driver=raw,node-name=disk,file.driver=file,file.filename=disk.img

Driver-specific options for "qcow2"
This is the image format block driver for qcow2 images. It is usually stacked on top of a
protocol level block driver such as "file".

"file"
Reference to or definition of the data source block driver node (e.g. a "file" driver node)

"backing"
Reference to or definition of the backing file block device (default is taken from the image
file). It is allowed to pass an empty string here in order to disable the default backing
file.

"lazy-refcounts"
Whether to enable the lazy refcounts feature (on/off; default is taken from the image file)

"cache-size"
The maximum total size of the L2 table and refcount block caches in bytes (default: 1048576
bytes or 8 clusters, whichever is larger)

"l2-cache-size"
The maximum size of the L2 table cache in bytes (default: 4/5 of the total cache size)

"refcount-cache-size"
The maximum size of the refcount block cache in bytes (default: 1/5 of the total cache size)

"cache-clean-interval"
Clean unused entries in the L2 and refcount caches. The interval is in seconds. The default
value is 0 and it disables this feature.

"pass-discard-request"
Whether discard requests to the qcow2 device should be forwarded to the data source (on/off;
default: on if discard=unmap is specified, off otherwise)

"pass-discard-snapshot"
Whether discard requests for the data source should be issued when a snapshot operation (e.g.
deleting a snapshot) frees clusters in the qcow2 file (on/off; default: on)

"pass-discard-other"
Whether discard requests for the data source should be issued on other occasions where a
cluster gets freed (on/off; default: off)

"overlap-check"
Which overlap checks to perform for writes to the image (none/constant/cached/all; default:
cached). For details or finer granularity control refer to the QAPI documentation of
"blockdev-add".

Example 1:

-blockdev driver=file,node-name=my_file,filename=/tmp/disk.qcow2
-blockdev driver=qcow2,node-name=hda,file=my_file,overlap-check=none,cache-size=16777216

Example 2:

-blockdev driver=qcow2,node-name=disk,file.driver=http,file.filename=http://example.com/image.qcow2

Driver-specific options for other drivers
Please refer to the QAPI documentation of the "blockdev-add" QMP command.

-drive option[,option[,option[,...]]]
Define a new drive. This includes creating a block driver node (the backend) as well as a guest
device, and is mostly a shortcut for defining the corresponding -blockdev and -device options.

-drive accepts all options that are accepted by -blockdev. In addition, it knows the following
options:

file=file
This option defines which disk image to use with this drive. If the filename contains comma, you
must double it (for instance, "file=my,,file" to use file "my,file").

Special files such as iSCSI devices can be specified using protocol specific URLs. See the
section for "Device URL Syntax" for more information.

if=interface
This option defines on which type on interface the drive is connected. Available types are: ide,
scsi, sd, mtd, floppy, pflash, virtio, none.

bus=bus,unit=unit
These options define where is connected the drive by defining the bus number and the unit id.

index=index
This option defines where is connected the drive by using an index in the list of available
connectors of a given interface type.

media=media
This option defines the type of the media: disk or cdrom.

cyls=c,heads=h,secs=s[,trans=t]
These options have the same definition as they have in -hdachs. These parameters are deprecated,
use the corresponding parameters of "-device" instead.

snapshot=snapshot
snapshot is "on" or "off" and controls snapshot mode for the given drive (see -snapshot).

cache=cache
cache is "none", "writeback", "unsafe", "directsync" or "writethrough" and controls how the host
cache is used to access block data. This is a shortcut that sets the cache.direct and
cache.no-flush options (as in -blockdev), and additionally cache.writeback, which provides a
default for the write-cache option of block guest devices (as in -device). The modes correspond
to the following settings:

│ cache.writeback cache.direct cache.no-flush
─────────────┼─────────────────────────────────────────────────
writeback │ on off off
none │ on on off
writethrough │ off off off
directsync │ off on off
unsafe │ on off on

The default mode is cache=writeback.

aio=aio
aio is "threads", or "native" and selects between pthread based disk I/O and native Linux AIO.

format=format
Specify which disk format will be used rather than detecting the format. Can be used to specify
format=raw to avoid interpreting an untrusted format header.

serial=serial
This option specifies the serial number to assign to the device. This parameter is deprecated,
use the corresponding parameter of "-device" instead.

addr=addr
Specify the controller's PCI address (if=virtio only). This parameter is deprecated, use the
corresponding parameter of "-device" instead.

werror=action,rerror=action
Specify which action to take on write and read errors. Valid actions are: "ignore" (ignore the
error and try to continue), "stop" (pause QEMU), "report" (report the error to the guest),
"enospc" (pause QEMU only if the host disk is full; report the error to the guest otherwise).
The default setting is werror=enospc and rerror=report.

copy-on-read=copy-on-read
copy-on-read is "on" or "off" and enables whether to copy read backing file sectors into the
image file.

bps=b,bps_rd=r,bps_wr=w
Specify bandwidth throttling limits in bytes per second, either for all request types or for
reads or writes only. Small values can lead to timeouts or hangs inside the guest. A safe
minimum for disks is 2 MB/s.

bps_max=bm,bps_rd_max=rm,bps_wr_max=wm
Specify bursts in bytes per second, either for all request types or for reads or writes only.
Bursts allow the guest I/O to spike above the limit temporarily.

iops=i,iops_rd=r,iops_wr=w
Specify request rate limits in requests per second, either for all request types or for reads or
writes only.

iops_max=bm,iops_rd_max=rm,iops_wr_max=wm
Specify bursts in requests per second, either for all request types or for reads or writes only.
Bursts allow the guest I/O to spike above the limit temporarily.

iops_size=is
Let every is bytes of a request count as a new request for iops throttling purposes. Use this
option to prevent guests from circumventing iops limits by sending fewer but larger requests.

group=g
Join a throttling quota group with given name g. All drives that are members of the same group
are accounted for together. Use this option to prevent guests from circumventing throttling
limits by using many small disks instead of a single larger disk.

By default, the cache.writeback=on mode is used. It will report data writes as completed as soon as
the data is present in the host page cache. This is safe as long as your guest OS makes sure to
correctly flush disk caches where needed. If your guest OS does not handle volatile disk write caches
correctly and your host crashes or loses power, then the guest may experience data corruption.

For such guests, you should consider using cache.writeback=off. This means that the host page cache
will be used to read and write data, but write notification will be sent to the guest only after QEMU
has made sure to flush each write to the disk. Be aware that this has a major impact on performance.

When using the -snapshot option, unsafe caching is always used.

Copy-on-read avoids accessing the same backing file sectors repeatedly and is useful when the backing
file is over a slow network. By default copy-on-read is off.

Instead of -cdrom you can use:

qemu-system-i386 -drive file=file,index=2,media=cdrom

Instead of -hda, -hdb, -hdc, -hdd, you can use:

qemu-system-i386 -drive file=file,index=0,media=disk
qemu-system-i386 -drive file=file,index=1,media=disk
qemu-system-i386 -drive file=file,index=2,media=disk
qemu-system-i386 -drive file=file,index=3,media=disk

You can open an image using pre-opened file descriptors from an fd set:

qemu-system-i386
-add-fd fd=3,set=2,opaque="rdwr:/path/to/file"
-add-fd fd=4,set=2,opaque="rdonly:/path/to/file"
-drive file=/dev/fdset/2,index=0,media=disk

You can connect a CDROM to the slave of ide0:

qemu-system-i386 -drive file=file,if=ide,index=1,media=cdrom

If you don't specify the "file=" argument, you define an empty drive:

qemu-system-i386 -drive if=ide,index=1,media=cdrom

Instead of -fda, -fdb, you can use:

qemu-system-i386 -drive file=file,index=0,if=floppy
qemu-system-i386 -drive file=file,index=1,if=floppy

By default, interface is "ide" and index is automatically incremented:

qemu-system-i386 -drive file=a -drive file=b"

is interpreted like:

qemu-system-i386 -hda a -hdb b

-mtdblock file
Use file as on-board Flash memory image.

-sd file
Use file as SecureDigital card image.

-pflash file
Use file as a parallel flash image.

-snapshot
Write to temporary files instead of disk image files. In this case, the raw disk image you use is not
written back. You can however force the write back by pressing C-a s.

-hdachs c,h,s,[,t]
Force hard disk 0 physical geometry (1 <= c <= 16383, 1 <= h <= 16, 1 <= s <= 63) and optionally
force the BIOS translation mode (t=none, lba or auto). Usually QEMU can guess all those parameters.
This option is deprecated, please use "-device ide-hd,cyls=c,heads=h,secs=s,..." instead.

-fsdev
fsdriver,id=id,path=path,[security_model=security_model][,writeout=writeout][,readonly][,socket=socket|sock_fd=sock_fd][,fmode=fmode][,dmode=dmode]
Define a new file system device. Valid options are:

fsdriver
This option specifies the fs driver backend to use. Currently "local", "handle" and "proxy" file
system drivers are supported.

id=id
Specifies identifier for this device

path=path
Specifies the export path for the file system device. Files under this path will be available to
the 9p client on the guest.

security_model=security_model
Specifies the security model to be used for this export path. Supported security models are
"passthrough", "mapped-xattr", "mapped-file" and "none". In "passthrough" security model, files
are stored using the same credentials as they are created on the guest. This requires QEMU to run
as root. In "mapped-xattr" security model, some of the file attributes like uid, gid, mode bits
and link target are stored as file attributes. For "mapped-file" these attributes are stored in
the hidden .virtfs_metadata directory. Directories exported by this security model cannot
interact with other unix tools. "none" security model is same as passthrough except the sever
won't report failures if it fails to set file attributes like ownership. Security model is
mandatory only for local fsdriver. Other fsdrivers (like handle, proxy) don't take security model
as a parameter.

writeout=writeout
This is an optional argument. The only supported value is "immediate". This means that host page
cache will be used to read and write data but write notification will be sent to the guest only
when the data has been reported as written by the storage subsystem.

readonly
Enables exporting 9p share as a readonly mount for guests. By default read-write access is given.

socket=socket
Enables proxy filesystem driver to use passed socket file for communicating with virtfs-proxy-
helper

sock_fd=sock_fd
Enables proxy filesystem driver to use passed socket descriptor for communicating with virtfs-
proxy-helper. Usually a helper like libvirt will create socketpair and pass one of the fds as
sock_fd

fmode=fmode
Specifies the default mode for newly created files on the host. Works only with security models
"mapped-xattr" and "mapped-file".

dmode=dmode
Specifies the default mode for newly created directories on the host. Works only with security
models "mapped-xattr" and "mapped-file".

-fsdev option is used along with -device driver "virtio-9p-pci".

-device virtio-9p-pci,fsdev=id,mount_tag=mount_tag
Options for virtio-9p-pci driver are:

fsdev=id
Specifies the id value specified along with -fsdev option

mount_tag=mount_tag
Specifies the tag name to be used by the guest to mount this export point

-virtfs
fsdriver[,path=path],mount_tag=mount_tag[,security_model=security_model][,writeout=writeout][,readonly][,socket=socket|sock_fd=sock_fd][,fmode=fmode][,dmode=dmode]
The general form of a Virtual File system pass-through options are:

fsdriver
This option specifies the fs driver backend to use. Currently "local", "handle" and "proxy" file
system drivers are supported.

id=id
Specifies identifier for this device

path=path
Specifies the export path for the file system device. Files under this path will be available to
the 9p client on the guest.

readonly
Enables exporting 9p share as a readonly mount for guests. By default read-write access is given.

socket=socket
Enables proxy filesystem driver to use passed socket file for communicating with virtfs-proxy-
helper. Usually a helper like libvirt will create socketpair and pass one of the fds as sock_fd

sock_fd
Enables proxy filesystem driver to use passed 'sock_fd' as the socket descriptor for interfacing
with virtfs-proxy-helper

fmode=fmode
Specifies the default mode for newly created files on the host. Works only with security models
"mapped-xattr" and "mapped-file".

dmode=dmode
Specifies the default mode for newly created directories on the host. Works only with security
models "mapped-xattr" and "mapped-file".

-virtfs_synth
Create synthetic file system image

USB options

-usb
Enable the USB driver (if it is not used by default yet).

-usbdevice devname
Add the USB device devname. Note that this option is deprecated, please use "-device usb-..."
instead.

mouse
Virtual Mouse. This will override the PS/2 mouse emulation when activated.

tablet
Pointer device that uses absolute coordinates (like a touchscreen). This means QEMU is able to
report the mouse position without having to grab the mouse. Also overrides the PS/2 mouse
emulation when activated.

disk:[format=format]:file
Mass storage device based on file. The optional format argument will be used rather than
detecting the format. Can be used to specify "format=raw" to avoid interpreting an untrusted
format header.

host:bus.addr
Pass through the host device identified by bus.addr (Linux only).

host:vendor_id:product_id
Pass through the host device identified by vendor_id:product_id (Linux only).

serial:[vendorid=vendor_id][,productid=product_id]:dev
Serial converter to host character device dev, see "-serial" for the available devices.

braille
Braille device. This will use BrlAPI to display the braille output on a real or fake device.

net:options
Network adapter that supports CDC ethernet and RNDIS protocols.

Display options

-display type
Select type of display to use. This option is a replacement for the old style -sdl/-curses/...
options. Valid values for type are

sdl Display video output via SDL (usually in a separate graphics window; see the SDL documentation
for other possibilities).

curses
Display video output via curses. For graphics device models which support a text mode, QEMU can
display this output using a curses/ncurses interface. Nothing is displayed when the graphics
device is in graphical mode or if the graphics device does not support a text mode. Generally
only the VGA device models support text mode.

none
Do not display video output. The guest will still see an emulated graphics card, but its output
will not be displayed to the QEMU user. This option differs from the -nographic option in that it
only affects what is done with video output; -nographic also changes the destination of the
serial and parallel port data.

gtk Display video output in a GTK window. This interface provides drop-down menus and other UI
elements to configure and control the VM during runtime.

vnc Start a VNC server on display <arg>

-nographic
Normally, if QEMU is compiled with graphical window support, it displays output such as guest
graphics, guest console, and the QEMU monitor in a window. With this option, you can totally disable
graphical output so that QEMU is a simple command line application. The emulated serial port is
redirected on the console and muxed with the monitor (unless redirected elsewhere explicitly).
Therefore, you can still use QEMU to debug a Linux kernel with a serial console. Use C-a h for help
on switching between the console and monitor.

-curses
Normally, if QEMU is compiled with graphical window support, it displays output such as guest
graphics, guest console, and the QEMU monitor in a window. With this option, QEMU can display the VGA
output when in text mode using a curses/ncurses interface. Nothing is displayed in graphical mode.

-no-frame
Do not use decorations for SDL windows and start them using the whole available screen space. This
makes the using QEMU in a dedicated desktop workspace more convenient.

-alt-grab
Use Ctrl-Alt-Shift to grab mouse (instead of Ctrl-Alt). Note that this also affects the special keys
(for fullscreen, monitor-mode switching, etc).

-ctrl-grab
Use Right-Ctrl to grab mouse (instead of Ctrl-Alt). Note that this also affects the special keys (for
fullscreen, monitor-mode switching, etc).

-no-quit
Disable SDL window close capability.

-sdl
Enable SDL.

-spice option[,option[,...]]
Enable the spice remote desktop protocol. Valid options are

port=<nr>
Set the TCP port spice is listening on for plaintext channels.

addr=<addr>
Set the IP address spice is listening on. Default is any address.

ipv4
ipv6
unix
Force using the specified IP version.

password=<secret>
Set the password you need to authenticate.

sasl
Require that the client use SASL to authenticate with the spice. The exact choice of
authentication method used is controlled from the system / user's SASL configuration file for the
'qemu' service. This is typically found in /etc/sasl2/qemu.conf. If running QEMU as an
unprivileged user, an environment variable SASL_CONF_PATH can be used to make it search alternate
locations for the service config. While some SASL auth methods can also provide data encryption
(eg GSSAPI), it is recommended that SASL always be combined with the 'tls' and 'x509' settings to
enable use of SSL and server certificates. This ensures a data encryption preventing compromise
of authentication credentials.

disable-ticketing
Allow client connects without authentication.

disable-copy-paste
Disable copy paste between the client and the guest.

disable-agent-file-xfer
Disable spice-vdagent based file-xfer between the client and the guest.

tls-port=<nr>
Set the TCP port spice is listening on for encrypted channels.

x509-dir=<dir>
Set the x509 file directory. Expects same filenames as -vnc $display,x509=$dir

x509-key-file=<file>
x509-key-password=<file>
x509-cert-file=<file>
x509-cacert-file=<file>
x509-dh-key-file=<file>
The x509 file names can also be configured individually.

tls-ciphers=<list>
Specify which ciphers to use.

jpeg-wan-compression=[auto|never|always]
zlib-glz-wan-compression=[auto|never|always]
Configure wan image compression (lossy for slow links). Default is auto.

streaming-video=[off|all|filter]
Configure video stream detection. Default is off.

agent-mouse=[on|off]
Enable/disable passing mouse events via vdagent. Default is on.

playback-compression=[on|off]
Enable/disable audio stream compression (using celt 0.5.1). Default is on.

seamless-migration=[on|off]
Enable/disable spice seamless migration. Default is off.

gl=[on|off]
Enable/disable OpenGL context. Default is off.

rendernode=<file>
DRM render node for OpenGL rendering. If not specified, it will pick the first available. (Since
2.9)

-portrait
Rotate graphical output 90 deg left (only PXA LCD).

-rotate deg
Rotate graphical output some deg left (only PXA LCD).

-vga type
Select type of VGA card to emulate. Valid values for type are

cirrus
Cirrus Logic GD5446 Video card. All Windows versions starting from Windows 95 should recognize
and use this graphic card. For optimal performances, use 16 bit color depth in the guest and the
host OS. (This card was the default before QEMU 2.2)

std Standard VGA card with Bochs VBE extensions. If your guest OS supports the VESA 2.0 VBE
extensions (e.g. Windows XP) and if you want to use high resolution modes (>= 1280x1024x16) then
you should use this option. (This card is the default since QEMU 2.2)

vmware
VMWare SVGA-II compatible adapter. Use it if you have sufficiently recent XFree86/XOrg server or
Windows guest with a driver for this card.

qxl QXL paravirtual graphic card. It is VGA compatible (including VESA 2.0 VBE support). Works best
with qxl guest drivers installed though. Recommended choice when using the spice protocol.

tcx (sun4m only) Sun TCX framebuffer. This is the default framebuffer for sun4m machines and offers
both 8-bit and 24-bit colour depths at a fixed resolution of 1024x768.

cg3 (sun4m only) Sun cgthree framebuffer. This is a simple 8-bit framebuffer for sun4m machines
available in both 1024x768 (OpenBIOS) and 1152x900 (OBP) resolutions aimed at people wishing to
run older Solaris versions.

virtio
Virtio VGA card.

none
Disable VGA card.

-full-screen
Start in full screen.

-g widthxheight[xdepth]
Set the initial graphical resolution and depth (PPC, SPARC only).

-vnc display[,option[,option[,...]]]
Normally, if QEMU is compiled with graphical window support, it displays output such as guest
graphics, guest console, and the QEMU monitor in a window. With this option, you can have QEMU listen
on VNC display display and redirect the VGA display over the VNC session. It is very useful to enable
the usb tablet device when using this option (option -device usb-tablet). When using the VNC display,
you must use the -k parameter to set the keyboard layout if you are not using en-us. Valid syntax for
the display is

to=L
With this option, QEMU will try next available VNC displays, until the number L, if the
origianlly defined "-vnc display" is not available, e.g. port 5900+display is already used by
another application. By default, to=0.

host:d
TCP connections will only be allowed from host on display d. By convention the TCP port is
5900+d. Optionally, host can be omitted in which case the server will accept connections from any
host.

unix:path
Connections will be allowed over UNIX domain sockets where path is the location of a unix socket
to listen for connections on.

none
VNC is initialized but not started. The monitor "change" command can be used to later start the
VNC server.

Following the display value there may be one or more option flags separated by commas. Valid options
are

reverse
Connect to a listening VNC client via a "reverse" connection. The client is specified by the
display. For reverse network connections (host:d,"reverse"), the d argument is a TCP port number,
not a display number.

websocket
Opens an additional TCP listening port dedicated to VNC Websocket connections. If a bare
websocket option is given, the Websocket port is 5700+display. An alternative port can be
specified with the syntax "websocket"=port.

If host is specified connections will only be allowed from this host. It is possible to control
the websocket listen address independently, using the syntax "websocket"=host:port.

If no TLS credentials are provided, the websocket connection runs in unencrypted mode. If TLS
credentials are provided, the websocket connection requires encrypted client connections.

password
Require that password based authentication is used for client connections.

The password must be set separately using the "set_password" command in the pcsys_monitor. The
syntax to change your password is: "set_password <protocol> <password>" where <protocol> could be
either "vnc" or "spice".

If you would like to change <protocol> password expiration, you should use "expire_password
<protocol> <expiration-time>" where expiration time could be one of the following options: now,
never, +seconds or UNIX time of expiration, e.g. +60 to make password expire in 60 seconds, or
1335196800 to make password expire on "Mon Apr 23 12:00:00 EDT 2012" (UNIX time for this date and
time).

You can also use keywords "now" or "never" for the expiration time to allow <protocol> password
to expire immediately or never expire.

tls-creds=ID
Provides the ID of a set of TLS credentials to use to secure the VNC server. They will apply to
both the normal VNC server socket and the websocket socket (if enabled). Setting TLS credentials
will cause the VNC server socket to enable the VeNCrypt auth mechanism. The credentials should
have been previously created using the -object tls-creds argument.

The tls-creds parameter obsoletes the tls, x509, and x509verify options, and as such it is not
permitted to set both new and old type options at the same time.

tls Require that client use TLS when communicating with the VNC server. This uses anonymous TLS
credentials so is susceptible to a man-in-the-middle attack. It is recommended that this option
be combined with either the x509 or x509verify options.

This option is now deprecated in favor of using the tls-creds argument.

x509=/path/to/certificate/dir
Valid if tls is specified. Require that x509 credentials are used for negotiating the TLS
session. The server will send its x509 certificate to the client. It is recommended that a
password be set on the VNC server to provide authentication of the client when this is used. The
path following this option specifies where the x509 certificates are to be loaded from. See the
vnc_security section for details on generating certificates.

This option is now deprecated in favour of using the tls-creds argument.

x509verify=/path/to/certificate/dir
Valid if tls is specified. Require that x509 credentials are used for negotiating the TLS
session. The server will send its x509 certificate to the client, and request that the client
send its own x509 certificate. The server will validate the client's certificate against the CA
certificate, and reject clients when validation fails. If the certificate authority is trusted,
this is a sufficient authentication mechanism. You may still wish to set a password on the VNC
server as a second authentication layer. The path following this option specifies where the x509
certificates are to be loaded from. See the vnc_security section for details on generating
certificates.

This option is now deprecated in favour of using the tls-creds argument.

sasl
Require that the client use SASL to authenticate with the VNC server. The exact choice of
authentication method used is controlled from the system / user's SASL configuration file for the
'qemu' service. This is typically found in /etc/sasl2/qemu.conf. If running QEMU as an
unprivileged user, an environment variable SASL_CONF_PATH can be used to make it search alternate
locations for the service config. While some SASL auth methods can also provide data encryption
(eg GSSAPI), it is recommended that SASL always be combined with the 'tls' and 'x509' settings to
enable use of SSL and server certificates. This ensures a data encryption preventing compromise
of authentication credentials. See the vnc_security section for details on using SASL
authentication.

acl Turn on access control lists for checking of the x509 client certificate and SASL party. For x509
certs, the ACL check is made against the certificate's distinguished name. This is something that
looks like "C=GB,O=ACME,L=Boston,CN=bob". For SASL party, the ACL check is made against the
username, which depending on the SASL plugin, may include a realm component, eg "bob" or
"bob@EXAMPLE.COM". When the acl flag is set, the initial access list will be empty, with a
"deny" policy. Thus no one will be allowed to use the VNC server until the ACLs have been loaded.
This can be achieved using the "acl" monitor command.

lossy
Enable lossy compression methods (gradient, JPEG, ...). If this option is set, VNC client may
receive lossy framebuffer updates depending on its encoding settings. Enabling this option can
save a lot of bandwidth at the expense of quality.

non-adaptive
Disable adaptive encodings. Adaptive encodings are enabled by default. An adaptive encoding will
try to detect frequently updated screen regions, and send updates in these regions using a lossy
encoding (like JPEG). This can be really helpful to save bandwidth when playing videos.
Disabling adaptive encodings restores the original static behavior of encodings like Tight.

share=[allow-exclusive|force-shared|ignore]
Set display sharing policy. 'allow-exclusive' allows clients to ask for exclusive access. As
suggested by the rfb spec this is implemented by dropping other connections. Connecting multiple
clients in parallel requires all clients asking for a shared session (vncviewer: -shared switch).
This is the default. 'force-shared' disables exclusive client access. Useful for shared desktop
sessions, where you don't want someone forgetting specify -shared disconnect everybody else.
'ignore' completely ignores the shared flag and allows everybody connect unconditionally.
Doesn't conform to the rfb spec but is traditional QEMU behavior.

key-delay-ms
Set keyboard delay, for key down and key up events, in milliseconds. Default is 10. Keyboards
are low-bandwidth devices, so this slowdown can help the device and guest to keep up and not lose
events in case events are arriving in bulk. Possible causes for the latter are flaky network
connections, or scripts for automated testing.

i386 target only

-win2k-hack
Use it when installing Windows 2000 to avoid a disk full bug. After Windows 2000 is installed, you no
longer need this option (this option slows down the IDE transfers).

-no-fd-bootchk
Disable boot signature checking for floppy disks in BIOS. May be needed to boot from old floppy
disks.

-no-acpi
Disable ACPI (Advanced Configuration and Power Interface) support. Use it if your guest OS complains
about ACPI problems (PC target machine only).

-no-hpet
Disable HPET support.

-acpitable [sig=str][,rev=n][,oem_id=str][,oem_table_id=str][,oem_rev=n]
[,asl_compiler_id=str][,asl_compiler_rev=n][,data=file1[:file2]...]
Add ACPI table with specified header fields and context from specified files. For file=, take whole
ACPI table from the specified files, including all ACPI headers (possible overridden by other
options). For data=, only data portion of the table is used, all header information is specified in
the command line. If a SLIC table is supplied to QEMU, then the SLIC's oem_id and oem_table_id
fields will override the same in the RSDT and the FADT (a.k.a. FACP), in order to ensure the field
matches required by the Microsoft SLIC spec and the ACPI spec.

-smbios file=binary
Load SMBIOS entry from binary file.

-smbios type=0[,vendor=str][,version=str][,date=str][,release=%d.%d][,uefi=on|off]
Specify SMBIOS type 0 fields

-smbios
type=1[,manufacturer=str][,product=str][,version=str][,serial=str][,uuid=uuid][,sku=str][,family=str]
Specify SMBIOS type 1 fields

-smbios
type=2[,manufacturer=str][,product=str][,version=str][,serial=str][,asset=str][,location=str][,family=str]
Specify SMBIOS type 2 fields

-smbios type=3[,manufacturer=str][,version=str][,serial=str][,asset=str][,sku=str]
Specify SMBIOS type 3 fields

-smbios type=4[,sock_pfx=str][,manufacturer=str][,version=str][,serial=str][,asset=str][,part=str]
Specify SMBIOS type 4 fields

-smbios
type=17[,loc_pfx=str][,bank=str][,manufacturer=str][,serial=str][,asset=str][,part=str][,speed=%d]
Specify SMBIOS type 17 fields

Network options

-net nic[,vlan=n][,macaddr=mac][,model=type] [,name=name][,addr=addr][,vectors=v]
Create a new Network Interface Card and connect it to VLAN n (n = 0 is the default). The NIC is an
e1000 by default on the PC target. Optionally, the MAC address can be changed to mac, the device
address set to addr (PCI cards only), and a name can be assigned for use in monitor commands.
Optionally, for PCI cards, you can specify the number v of MSI-X vectors that the card should have;
this option currently only affects virtio cards; set v = 0 to disable MSI-X. If no -net option is
specified, a single NIC is created. QEMU can emulate several different models of network card.
Valid values for type are "virtio", "i82551", "i82557b", "i82559er", "ne2k_pci", "ne2k_isa", "pcnet",
"rtl8139", "e1000", "smc91c111", "lance" and "mcf_fec". Not all devices are supported on all
targets. Use "-net nic,model=help" for a list of available devices for your target.

-netdev user,id=id[,option][,option][,...]
-net user[,option][,option][,...]
Use the user mode network stack which requires no administrator privilege to run. Valid options are:

vlan=n
Connect user mode stack to VLAN n (n = 0 is the default).

id=id
name=name
Assign symbolic name for use in monitor commands.

ipv4 and ipv6 specify that either IPv4 or IPv6 must be enabled. If neither is specified both
protocols are enabled.

net=addr[/mask]
Set IP network address the guest will see. Optionally specify the netmask, either in the form
a.b.c.d or as number of valid top-most bits. Default is 10.0.2.0/24.

host=addr
Specify the guest-visible address of the host. Default is the 2nd IP in the guest network, i.e.
x.x.x.2.

ipv6-net=addr[/int]
Set IPv6 network address the guest will see (default is fec0::/64). The network prefix is given
in the usual hexadecimal IPv6 address notation. The prefix size is optional, and is given as the
number of valid top-most bits (default is 64).

ipv6-host=addr
Specify the guest-visible IPv6 address of the host. Default is the 2nd IPv6 in the guest network,
i.e. xxxx::2.

restrict=on|off
If this option is enabled, the guest will be isolated, i.e. it will not be able to contact the
host and no guest IP packets will be routed over the host to the outside. This option does not
affect any explicitly set forwarding rules.

hostname=name
Specifies the client hostname reported by the built-in DHCP server.

dhcpstart=addr
Specify the first of the 16 IPs the built-in DHCP server can assign. Default is the 15th to 31st
IP in the guest network, i.e. x.x.x.15 to x.x.x.31.

dns=addr
Specify the guest-visible address of the virtual nameserver. The address must be different from
the host address. Default is the 3rd IP in the guest network, i.e. x.x.x.3.

ipv6-dns=addr
Specify the guest-visible address of the IPv6 virtual nameserver. The address must be different
from the host address. Default is the 3rd IP in the guest network, i.e. xxxx::3.

dnssearch=domain
Provides an entry for the domain-search list sent by the built-in DHCP server. More than one
domain suffix can be transmitted by specifying this option multiple times. If supported, this
will cause the guest to automatically try to append the given domain suffix(es) in case a domain
name can not be resolved.

Example:

qemu -net user,dnssearch=mgmt.example.org,dnssearch=example.org [...]

domainname=domain
Specifies the client domain name reported by the built-in DHCP server.

tftp=dir
When using the user mode network stack, activate a built-in TFTP server. The files in dir will be
exposed as the root of a TFTP server. The TFTP client on the guest must be configured in binary
mode (use the command "bin" of the Unix TFTP client).

bootfile=file
When using the user mode network stack, broadcast file as the BOOTP filename. In conjunction with
tftp, this can be used to network boot a guest from a local directory.

Example (using pxelinux):

qemu-system-i386 -hda linux.img -boot n -net user,tftp=/path/to/tftp/files,bootfile=/pxelinux.0

smb=dir[,smbserver=addr]
When using the user mode network stack, activate a built-in SMB server so that Windows OSes can
access to the host files in dir transparently. The IP address of the SMB server can be set to
addr. By default the 4th IP in the guest network is used, i.e. x.x.x.4.

In the guest Windows OS, the line:

10.0.2.4 smbserver

must be added in the file C:\WINDOWS\LMHOSTS (for windows 9x/Me) or
C:\WINNT\SYSTEM32\DRIVERS\ETC\LMHOSTS (Windows NT/2000).

Then dir can be accessed in \\smbserver\qemu.

Note that a SAMBA server must be installed on the host OS. QEMU was tested successfully with
smbd versions from Red Hat 9, Fedora Core 3 and OpenSUSE 11.x.

hostfwd=[tcp|udp]:[hostaddr]:hostport-[guestaddr]:guestport
Redirect incoming TCP or UDP connections to the host port hostport to the guest IP address
guestaddr on guest port guestport. If guestaddr is not specified, its value is x.x.x.15 (default
first address given by the built-in DHCP server). By specifying hostaddr, the rule can be bound
to a specific host interface. If no connection type is set, TCP is used. This option can be given
multiple times.

For example, to redirect host X11 connection from screen 1 to guest screen 0, use the following:

# on the host
qemu-system-i386 -net user,hostfwd=tcp:127.0.0.1:6001-:6000 [...]
# this host xterm should open in the guest X11 server
xterm -display :1

To redirect telnet connections from host port 5555 to telnet port on the guest, use the
following:

# on the host
qemu-system-i386 -net user,hostfwd=tcp::5555-:23 [...]
telnet localhost 5555

Then when you use on the host "telnet localhost 5555", you connect to the guest telnet server.

guestfwd=[tcp]:server:port-dev
guestfwd=[tcp]:server:port-cmd:command
Forward guest TCP connections to the IP address server on port port to the character device dev
or to a program executed by cmd:command which gets spawned for each connection. This option can
be given multiple times.

You can either use a chardev directly and have that one used throughout QEMU's lifetime, like in
the following example:

# open 10.10.1.1:4321 on bootup, connect 10.0.2.100:1234 to it whenever
# the guest accesses it
qemu -net user,guestfwd=tcp:10.0.2.100:1234-tcp:10.10.1.1:4321 [...]

Or you can execute a command on every TCP connection established by the guest, so that QEMU
behaves similar to an inetd process for that virtual server:

# call "netcat 10.10.1.1 4321" on every TCP connection to 10.0.2.100:1234
# and connect the TCP stream to its stdin/stdout
qemu -net 'user,guestfwd=tcp:10.0.2.100:1234-cmd:netcat 10.10.1.1 4321'

Note: Legacy stand-alone options -tftp, -bootp, -smb and -redir are still processed and applied to
-net user. Mixing them with the new configuration syntax gives undefined results. Their use for new
applications is discouraged as they will be removed from future versions.

-netdev tap,id=id[,fd=h][,ifname=name][,script=file][,downscript=dfile][,br=bridge][,helper=helper]
-net
tap[,vlan=n][,name=name][,fd=h][,ifname=name][,script=file][,downscript=dfile][,br=bridge][,helper=helper]
Connect the host TAP network interface name to VLAN n.

Use the network script file to configure it and the network script dfile to deconfigure it. If name
is not provided, the OS automatically provides one. The default network configure script is
/etc/qemu-ifup and the default network deconfigure script is /etc/qemu-ifdown. Use script=no or
downscript=no to disable script execution.

If running QEMU as an unprivileged user, use the network helper helper to configure the TAP interface
and attach it to the bridge. The default network helper executable is /path/to/qemu-bridge-helper
and the default bridge device is br0.

fd=h can be used to specify the handle of an already opened host TAP interface.

Examples:

#launch a QEMU instance with the default network script
qemu-system-i386 linux.img -net nic -net tap

#launch a QEMU instance with two NICs, each one connected
#to a TAP device
qemu-system-i386 linux.img \
-net nic,vlan=0 -net tap,vlan=0,ifname=tap0 \
-net nic,vlan=1 -net tap,vlan=1,ifname=tap1

#launch a QEMU instance with the default network helper to
#connect a TAP device to bridge br0
qemu-system-i386 linux.img \
-net nic -net tap,"helper=/path/to/qemu-bridge-helper"

-netdev bridge,id=id[,br=bridge][,helper=helper]
-net bridge[,vlan=n][,name=name][,br=bridge][,helper=helper]
Connect a host TAP network interface to a host bridge device.

Use the network helper helper to configure the TAP interface and attach it to the bridge. The default
network helper executable is /path/to/qemu-bridge-helper and the default bridge device is br0.

Examples:

#launch a QEMU instance with the default network helper to
#connect a TAP device to bridge br0
qemu-system-i386 linux.img -net bridge -net nic,model=virtio

#launch a QEMU instance with the default network helper to
#connect a TAP device to bridge qemubr0
qemu-system-i386 linux.img -net bridge,br=qemubr0 -net nic,model=virtio

-netdev socket,id=id[,fd=h][,listen=[host]:port][,connect=host:port]
-net socket[,vlan=n][,name=name][,fd=h] [,listen=[host]:port][,connect=host:port]
Connect the VLAN n to a remote VLAN in another QEMU virtual machine using a TCP socket connection. If
listen is specified, QEMU waits for incoming connections on port (host is optional). connect is used
to connect to another QEMU instance using the listen option. fd=h specifies an already opened TCP
socket.

Example:

# launch a first QEMU instance
qemu-system-i386 linux.img \
-net nic,macaddr=52:54:00:12:34:56 \
-net socket,listen=:1234
# connect the VLAN 0 of this instance to the VLAN 0
# of the first instance
qemu-system-i386 linux.img \
-net nic,macaddr=52:54:00:12:34:57 \
-net socket,connect=127.0.0.1:1234

-netdev socket,id=id[,fd=h][,mcast=maddr:port[,localaddr=addr]]
-net socket[,vlan=n][,name=name][,fd=h][,mcast=maddr:port[,localaddr=addr]]
Create a VLAN n shared with another QEMU virtual machines using a UDP multicast socket, effectively
making a bus for every QEMU with same multicast address maddr and port. NOTES:

1. Several QEMU can be running on different hosts and share same bus (assuming correct multicast
setup for these hosts).

2. mcast support is compatible with User Mode Linux (argument ethN=mcast), see
<http://user-mode-linux.sf.net>.

3. Use fd=h to specify an already opened UDP multicast socket.

Example:

# launch one QEMU instance
qemu-system-i386 linux.img \
-net nic,macaddr=52:54:00:12:34:56 \
-net socket,mcast=230.0.0.1:1234
# launch another QEMU instance on same "bus"
qemu-system-i386 linux.img \
-net nic,macaddr=52:54:00:12:34:57 \
-net socket,mcast=230.0.0.1:1234
# launch yet another QEMU instance on same "bus"
qemu-system-i386 linux.img \
-net nic,macaddr=52:54:00:12:34:58 \
-net socket,mcast=230.0.0.1:1234

Example (User Mode Linux compat.):

# launch QEMU instance (note mcast address selected
# is UML's default)
qemu-system-i386 linux.img \
-net nic,macaddr=52:54:00:12:34:56 \
-net socket,mcast=239.192.168.1:1102
# launch UML
/path/to/linux ubd0=/path/to/root_fs eth0=mcast

Example (send packets from host's 1.2.3.4):

qemu-system-i386 linux.img \
-net nic,macaddr=52:54:00:12:34:56 \
-net socket,mcast=239.192.168.1:1102,localaddr=1.2.3.4

-netdev
l2tpv3,id=id,src=srcaddr,dst=dstaddr[,srcport=srcport][,dstport=dstport],txsession=txsession[,rxsession=rxsession][,ipv6][,udp][,cookie64][,counter][,pincounter][,txcookie=txcookie][,rxcookie=rxcookie][,offset=offset]
-net
l2tpv3[,vlan=n][,name=name],src=srcaddr,dst=dstaddr[,srcport=srcport][,dstport=dstport],txsession=txsession[,rxsession=rxsession][,ipv6][,udp][,cookie64][,counter][,pincounter][,txcookie=txcookie][,rxcookie=rxcookie][,offset=offset]
Connect VLAN n to L2TPv3 pseudowire. L2TPv3 (RFC3391) is a popular protocol to transport Ethernet
(and other Layer 2) data frames between two systems. It is present in routers, firewalls and the
Linux kernel (from version 3.3 onwards).

This transport allows a VM to communicate to another VM, router or firewall directly.

src=srcaddr
source address (mandatory)

dst=dstaddr
destination address (mandatory)

udp select udp encapsulation (default is ip).

srcport=srcport
source udp port.

dstport=dstport
destination udp port.

ipv6
force v6, otherwise defaults to v4.

rxcookie=rxcookie
txcookie=txcookie
Cookies are a weak form of security in the l2tpv3 specification. Their function is mostly to prevent
misconfiguration. By default they are 32 bit.

cookie64
Set cookie size to 64 bit instead of the default 32

counter=off
Force a 'cut-down' L2TPv3 with no counter as in draft-mkonstan-l2tpext-keyed-ipv6-tunnel-00

pincounter=on
Work around broken counter handling in peer. This may also help on networks which have packet
reorder.

offset=offset
Add an extra offset between header and data

For example, to attach a VM running on host 4.3.2.1 via L2TPv3 to the bridge br-lan on the remote
Linux host 1.2.3.4:

# Setup tunnel on linux host using raw ip as encapsulation
# on 1.2.3.4
ip l2tp add tunnel remote 4.3.2.1 local 1.2.3.4 tunnel_id 1 peer_tunnel_id 1 \
encap udp udp_sport 16384 udp_dport 16384
ip l2tp add session tunnel_id 1 name vmtunnel0 session_id \
0xFFFFFFFF peer_session_id 0xFFFFFFFF
ifconfig vmtunnel0 mtu 1500
ifconfig vmtunnel0 up
brctl addif br-lan vmtunnel0

# on 4.3.2.1
# launch QEMU instance - if your network has reorder or is very lossy add ,pincounter

qemu-system-i386 linux.img -net nic -net l2tpv3,src=4.2.3.1,dst=1.2.3.4,udp,srcport=16384,dstport=16384,rxsession=0xffffffff,txsession=0xffffffff,counter

-netdev vde,id=id[,sock=socketpath][,port=n][,group=groupname][,mode=octalmode]
-net vde[,vlan=n][,name=name][,sock=socketpath] [,port=n][,group=groupname][,mode=octalmode]
Connect VLAN n to PORT n of a vde switch running on host and listening for incoming connections on
socketpath. Use GROUP groupname and MODE octalmode to change default ownership and permissions for
communication port. This option is only available if QEMU has been compiled with vde support enabled.

Example:

# launch vde switch
vde_switch -F -sock /tmp/myswitch
# launch QEMU instance
qemu-system-i386 linux.img -net nic -net vde,sock=/tmp/myswitch

-netdev hubport,id=id,hubid=hubid
Create a hub port on QEMU "vlan" hubid.

The hubport netdev lets you connect a NIC to a QEMU "vlan" instead of a single netdev. "-net" and
"-device" with parameter vlan create the required hub automatically.

-netdev vhost-user,chardev=id[,vhostforce=on|off][,queues=n]
Establish a vhost-user netdev, backed by a chardev id. The chardev should be a unix domain socket
backed one. The vhost-user uses a specifically defined protocol to pass vhost ioctl replacement
messages to an application on the other end of the socket. On non-MSIX guests, the feature can be
forced with vhostforce. Use 'queues=n' to specify the number of queues to be created for multiqueue
vhost-user.

Example:

qemu -m 512 -object memory-backend-file,id=mem,size=512M,mem-path=/hugetlbfs,share=on \
-numa node,memdev=mem \
-chardev socket,id=chr0,path=/path/to/socket \
-netdev type=vhost-user,id=net0,chardev=chr0 \
-device virtio-net-pci,netdev=net0

-net dump[,vlan=n][,file=file][,len=len]
Dump network traffic on VLAN n to file file (qemu-vlan0.pcap by default). At most len bytes (64k by
default) per packet are stored. The file format is libpcap, so it can be analyzed with tools such as
tcpdump or Wireshark. Note: For devices created with '-netdev', use '-object filter-dump,...'
instead.

-net none
Indicate that no network devices should be configured. It is used to override the default
configuration (-net nic -net user) which is activated if no -net options are provided.

Character device options

The general form of a character device option is:

-chardev backend ,id=id [,mux=on|off] [,options]
Backend is one of: null, socket, udp, msmouse, vc, ringbuf, file, pipe, console, serial, pty, stdio,
braille, tty, parallel, parport, spicevmc. spiceport. The specific backend will determine the
applicable options.

Use "-chardev help" to print all available chardev backend types.

All devices must have an id, which can be any string up to 127 characters long. It is used to
uniquely identify this device in other command line directives.

A character device may be used in multiplexing mode by multiple front-ends. Specify mux=on to enable
this mode. A multiplexer is a "1:N" device, and here the "1" end is your specified chardev backend,
and the "N" end is the various parts of QEMU that can talk to a chardev. If you create a chardev
with id=myid and mux=on, QEMU will create a multiplexer with your specified ID, and you can then
configure multiple front ends to use that chardev ID for their input/output. Up to four different
front ends can be connected to a single multiplexed chardev. (Without multiplexing enabled, a chardev
can only be used by a single front end.) For instance you could use this to allow a single stdio
chardev to be used by two serial ports and the QEMU monitor:

-chardev stdio,mux=on,id=char0 \
-mon chardev=char0,mode=readline \
-serial chardev:char0 \
-serial chardev:char0

You can have more than one multiplexer in a system configuration; for instance you could have a TCP
port multiplexed between UART 0 and UART 1, and stdio multiplexed between the QEMU monitor and a
parallel port:

-chardev stdio,mux=on,id=char0 \
-mon chardev=char0,mode=readline \
-parallel chardev:char0 \
-chardev tcp,...,mux=on,id=char1 \
-serial chardev:char1 \
-serial chardev:char1

When you're using a multiplexed character device, some escape sequences are interpreted in the input.

Note that some other command line options may implicitly create multiplexed character backends; for
instance -serial mon:stdio creates a multiplexed stdio backend connected to the serial port and the
QEMU monitor, and -nographic also multiplexes the console and the monitor to stdio.

There is currently no support for multiplexing in the other direction (where a single QEMU front end
takes input and output from multiple chardevs).

Every backend supports the logfile option, which supplies the path to a file to record all data
transmitted via the backend. The logappend option controls whether the log file will be truncated or
appended to when opened.

Further options to each backend are described below.

-chardev null ,id=id
A void device. This device will not emit any data, and will drop any data it receives. The null
backend does not take any options.

-chardev socket ,id=id [TCP options or unix options] [,server] [,nowait] [,telnet] [,reconnect=seconds]
[,tls-creds=id]
Create a two-way stream socket, which can be either a TCP or a unix socket. A unix socket will be
created if path is specified. Behaviour is undefined if TCP options are specified for a unix socket.

server specifies that the socket shall be a listening socket.

nowait specifies that QEMU should not block waiting for a client to connect to a listening socket.

telnet specifies that traffic on the socket should interpret telnet escape sequences.

reconnect sets the timeout for reconnecting on non-server sockets when the remote end goes away.
qemu will delay this many seconds and then attempt to reconnect. Zero disables reconnecting, and is
the default.

tls-creds requests enablement of the TLS protocol for encryption, and specifies the id of the TLS
credentials to use for the handshake. The credentials must be previously created with the -object
tls-creds argument.

TCP and unix socket options are given below:

TCP options: port=port [,host=host] [,to=to] [,ipv4] [,ipv6] [,nodelay]
host for a listening socket specifies the local address to be bound. For a connecting socket
species the remote host to connect to. host is optional for listening sockets. If not specified
it defaults to 0.0.0.0.

port for a listening socket specifies the local port to be bound. For a connecting socket
specifies the port on the remote host to connect to. port can be given as either a port number
or a service name. port is required.

to is only relevant to listening sockets. If it is specified, and port cannot be bound, QEMU will
attempt to bind to subsequent ports up to and including to until it succeeds. to must be
specified as a port number.

ipv4 and ipv6 specify that either IPv4 or IPv6 must be used. If neither is specified the socket
may use either protocol.

nodelay disables the Nagle algorithm.

unix options: path=path
path specifies the local path of the unix socket. path is required.

-chardev udp ,id=id [,host=host] ,port=port [,localaddr=localaddr] [,localport=localport] [,ipv4] [,ipv6]
Sends all traffic from the guest to a remote host over UDP.

host specifies the remote host to connect to. If not specified it defaults to "localhost".

port specifies the port on the remote host to connect to. port is required.

localaddr specifies the local address to bind to. If not specified it defaults to 0.0.0.0.

localport specifies the local port to bind to. If not specified any available local port will be
used.

ipv4 and ipv6 specify that either IPv4 or IPv6 must be used. If neither is specified the device may
use either protocol.

-chardev msmouse ,id=id
Forward QEMU's emulated msmouse events to the guest. msmouse does not take any options.

-chardev vc ,id=id [[,width=width] [,height=height]] [[,cols=cols] [,rows=rows]]
Connect to a QEMU text console. vc may optionally be given a specific size.

width and height specify the width and height respectively of the console, in pixels.

cols and rows specify that the console be sized to fit a text console with the given dimensions.

-chardev ringbuf ,id=id [,size=size]
Create a ring buffer with fixed size size. size must be a power of two and defaults to "64K".

-chardev file ,id=id ,path=path
Log all traffic received from the guest to a file.

path specifies the path of the file to be opened. This file will be created if it does not already
exist, and overwritten if it does. path is required.

-chardev pipe ,id=id ,path=path
Create a two-way connection to the guest. The behaviour differs slightly between Windows hosts and
other hosts:

On Windows, a single duplex pipe will be created at \\.pipe\path.

On other hosts, 2 pipes will be created called path.in and path.out. Data written to path.in will be
received by the guest. Data written by the guest can be read from path.out. QEMU will not create
these fifos, and requires them to be present.

path forms part of the pipe path as described above. path is required.

-chardev console ,id=id
Send traffic from the guest to QEMU's standard output. console does not take any options.

console is only available on Windows hosts.

-chardev serial ,id=id ,path=path
Send traffic from the guest to a serial device on the host.

On Unix hosts serial will actually accept any tty device, not only serial lines.

path specifies the name of the serial device to open.

-chardev pty ,id=id
Create a new pseudo-terminal on the host and connect to it. pty does not take any options.

pty is not available on Windows hosts.

-chardev stdio ,id=id [,signal=on|off]
Connect to standard input and standard output of the QEMU process.

signal controls if signals are enabled on the terminal, that includes exiting QEMU with the key
sequence Control-c. This option is enabled by default, use signal=off to disable it.

-chardev braille ,id=id
Connect to a local BrlAPI server. braille does not take any options.

-chardev tty ,id=id ,path=path
tty is only available on Linux, Sun, FreeBSD, NetBSD, OpenBSD and DragonFlyBSD hosts. It is an alias
for serial.

path specifies the path to the tty. path is required.

-chardev parallel ,id=id ,path=path
-chardev parport ,id=id ,path=path
parallel is only available on Linux, FreeBSD and DragonFlyBSD hosts.

Connect to a local parallel port.

path specifies the path to the parallel port device. path is required.

-chardev spicevmc ,id=id ,debug=debug, name=name
spicevmc is only available when spice support is built in.

debug debug level for spicevmc

name name of spice channel to connect to

Connect to a spice virtual machine channel, such as vdiport.

-chardev spiceport ,id=id ,debug=debug, name=name
spiceport is only available when spice support is built in.

debug debug level for spicevmc

name name of spice port to connect to

Connect to a spice port, allowing a Spice client to handle the traffic identified by a name
(preferably a fqdn).

Device URL Syntax

In addition to using normal file images for the emulated storage devices, QEMU can also use networked
resources such as iSCSI devices. These are specified using a special URL syntax.

iSCSI
iSCSI support allows QEMU to access iSCSI resources directly and use as images for the guest storage.
Both disk and cdrom images are supported.

Syntax for specifying iSCSI LUNs is "iscsi://<target-ip>[:<port>]/<target-iqn>/<lun>"

By default qemu will use the iSCSI initiator-name 'iqn.2008-11.org.linux-kvm[:<name>]' but this can
also be set from the command line or a configuration file.

Since version Qemu 2.4 it is possible to specify a iSCSI request timeout to detect stalled requests
and force a reestablishment of the session. The timeout is specified in seconds. The default is 0
which means no timeout. Libiscsi 1.15.0 or greater is required for this feature.

Example (without authentication):

qemu-system-i386 -iscsi initiator-name=iqn.2001-04.com.example:my-initiator \
-cdrom iscsi://192.0.2.1/iqn.2001-04.com.example/2 \
-drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1

Example (CHAP username/password via URL):

qemu-system-i386 -drive file=iscsi://user%password@192.0.2.1/iqn.2001-04.com.example/1

Example (CHAP username/password via environment variables):

LIBISCSI_CHAP_USERNAME="user" \
LIBISCSI_CHAP_PASSWORD="password" \
qemu-system-i386 -drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1

iSCSI support is an optional feature of QEMU and only available when compiled and linked against
libiscsi.

iSCSI parameters such as username and password can also be specified via a configuration file. See
qemu-doc for more information and examples.

NBD QEMU supports NBD (Network Block Devices) both using TCP protocol as well as Unix Domain Sockets.

Syntax for specifying a NBD device using TCP "nbd:<server-ip>:<port>[:exportname=<export>]"

Syntax for specifying a NBD device using Unix Domain Sockets
"nbd:unix:<domain-socket>[:exportname=<export>]"

Example for TCP

qemu-system-i386 --drive file=nbd:192.0.2.1:30000

Example for Unix Domain Sockets

qemu-system-i386 --drive file=nbd:unix:/tmp/nbd-socket

SSH QEMU supports SSH (Secure Shell) access to remote disks.

Examples:

qemu-system-i386 -drive file=ssh://user@host/path/to/disk.img
qemu-system-i386 -drive file.driver=ssh,file.user=user,file.host=host,file.port=22,file.path=/path/to/disk.img

Currently authentication must be done using ssh-agent. Other authentication methods may be supported
in future.

Sheepdog
Sheepdog is a distributed storage system for QEMU. QEMU supports using either local sheepdog devices
or remote networked devices.

Syntax for specifying a sheepdog device

sheepdog[+tcp|+unix]://[host:port]/vdiname[?socket=path][#snapid|#tag]

Example

qemu-system-i386 --drive file=sheepdog://192.0.2.1:30000/MyVirtualMachine

See also <https://sheepdog.github.io/sheepdog/>.

GlusterFS
GlusterFS is a user space distributed file system. QEMU supports the use of GlusterFS volumes for
hosting VM disk images using TCP, Unix Domain Sockets and RDMA transport protocols.

Syntax for specifying a VM disk image on GlusterFS volume is

URI:
gluster[+type]://[host[:port]]/volume/path[?socket=...][,debug=N][,logfile=...]

JSON:
'json:{"driver":"qcow2","file":{"driver":"gluster","volume":"testvol","path":"a.img","debug":N,"logfile":"...",
"server":[{"type":"tcp","host":"...","port":"..."},
{"type":"unix","socket":"..."}]}}'

Example

URI:
qemu-system-x86_64 --drive file=gluster://192.0.2.1/testvol/a.img,
file.debug=9,file.logfile=/var/log/qemu-gluster.log

JSON:
qemu-system-x86_64 'json:{"driver":"qcow2",
"file":{"driver":"gluster",
"volume":"testvol","path":"a.img",
"debug":9,"logfile":"/var/log/qemu-gluster.log",
"server":[{"type":"tcp","host":"1.2.3.4","port":24007},
{"type":"unix","socket":"/var/run/glusterd.socket"}]}}'
qemu-system-x86_64 -drive driver=qcow2,file.driver=gluster,file.volume=testvol,file.path=/path/a.img,
file.debug=9,file.logfile=/var/log/qemu-gluster.log,
file.server.0.type=tcp,file.server.0.host=1.2.3.4,file.server.0.port=24007,
file.server.1.type=unix,file.server.1.socket=/var/run/glusterd.socket

See also <http://www.gluster.org>.

HTTP/HTTPS/FTP/FTPS
QEMU supports read-only access to files accessed over http(s) and ftp(s).

Syntax using a single filename:

where:

protocol
'http', 'https', 'ftp', or 'ftps'.

username
Optional username for authentication to the remote server.

password
Optional password for authentication to the remote server.

host
Address of the remote server.

path
Path on the remote server, including any query string.

The following options are also supported:

url The full URL when passing options to the driver explicitly.

readahead
The amount of data to read ahead with each range request to the remote server. This value may
optionally have the suffix 'T', 'G', 'M', 'K', 'k' or 'b'. If it does not have a suffix, it will
be assumed to be in bytes. The value must be a multiple of 512 bytes. It defaults to 256k.

sslverify
Whether to verify the remote server's certificate when connecting over SSL. It can have the value
'on' or 'off'. It defaults to 'on'.

cookie
Send this cookie (it can also be a list of cookies separated by ';') with each outgoing request.
Only supported when using protocols such as HTTP which support cookies, otherwise ignored.

timeout
Set the timeout in seconds of the CURL connection. This timeout is the time that CURL waits for a
response from the remote server to get the size of the image to be downloaded. If not set, the
default timeout of 5 seconds is used.

Note that when passing options to qemu explicitly, driver is the value of <protocol>.

Example: boot from a remote Fedora 20 live ISO image

qemu-system-x86_64 --drive media=cdrom,file=http://dl.fedoraproject.org/pub/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso,readonly

qemu-system-x86_64 --drive media=cdrom,file.driver=http,file.url=http://dl.fedoraproject.org/pub/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso,readonly

Example: boot from a remote Fedora 20 cloud image using a local overlay for writes, copy-on-read, and
a readahead of 64k

qemu-img create -f qcow2 -o backing_file='json:{"file.driver":"http",, "file.url":"https://dl.fedoraproject.org/pub/fedora/linux/releases/20/Images/x86_64/Fedora-x86_64-20-20131211.1-sda.qcow2",, "file.readahead":"64k"}' /tmp/Fedora-x86_64-20-20131211.1-sda.qcow2

qemu-system-x86_64 -drive file=/tmp/Fedora-x86_64-20-20131211.1-sda.qcow2,copy-on-read=on

Example: boot from an image stored on a VMware vSphere server with a self-signed certificate using a
local overlay for writes, a readahead of 64k and a timeout of 10 seconds.

qemu-img create -f qcow2 -o backing_file='json:{"file.driver":"https",, "file.url":"https://user:password@vsphere.example.com/folder/test/test-flat.vmdk?dcPath=Datacenter&dsName=datastore1",, "file.sslverify":"off",, "file.readahead":"64k",, "file.timeout":10}' /tmp/test.qcow2

qemu-system-x86_64 -drive file=/tmp/test.qcow2

Bluetooth(R) options

-bt hci[...]
Defines the function of the corresponding Bluetooth HCI. -bt options are matched with the HCIs
present in the chosen machine type. For example when emulating a machine with only one HCI built
into it, only the first "-bt hci[...]" option is valid and defines the HCI's logic. The Transport
Layer is decided by the machine type. Currently the machines "n800" and "n810" have one HCI and all
other machines have none.

The following three types are recognized:

-bt hci,null
(default) The corresponding Bluetooth HCI assumes no internal logic and will not respond to any
HCI commands or emit events.

-bt hci,host[:id]
("bluez" only) The corresponding HCI passes commands / events to / from the physical HCI
identified by the name id (default: "hci0") on the computer running QEMU. Only available on
"bluez" capable systems like Linux.

-bt hci[,vlan=n]
Add a virtual, standard HCI that will participate in the Bluetooth scatternet n (default 0).
Similarly to -net VLANs, devices inside a bluetooth network n can only communicate with other
devices in the same network (scatternet).

-bt vhci[,vlan=n]
(Linux-host only) Create a HCI in scatternet n (default 0) attached to the host bluetooth stack
instead of to the emulated target. This allows the host and target machines to participate in a
common scatternet and communicate. Requires the Linux "vhci" driver installed. Can be used as
following:

qemu-system-i386 [...OPTIONS...] -bt hci,vlan=5 -bt vhci,vlan=5

-bt device:dev[,vlan=n]
Emulate a bluetooth device dev and place it in network n (default 0). QEMU can only emulate one type
of bluetooth devices currently:

keyboard
Virtual wireless keyboard implementing the HIDP bluetooth profile.

TPM device options

The general form of a TPM device option is:

-tpmdev backend ,id=id [,options]
Backend type must be either one of the following: passthrough, emulator.

The specific backend type will determine the applicable options. The "-tpmdev" option creates the
TPM backend and requires a "-device" option that specifies the TPM frontend interface model.

Options to each backend are described below.

Use 'help' to print all available TPM backend types.

qemu -tpmdev help

-tpmdev passthrough, id=id, path=path, cancel-path=cancel-path
(Linux-host only) Enable access to the host's TPM using the passthrough driver.

path specifies the path to the host's TPM device, i.e., on a Linux host this would be "/dev/tpm0".
path is optional and by default "/dev/tpm0" is used.

cancel-path specifies the path to the host TPM device's sysfs entry allowing for cancellation of an
ongoing TPM command. cancel-path is optional and by default QEMU will search for the sysfs entry to
use.

Some notes about using the host's TPM with the passthrough driver:

The TPM device accessed by the passthrough driver must not be used by any other application on the
host.

Since the host's firmware (BIOS/UEFI) has already initialized the TPM, the VM's firmware (BIOS/UEFI)
will not be able to initialize the TPM again and may therefore not show a TPM-specific menu that
would otherwise allow the user to configure the TPM, e.g., allow the user to enable/disable or
activate/deactivate the TPM. Further, if TPM ownership is released from within a VM then the host's
TPM will get disabled and deactivated. To enable and activate the TPM again afterwards, the host has
to be rebooted and the user is required to enter the firmware's menu to enable and activate the TPM.
If the TPM is left disabled and/or deactivated most TPM commands will fail.

To create a passthrough TPM use the following two options:

-tpmdev passthrough,id=tpm0 -device tpm-tis,tpmdev=tpm0

Note that the "-tpmdev" id is "tpm0" and is referenced by "tpmdev=tpm0" in the device option.

-tpmdev emulator, id=id, chardev=dev
(Linux-host only) Enable access to a TPM emulator using Unix domain socket based chardev backend.

chardev specifies the unique ID of a character device backend that provides connection to the
software TPM server.

To create a TPM emulator backend device with chardev socket backend:

-chardev socket,id=chrtpm,path=/tmp/swtpm-sock -tpmdev emulator,id=tpm0,chardev=chrtpm -device tpm-tis,tpmdev=tpm0

Linux/Multiboot boot specific

When using these options, you can use a given Linux or Multiboot kernel without installing it in the disk
image. It can be useful for easier testing of various kernels.

-kernel bzImage
Use bzImage as kernel image. The kernel can be either a Linux kernel or in multiboot format.

-append cmdline
Use cmdline as kernel command line

-initrd file
Use file as initial ram disk.

-initrd "file1 arg=foo,file2"
This syntax is only available with multiboot.

Use file1 and file2 as modules and pass arg=foo as parameter to the first module.

-dtb file
Use file as a device tree binary (dtb) image and pass it to the kernel on boot.

Debug/Expert options

-fw_cfg [name=]name,file=file
Add named fw_cfg entry with contents from file file.

-fw_cfg [name=]name,string=str
Add named fw_cfg entry with contents from string str.

The terminating NUL character of the contents of str will not be included as part of the fw_cfg item
data. To insert contents with embedded NUL characters, you have to use the file parameter.

The fw_cfg entries are passed by QEMU through to the guest.

Example:

-fw_cfg name=opt/com.mycompany/blob,file=./my_blob.bin

creates an fw_cfg entry named opt/com.mycompany/blob with contents from ./my_blob.bin.

-serial dev
Redirect the virtual serial port to host character device dev. The default device is "vc" in
graphical mode and "stdio" in non graphical mode.

This option can be used several times to simulate up to 4 serial ports.

Use "-serial none" to disable all serial ports.

Available character devices are:

vc[:WxH]
Virtual console. Optionally, a width and height can be given in pixel with

vc:800x600

It is also possible to specify width or height in characters:

vc:80Cx24C

pty [Linux only] Pseudo TTY (a new PTY is automatically allocated)

none
No device is allocated.

null
void device

chardev:id
Use a named character device defined with the "-chardev" option.

/dev/XXX
[Linux only] Use host tty, e.g. /dev/ttyS0. The host serial port parameters are set according to
the emulated ones.

/dev/parportN
[Linux only, parallel port only] Use host parallel port N. Currently SPP and EPP parallel port
features can be used.

file:filename
Write output to filename. No character can be read.

stdio
[Unix only] standard input/output

pipe:filename
name pipe filename

COMn
[Windows only] Use host serial port n

udp:[remote_host]:remote_port[@[src_ip]:src_port]
This implements UDP Net Console. When remote_host or src_ip are not specified they default to
0.0.0.0. When not using a specified src_port a random port is automatically chosen.

If you just want a simple readonly console you can use "netcat" or "nc", by starting QEMU with:
"-serial udp::4555" and nc as: "nc -u -l -p 4555". Any time QEMU writes something to that port it
will appear in the netconsole session.

If you plan to send characters back via netconsole or you want to stop and start QEMU a lot of
times, you should have QEMU use the same source port each time by using something like "-serial
udp::4555@4556" to QEMU. Another approach is to use a patched version of netcat which can listen
to a TCP port and send and receive characters via udp. If you have a patched version of netcat
which activates telnet remote echo and single char transfer, then you can use the following
options to set up a netcat redirector to allow telnet on port 5555 to access the QEMU port.

"QEMU Options:"
-serial udp::4555@4556

"netcat options:"
-u -P 4555 -L 0.0.0.0:4556 -t -p 5555 -I -T

"telnet options:"
localhost 5555

tcp:[host]:port[,server][,nowait][,nodelay][,reconnect=seconds]
The TCP Net Console has two modes of operation. It can send the serial I/O to a location or wait
for a connection from a location. By default the TCP Net Console is sent to host at the port.
If you use the server option QEMU will wait for a client socket application to connect to the
port before continuing, unless the "nowait" option was specified. The "nodelay" option disables
the Nagle buffering algorithm. The "reconnect" option only applies if noserver is set, if the
connection goes down it will attempt to reconnect at the given interval. If host is omitted,
0.0.0.0 is assumed. Only one TCP connection at a time is accepted. You can use "telnet" to
connect to the corresponding character device.

"Example to send tcp console to 192.168.0.2 port 4444"
-serial tcp:192.168.0.2:4444

"Example to listen and wait on port 4444 for connection"
-serial tcp::4444,server

"Example to not wait and listen on ip 192.168.0.100 port 4444"
-serial tcp:192.168.0.100:4444,server,nowait

telnet:host:port[,server][,nowait][,nodelay]
The telnet protocol is used instead of raw tcp sockets. The options work the same as if you had
specified "-serial tcp". The difference is that the port acts like a telnet server or client
using telnet option negotiation. This will also allow you to send the MAGIC_SYSRQ sequence if
you use a telnet that supports sending the break sequence. Typically in unix telnet you do it
with Control-] and then type "send break" followed by pressing the enter key.

unix:path[,server][,nowait][,reconnect=seconds]
A unix domain socket is used instead of a tcp socket. The option works the same as if you had
specified "-serial tcp" except the unix domain socket path is used for connections.

mon:dev_string
This is a special option to allow the monitor to be multiplexed onto another serial port. The
monitor is accessed with key sequence of Control-a and then pressing c. dev_string should be any
one of the serial devices specified above. An example to multiplex the monitor onto a telnet
server listening on port 4444 would be:

"-serial mon:telnet::4444,server,nowait"

When the monitor is multiplexed to stdio in this way, Ctrl+C will not terminate QEMU any more but
will be passed to the guest instead.

braille
Braille device. This will use BrlAPI to display the braille output on a real or fake device.

msmouse
Three button serial mouse. Configure the guest to use Microsoft protocol.

-parallel dev
Redirect the virtual parallel port to host device dev (same devices as the serial port). On Linux
hosts, /dev/parportN can be used to use hardware devices connected on the corresponding host parallel
port.

This option can be used several times to simulate up to 3 parallel ports.

Use "-parallel none" to disable all parallel ports.

-monitor dev
Redirect the monitor to host device dev (same devices as the serial port). The default device is
"vc" in graphical mode and "stdio" in non graphical mode. Use "-monitor none" to disable the default
monitor.

-qmp dev
Like -monitor but opens in 'control' mode.

-qmp-pretty dev
Like -qmp but uses pretty JSON formatting.

-mon [chardev=]name[,mode=readline|control]
Setup monitor on chardev name.

-debugcon dev
Redirect the debug console to host device dev (same devices as the serial port). The debug console
is an I/O port which is typically port 0xe9; writing to that I/O port sends output to this device.
The default device is "vc" in graphical mode and "stdio" in non graphical mode.

-pidfile file
Store the QEMU process PID in file. It is useful if you launch QEMU from a script.

-singlestep
Run the emulation in single step mode.

-S Do not start CPU at startup (you must type 'c' in the monitor).

-realtime mlock=on|off
Run qemu with realtime features. mlocking qemu and guest memory can be enabled via mlock=on (enabled
by default).

-gdb dev
Wait for gdb connection on device dev. Typical connections will likely be TCP-based, but also UDP,
pseudo TTY, or even stdio are reasonable use case. The latter is allowing to start QEMU from within
gdb and establish the connection via a pipe:

(gdb) target remote | exec qemu-system-i386 -gdb stdio ...

-s Shorthand for -gdb tcp::1234, i.e. open a gdbserver on TCP port 1234.

-d item1[,...]
Enable logging of specified items. Use '-d help' for a list of log items.

-D logfile
Output log in logfile instead of to stderr

-dfilter range1[,...]
Filter debug output to that relevant to a range of target addresses. The filter spec can be either
start+size, start-size or start..end where start end and size are the addresses and sizes required.
For example:

-dfilter 0x8000..0x8fff,0xffffffc000080000+0x200,0xffffffc000060000-0x1000

Will dump output for any code in the 0x1000 sized block starting at 0x8000 and the 0x200 sized block
starting at 0xffffffc000080000 and another 0x1000 sized block starting at 0xffffffc00005f000.

-L path
Set the directory for the BIOS, VGA BIOS and keymaps.

To list all the data directories, use "-L help".

-bios file
Set the filename for the BIOS.

-enable-kvm
Enable KVM full virtualization support. This option is only available if KVM support is enabled when
compiling.

-enable-hax
Enable HAX (Hardware-based Acceleration eXecution) support. This option is only available if HAX
support is enabled when compiling. HAX is only applicable to MAC and Windows platform, and thus does
not conflict with KVM.

-xen-domid id
Specify xen guest domain id (XEN only).

-xen-create
Create domain using xen hypercalls, bypassing xend. Warning: should not be used when xend is in use
(XEN only).

-xen-attach
Attach to existing xen domain. xend will use this when starting QEMU (XEN only). Restrict set of
available xen operations to specified domain id (XEN only).

-no-reboot
Exit instead of rebooting.

-no-shutdown
Don't exit QEMU on guest shutdown, but instead only stop the emulation. This allows for instance
switching to monitor to commit changes to the disk image.

-loadvm file
Start right away with a saved state ("loadvm" in monitor)

-daemonize
Daemonize the QEMU process after initialization. QEMU will not detach from standard IO until it is
ready to receive connections on any of its devices. This option is a useful way for external
programs to launch QEMU without having to cope with initialization race conditions.

-option-rom file
Load the contents of file as an option ROM. This option is useful to load things like EtherBoot.

-rtc [base=utc|localtime|date][,clock=host|vm][,driftfix=none|slew]
Specify base as "utc" or "localtime" to let the RTC start at the current UTC or local time,
respectively. "localtime" is required for correct date in MS-DOS or Windows. To start at a specific
point in time, provide date in the format "2006-06-17T16:01:21" or "2006-06-17". The default base is
UTC.

By default the RTC is driven by the host system time. This allows using of the RTC as accurate
reference clock inside the guest, specifically if the host time is smoothly following an accurate
external reference clock, e.g. via NTP. If you want to isolate the guest time from the host, you can
set clock to "rt" instead. To even prevent it from progressing during suspension, you can set it to
"vm".

Enable driftfix (i386 targets only) if you experience time drift problems, specifically with Windows'
ACPI HAL. This option will try to figure out how many timer interrupts were not processed by the
Windows guest and will re-inject them.

-icount [shift=N|auto][,rr=record|replay,rrfile=filename,rrsnapshot=snapshot]
Enable virtual instruction counter. The virtual cpu will execute one instruction every 2^N ns of
virtual time. If "auto" is specified then the virtual cpu speed will be automatically adjusted to
keep virtual time within a few seconds of real time.

When the virtual cpu is sleeping, the virtual time will advance at default speed unless sleep=on|off
is specified. With sleep=on|off, the virtual time will jump to the next timer deadline instantly
whenever the virtual cpu goes to sleep mode and will not advance if no timer is enabled. This
behavior give deterministic execution times from the guest point of view.

Note that while this option can give deterministic behavior, it does not provide cycle accurate
emulation. Modern CPUs contain superscalar out of order cores with complex cache hierarchies. The
number of instructions executed often has little or no correlation with actual performance.

align=on will activate the delay algorithm which will try to synchronise the host clock and the
virtual clock. The goal is to have a guest running at the real frequency imposed by the shift option.
Whenever the guest clock is behind the host clock and if align=on is specified then we print a
message to the user to inform about the delay. Currently this option does not work when shift is
"auto". Note: The sync algorithm will work for those shift values for which the guest clock runs
ahead of the host clock. Typically this happens when the shift value is high (how high depends on the
host machine).

When rr option is specified deterministic record/replay is enabled. Replay log is written into
filename file in record mode and read from this file in replay mode.

Option rrsnapshot is used to create new vm snapshot named snapshot at the start of execution
recording. In replay mode this option is used to load the initial VM state.

-watchdog model
Create a virtual hardware watchdog device. Once enabled (by a guest action), the watchdog must be
periodically polled by an agent inside the guest or else the guest will be restarted. Choose a model
for which your guest has drivers.

The model is the model of hardware watchdog to emulate. Use "-watchdog help" to list available
hardware models. Only one watchdog can be enabled for a guest.

The following models may be available:

ib700
iBASE 700 is a very simple ISA watchdog with a single timer.

i6300esb
Intel 6300ESB I/O controller hub is a much more featureful PCI-based dual-timer watchdog.

diag288
A virtual watchdog for s390x backed by the diagnose 288 hypercall (currently KVM only).

-watchdog-action action
The action controls what QEMU will do when the watchdog timer expires. The default is "reset"
(forcefully reset the guest). Other possible actions are: "shutdown" (attempt to gracefully shutdown
the guest), "poweroff" (forcefully poweroff the guest), "pause" (pause the guest), "debug" (print a
debug message and continue), or "none" (do nothing).

Note that the "shutdown" action requires that the guest responds to ACPI signals, which it may not be
able to do in the sort of situations where the watchdog would have expired, and thus
"-watchdog-action shutdown" is not recommended for production use.

Examples:

"-watchdog i6300esb -watchdog-action pause"
"-watchdog ib700"
-echr numeric_ascii_value
Change the escape character used for switching to the monitor when using monitor and serial sharing.
The default is 0x01 when using the "-nographic" option. 0x01 is equal to pressing "Control-a". You
can select a different character from the ascii control keys where 1 through 26 map to Control-a
through Control-z. For instance you could use the either of the following to change the escape
character to Control-t.

"-echr 0x14"
"-echr 20"
-virtioconsole c
Set virtio console.

This option is maintained for backward compatibility.

Please use "-device virtconsole" for the new way of invocation.

-show-cursor
Show cursor.

-tb-size n
Set TB size.

-incoming tcp:[host]:port[,to=maxport][,ipv4][,ipv6]
-incoming rdma:host:port[,ipv4][,ipv6]
Prepare for incoming migration, listen on a given tcp port.

-incoming unix:socketpath
Prepare for incoming migration, listen on a given unix socket.

-incoming fd:fd
Accept incoming migration from a given filedescriptor.

-incoming exec:cmdline
Accept incoming migration as an output from specified external command.

-incoming defer
Wait for the URI to be specified via migrate_incoming. The monitor can be used to change settings
(such as migration parameters) prior to issuing the migrate_incoming to allow the migration to begin.

-only-migratable
Only allow migratable devices. Devices will not be allowed to enter an unmigratable state.

-nodefaults
Don't create default devices. Normally, QEMU sets the default devices like serial port, parallel
port, virtual console, monitor device, VGA adapter, floppy and CD-ROM drive and others. The
"-nodefaults" option will disable all those default devices.

-chroot dir
Immediately before starting guest execution, chroot to the specified directory. Especially useful in
combination with -runas.

-runas user
Immediately before starting guest execution, drop root privileges, switching to the specified user.

-prom-env variable=value
Set OpenBIOS nvram variable to given value (PPC, SPARC only).

-semihosting
Enable semihosting mode (ARM, M68K, Xtensa, MIPS only).

-semihosting-config [enable=on|off][,target=native|gdb|auto][,arg=str[,...]]
Enable and configure semihosting (ARM, M68K, Xtensa, MIPS only).

target="native|gdb|auto"
Defines where the semihosting calls will be addressed, to QEMU ("native") or to GDB ("gdb"). The
default is "auto", which means "gdb" during debug sessions and "native" otherwise.

arg=str1,arg=str2,...
Allows the user to pass input arguments, and can be used multiple times to build up a list. The
old-style "-kernel"/"-append" method of passing a command line is still supported for backward
compatibility. If both the "--semihosting-config arg" and the "-kernel"/"-append" are specified,
the former is passed to semihosting as it always takes precedence.

-old-param
Old param mode (ARM only).

-sandbox arg[,obsolete=string][,elevateprivileges=string][,spawn=string][,resourcecontrol=string]
Enable Seccomp mode 2 system call filter. 'on' will enable syscall filtering and 'off' will disable
it. The default is 'off'.

obsolete=string
Enable Obsolete system calls

elevateprivileges=string
Disable set*uid|gid system calls

spawn=string
Disable *fork and execve

resourcecontrol=string
Disable process affinity and schedular priority

-readconfig file
Read device configuration from file. This approach is useful when you want to spawn QEMU process with
many command line options but you don't want to exceed the command line character limit.

-writeconfig file
Write device configuration to file. The file can be either filename to save command line and device
configuration into file or dash "-") character to print the output to stdout. This can be later used
as input file for "-readconfig" option.

-no-user-config
The "-no-user-config" option makes QEMU not load any of the user-provided config files on sysconfdir.

-trace [[enable=]pattern][,events=file][,file=file]
Specify tracing options.

[enable=]pattern
Immediately enable events matching pattern. The file must contain one event name (as listed in
the trace-events-all file) per line; globbing patterns are accepted too. This option is only
available if QEMU has been compiled with the simple, log or ftrace tracing backend. To specify
multiple events or patterns, specify the -trace option multiple times.

Use "-trace help" to print a list of names of trace points.

events=file
Immediately enable events listed in file. The file must contain one event name (as listed in the
trace-events-all file) per line; globbing patterns are accepted too. This option is only
available if QEMU has been compiled with the simple, log or ftrace tracing backend.

file=file
Log output traces to file. This option is only available if QEMU has been compiled with the
simple tracing backend.

-enable-fips
Enable FIPS 140-2 compliance mode.

-msg timestamp[=on|off]
prepend a timestamp to each log message.(default:on)

-dump-vmstate file
Dump json-encoded vmstate information for current machine type to file in file

Generic object creation

-object typename[,prop1=value1,...]
Create a new object of type typename setting properties in the order they are specified. Note that
the 'id' property must be set. These objects are placed in the '/objects' path.

-object memory-backend-file,id=id,size=size,mem-path=dir,share=on|off,discard-data=on|off,align=align
Creates a memory file backend object, which can be used to back the guest RAM with huge pages.
The id parameter is a unique ID that will be used to reference this memory region when
configuring the -numa argument. The size option provides the size of the memory region, and
accepts common suffixes, eg 500M. The mem-path provides the path to either a shared memory or
huge page filesystem mount. The share boolean option determines whether the memory region is
marked as private to QEMU, or shared. The latter allows a co-operating external process to access
the QEMU memory region. Setting the discard-data boolean option to on indicates that file
contents can be destroyed when QEMU exits, to avoid unnecessarily flushing data to the backing
file. Note that discard-data is only an optimization, and QEMU might not discard file contents
if it aborts unexpectedly or is terminated using SIGKILL.

The align option specifies the base address alignment when QEMU mmap(2) mem-path, and accepts
common suffixes, eg 2M. Some backend store specified by mem-path requires an alignment different
than the default one used by QEMU, eg the device DAX /dev/dax0.0 requires 2M alignment rather
than 4K. In such cases, users can specify the required alignment via this option.

-object rng-random,id=id,filename=/dev/random
Creates a random number generator backend which obtains entropy from a device on the host. The id
parameter is a unique ID that will be used to reference this entropy backend from the virtio-rng
device. The filename parameter specifies which file to obtain entropy from and if omitted
defaults to /dev/random.

-object rng-egd,id=id,chardev=chardevid
Creates a random number generator backend which obtains entropy from an external daemon running
on the host. The id parameter is a unique ID that will be used to reference this entropy backend
from the virtio-rng device. The chardev parameter is the unique ID of a character device backend
that provides the connection to the RNG daemon.

-object tls-creds-anon,id=id,endpoint=endpoint,dir=/path/to/cred/dir,verify-peer=on|off
Creates a TLS anonymous credentials object, which can be used to provide TLS support on network
backends. The id parameter is a unique ID which network backends will use to access the
credentials. The endpoint is either server or client depending on whether the QEMU network
backend that uses the credentials will be acting as a client or as a server. If verify-peer is
enabled (the default) then once the handshake is completed, the peer credentials will be
verified, though this is a no-op for anonymous credentials.

The dir parameter tells QEMU where to find the credential files. For server endpoints, this
directory may contain a file dh-params.pem providing diffie-hellman parameters to use for the TLS
server. If the file is missing, QEMU will generate a set of DH parameters at startup. This is a
computationally expensive operation that consumes random pool entropy, so it is recommended that
a persistent set of parameters be generated upfront and saved.

-object tls-creds-x509,id=id,endpoint=endpoint,dir=/path/to/cred/dir,verify-peer=on|off,passwordid=id
Creates a TLS anonymous credentials object, which can be used to provide TLS support on network
backends. The id parameter is a unique ID which network backends will use to access the
credentials. The endpoint is either server or client depending on whether the QEMU network
backend that uses the credentials will be acting as a client or as a server. If verify-peer is
enabled (the default) then once the handshake is completed, the peer credentials will be
verified. With x509 certificates, this implies that the clients must be provided with valid
client certificates too.

For x509 certificate credentials the directory will contain further files providing the x509
certificates. The certificates must be stored in PEM format, in filenames ca-cert.pem, ca-crl.pem
(optional), server-cert.pem (only servers), server-key.pem (only servers), client-cert.pem (only
clients), and client-key.pem (only clients).

For the server-key.pem and client-key.pem files which contain sensitive private keys, it is
possible to use an encrypted version by providing the passwordid parameter. This provides the ID
of a previously created "secret" object containing the password for decryption.

-object filter-buffer,id=id,netdev=netdevid,interval=t[,queue=all|rx|tx][,status=on|off]
Interval t can't be 0, this filter batches the packet delivery: all packets arriving in a given
interval on netdev netdevid are delayed until the end of the interval. Interval is in
microseconds. status is optional that indicate whether the netfilter is on (enabled) or off
(disabled), the default status for netfilter will be 'on'.

queue all|rx|tx is an option that can be applied to any netfilter.

all: the filter is attached both to the receive and the transmit queue of the netdev (default).

rx: the filter is attached to the receive queue of the netdev, where it will receive packets sent
to the netdev.

tx: the filter is attached to the transmit queue of the netdev, where it will receive packets
sent by the netdev.

-object filter-mirror,id=id,netdev=netdevid,outdev=chardevid,queue=all|rx|tx[,vnet_hdr_support]
filter-mirror on netdev netdevid,mirror net packet to chardevchardevid, if it has the
vnet_hdr_support flag, filter-mirror will mirror packet with vnet_hdr_len.

-object
filter-redirector,id=id,netdev=netdevid,indev=chardevid,outdev=chardevid,queue=all|rx|tx[,vnet_hdr_support]
filter-redirector on netdev netdevid,redirect filter's net packet to chardev chardevid,and
redirect indev's packet to filter.if it has the vnet_hdr_support flag, filter-redirector will
redirect packet with vnet_hdr_len. Create a filter-redirector we need to differ outdev id from
indev id, id can not be the same. we can just use indev or outdev, but at least one of indev or
outdev need to be specified.

-object filter-rewriter,id=id,netdev=netdevid,queue=all|rx|tx,[vnet_hdr_support]
Filter-rewriter is a part of COLO project.It will rewrite tcp packet to secondary from primary to
keep secondary tcp connection,and rewrite tcp packet to primary from secondary make tcp packet
can be handled by client.if it has the vnet_hdr_support flag, we can parse packet with vnet
header.

usage: colo secondary: -object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0 -object
filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1 -object
filter-rewriter,id=rew0,netdev=hn0,queue=all

-object filter-dump,id=id,netdev=dev[,file=filename][,maxlen=len]
Dump the network traffic on netdev dev to the file specified by filename. At most len bytes (64k
by default) per packet are stored. The file format is libpcap, so it can be analyzed with tools
such as tcpdump or Wireshark.

-object
colo-compare,id=id,primary_in=chardevid,secondary_in=chardevid,outdev=chardevid[,vnet_hdr_support]
Colo-compare gets packet from primary_inchardevid and secondary_inchardevid, than compare primary
packet with secondary packet. If the packets are same, we will output primary packet to
outdevchardevid, else we will notify colo-frame do checkpoint and send primary packet to
outdevchardevid. if it has the vnet_hdr_support flag, colo compare will send/recv packet with
vnet_hdr_len.

we must use it with the help of filter-mirror and filter-redirector.

primary:
-netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown
-device e1000,id=e0,netdev=hn0,mac=52:a4:00:12:78:66
-chardev socket,id=mirror0,host=3.3.3.3,port=9003,server,nowait
-chardev socket,id=compare1,host=3.3.3.3,port=9004,server,nowait
-chardev socket,id=compare0,host=3.3.3.3,port=9001,server,nowait
-chardev socket,id=compare0-0,host=3.3.3.3,port=9001
-chardev socket,id=compare_out,host=3.3.3.3,port=9005,server,nowait
-chardev socket,id=compare_out0,host=3.3.3.3,port=9005
-object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0
-object filter-redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out
-object filter-redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0
-object colo-compare,id=comp0,primary_in=compare0-0,secondary_in=compare1,outdev=compare_out0

secondary:
-netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,down script=/etc/qemu-ifdown
-device e1000,netdev=hn0,mac=52:a4:00:12:78:66
-chardev socket,id=red0,host=3.3.3.3,port=9003
-chardev socket,id=red1,host=3.3.3.3,port=9004
-object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0
-object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1

If you want to know the detail of above command line, you can read the colo-compare git log.

-object cryptodev-backend-builtin,id=id[,queues=queues]
Creates a cryptodev backend which executes crypto opreation from the QEMU cipher APIS. The id
parameter is a unique ID that will be used to reference this cryptodev backend from the virtio-
crypto device. The queues parameter is optional, which specify the queue number of cryptodev
backend, the default of queues is 1.

# qemu-system-x86_64 \
[...] \
-object cryptodev-backend-builtin,id=cryptodev0 \
-device virtio-crypto-pci,id=crypto0,cryptodev=cryptodev0 \
[...]

-object secret,id=id,data=string,format=raw|base64[,keyid=secretid,iv=string]
-object secret,id=id,file=filename,format=raw|base64[,keyid=secretid,iv=string]
Defines a secret to store a password, encryption key, or some other sensitive data. The sensitive
data can either be passed directly via the data parameter, or indirectly via the file parameter.
Using the data parameter is insecure unless the sensitive data is encrypted.

The sensitive data can be provided in raw format (the default), or base64. When encoded as JSON,
the raw format only supports valid UTF-8 characters, so base64 is recommended for sending binary
data. QEMU will convert from which ever format is provided to the format it needs internally. eg,
an RBD password can be provided in raw format, even though it will be base64 encoded when passed
onto the RBD sever.

For added protection, it is possible to encrypt the data associated with a secret using the
AES-256-CBC cipher. Use of encryption is indicated by providing the keyid and iv parameters. The
keyid parameter provides the ID of a previously defined secret that contains the AES-256
decryption key. This key should be 32-bytes long and be base64 encoded. The iv parameter provides
the random initialization vector used for encryption of this particular secret and should be a
base64 encrypted string of the 16-byte IV.

The simplest (insecure) usage is to provide the secret inline

# $QEMU -object secret,id=sec0,data=letmein,format=raw

The simplest secure usage is to provide the secret via a file

# printf "letmein" > mypasswd.txt # $QEMU -object secret,id=sec0,file=mypasswd.txt,format=raw

For greater security, AES-256-CBC should be used. To illustrate usage, consider the openssl
command line tool which can encrypt the data. Note that when encrypting, the plaintext must be
padded to the cipher block size (32 bytes) using the standard PKCS#5/6 compatible padding
algorithm.

First a master key needs to be created in base64 encoding:

# openssl rand -base64 32 > key.b64
# KEY=$(base64 -d key.b64 | hexdump -v -e '/1 "%02X"')

Each secret to be encrypted needs to have a random initialization vector generated. These do not
need to be kept secret

# openssl rand -base64 16 > iv.b64
# IV=$(base64 -d iv.b64 | hexdump -v -e '/1 "%02X"')

The secret to be defined can now be encrypted, in this case we're telling openssl to base64
encode the result, but it could be left as raw bytes if desired.

# SECRET=$(printf "letmein" |
openssl enc -aes-256-cbc -a -K $KEY -iv $IV)

When launching QEMU, create a master secret pointing to "key.b64" and specify that to be used to
decrypt the user password. Pass the contents of "iv.b64" to the second secret

# $QEMU \
-object secret,id=secmaster0,format=base64,file=key.b64 \
-object secret,id=sec0,keyid=secmaster0,format=base64,\
data=$SECRET,iv=$(<iv.b64)

During the graphical emulation, you can use special key combinations to change modes. The default key
mappings are shown below, but if you use "-alt-grab" then the modifier is Ctrl-Alt-Shift (instead of
Ctrl-Alt) and if you use "-ctrl-grab" then the modifier is the right Ctrl key (instead of Ctrl-Alt):

Ctrl-Alt-f
Toggle full screen

Ctrl-Alt-+
Enlarge the screen

Ctrl-Alt--
Shrink the screen

Ctrl-Alt-u
Restore the screen's un-scaled dimensions

Ctrl-Alt-n
Switch to virtual console 'n'. Standard console mappings are:

1 Target system display

2 Monitor

3 Serial port

Ctrl-Alt
Toggle mouse and keyboard grab.

In the virtual consoles, you can use Ctrl-Up, Ctrl-Down, Ctrl-PageUp and Ctrl-PageDown to move in the
back log.

During emulation, if you are using a character backend multiplexer (which is the default if you are using
-nographic) then several commands are available via an escape sequence. These key sequences all start
with an escape character, which is Ctrl-a by default, but can be changed with -echr. The list below
assumes you're using the default.

Ctrl-a h
Print this help

Ctrl-a x
Exit emulator

Ctrl-a s
Save disk data back to file (if -snapshot)

Ctrl-a t
Toggle console timestamps

Ctrl-a b
Send break (magic sysrq in Linux)

Ctrl-a c
Rotate between the frontends connected to the multiplexer (usually this switches between the monitor
and the console)

Ctrl-a Ctrl-a
Send the escape character to the frontend

The following options are specific to the PowerPC emulation:

-g WxH[xDEPTH]
Set the initial VGA graphic mode. The default is 800x600x32.

-prom-env string
Set OpenBIOS variables in NVRAM, for example:

qemu-system-ppc -prom-env 'auto-boot?=false' \
-prom-env 'boot-device=hd:2,\yaboot' \
-prom-env 'boot-args=conf=hd:2,\yaboot.conf'

These variables are not used by Open Hack'Ware.

The following options are specific to the Sparc32 emulation:

-g WxHx[xDEPTH]
Set the initial graphics mode. For TCX, the default is 1024x768x8 with the option of 1024x768x24. For
cgthree, the default is 1024x768x8 with the option of 1152x900x8 for people who wish to use OBP.

-prom-env string
Set OpenBIOS variables in NVRAM, for example:

qemu-system-sparc -prom-env 'auto-boot?=false' \
-prom-env 'boot-device=sd(0,2,0):d' -prom-env 'boot-args=linux single'

-M [SS-4|SS-5|SS-10|SS-20|SS-600MP|LX|Voyager|SPARCClassic] [|SPARCbook]
Set the emulated machine type. Default is SS-5.

The following options are specific to the Sparc64 emulation:

-prom-env string
Set OpenBIOS variables in NVRAM, for example:

qemu-system-sparc64 -prom-env 'auto-boot?=false'

-M [sun4u|sun4v|niagara]
Set the emulated machine type. The default is sun4u.

The following options are specific to the ARM emulation:

-semihosting
Enable semihosting syscall emulation.

On ARM this implements the "Angel" interface.

Note that this allows guest direct access to the host filesystem, so should only be used with trusted
guest OS.

The following options are specific to the ColdFire emulation:

-semihosting
Enable semihosting syscall emulation.

On M68K this implements the "ColdFire GDB" interface used by libgloss.

Note that this allows guest direct access to the host filesystem, so should only be used with trusted
guest OS.

The following options are specific to the Xtensa emulation:

-semihosting
Enable semihosting syscall emulation.

Xtensa semihosting provides basic file IO calls, such as open/read/write/seek/select. Tensilica
baremetal libc for ISS and linux platform "sim" use this interface.

Note that this allows guest direct access to the host filesystem, so should only be used with trusted
guest OS.

AUTHOR

       Fabrice Bellard

                                                   2023-03-02                                          QEMU.1(1)

NAME

SYNOPSIS

DESCRIPTION

OPTIONS

SEE ALSO

AUTHOR