Invocationqemu-system-i386 [options] [disk_image]
disk_image is a raw hard disk image for IDE hard disk 0. Some
targets do not need a disk image.
Standard options:
-hDisplay help and exit
-versionDisplay version information and exit
-machineSelect the emulated machine by name. Use -machine help to list
available machines. Supported machine properties are:
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.
Controls in-kernel irqchip support for the chosen accelerator when available.
Enables IGD GFX passthrough support for the chosen machine when available.
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.
Include guest memory in a core dump. The default is on.
Enables or disables memory merge support. This feature, when supported by
the host, de-duplicates identical memory pages among VMs instances
(enabled by default).
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.
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.
Enables or disables NVDIMM support. The default is off.
-cpuSelect CPU model (-cpu help for list and additional feature selection)
-smpSimulate 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.
-numaSimulate a multi node NUMA system. If ‘mem’, ‘memdev’
and ‘cpus’ are omitted, resources are split equally. Also, note
that the - 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 , options
to allocate RAM and VCPUs respectively, and possibly
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-fdAdd a file descriptor to an fd set. Valid options are:
This option defines the file descriptor of which a duplicate is added to fd set.
The file descriptor cannot be stdin, stdout, or stderr.
This option defines the ID of the fd set to add the file descriptor to.
This option defines a free-form string that can be used to describe fd.
You can open an image using pre-opened file descriptors from an fd set:
qemu-system-i386
-add-fd fd=3,set=2,opaque="rdwr:/path/to/file"
-add-fd fd=4,set=2,opaque="rdonly:/path/to/file"
-drive file=/dev/fdset/2,index=0,media=disk
-setSet parameter arg for item id of type group-globalSet 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 -.
-global driver.prop=value is shorthand for -global
driver=driver,property=prop,value=value. The
longhand syntax works even when driver contains a dot.
-bootSpecify 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
.
Interactive boot menus/prompts can be enabled via 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 as far as firmware/BIOS
supports it. This only effects when boot priority is changed by
bootindex options. The default is non-strict boot.
# try to boot from network first, then from hard disk
qemu-system-i386 -boot order=nc
# boot from CD-ROM first, switch back to default order after reboot
qemu-system-i386 -boot once=d
# boot with a splash picture for 5 seconds.
qemu-system-i386 -boot menu=on,splash=/root/boot.bmp,splash-time=5000
Note: The legacy format ’-boot drives’ is still supported but its
use is discouraged as it may be removed from future versions.
-mSets 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-pathAllocate guest RAM from a temporarily created file in path.
-mem-preallocPreallocate memory when using -mem-path.
-kUse 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-helpWill show the audio subsystem help: list of drivers, tunable
parameters.
-soundhwEnable 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
-balloonDisable balloon device.
Enable virtio balloon device (default), optionally with PCI address
addr.
-deviceAdd 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.
Add a KCS IPMI interafce on the ISA bus. This also adds a
corresponding ACPI and SMBIOS entries, if appropriate.
The BMC to connect to, one of ipmi-bmc-sim or ipmi-bmc-extern above.
Define the I/O address of the interface. The default is 0xca0 for KCS.
Define the interrupt to use. The default is 5. To disable interrupts,
set this to 0.
Like the KCS interface, but defines a BT interface. The default port is
0xe4 and the default interrupt is 5.
-nameSets 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.
-uuidSet system UUID.
Block device options:
-fda-fdbUse file as floppy disk 0/1 image (see disk_images).
-hda-hdb-hdc-hddUse file as hard disk 0, 1, 2 or 3 image (see disk_images).
-cdromUse file as CD-ROM image (you cannot use and
at the same time). You can use the host CD-ROM by
using /dev/cdrom as filename (see host_drives).
-driveDefine a new drive. Valid options are:
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.
This option defines on which type on interface the drive is connected.
Available types are: ide, scsi, sd, mtd, floppy, pflash, virtio.
These options define where is connected the drive by defining the bus number and
the unit id.
This option defines where is connected the drive by using an index in the list
of available connectors of a given interface type.
This option defines the type of the media: disk or cdrom.
These options have the same definition as they have in .
snapshot is "on" or "off" and controls snapshot mode for the given drive
(see ).
cache is "none", "writeback", "unsafe", "directsync" or "writethrough" and controls how the host cache is used to access block data.
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.
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.
This option specifies the serial number to assign to the device.
Specify the controller’s PCI address (if=virtio only).
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 and .
Open drive 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 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 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 . 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 . 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
.
In case you don’t care about data integrity over host failures, use
. 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 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 you can use:
qemu-system-i386 -drive file=file,index=2,media=cdrom
Instead of , , , , you can
use:
qemu-system-i386 -drive file=file,index=0,media=disk
qemu-system-i386 -drive file=file,index=1,media=disk
qemu-system-i386 -drive file=file,index=2,media=disk
qemu-system-i386 -drive file=file,index=3,media=disk
You can open an image using pre-opened file descriptors from an fd set:
qemu-system-i386
-add-fd fd=3,set=2,opaque="rdwr:/path/to/file"
-add-fd fd=4,set=2,opaque="rdonly:/path/to/file"
-drive file=/dev/fdset/2,index=0,media=disk
You can connect a CDROM to the slave of ide0:
qemu-system-i386 -drive file=file,if=ide,index=1,media=cdrom
If you don’t specify the "file=" argument, you define an empty drive:
qemu-system-i386 -drive if=ide,index=1,media=cdrom
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 , , 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
-mtdblockUse file as on-board Flash memory image.
-sdUse file as SecureDigital card image.
-pflashUse file as a parallel flash image.
-snapshotWrite 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).
-hdachsForce 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.
-fsdevDefine a new file system device. Valid options are:
This option specifies the fs driver backend to use.
Currently "local", "handle" and "proxy" file system drivers are supported.
Specifies identifier for this device
Specifies the export path for the file system device. Files under
this path will be available to the 9p client on the guest.
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.
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.
Enables proxy filesystem driver to use passed socket file for communicating
with virtfs-proxy-helper
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".
Options for virtio-9p-pci driver are:
Specifies the id value specified along with -fsdev option
Specifies the tag name to be used by the guest to mount this export point
-virtfsThe general form of a Virtual File system pass-through options are:
This option specifies the fs driver backend to use.
Currently "local", "handle" and "proxy" file system drivers are supported.
Specifies identifier for this device
Specifies the export path for the file system device. Files under
this path will be available to the 9p client on the guest.
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.
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.
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
Enables proxy filesystem driver to use passed ’sock_fd’ as the socket
descriptor for interfacing with virtfs-proxy-helper
-virtfs_synthCreate synthetic file system image
USB options:
-usbEnable the USB driver (will be the default soon)
-usbdeviceAdd the USB device devname. See usb_devices.
Virtual Mouse. This will override the PS/2 mouse emulation when activated.
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.
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).
Pass through the host device identified by vendor_id:product_id
(Linux only).
Serial converter to host character device dev, see -serial for the
available devices.
Braille device. This will use BrlAPI to display the braille output on a real
or fake device.
Network adapter that supports CDC ethernet and RNDIS protocols.
Display options:
-displaySelect type of display to use. This option is a replacement for the
old style -sdl/-curses/... options. Valid values for type are
Display video output via SDL (usually in a separate graphics
window; see the SDL documentation for other possibilities).
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.
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.
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.
Start a VNC server on display <arg>
-nographicNormally, 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.
-cursesNormally, 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-frameDo 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-grabUse 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-grabUse Right-Ctrl to grab mouse (instead of Ctrl-Alt). Note that this also
affects the special keys (for fullscreen, monitor-mode switching, etc).
-no-quitDisable SDL window close capability.
-sdlEnable SDL.
-spiceEnable the spice remote desktop protocol. Valid options are
Set the TCP port spice is listening on for plaintext channels.
Set the IP address spice is listening on. Default is any address.
Force using the specified IP version.
Set the password you need to authenticate.
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.
Allow client connects without authentication.
Disable copy paste between the client and the guest.
Disable spice-vdagent based file-xfer between the client and the guest.
Set the TCP port spice is listening on for encrypted channels.
Set the x509 file directory. Expects same filenames as -vnc $display,x509=$dir
The x509 file names can also be configured individually.
Specify which ciphers to use.
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.
Configure image compression (lossless).
Default is auto_glz.
Configure wan image compression (lossy for slow links).
Default is auto.
Configure video stream detection. Default is off.
Enable/disable passing mouse events via vdagent. Default is on.
Enable/disable audio stream compression (using celt 0.5.1). Default is on.
Enable/disable spice seamless migration. Default is off.
Enable/disable OpenGL context. Default is off.
-portraitRotate graphical output 90 deg left (only PXA LCD).
-rotateRotate graphical output some deg left (only PXA LCD).
-vgaSelect type of VGA card to emulate. Valid values for type are
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)
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 SVGA-II compatible adapter. Use it if you have sufficiently
recent XFree86/XOrg server or Windows guest with a driver for this
card.
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.
(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.
(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 VGA card.
Disable VGA card.
-full-screenStart in full screen.
-gSet the initial graphical resolution and depth (PPC, SPARC only).
-vncNormally, 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 ). When using the VNC display, you
must use the parameter to set the keyboard layout if you are
not using en-us. Valid syntax for the display is
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.
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.
Connections will be allowed over UNIX domain sockets where path is the
location of a unix socket to listen for connections on.
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
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.
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.
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 argument.
The parameter obsoletes the ,
, and options, and as such
it is not permitted to set both new and old type options at
the same time.
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
or options.
This option is now deprecated in favor of using the
argument.
Valid if 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
argument.
Valid if 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
argument.
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.
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 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.
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.
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.
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-hackUse 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-bootchkDisable boot signature checking for floppy disks in BIOS. May
be needed to boot from old floppy disks.
-no-acpiDisable ACPI (Advanced Configuration and Power Interface) support. Use
it if your guest OS complains about ACPI problems (PC target machine
only).
-no-hpetDisable HPET support.
-acpitableAdd 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.
-smbiosLoad SMBIOS entry from binary file.
Specify SMBIOS type 0 fields
Specify SMBIOS type 1 fields
Specify SMBIOS type 2 fields
Specify SMBIOS type 3 fields
Specify SMBIOS type 4 fields
Specify SMBIOS type 17 fields
Network options:
-netCreate 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 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.
-netdevUse the user mode network stack which requires no administrator
privilege to run. Valid options are:
Connect user mode stack to VLAN n (n = 0 is the default).
Assign symbolic name for use in monitor commands.
and 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.
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.
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.
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 [...]
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).
When using the user mode network stack, broadcast file as the BOOTP
filename. In conjunction with , 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.
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.
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 or
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.
=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"
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
Connect the VLAN n to a remote VLAN in another QEMU virtual
machine using a TCP socket connection. If is
specified, QEMU waits for incoming connections on port
(host is optional). is used to connect to
another QEMU instance using the option. =h
specifies an already opened TCP socket.
Example:
# launch a first QEMU instance
qemu-system-i386 linux.img \
-net nic,macaddr=52:54:00:12:34:56 \
-net socket,listen=:1234
# connect the VLAN 0 of this instance to the VLAN 0
# of the first instance
qemu-system-i386 linux.img \
-net nic,macaddr=52:54:00:12:34:57 \
-net socket,connect=127.0.0.1:1234
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:
Several QEMU can be running on different hosts and share same bus (assuming
correct multicast setup for these hosts).
mcast support is compatible with User Mode Linux (argument ), see
http://user-mode-linux.sf.net.
Use to specify an already opened UDP multicast socket.
Example:
# launch one QEMU instance
qemu-system-i386 linux.img \
-net nic,macaddr=52:54:00:12:34:56 \
-net socket,mcast=230.0.0.1:1234
# launch another QEMU instance on same "bus"
qemu-system-i386 linux.img \
-net nic,macaddr=52:54:00:12:34:57 \
-net socket,mcast=230.0.0.1:1234
# launch yet another QEMU instance on same "bus"
qemu-system-i386 linux.img \
-net nic,macaddr=52:54:00:12:34:58 \
-net socket,mcast=230.0.0.1:1234
Example (User Mode Linux compat.):
# launch QEMU instance (note mcast address selected
# is UML's default)
qemu-system-i386 linux.img \
-net nic,macaddr=52:54:00:12:34:56 \
-net socket,mcast=239.192.168.1:1102
# launch UML
/path/to/linux ubd0=/path/to/root_fs eth0=mcast
Example (send packets from host’s 1.2.3.4):
qemu-system-i386 linux.img \
-net nic,macaddr=52:54:00:12:34:56 \
-net socket,mcast=239.192.168.1:1102,localaddr=1.2.3.4
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.
source address (mandatory)
destination address (mandatory)
select udp encapsulation (default is ip).
source udp port.
destination udp port.
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.
Set cookie size to 64 bit instead of the default 32
Force a ’cut-down’ L2TPv3 with no counter as in
draft-mkonstan-l2tpext-keyed-ipv6-tunnel-00
Work around broken counter handling in peer. This may also help on
networks which have packet reorder.
Add an extra offset between header and data
For example, to attach a VM running on host 4.3.2.1 via L2TPv3 to the bridge br-lan
on the remote Linux host 1.2.3.4:
# Setup tunnel on linux host using raw ip as encapsulation
# on 1.2.3.4
ip l2tp add tunnel remote 4.3.2.1 local 1.2.3.4 tunnel_id 1 peer_tunnel_id 1 \
encap udp udp_sport 16384 udp_dport 16384
ip l2tp add session tunnel_id 1 name vmtunnel0 session_id \
0xFFFFFFFF peer_session_id 0xFFFFFFFF
ifconfig vmtunnel0 mtu 1500
ifconfig vmtunnel0 up
brctl addif br-lan vmtunnel0
# on 4.3.2.1
# launch QEMU instance - if your network has reorder or is very lossy add ,pincounter
qemu-system-i386 linux.img -net nic -net l2tpv3,src=4.2.3.1,dst=1.2.3.4,udp,srcport=16384,dstport=16384,rxsession=0xffffffff,txsession=0xffffffff,counter
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
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 create the
required hub automatically.
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
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.
Indicate that no network devices should be configured. It is used to
override the default configuration () which
is activated if no options are provided.
Character device options:
The general form of a character device option is:
-chardevBackend is one of:
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
.
.
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 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 and , QEMU will
create a multiplexer with your specified ID, and you can then configure multiple
front ends to use that chardev ID for their input/output. Up to four different
front ends can be connected to a single multiplexed chardev. (Without
multiplexing enabled, a chardev can only be used by a single front end.)
For instance you could use this to allow a single stdio chardev to be used by
two serial ports and the QEMU monitor:
-chardev stdio,mux=on,id=char0 \
-mon chardev=char0,mode=readline \
-serial chardev:char0 \
-serial chardev:char0
You can have more than one multiplexer in a system configuration; for instance
you could have a TCP port multiplexed between UART 0 and UART 1, and stdio
multiplexed between the QEMU monitor and a parallel port:
-chardev stdio,mux=on,id=char0 \
-mon chardev=char0,mode=readline \
-parallel chardev:char0 \
-chardev tcp,...,mux=on,id=char1 \
-serial chardev:char1 \
-serial chardev:char1
When you’re using a multiplexed character device, some escape sequences are
interpreted in the input. See Keys in the character backend
multiplexer.
Note that some other command line options may implicitly create multiplexed
character backends; for instance creates a
multiplexed stdio backend connected to the serial port and the QEMU monitor,
and 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 option, which supplies the path
to a file to record all data transmitted via the backend. The
option controls whether the log file will be truncated or appended to when
opened.
Further options to each backend are described below.
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.
Create a two-way stream socket, which can be either a TCP or a unix socket. A
unix socket will be created if is specified. Behaviour is
undefined if TCP options are specified for a unix socket.
specifies that the socket shall be a listening socket.
specifies that QEMU should not block waiting for a client to
connect to a listening socket.
specifies that traffic on the socket should interpret telnet
escape sequences.
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.
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
argument.
TCP and unix socket options are given below:
for a listening socket specifies the local address to be bound.
For a connecting socket species the remote host to connect to. is
optional for listening sockets. If not specified it defaults to 0.0.0.0.
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.
can be given as either a port number or a service name.
is required.
is only relevant to listening sockets. If it is specified, and
cannot be bound, QEMU will attempt to bind to subsequent ports up
to and including until it succeeds. must be specified
as a port number.
and specify that either IPv4 or IPv6 must be used.
If neither is specified the socket may use either protocol.
disables the Nagle algorithm.
specifies the local path of the unix socket. is
required.
Sends all traffic from the guest to a remote host over UDP.
specifies the remote host to connect to. If not specified it
defaults to localhost.
specifies the port on the remote host to connect to.
is required.
specifies the local address to bind to. If not specified it
defaults to 0.0.0.0.
specifies the local port to bind to. If not specified any
available local port will be used.
and specify that either IPv4 or IPv6 must be used.
If neither is specified the device may use either protocol.
Forward QEMU’s emulated msmouse events to the guest. does not
take any options.
Connect to a QEMU text console. may optionally be given a specific
size.
and specify the width and height respectively of
the console, in pixels.
and specify that the console be sized to fit a text
console with the given dimensions.
Create a ring buffer with fixed size .
size must be a power of two and defaults to 64K.
Log all traffic received from the guest to a file.
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.
is required.
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\.
On other hosts, 2 pipes will be created called .in and
.out. Data written to .in will be
received by the guest. Data written by the guest can be read from
.out. QEMU will not create these fifos, and requires them to
be present.
forms part of the pipe path as described above. is
required.
Send traffic from the guest to QEMU’s standard output. does not
take any options.
is only available on Windows hosts.
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.
specifies the name of the serial device to open.
Create a new pseudo-terminal on the host and connect to it. does
not take any options.
is not available on Windows hosts.
Connect to standard input and standard output of the QEMU process.
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 to disable it.
is not available on Windows hosts.
Connect to a local BrlAPI server. does not take any options.
is only available on Linux, Sun, FreeBSD, NetBSD, OpenBSD and
DragonFlyBSD hosts. It is an alias for .
specifies the path to the tty. is required.
is only available on Linux, FreeBSD and DragonFlyBSD hosts.
Connect to a local parallel port.
specifies the path to the parallel port device. is
required.
is only available when spice support is built in.
debug level for spicevmc
name of spice channel to connect to
Connect to a spice virtual machine channel, such as vdiport.
is only available when spice support is built in.
debug level for spicevmc
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 support allows QEMU to access iSCSI resources directly and use as
images for the guest storage. Both disk and cdrom images are supported.
Syntax for specifying iSCSI LUNs is
“iscsi://<target-ip>[:<port>]/<target-iqn>/<lun>”
By default qemu will use the iSCSI initiator-name
’iqn.2008-11.org.linux-kvm[:<name>]’ but this can also be set from the command
line or a configuration file.
Since version Qemu 2.4 it is possible to specify a iSCSI request timeout to detect
stalled requests and force a reestablishment of the session. The timeout
is specified in seconds. The default is 0 which means no timeout. Libiscsi
1.15.0 or greater is required for this feature.
Example (without authentication):
qemu-system-i386 -iscsi initiator-name=iqn.2001-04.com.example:my-initiator \
-cdrom iscsi://192.0.2.1/iqn.2001-04.com.example/2 \
-drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1
Example (CHAP username/password via URL):
qemu-system-i386 -drive file=iscsi://user%password@192.0.2.1/iqn.2001-04.com.example/1
Example (CHAP username/password via environment variables):
LIBISCSI_CHAP_USERNAME="user" \
LIBISCSI_CHAP_PASSWORD="password" \
qemu-system-i386 -drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1
iSCSI support is an optional feature of QEMU and only available when
compiled and linked against libiscsi.
iSCSI parameters such as username and password can also be specified via
a configuration file. See qemu-doc for more information and examples.
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
QEMU supports SSH (Secure Shell) access to remote disks.
Examples:
qemu-system-i386 -drive file=ssh://user@host/path/to/disk.img
qemu-system-i386 -drive file.driver=ssh,file.user=user,file.host=host,file.port=22,file.path=/path/to/disk.img
Currently authentication must be done using ssh-agent. Other
authentication methods may be supported in future.
Sheepdog is a distributed storage system for QEMU.
QEMU supports using either local sheepdog devices or remote networked
devices.
Syntax for specifying a sheepdog device
sheepdog[+tcp|+unix]://[host:port]/vdiname[?socket=path][#snapid|#tag]
Example
qemu-system-i386 --drive file=sheepdog://192.0.2.1:30000/MyVirtualMachine
See also http://http://www.osrg.net/sheepdog/.
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
See also http://www.gluster.org.
QEMU supports read-only access to files accessed over http(s), ftp(s) and tftp.
Syntax using a single filename:
<protocol>://[<username>[:<password>]@]<host>/<path>
where:
’http’, ’https’, ’ftp’, ’ftps’, or ’tftp’.
Optional username for authentication to the remote server.
Optional password for authentication to the remote server.
Address of the remote server.
Path on the remote server, including any query string.
The following options are also supported:
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.
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.
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, is the value
of <protocol>.
Example: boot from a remote Fedora 20 live ISO image
qemu-system-x86_64 --drive media=cdrom,file=http://dl.fedoraproject.org/pub/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso,readonly
qemu-system-x86_64 --drive media=cdrom,file.driver=http,file.url=http://dl.fedoraproject.org/pub/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso,readonly
Example: boot from a remote Fedora 20 cloud image using a local overlay for
writes, copy-on-read, and a readahead of 64k
qemu-img create -f qcow2 -o backing_file='json:{"file.driver":"http",, "file.url":"https://dl.fedoraproject.org/pub/fedora/linux/releases/20/Images/x86_64/Fedora-x86_64-20-20131211.1-sda.qcow2",, "file.readahead":"64k"}' /tmp/Fedora-x86_64-20-20131211.1-sda.qcow2
qemu-system-x86_64 -drive file=/tmp/Fedora-x86_64-20-20131211.1-sda.qcow2,copy-on-read=on
Example: boot from an image stored on a VMware vSphere server with a self-signed
certificate using a local overlay for writes, a readahead of 64k and a timeout
of 10 seconds.
qemu-img create -f qcow2 -o backing_file='json:{"file.driver":"https",, "file.url":"https://user:password@vsphere.example.com/folder/test/test-flat.vmdk?dcPath=Datacenter&dsName=datastore1",, "file.sslverify":"off",, "file.readahead":"64k",, "file.timeout":10}' /tmp/test.qcow2
qemu-system-x86_64 -drive file=/tmp/test.qcow2
Bluetooth(R) options:
-btDefines 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:
(default) The corresponding Bluetooth HCI assumes no internal logic
and will not respond to any HCI commands or emit events.
(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.
Add a virtual, standard HCI that will participate in the Bluetooth
scatternet n (default 0). Similarly to
VLANs, devices inside a bluetooth network n can only communicate
with other devices in the same network (scatternet).
(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
Emulate a bluetooth device dev and place it in network n
(default 0). QEMU can only emulate one type of bluetooth devices
currently:
Virtual wireless keyboard implementing the HIDP bluetooth profile.
TPM device options:
The general form of a TPM device option is:
-tpmdevBackend type must be:
.
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
(Linux-host only) Enable access to the host’s TPM using the passthrough
driver.
specifies the path to the host’s TPM device, i.e., on
a Linux host this would be /dev/tpm0.
is optional and by default /dev/tpm0 is used.
specifies the path to the host TPM device’s sysfs
entry allowing for cancellation of an ongoing TPM command.
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.
-kernelUse bzImage as kernel image. The kernel can be either a Linux kernel
or in multiboot format.
-appendUse cmdline as kernel command line
-initrdUse file as initial ram disk.
This syntax is only available with multiboot.
Use file1 and file2 as modules and pass arg=foo as parameter to the
first module.
-dtbUse file as a device tree binary (dtb) image and pass it to the kernel
on boot.
Debug/Expert options:
-fw_cfgAdd named fw_cfg entry with contents from file file.
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.
-serialRedirect 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:
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
[Linux only] Pseudo TTY (a new PTY is automatically allocated)
No device is allocated.
void device
Use a named character device defined with the -chardev option.
[Linux only] Use host tty, e.g. /dev/ttyS0. The host serial port
parameters are set according to the emulated ones.
[Linux only, parallel port only] Use host parallel port
N. Currently SPP and EPP parallel port features can be used.
Write output to filename. No character can be read.
[Unix only] standard input/output
name pipe filename[Windows only] Use host serial port nThis 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
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
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.
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.
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,nowaitWhen 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 device. This will use BrlAPI to display the braille output on a real
or fake device.
Three button serial mouse. Configure the guest to use Microsoft protocol.
-parallelRedirect 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.
-monitorRedirect 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.
-qmpLike -monitor but opens in ’control’ mode.
-qmp-prettyLike -qmp but uses pretty JSON formatting.
-monSetup monitor on chardev name.
-debugconRedirect 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.
-pidfileStore the QEMU process PID in file. It is useful if you launch QEMU
from a script.
-singlestepRun the emulation in single step mode.
-SDo not start CPU at startup (you must type ’c’ in the monitor).
-realtimeRun qemu with realtime features.
mlocking qemu and guest memory can be enabled via
(enabled by default).
-gdbWait 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 ...
-sShorthand for -gdb tcp::1234, i.e. open a gdbserver on TCP port 1234
(see gdb_usage).
-dEnable logging of specified items. Use ’-d help’ for a list of log items.
-DOutput log in logfile instead of to stderr
-dfilterFilter 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 startend 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.
-LSet the directory for the BIOS, VGA BIOS and keymaps.
To list all the data directories, use -L help.
-biosSet the filename for the BIOS.
-enable-kvmEnable KVM full virtualization support. This option is only available
if KVM support is enabled when compiling.
-xen-domidSpecify xen guest domain id (XEN only).
-xen-createCreate domain using xen hypercalls, bypassing xend.
Warning: should not be used when xend is in use (XEN only).
-xen-attachAttach to existing xen domain.
xend will use this when starting QEMU (XEN only).
-no-rebootExit instead of rebooting.
-no-shutdownDon’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.
-loadvmStart right away with a saved state (loadvm in monitor)
-daemonizeDaemonize 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-romLoad the contents of file as an option ROM.
This option is useful to load things like EtherBoot.
-rtcSpecify 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
to rt instead. To even prevent it from progressing during suspension,
you can set it to vm.
Enable (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.
-icountEnable 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 is specified.
With , 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.
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
is specified then we print a message to the user
to inform about the delay.
Currently this option does not work when 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 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.
-watchdogCreate 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:
iBASE 700 is a very simple ISA watchdog with a single timer.
Intel 6300ESB I/O controller hub is a much more featureful PCI-based
dual-timer watchdog.
A virtual watchdog for s390x backed by the diagnose 288 hypercall
(currently KVM only).
-watchdog-actionThe 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-echrChange 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-virtioconsoleSet virtio console.
This option is maintained for backward compatibility.
Please use -device virtconsole for the new way of invocation.
-show-cursorShow cursor.
-tb-sizeSet TB size.
-incomingPrepare for incoming migration, listen on a given tcp port.
Prepare for incoming migration, listen on a given unix socket.
Accept incoming migration from a given filedescriptor.
Accept incoming migration as an output from specified external command.
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.
-nodefaultsDon’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.
-chrootImmediately before starting guest execution, chroot to the specified
directory. Especially useful in combination with -runas.
-runasImmediately before starting guest execution, drop root privileges, switching
to the specified user.
-prom-envSet OpenBIOS nvram variable to given value (PPC, SPARC only).
-semihostingEnable semihosting mode (ARM, M68K, Xtensa, MIPS only).
-semihosting-configEnable and configure semihosting (ARM, M68K, Xtensa, MIPS only).
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.
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 (ARM)Old param mode (ARM only).
-sandboxEnable Seccomp mode 2 system call filter. ’on’ will enable syscall filtering and ’off’ will
disable it. The default is ’off’.
-readconfigRead 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.
-writeconfigWrite 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.
-nodefconfigNormally 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-configThe -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.
-traceSpecify tracing options.
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 option multiple times.
Use -trace help to print a list of names of trace points.
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.
Log output traces to file.
This option is only available if QEMU has been compiled with
the simple tracing backend.
-enable-fipsEnable FIPS 140-2 compliance mode.
-msgprepend a timestamp to each log message.(default:on)
-dump-vmstateDump json-encoded vmstate information for current machine type to file
in file
Generic object creation
-objectCreate 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.
Creates a memory file backend object, which can be used to back
the guest RAM with huge pages. The parameter is a
unique ID that will be used to reference this memory region
when configuring the argument. The
option provides the size of the memory region, and accepts
common suffixes, eg . The provides
the path to either a shared memory or huge page filesystem mount.
The 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.
Creates a random number generator backend which obtains entropy from
a device on the host. The parameter is a unique ID that
will be used to reference this entropy backend from the
device. The parameter specifies which file to obtain
entropy from and if omitted defaults to .
Creates a random number generator backend which obtains entropy from
an external daemon running on the host. The parameter is
a unique ID that will be used to reference this entropy backend from
the device. The parameter is
the unique ID of a character device backend that provides the connection
to the RNG daemon.
Creates a TLS anonymous credentials object, which can be used to provide
TLS support on network backends. The parameter is a unique
ID which network backends will use to access the credentials. The
is either or depending
on whether the QEMU network backend that uses the credentials will be
acting as a client or as a server. If 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 parameter is a unique
ID which network backends will use to access the credentials. The
is either or depending
on whether the QEMU network backend that uses the credentials will be
acting as a client or as a server. If 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.
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.
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.
: the filter is attached both to the receive and the transmit
queue of the netdev (default).
: the filter is attached to the receive queue of the netdev,
where it will receive packets sent to the netdev.
: the filter is attached to the transmit queue of the netdev,
where it will receive packets sent by the netdev.
filter-mirror on netdev netdevid,mirror net packet to chardev
chardevidoutdev=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.
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
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.
outdev=chardevidColo-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.
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 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 \
[...]
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)