# Invocation¶

 man begin SYNOPSIS
qemu-system-i386 [options] [disk_image]
man end


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

Standard options:

-h
-h

Display help and exit

-version
-version

Display version information and exit

-machine [type=]name[,prop=value[,...]]
-machine

Select the emulated machine by name. Use -machine help to list available machines. Supported machine properties are:

accel=accels1[:accels2[:...]]
This is used to enable an accelerator. Depending on the target architecture, kvm, xen, 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.
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.
-cpu model
-cpu

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

-smp

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=cpu[-cpu]][,nodeid=node]
-numa node[,memdev=id][,cpus=cpu[-cpu]][,nodeid=node]
-numa

Simulate a multi node NUMA system. If ‘mem’, ‘memdev’ and ‘cpus’ are omitted, resources are split equally. Also, note that the -numa option doesn’t allocate any of the specified resources. That is, 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, and possibly -object to specify the memory backend for the ‘memdev’ suboption.

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

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
-drive file=/dev/fdset/2,index=0,media=disk

-set group.id.arg=value
-set

Set parameter arg for item id of type group

-global driver.prop=value
-global driver=driver,property=property,value=value
-global

Set default value of driver’s property prop to value, e.g.:

qemu-system-i386 -global ide-drive.physical_block_size=4096 -drive file=file,if=ide,index=0,media=disk


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

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.

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.


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]
-m

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
-mem-path

Allocate guest RAM from a temporarily created file in path.

-mem-prealloc
-mem-prealloc

Preallocate memory when using -mem-path.

-k language
-k

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
-audio-help

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

-soundhw card1[,card2,...] or -soundhw all
-soundhw

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
-balloon

Disable balloon device.

-device driver[,prop[=value][,...]]
-device

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:

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.

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
-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
-uuid

Set system UUID.

Block device options:

-fda file
-fdb file
-fda-fdb

Use file as floppy disk 0/1 image (see disk_images).

-hda file
-hdb file
-hdc file
-hdd file
-hda-hdb-hdc-hdd

Use file as hard disk 0, 1, 2 or 3 image (see disk_images).

-cdrom file
-cdrom

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 (see host_drives).

-drive option[,option[,option[,...]]]
-drive

Define a new drive. Valid options are:

file=file

This option defines which disk image (see disk_images) 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.
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.
These options have the same definition as they have in -hdachs.
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.
aio=aio
aio is “threads”, or “native” and selects between pthread based disk I/O and native Linux AIO.
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.
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.
Specify the controller’s PCI address (if=virtio only).
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.
Open drive file as read-only. Guest write attempts will fail.
copy-on-read is “on” or “off” and enables whether to copy read backing file sectors into the image file.
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.

By default, the cache=writeback 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=writethrough. 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.

The host page cache can be avoided entirely with cache=none. This will attempt to do disk IO directly to the guest’s memory. QEMU may still perform an internal copy of the data. Note that this is considered a writeback mode and the guest OS must handle the disk write cache correctly in order to avoid data corruption on host crashes.

The host page cache can be avoided while only sending write notifications to the guest when the data has been flushed to the disk using cache=directsync.

In case you don’t care about data integrity over host failures, use cache=unsafe. 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. 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
-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


You can connect a SCSI disk with unit ID 6 on the bus #0:

qemu-system-i386 -drive file=file,if=scsi,bus=0,unit=6


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
-mtdblock

Use file as on-board Flash memory image.

-sd file
-sd

Use file as SecureDigital card image.

-pflash file
-pflash

Use file as a parallel flash image.

-snapshot
-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 (see disk_images).

-hdachs c,h,s,[,t]
-hdachs

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 useful for old MS-DOS disk images.

-fsdev

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.
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

-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

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.
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.
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
-virtfs_synth
-virtfs_synth

Create synthetic file system image

USB options:

-usb
-usb

Enable the USB driver (will be the default soon)

-usbdevice devname
-usbdevice

Add the USB device devname. See usb_devices.

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.
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
-display

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
-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
-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
-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
-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
-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
-no-quit

Disable SDL window close capability.

-sdl
-sdl

Enable SDL.

-spice option[,option[,...]]
-spice

Enable the spice remote desktop protocol. Valid options are

port=<nr>
Set the TCP port spice is listening on for plaintext channels.
Set the IP address spice is listening on. Default is any address.
ipv4
ipv6
unix
Force using the specified IP version.
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-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.
tls-channel=[main|display|cursor|inputs|record|playback]
plaintext-channel=[main|display|cursor|inputs|record|playback]
Force specific channel to be used with or without TLS encryption. The options can be specified multiple times to configure multiple channels. The special name “default” can be used to set the default mode. For channels which are not explicitly forced into one mode the spice client is allowed to pick tls/plaintext as he pleases.
image-compression=[auto_glz|auto_lz|quic|glz|lz|off]
Configure image compression (lossless). Default is auto_glz.
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.
-portrait
-portrait

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

-rotate deg
-rotate

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

-vga type
-vga

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 one is the default)
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.
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
-full-screen

Start in full screen.

-g widthxheight[xdepth]
-g

Set the initial graphical resolution and depth (PPC, SPARC only).

-vnc display[,option[,option[,...]]]
-vnc

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 -usbdevice 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. By definition the Websocket port is 5700+display. If host is specified connections will only be allowed from this host. As an alternative the Websocket port could be specified by using websocket=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.

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.
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 1. 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
-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
-no-fd-bootchk

Disable boot signature checking for floppy disks in BIOS. May be needed to boot from old floppy disks.

-no-acpi
-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
-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]...]
-acpitable

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
-smbios

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

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][,...]
-netdev
-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.

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

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


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.

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 socket,listen=:1234
# connect the VLAN 0 of this instance to the VLAN 0
# of the first instance
qemu-system-i386 linux.img \
-net socket,connect=127.0.0.1:1234


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 socket,mcast=230.0.0.1:1234
# launch another QEMU instance on same "bus"
qemu-system-i386 linux.img \
-net socket,mcast=230.0.0.1:1234
# launch yet another QEMU instance on same "bus"
qemu-system-i386 linux.img \
-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 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 \


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.

udp
select udp encapsulation (default is ip).
srcport=srcport
source udp port.
dstport=dstport
destination udp port.
ipv6
force v6, otherwise defaults to v4.
Cookies are a weak form of security in the l2tpv3 specification. Their function is mostly to prevent misconfiguration. By default they are 32 bit.
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

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

# 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,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]
-chardev

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 \
-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 \
-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. See Keys in the character backend multiplexer.

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.

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.

stdio is not available on Windows hosts.

-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


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


LIBISCSI_CHAP_USERNAME="user" \
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.

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

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


GlusterFS

GlusterFS is an 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

gluster[+transport]://[server[:port]]/volname/image[?socket=...]


Example

qemu-system-x86_64 --drive file=gluster://192.0.2.1/testvol/a.img


HTTP/HTTPS/FTP/FTPS/TFTP

Syntax using a single filename:

<protocol>://[<username>[:<password>]@]<host>/<path>


where:

protocol
’http’, ’https’, ’ftp’, ’ftps’, or ’tftp’.
Optional username for authentication to the remote server.
Optional password for authentication to the remote server.
host
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.
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’.
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



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



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[...]
-bt

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]
-tpmdev

Backend type must be: passthrough.

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.

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
-kernel

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

-append cmdline
-append

Use cmdline as kernel command line

-initrd file
-initrd

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
-dtb

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
-fw_cfg

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
-serial

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 step 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
-parallel

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
-monitor

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
-qmp

Like -monitor but opens in ’control’ mode.

-qmp-pretty dev
-qmp-pretty

Like -qmp but uses pretty JSON formatting.

-mon

Setup monitor on chardev name.

-debugcon dev
-debugcon

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
-pidfile

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

-singlestep
-singlestep

Run the emulation in single step mode.

-S
-S

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

-realtime mlock=on|off
-realtime

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

-gdb dev
-gdb

Wait for gdb connection on device dev (see gdb_usage). 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
-s

Shorthand for -gdb tcp::1234, i.e. open a gdbserver on TCP port 1234 (see gdb_usage).

-d item1[,...]
-d

Enable logging of specified items. Use ’-d help’ for a list of log items.

-D logfile
-D

-dfilter range1[,...]
-dfilter

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
-L

Set the directory for the BIOS, VGA BIOS and keymaps.

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

-bios file
-bios

Set the filename for the BIOS.

-enable-kvm
-enable-kvm

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

-xen-domid id
-xen-domid

Specify xen guest domain id (XEN only).

-xen-create
-xen-create

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

-xen-attach
-xen-attach

Attach to existing xen domain. xend will use this when starting QEMU (XEN only).

-no-reboot
-no-reboot

-no-shutdown
-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.

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

-daemonize
-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
-option-rom

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]
-rtc

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]
-icount

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.

-watchdog model
-watchdog

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
-watchdog-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
-echr

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
-virtioconsole

Set virtio console.

This option is maintained for backward compatibility.

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

-show-cursor
-show-cursor

Show cursor.

-tb-size n
-tb-size

Set TB size.

-incoming tcp:[host]:port[,to=maxport][,ipv4][,ipv6]
-incoming rdma:host:port[,ipv4][,ipv6]
-incoming

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.
-nodefaults
-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
-chroot

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

-runas user
-runas

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

-prom-env variable=value
-prom-env

Set OpenBIOS nvram variable to given value (PPC, SPARC only).

-semihosting
-semihosting

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

-semihosting-config [enable=on|off][,target=native|gdb|auto][,arg=str[,...]]
-semihosting-config

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 (ARM)

Old param mode (ARM only).

-sandbox arg
-sandbox

Enable Seccomp mode 2 system call filter. ’on’ will enable syscall filtering and ’off’ will disable it. The default is ’off’.

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
-writeconfig

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.

-nodefconfig
-nodefconfig

Normally QEMU loads configuration files from sysconfdir and datadir at startup. The -nodefconfig option will prevent QEMU from loading any of those config files.

-no-user-config
-no-user-config

The -no-user-config option makes QEMU not load any of the user-provided config files on sysconfdir, but won’t make it skip the QEMU-provided config files from datadir.

-trace [[enable=]pattern][,events=file][,file=file]
-trace

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, stderr 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, stderr 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

Enable FIPS 140-2 compliance mode.

-msg timestamp[=on|off]
-msg

prepend a timestamp to each log message.(default:on)

-dump-vmstate file
-dump-vmstate

Dump json-encoded vmstate information for current machine type to file in file Generic object creation

-object typename[,prop1=value1,...]
-object

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
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.
-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.

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.

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.

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]
filter-mirror on netdev netdevid,mirror net packet to chardev chardevid
-object filter-redirector,id=id,netdev=netdevid,indev=chardevid,

outdev=chardevid[,queue=all|rx|tx]

filter-redirector on netdev netdevid,redirect filter’s net packet to chardev chardevid,and redirect indev’s packet to filter. 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,rewriter-mode=mode[,queue=all|rx|tx]

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.

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

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.

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


# $QEMU -object secret,id=sec0,data=letmein,format=raw  The simplest secure usage is to provide the secret via a file # echo -n “letmein” > mypasswd.txt #$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=$(echo -n "letmein" | openssl enc -aes-256-cbc -a -K$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)