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qemu-system-x86_64.man.txt
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qemu-system-x86_64.man.txt
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QEMU(1) QEMU QEMU(1)
NAME
qemu - QEMU User Documentation
SYNOPSIS
qemu-system-x86_64 [options] [disk_image]
DESCRIPTION
The QEMU PC System emulator simulates the following peripherals:
• i440FX host PCI bridge and PIIX3 PCI to ISA bridge
• Cirrus CLGD 5446 PCI VGA card or dummy VGA card with Bochs VESA extensions (hardware level, including all non standard modes).
• PS/2 mouse and keyboard
• 2 PCI IDE interfaces with hard disk and CD-ROM support
• Floppy disk
• PCI and ISA network adapters
• Serial ports
• IPMI BMC, either and internal or external one
• Creative SoundBlaster 16 sound card
• ENSONIQ AudioPCI ES1370 sound card
• Intel 82801AA AC97 Audio compatible sound card
• Intel HD Audio Controller and HDA codec
• Adlib (OPL2) - Yamaha YM3812 compatible chip
• Gravis Ultrasound GF1 sound card
• CS4231A compatible sound card
• PC speaker
• PCI UHCI, OHCI, EHCI or XHCI USB controller and a virtual USB-1.1 hub.
SMP is supported with up to 255 CPUs.
QEMU uses the PC BIOS from the Seabios project and the Plex86/Bochs LGPL VGA BIOS.
QEMU uses YM3812 emulation by Tatsuyuki Satoh.
QEMU uses GUS emulation (GUSEMU32 http://www.deinmeister.de/gusemu/) by Tibor "TS" Schütz.
Note that, by default, GUS shares IRQ(7) with parallel ports and so QEMU must be told to not have parallel ports to have working GUS.
qemu-system-x86_64 dos.img -device gus -parallel none
Alternatively:
qemu-system-x86_64 dos.img -device gus,irq=5
Or some other unclaimed IRQ.
CS4231A is the chip used in Windows Sound System and GUSMAX products
The PC speaker audio device can be configured using the pcspk-audiodev machine property, i.e.
qemu-system-x86_64 some.img -audiodev <backend>,id=<name> -machine pcspk-audiodev=<name>
OPTIONS
disk_image is a raw hard disk image for IDE hard disk 0. Some targets do not need a disk image.
Standard options
-h Display help and exit
-version
Display version information and exit
-machine [type=]name[,prop=value[,...]]
Select the emulated machine by name. Use -machine help to list available machines.
For architectures which aim to support live migration compatibility across releases, each release will introduce a new versioned machine type. For example, the 2.8.0
release introduced machine types "pc-i440fx-2.8" and "pc-q35-2.8" for the x86_64/i686 architectures.
To allow live migration of guests from QEMU version 2.8.0, to QEMU version 2.9.0, the 2.9.0 version must support the "pc-i440fx-2.8" and "pc-q35-2.8" machines too. To
allow users live migrating VMs to skip multiple intermediate releases when upgrading, new releases of QEMU will support machine types from many previous versions.
Supported machine properties are:
accel=accels1[:accels2[:...]]
This is used to enable an accelerator. Depending on the target architecture, kvm, xen, hax, hvf, nvmm, whpx 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.
vmport=on|off|auto
Enables emulation of VMWare IO port, for vmmouse etc. auto says to select the value based on accel. For accel=xen the default is off otherwise the default is
on.
dump-guest-core=on|off
Include guest memory in a core dump. The default is on.
mem-merge=on|off
Enables or disables memory merge support. This feature, when supported by the host, de-duplicates identical memory pages among VMs instances (enabled by de‐
fault).
aes-key-wrap=on|off
Enables or disables AES key wrapping support on s390-ccw hosts. This feature controls whether AES wrapping keys will be created to allow execution of AES
cryptographic functions. The default is on.
dea-key-wrap=on|off
Enables or disables DEA key wrapping support on s390-ccw hosts. This feature controls whether DEA wrapping keys will be created to allow execution of DEA
cryptographic functions. The default is on.
nvdimm=on|off
Enables or disables NVDIMM support. The default is off.
memory-encryption=
Memory encryption object to use. The default is none.
hmat=on|off
Enables or disables ACPI Heterogeneous Memory Attribute Table (HMAT) support. The default is off.
memory-backend='id'
An alternative to legacy -mem-path and mem-prealloc options. Allows to use a memory backend as main RAM.
For example:
-object memory-backend-file,id=pc.ram,size=512M,mem-path=/hugetlbfs,prealloc=on,share=on
-machine memory-backend=pc.ram
-m 512M
Migration compatibility note:
• as backend id one shall use value of 'default-ram-id', advertised by machine type (available via query-machines QMP command), if migration to/from old QEMU
(<5.0) is expected.
• for machine types 4.0 and older, user shall use x-use-canonical-path-for-ramblock-id=off backend option if migration to/from old QEMU (<5.0) is expected.
For example:
-object memory-backend-ram,id=pc.ram,size=512M,x-use-canonical-path-for-ramblock-id=off
-machine memory-backend=pc.ram
-m 512M
sgx-epc.0.memdev=@var{memid}
Define an SGX EPC section.
-cpu model
Select CPU model (-cpu help for list and additional feature selection)
-accel name[,prop=value[,...]]
This is used to enable an accelerator. Depending on the target architecture, kvm, xen, hax, hvf, nvmm, whpx 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.
igd-passthru=on|off
When Xen is in use, this option controls whether Intel integrated graphics devices can be passed through to the guest (default=off)
kernel-irqchip=on|off|split
Controls KVM in-kernel irqchip support. The default is full acceleration of the interrupt controllers. On x86, split irqchip reduces the kernel attack surface,
at a performance cost for non-MSI interrupts. Disabling the in-kernel irqchip completely is not recommended except for debugging purposes.
kvm-shadow-mem=size
Defines the size of the KVM shadow MMU.
split-wx=on|off
Controls the use of split w^x mapping for the TCG code generation buffer. Some operating systems require this to be enabled, and in such a case this will de‐
fault on. On other operating systems, this will default off, but one may enable this for testing or debugging.
tb-size=n
Controls the size (in MiB) of the TCG translation block cache.
thread=single|multi
Controls number of TCG threads. When the TCG is multi-threaded there will be one thread per vCPU therefore taking advantage of additional host cores. The de‐
fault is to enable multi-threading where both the back-end and front-ends support it and no incompatible TCG features have been enabled (e.g. icount/replay).
dirty-ring-size=n
When the KVM accelerator is used, it controls the size of the per-vCPU dirty page ring buffer (number of entries for each vCPU). It should be a value that is
power of two, and it should be 1024 or bigger (but still less than the maximum value that the kernel supports). 4096 could be a good initial value if you have
no idea which is the best. Set this value to 0 to disable the feature. By default, this feature is disabled (dirty-ring-size=0). When enabled, KVM will in‐
stead record dirty pages in a bitmap.
-smp [[cpus=]n][,maxcpus=maxcpus][,sockets=sockets][,dies=dies][,cores=cores][,threads=threads]
Simulate a SMP system with 'n' CPUs initially present on the machine type board. On boards supporting CPU hotplug, the optional 'maxcpus' parameter can be set to en‐
able further CPUs to be added at runtime. When both parameters are omitted, the maximum number of CPUs will be calculated from the provided topology members and the
initial CPU count will match the maximum number. When only one of them is given then the omitted one will be set to its counterpart's value. Both parameters may be
specified, but the maximum number of CPUs must be equal to or greater than the initial CPU count. Both parameters are subject to an upper limit that is determined by
the specific machine type chosen.
To control reporting of CPU topology information, the number of sockets, dies per socket, cores per die, and threads per core can be specified. The sum `` sockets *
cores * dies * threads `` must be equal to the maximum CPU count. CPU targets may only support a subset of the topology parameters. Where a CPU target does not sup‐
port use of a particular topology parameter, its value should be assumed to be 1 for the purpose of computing the CPU maximum count.
Either the initial CPU count, or at least one of the topology parameters must be specified. The specified parameters must be greater than zero, explicit configuration
like "cpus=0" is not allowed. Values for any omitted parameters will be computed from those which are given. Historically preference was given to the coarsest topol‐
ogy parameters when computing missing values (ie sockets preferred over cores, which were preferred over threads), however, this behaviour is considered liable to
change. Prior to 6.2 the preference was sockets over cores over threads. Since 6.2 the preference is cores over sockets over threads.
-numa node[,mem=size][,cpus=firstcpu[-lastcpu]][,nodeid=node][,initiator=initiator]
-numa node[,memdev=id][,cpus=firstcpu[-lastcpu]][,nodeid=node][,initiator=initiator]
-numa dist,src=source,dst=destination,val=distance
-numa cpu,node-id=node[,socket-id=x][,core-id=y][,thread-id=z]
-numa hmat-lb,initiator=node,target=node,hierarchy=hierarchy,data-type=tpye[,latency=lat][,bandwidth=bw]
-numa hmat-cache,node-id=node,size=size,level=level[,associativity=str][,policy=str][,line=size]
Define a NUMA node and assign RAM and VCPUs to it. Set the NUMA distance from a source node to a destination node. Set the ACPI Heterogeneous Memory Attributes for
the given nodes.
Legacy VCPU assignment uses 'cpus' option where firstcpu and lastcpu are CPU indexes. Each 'cpus' option represent a contiguous range of CPU indexes (or a single VCPU
if lastcpu is omitted). A non-contiguous set of VCPUs can be represented by providing multiple 'cpus' options. If 'cpus' is omitted on all nodes, VCPUs are automati‐
cally split between them.
For example, the following option assigns VCPUs 0, 1, 2 and 5 to a NUMA node:
-numa node,cpus=0-2,cpus=5
'cpu' option is a new alternative to 'cpus' option which uses 'socket-id|core-id|thread-id' properties to assign CPU objects to a node using topology layout proper‐
ties of CPU. The set of properties is machine specific, and depends on used machine type/'smp' options. It could be queried with 'hotpluggable-cpus' monitor command.
'node-id' property specifies node to which CPU object will be assigned, it's required for node to be declared with 'node' option before it's used with 'cpu' option.
For example:
-M pc \
-smp 1,sockets=2,maxcpus=2 \
-numa node,nodeid=0 -numa node,nodeid=1 \
-numa cpu,node-id=0,socket-id=0 -numa cpu,node-id=1,socket-id=1
Legacy 'mem' assigns a given RAM amount to a node (not supported for 5.1 and newer machine types). 'memdev' assigns RAM from a given memory backend device to a node.
If 'mem' and 'memdev' are omitted in all nodes, RAM is split equally between them.
'mem' and 'memdev' are mutually exclusive. Furthermore, if one node uses 'memdev', all of them have to use it.
'initiator' is an additional option that points to an initiator NUMA node that has best performance (the lowest latency or largest bandwidth) to this NUMA node. Note
that this option can be set only when the machine property 'hmat' is set to 'on'.
Following example creates a machine with 2 NUMA nodes, node 0 has CPU. node 1 has only memory, and its initiator is node 0. Note that because node 0 has CPU, by de‐
fault the initiator of node 0 is itself and must be itself.
-machine hmat=on \
-m 2G,slots=2,maxmem=4G \
-object memory-backend-ram,size=1G,id=m0 \
-object memory-backend-ram,size=1G,id=m1 \
-numa node,nodeid=0,memdev=m0 \
-numa node,nodeid=1,memdev=m1,initiator=0 \
-smp 2,sockets=2,maxcpus=2 \
-numa cpu,node-id=0,socket-id=0 \
-numa cpu,node-id=0,socket-id=1
source and destination are NUMA node IDs. distance is the NUMA distance from source to destination. The distance from a node to itself is always 10. If any pair of
nodes is given a distance, then all pairs must be given distances. Although, when distances are only given in one direction for each pair of nodes, then the distances
in the opposite directions are assumed to be the same. If, however, an asymmetrical pair of distances is given for even one node pair, then all node pairs must be
provided distance values for both directions, even when they are symmetrical. When a node is unreachable from another node, set the pair's distance to 255.
Note that the -numa option doesn't allocate any of the specified resources, it just assigns existing resources to NUMA nodes. This means that one still has to use the
-m, -smp options to allocate RAM and VCPUs respectively.
Use 'hmat-lb' to set System Locality Latency and Bandwidth Information between initiator and target NUMA nodes in ACPI Heterogeneous Attribute Memory Table (HMAT).
Initiator NUMA node can create memory requests, usually it has one or more processors. Target NUMA node contains addressable memory.
In 'hmat-lb' option, node are NUMA node IDs. hierarchy is the memory hierarchy of the target NUMA node: if hierarchy is 'memory', the structure represents the memory
performance; if hierarchy is 'first-level|second-level|third-level', this structure represents aggregated performance of memory side caches for each domain. type of
'data-type' is type of data represented by this structure instance: if 'hierarchy' is 'memory', 'data-type' is 'access|read|write' latency or 'access|read|write'
bandwidth of the target memory; if 'hierarchy' is 'first-level|second-level|third-level', 'data-type' is 'access|read|write' hit latency or 'access|read|write' hit
bandwidth of the target memory side cache.
lat is latency value in nanoseconds. bw is bandwidth value, the possible value and units are NUM[M|G|T], mean that the bandwidth value are NUM byte per second (or
MB/s, GB/s or TB/s depending on used suffix). Note that if latency or bandwidth value is 0, means the corresponding latency or bandwidth information is not provided.
In 'hmat-cache' option, node-id is the NUMA-id of the memory belongs. size is the size of memory side cache in bytes. level is the cache level described in this
structure, note that the cache level 0 should not be used with 'hmat-cache' option. associativity is the cache associativity, the possible value is 'none/direct(di‐
rect-mapped)/complex(complex cache indexing)'. policy is the write policy. line is the cache Line size in bytes.
For example, the following options describe 2 NUMA nodes. Node 0 has 2 cpus and a ram, node 1 has only a ram. The processors in node 0 access memory in node 0 with
access-latency 5 nanoseconds, access-bandwidth is 200 MB/s; The processors in NUMA node 0 access memory in NUMA node 1 with access-latency 10 nanoseconds, ac‐
cess-bandwidth is 100 MB/s. And for memory side cache information, NUMA node 0 and 1 both have 1 level memory cache, size is 10KB, policy is write-back, the cache
Line size is 8 bytes:
-machine hmat=on \
-m 2G \
-object memory-backend-ram,size=1G,id=m0 \
-object memory-backend-ram,size=1G,id=m1 \
-smp 2,sockets=2,maxcpus=2 \
-numa node,nodeid=0,memdev=m0 \
-numa node,nodeid=1,memdev=m1,initiator=0 \
-numa cpu,node-id=0,socket-id=0 \
-numa cpu,node-id=0,socket-id=1 \
-numa hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-latency,latency=5 \
-numa hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-bandwidth,bandwidth=200M \
-numa hmat-lb,initiator=0,target=1,hierarchy=memory,data-type=access-latency,latency=10 \
-numa hmat-lb,initiator=0,target=1,hierarchy=memory,data-type=access-bandwidth,bandwidth=100M \
-numa hmat-cache,node-id=0,size=10K,level=1,associativity=direct,policy=write-back,line=8 \
-numa hmat-cache,node-id=1,size=10K,level=1,associativity=direct,policy=write-back,line=8
-add-fd fd=fd,set=set[,opaque=opaque]
Add a file descriptor to an fd set. Valid options are:
fd=fd This option defines the file descriptor of which a duplicate is added to fd set. The file descriptor cannot be stdin, stdout, or stderr.
set=set
This option defines the ID of the fd set to add the file descriptor to.
opaque=opaque
This option defines a free-form string that can be used to describe fd.
You can open an image using pre-opened file descriptors from an fd set:
qemu-system-x86_64 \
-add-fd fd=3,set=2,opaque="rdwr:/path/to/file" \
-add-fd fd=4,set=2,opaque="rdonly:/path/to/file" \
-drive file=/dev/fdset/2,index=0,media=disk
-set group.id.arg=value
Set parameter arg for item id of type group
-global driver.prop=value
-global driver=driver,property=property,value=value
Set default value of driver's property prop to value, e.g.:
qemu-system-x86_64 -global ide-hd.physical_block_size=4096 disk-image.img
In particular, you can use this to set driver properties for devices which are created automatically by the machine model. To create a device which is not created au‐
tomatically and set properties on it, use -device.
-global driver.prop=value is shorthand for -global driver=driver,property=prop,value=value. The longhand syntax works even when driver contains a dot.
-boot [order=drives][,once=drives][,menu=on|off][,splash=sp_name][,splash-time=sp_time][,reboot-timeout=rb_timeout][,strict=on|off]
Specify boot order drives as a string of drive letters. Valid drive letters depend on the target architecture. The x86 PC uses: a, b (floppy 1 and 2), c (first hard
disk), d (first CD-ROM), n-p (Etherboot from network adapter 1-4), hard disk boot is the default. To apply a particular boot order only on the first startup, specify
it via once. Note that the order or once parameter should not be used together with the bootindex property of devices, since the firmware implementations normally do
not support both at the same time.
Interactive boot menus/prompts can be enabled via menu=on as far as firmware/BIOS supports them. The default is non-interactive boot.
A splash picture could be passed to bios, enabling user to show it as logo, when option splash=sp_name is given and menu=on, If firmware/BIOS supports them. Currently
Seabios for X86 system support it. limitation: The splash file could be a jpeg file or a BMP file in 24 BPP format(true color). The resolution should be supported by
the SVGA mode, so the recommended is 320x240, 640x480, 800x640.
A timeout could be passed to bios, guest will pause for rb_timeout ms when boot failed, then reboot. If rb_timeout is '-1', guest will not reboot, qemu passes '-1' to
bios by default. Currently Seabios for X86 system support it.
Do strict boot via strict=on as far as firmware/BIOS supports it. This only effects when boot priority is changed by bootindex options. The default is non-strict
boot.
# try to boot from network first, then from hard disk
qemu-system-x86_64 -boot order=nc
# boot from CD-ROM first, switch back to default order after reboot
qemu-system-x86_64 -boot once=d
# boot with a splash picture for 5 seconds.
qemu-system-x86_64 -boot menu=on,splash=/root/boot.bmp,splash-time=5000
Note: The legacy format '-boot drives' is still supported but its use is discouraged as it may be removed from future versions.
-m [size=]megs[,slots=n,maxmem=size]
Sets guest startup RAM size to megs megabytes. Default is 128 MiB. Optionally, a suffix of "M" or "G" can be used to signify a value in megabytes or gigabytes re‐
spectively. Optional pair slots, maxmem could be used to set amount of hotpluggable memory slots and maximum amount of memory. Note that maxmem must be aligned to the
page size.
For example, the following command-line sets the guest startup RAM size to 1GB, creates 3 slots to hotplug additional memory and sets the maximum memory the guest can
reach to 4GB:
qemu-system-x86_64 -m 1G,slots=3,maxmem=4G
If slots and maxmem are not specified, memory hotplug won't be enabled and the guest startup RAM will never increase.
-mem-path path
Allocate guest RAM from a temporarily created file in path.
-mem-prealloc
Preallocate memory when using -mem-path.
-k language
Use keyboard layout language (for example fr for French). This option is only needed where it is not easy to get raw PC keycodes (e.g. on Macs, with some X11 servers
or with a VNC or curses display). You don't normally need to use it on PC/Linux or PC/Windows hosts.
The available layouts are:
ar de-ch es fo fr-ca hu ja mk no pt-br sv
da en-gb et fr fr-ch is lt nl pl ru th
de en-us fi fr-be hr it lv nl-be pt sl tr
The default is en-us.
-audio-help
Will show the -audiodev equivalent of the currently specified (deprecated) environment variables.
-audiodev [driver=]driver,id=id[,prop[=value][,...]]
Adds a new audio backend driver identified by id. There are global and driver specific properties. Some values can be set differently for input and output, they're
marked with in|out.. You can set the input's property with in.prop and the output's property with out.prop. For example:
-audiodev alsa,id=example,in.frequency=44110,out.frequency=8000
-audiodev alsa,id=example,out.channels=1 # leaves in.channels unspecified
NOTE: parameter validation is known to be incomplete, in many cases specifying an invalid option causes QEMU to print an error message and continue emulation without
sound.
Valid global options are:
id=identifier
Identifies the audio backend.
timer-period=period
Sets the timer period used by the audio subsystem in microseconds. Default is 10000 (10 ms).
in|out.mixing-engine=on|off
Use QEMU's mixing engine to mix all streams inside QEMU and convert audio formats when not supported by the backend. When off, fixed-settings must be off too.
Note that disabling this option means that the selected backend must support multiple streams and the audio formats used by the virtual cards, otherwise you'll
get no sound. It's not recommended to disable this option unless you want to use 5.1 or 7.1 audio, as mixing engine only supports mono and stereo audio. De‐
fault is on.
in|out.fixed-settings=on|off
Use fixed settings for host audio. When off, it will change based on how the guest opens the sound card. In this case you must not specify frequency, channels
or format. Default is on.
in|out.frequency=frequency
Specify the frequency to use when using fixed-settings. Default is 44100Hz.
in|out.channels=channels
Specify the number of channels to use when using fixed-settings. Default is 2 (stereo).
in|out.format=format
Specify the sample format to use when using fixed-settings. Valid values are: s8, s16, s32, u8, u16, u32, f32. Default is s16.
in|out.voices=voices
Specify the number of voices to use. Default is 1.
in|out.buffer-length=usecs
Sets the size of the buffer in microseconds.
-audiodev none,id=id[,prop[=value][,...]]
Creates a dummy backend that discards all outputs. This backend has no backend specific properties.
-audiodev alsa,id=id[,prop[=value][,...]]
Creates backend using the ALSA. This backend is only available on Linux.
ALSA specific options are:
in|out.dev=device
Specify the ALSA device to use for input and/or output. Default is default.
in|out.period-length=usecs
Sets the period length in microseconds.
in|out.try-poll=on|off
Attempt to use poll mode with the device. Default is on.
threshold=threshold
Threshold (in microseconds) when playback starts. Default is 0.
-audiodev coreaudio,id=id[,prop[=value][,...]]
Creates a backend using Apple's Core Audio. This backend is only available on Mac OS and only supports playback.
Core Audio specific options are:
in|out.buffer-count=count
Sets the count of the buffers.
-audiodev dsound,id=id[,prop[=value][,...]]
Creates a backend using Microsoft's DirectSound. This backend is only available on Windows and only supports playback.
DirectSound specific options are:
latency=usecs
Add extra usecs microseconds latency to playback. Default is 10000 (10 ms).
-audiodev oss,id=id[,prop[=value][,...]]
Creates a backend using OSS. This backend is available on most Unix-like systems.
OSS specific options are:
in|out.dev=device
Specify the file name of the OSS device to use. Default is /dev/dsp.
in|out.buffer-count=count
Sets the count of the buffers.
in|out.try-poll=on|of
Attempt to use poll mode with the device. Default is on.
try-mmap=on|off
Try using memory mapped device access. Default is off.
exclusive=on|off
Open the device in exclusive mode (vmix won't work in this case). Default is off.
dsp-policy=policy
Sets the timing policy (between 0 and 10, where smaller number means smaller latency but higher CPU usage). Use -1 to use buffer sizes specified by buffer and
buffer-count. This option is ignored if you do not have OSS 4. Default is 5.
-audiodev pa,id=id[,prop[=value][,...]]
Creates a backend using PulseAudio. This backend is available on most systems.
PulseAudio specific options are:
server=server
Sets the PulseAudio server to connect to.
in|out.name=sink
Use the specified source/sink for recording/playback.
in|out.latency=usecs
Desired latency in microseconds. The PulseAudio server will try to honor this value but actual latencies may be lower or higher.
-audiodev sdl,id=id[,prop[=value][,...]]
Creates a backend using SDL. This backend is available on most systems, but you should use your platform's native backend if possible.
SDL specific options are:
in|out.buffer-count=count
Sets the count of the buffers.
-audiodev spice,id=id[,prop[=value][,...]]
Creates a backend that sends audio through SPICE. This backend requires -spice and automatically selected in that case, so usually you can ignore this option. This
backend has no backend specific properties.
-audiodev wav,id=id[,prop[=value][,...]]
Creates a backend that writes audio to a WAV file.
Backend specific options are:
path=path
Write recorded audio into the specified file. Default is qemu.wav.
-soundhw card1[,card2,...] or -soundhw all
Enable audio and selected sound hardware. Use 'help' to print all available sound hardware. For example:
qemu-system-x86_64 -soundhw sb16,adlib disk.img
qemu-system-x86_64 -soundhw es1370 disk.img
qemu-system-x86_64 -soundhw ac97 disk.img
qemu-system-x86_64 -soundhw hda disk.img
qemu-system-x86_64 -soundhw all disk.img
qemu-system-x86_64 -soundhw help
Note that Linux's i810_audio OSS kernel (for AC97) module might require manually specifying clocking.
modprobe i810_audio clocking=48000
-device driver[,prop[=value][,...]]
Add device driver. prop=value sets driver properties. Valid properties depend on the driver. To get help on possible drivers and properties, use -device help and -de‐
vice driver,help.
Some drivers are:
-device ipmi-bmc-sim,id=id[,prop[=value][,...]]
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.
id=id The BMC id for interfaces to use this device.
slave_addr=val
Define slave address to use for the BMC. The default is 0x20.
sdrfile=file
file containing raw Sensor Data Records (SDR) data. The default is none.
fruareasize=val
size of a Field Replaceable Unit (FRU) area. The default is 1024.
frudatafile=file
file containing raw Field Replaceable Unit (FRU) inventory data. The default is none.
guid=uuid
value for the GUID for the BMC, in standard UUID format. If this is set, get "Get GUID" command to the BMC will return it. Otherwise "Get GUID" will return an
error.
-device ipmi-bmc-extern,id=id,chardev=id[,slave_addr=val]
Add a connection to an external IPMI BMC simulator. Instead of locally emulating the BMC like the above item, instead connect to an external entity that provides the
IPMI services.
A connection is made to an external BMC simulator. If you do this, it is strongly recommended that you use the "reconnect=" chardev option to reconnect to the simula‐
tor if the connection is lost. Note that if this is not used carefully, it can be a security issue, as the interface has the ability to send resets, NMIs, and power
off the VM. It's best if QEMU makes a connection to an external simulator running on a secure port on localhost, so neither the simulator nor QEMU is exposed to any
outside network.
See the "lanserv/README.vm" file in the OpenIPMI library for more details on the external interface.
-device isa-ipmi-kcs,bmc=id[,ioport=val][,irq=val]
Add a KCS IPMI interafce on the ISA bus. This also adds a corresponding ACPI and SMBIOS entries, if appropriate.
bmc=id The BMC to connect to, one of ipmi-bmc-sim or ipmi-bmc-extern above.
ioport=val
Define the I/O address of the interface. The default is 0xca0 for KCS.
irq=val
Define the interrupt to use. The default is 5. To disable interrupts, set this to 0.
-device isa-ipmi-bt,bmc=id[,ioport=val][,irq=val]
Like the KCS interface, but defines a BT interface. The default port is 0xe4 and the default interrupt is 5.
-device pci-ipmi-kcs,bmc=id
Add a KCS IPMI interafce on the PCI bus.
bmc=id The BMC to connect to, one of ipmi-bmc-sim or ipmi-bmc-extern above.
-device pci-ipmi-bt,bmc=id
Like the KCS interface, but defines a BT interface on the PCI bus.
-device intel-iommu[,option=...]
This is only supported by -machine q35, which will enable Intel VT-d emulation within the guest. It supports below options:
intremap=on|off (default: auto)
This enables interrupt remapping feature. It's required to enable complete x2apic. Currently it only supports kvm kernel-irqchip modes off or split, while
full kernel-irqchip is not yet supported. The default value is "auto", which will be decided by the mode of kernel-irqchip.
caching-mode=on|off (default: off)
This enables caching mode for the VT-d emulated device. When caching-mode is enabled, each guest DMA buffer mapping will generate an IOTLB invalidation from
the guest IOMMU driver to the vIOMMU device in a synchronous way. It is required for -device vfio-pci to work with the VT-d device, because host assigned de‐
vices requires to setup the DMA mapping on the host before guest DMA starts.
device-iotlb=on|off (default: off)
This enables device-iotlb capability for the emulated VT-d device. So far virtio/vhost should be the only real user for this parameter, paired with ats=on
configured for the device.
aw-bits=39|48 (default: 39)
This decides the address width of IOVA address space. The address space has 39 bits width for 3-level IOMMU page tables, and 48 bits for 4-level IOMMU page
tables.
Please also refer to the wiki page for general scenarios of VT-d emulation in QEMU: https://wiki.qemu.org/Features/VT-d.
-name name
Sets the name of the guest. This name will be displayed in the SDL window caption. The name will also be used for the VNC server. Also optionally set the top visible
process name in Linux. Naming of individual threads can also be enabled on Linux to aid debugging.
-uuid uuid
Set system UUID.
Block device options
-fda file
-fdb file
Use file as floppy disk 0/1 image (see the disk images chapter in the System Emulation Users Guide).
-hda file
-hdb file
-hdc file
-hdd file
Use file as hard disk 0, 1, 2 or 3 image (see the disk images chapter in the System Emulation Users Guide).
-cdrom file
Use file as CD-ROM image (you cannot use -hdc and -cdrom at the same time). You can use the host CD-ROM by using /dev/cdrom as filename.
-blockdev option[,option[,option[,...]]]
Define a new block driver node. Some of the options apply to all block drivers, other options are only accepted for a specific block driver. See below for a list of
generic options and options for the most common block drivers.
Options that expect a reference to another node (e.g. file) can be given in two ways. Either you specify the node name of an already existing node (file=node-name),
or you define a new node inline, adding options for the referenced node after a dot (file.filename=path,file.aio=native).
A block driver node created with -blockdev can be used for a guest device by specifying its node name for the drive property in a -device argument that defines a
block device.
Valid options for any block driver node:
driver Specifies the block driver to use for the given node.
node-name
This defines the name of the block driver node by which it will be referenced later. The name must be unique, i.e. it must not match the name of a dif‐
ferent block driver node, or (if you use -drive as well) the ID of a drive.
If no node name is specified, it is automatically generated. The generated node name is not intended to be predictable and changes between QEMU invoca‐
tions. For the top level, an explicit node name must be specified.
read-only
Open the node read-only. Guest write attempts will fail.
Note that some block drivers support only read-only access, either generally or in certain configurations. In this case, the default value read-only=off
does not work and the option must be specified explicitly.
auto-read-only
If auto-read-only=on is set, QEMU may fall back to read-only usage even when read-only=off is requested, or even switch between modes as needed, e.g.
depending on whether the image file is writable or whether a writing user is attached to the node.
force-share
Override the image locking system of QEMU by forcing the node to utilize weaker shared access for permissions where it would normally request exclusive
access. When there is the potential for multiple instances to have the same file open (whether this invocation of QEMU is the first or the second in‐
stance), both instances must permit shared access for the second instance to succeed at opening the file.
Enabling force-share=on requires read-only=on.
cache.direct
The host page cache can be avoided with cache.direct=on. This will attempt to do disk IO directly to the guest's memory. QEMU may still perform an in‐
ternal copy of the data.
cache.no-flush
In case you don't care about data integrity over host failures, you can use cache.no-flush=on. This option tells QEMU that it never needs to write any
data to the disk but can instead keep things in cache. If anything goes wrong, like your host losing power, the disk storage getting disconnected acci‐
dentally, etc. your image will most probably be rendered unusable.
discard=discard
discard is one of "ignore" (or "off") or "unmap" (or "on") and controls whether discard (also known as trim or unmap) requests are ignored or passed to
the filesystem. Some machine types may not support discard requests.
detect-zeroes=detect-zeroes
detect-zeroes is "off", "on" or "unmap" and enables the automatic conversion of plain zero writes by the OS to driver specific optimized zero write com‐
mands. You may even choose "unmap" if discard is set to "unmap" to allow a zero write to be converted to an unmap operation.
Driver-specific options for file
This is the protocol-level block driver for accessing regular files.
filename
The path to the image file in the local filesystem
aio Specifies the AIO backend (threads/native/io_uring, default: threads)
locking
Specifies whether the image file is protected with Linux OFD / POSIX locks. The default is to use the Linux Open File Descriptor API if available, oth‐
erwise no lock is applied. (auto/on/off, default: auto)
Example:
-blockdev driver=file,node-name=disk,filename=disk.img
Driver-specific options for raw
This is the image format block driver for raw images. It is usually stacked on top of a protocol level block driver such as file.
file Reference to or definition of the data source block driver node (e.g. a file driver node)
Example 1:
-blockdev driver=file,node-name=disk_file,filename=disk.img
-blockdev driver=raw,node-name=disk,file=disk_file
Example 2:
-blockdev driver=raw,node-name=disk,file.driver=file,file.filename=disk.img
Driver-specific options for qcow2
This is the image format block driver for qcow2 images. It is usually stacked on top of a protocol level block driver such as file.
file Reference to or definition of the data source block driver node (e.g. a file driver node)
backing
Reference to or definition of the backing file block device (default is taken from the image file). It is allowed to pass null here in order to disable
the default backing file.
lazy-refcounts
Whether to enable the lazy refcounts feature (on/off; default is taken from the image file)
cache-size
The maximum total size of the L2 table and refcount block caches in bytes (default: the sum of l2-cache-size and refcount-cache-size)
l2-cache-size
The maximum size of the L2 table cache in bytes (default: if cache-size is not specified - 32M on Linux platforms, and 8M on non-Linux platforms; other‐
wise, as large as possible within the cache-size, while permitting the requested or the minimal refcount cache size)
refcount-cache-size
The maximum size of the refcount block cache in bytes (default: 4 times the cluster size; or if cache-size is specified, the part of it which is not
used for the L2 cache)
cache-clean-interval
Clean unused entries in the L2 and refcount caches. The interval is in seconds. The default value is 600 on supporting platforms, and 0 on other plat‐
forms. Setting it to 0 disables this feature.
pass-discard-request
Whether discard requests to the qcow2 device should be forwarded to the data source (on/off; default: on if discard=unmap is specified, off otherwise)
pass-discard-snapshot
Whether discard requests for the data source should be issued when a snapshot operation (e.g. deleting a snapshot) frees clusters in the qcow2 file
(on/off; default: on)
pass-discard-other
Whether discard requests for the data source should be issued on other occasions where a cluster gets freed (on/off; default: off)
overlap-check
Which overlap checks to perform for writes to the image (none/constant/cached/all; default: cached). For details or finer granularity control refer to
the QAPI documentation of blockdev-add.
Example 1:
-blockdev driver=file,node-name=my_file,filename=/tmp/disk.qcow2
-blockdev driver=qcow2,node-name=hda,file=my_file,overlap-check=none,cache-size=16777216
Example 2:
-blockdev driver=qcow2,node-name=disk,file.driver=http,file.filename=http://example.com/image.qcow2
Driver-specific options for other drivers
Please refer to the QAPI documentation of the blockdev-add QMP command.
-drive option[,option[,option[,...]]]
Define a new drive. This includes creating a block driver node (the backend) as well as a guest device, and is mostly a shortcut for defining the corresponding
-blockdev and -device options.
-drive accepts all options that are accepted by -blockdev. In addition, it knows the following options:
file=file
This option defines which disk image (see the disk images chapter in the System Emulation Users Guide) to use with this drive. If the filename contains comma,
you must double it (for instance, "file=my,,file" to use file "my,file").
Special files such as iSCSI devices can be specified using protocol specific URLs. See the section for "Device URL Syntax" for more information.
if=interface
This option defines on which type on interface the drive is connected. Available types are: ide, scsi, sd, mtd, floppy, pflash, virtio, none.
bus=bus,unit=unit
These options define where is connected the drive by defining the bus number and the unit id.
index=index
This option defines where is connected the drive by using an index in the list of available connectors of a given interface type.
media=media
This option defines the type of the media: disk or cdrom.
snapshot=snapshot
snapshot is "on" or "off" and controls snapshot mode for the given drive (see -snapshot).
cache=cache
cache is "none", "writeback", "unsafe", "directsync" or "writethrough" and controls how the host cache is used to access block data. This is a shortcut that
sets the cache.direct and cache.no-flush options (as in -blockdev), and additionally cache.writeback, which provides a default for the write-cache option of
block guest devices (as in -device). The modes correspond to the following settings:
┌─────────────┬─────────────────┬──────────────┬────────────────┐
│ │ cache.writeback │ cache.direct │ cache.no-flush │
├─────────────┼─────────────────┼──────────────┼────────────────┤
│writeback │ on │ off │ off │
├─────────────┼─────────────────┼──────────────┼────────────────┤
│none │ on │ on │ off │
├─────────────┼─────────────────┼──────────────┼────────────────┤
│writethrough │ off │ off │ off │
├─────────────┼─────────────────┼──────────────┼────────────────┤
│directsync │ off │ on │ off │
├─────────────┼─────────────────┼──────────────┼────────────────┤
│unsafe │ on │ off │ on │
└─────────────┴─────────────────┴──────────────┴────────────────┘
The default mode is cache=writeback.
aio=aio
aio is "threads", "native", or "io_uring" and selects between pthread based disk I/O, native Linux AIO, or Linux io_uring API.
format=format
Specify which disk format will be used rather than detecting the format. Can be used to specify format=raw to avoid interpreting an untrusted format header.
werror=action,rerror=action
Specify which action to take on write and read errors. Valid actions are: "ignore" (ignore the error and try to continue), "stop" (pause QEMU), "report" (re‐
port 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 wer‐
ror=enospc and rerror=report.
copy-on-read=copy-on-read
copy-on-read is "on" or "off" and enables whether to copy read backing file sectors into the image file.
bps=b,bps_rd=r,bps_wr=w
Specify bandwidth throttling limits in bytes per second, either for all request types or for reads or writes only. Small values can lead to timeouts or hangs
inside the guest. A safe minimum for disks is 2 MB/s.
bps_max=bm,bps_rd_max=rm,bps_wr_max=wm
Specify bursts in bytes per second, either for all request types or for reads or writes only. Bursts allow the guest I/O to spike above the limit temporarily.
iops=i,iops_rd=r,iops_wr=w
Specify request rate limits in requests per second, either for all request types or for reads or writes only.
iops_max=bm,iops_rd_max=rm,iops_wr_max=wm
Specify bursts in requests per second, either for all request types or for reads or writes only. Bursts allow the guest I/O to spike above the limit temporar‐
ily.
iops_size=is
Let every is bytes of a request count as a new request for iops throttling purposes. Use this option to prevent guests from circumventing iops limits by send‐
ing fewer but larger requests.
group=g
Join a throttling quota group with given name g. All drives that are members of the same group are accounted for together. Use this option to prevent guests
from circumventing throttling limits by using many small disks instead of a single larger disk.
By default, the cache.writeback=on mode is used. It will report data writes as completed as soon as the data is present in the host page cache. This is safe as long
as your guest OS makes sure to correctly flush disk caches where needed. If your guest OS does not handle volatile disk write caches correctly and your host crashes
or loses power, then the guest may experience data corruption.
For such guests, you should consider using cache.writeback=off. This means that the host page cache will be used to read and write data, but write notification will
be sent to the guest only after QEMU has made sure to flush each write to the disk. Be aware that this has a major impact on performance.
When using the -snapshot option, unsafe caching is always used.
Copy-on-read avoids accessing the same backing file sectors repeatedly and is useful when the backing file is over a slow network. By default copy-on-read is off.
Instead of -cdrom you can use:
qemu-system-x86_64 -drive file=file,index=2,media=cdrom
Instead of -hda, -hdb, -hdc, -hdd, you can use:
qemu-system-x86_64 -drive file=file,index=0,media=disk
qemu-system-x86_64 -drive file=file,index=1,media=disk
qemu-system-x86_64 -drive file=file,index=2,media=disk
qemu-system-x86_64 -drive file=file,index=3,media=disk
You can open an image using pre-opened file descriptors from an fd set:
qemu-system-x86_64 \
-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-x86_64 -drive file=file,if=ide,index=1,media=cdrom
If you don't specify the "file=" argument, you define an empty drive:
qemu-system-x86_64 -drive if=ide,index=1,media=cdrom
Instead of -fda, -fdb, you can use:
qemu-system-x86_64 -drive file=file,index=0,if=floppy
qemu-system-x86_64 -drive file=file,index=1,if=floppy
By default, interface is "ide" and index is automatically incremented:
qemu-system-x86_64 -drive file=a -drive file=b"
is interpreted like:
qemu-system-x86_64 -hda a -hdb b
-mtdblock file
Use file as on-board Flash memory image.
-sd file
Use file as SecureDigital card image.
-pflash file
Use file as a parallel flash image.
-snapshot
Write to temporary files instead of disk image files. In this case, the raw disk image you use is not written back. You can however force the write back by pressing
C-a s (see the disk images chapter in the System Emulation Users Guide).
-fsdev local,id=id,path=path,security_model=security_model [,writeout=writeout][,readonly=on][,fmode=fmode][,dmode=dmode] [,throttling.option=value[,throttling.op‐
tion=value[,...]]]
-fsdev proxy,id=id,socket=socket[,writeout=writeout][,readonly=on]
-fsdev proxy,id=id,sock_fd=sock_fd[,writeout=writeout][,readonly=on]
-fsdev synth,id=id[,readonly=on]
Define a new file system device. Valid options are:
local Accesses to the filesystem are done by QEMU.
proxy Accesses to the filesystem are done by virtfs-proxy-helper(1).
synth Synthetic filesystem, only used by QTests.
id=id Specifies identifier for this device.
path=path
Specifies the export path for the file system device. Files under this path will be available to the 9p client on the guest.
security_model=security_model
Specifies the security model to be used for this export path. Supported security models are "passthrough", "mapped-xattr", "mapped-file" and "none". In
"passthrough" security model, files are stored using the same credentials as they are created on the guest. This requires QEMU to run as root. In
"mapped-xattr" security model, some of the file attributes like uid, gid, mode bits and link target are stored as file attributes. For "mapped-file" these at‐
tributes are stored in the hidden .virtfs_metadata directory. Directories exported by this security model cannot interact with other unix tools. "none" secu‐
rity 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 proxy) don't take security model as a parameter.
writeout=writeout
This is an optional argument. The only supported value is "immediate". This means that host page cache will be used to read and write data but write notifica‐
tion will be sent to the guest only when the data has been reported as written by the storage subsystem.
readonly=on
Enables exporting 9p share as a readonly mount for guests. By default read-write access is given.
socket=socket
Enables proxy filesystem driver to use passed socket file for communicating with virtfs-proxy-helper(1).
sock_fd=sock_fd
Enables proxy filesystem driver to use passed socket descriptor for communicating with virtfs-proxy-helper(1). Usually a helper like libvirt will create sock‐
etpair and pass one of the fds as sock_fd.
fmode=fmode
Specifies the default mode for newly created files on the host. Works only with security models "mapped-xattr" and "mapped-file".
dmode=dmode
Specifies the default mode for newly created directories on the host. Works only with security models "mapped-xattr" and "mapped-file".
throttling.bps-total=b,throttling.bps-read=r,throttling.bps-write=w
Specify bandwidth throttling limits in bytes per second, either for all request types or for reads or writes only.
throttling.bps-total-max=bm,bps-read-max=rm,bps-write-max=wm
Specify bursts in bytes per second, either for all request types or for reads or writes only. Bursts allow the guest I/O to spike above the limit temporarily.
throttling.iops-total=i,throttling.iops-read=r, throttling.iops-write=w
Specify request rate limits in requests per second, either for all request types or for reads or writes only.
throttling.iops-total-max=im,throttling.iops-read-max=irm, throttling.iops-write-max=iwm
Specify bursts in requests per second, either for all request types or for reads or writes only. Bursts allow the guest I/O to spike above the limit temporar‐
ily.
throttling.iops-size=is
Let every is bytes of a request count as a new request for iops throttling purposes.