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qemu-options.hx
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HXCOMM Use DEFHEADING() to define headings in both help text and texi
HXCOMM Text between STEXI and ETEXI are copied to texi version and
HXCOMM discarded from C version
HXCOMM DEF(option, HAS_ARG/0, opt_enum, opt_help, arch_mask) is used to
HXCOMM construct option structures, enums and help message for specified
HXCOMM architectures.
HXCOMM HXCOMM can be used for comments, discarded from both texi and C
DEFHEADING(Standard options:)
STEXI
@table @option
ETEXI
DEF("help", 0, QEMU_OPTION_h,
"-h or -help display this help and exit\n", QEMU_ARCH_ALL)
STEXI
@item -h
@findex -h
Display help and exit
ETEXI
DEF("version", 0, QEMU_OPTION_version,
"-version display version information and exit\n", QEMU_ARCH_ALL)
STEXI
@item -version
@findex -version
Display version information and exit
ETEXI
DEF("machine", HAS_ARG, QEMU_OPTION_machine, \
"-machine [type=]name[,prop[=value][,...]]\n"
" selects emulated machine ('-machine help' for list)\n"
" property accel=accel1[:accel2[:...]] selects accelerator\n"
" supported accelerators are kvm, xen, hax, hvf, whpx or tcg (default: tcg)\n"
" kernel_irqchip=on|off|split controls accelerated irqchip support (default=off)\n"
" vmport=on|off|auto controls emulation of vmport (default: auto)\n"
" kvm_shadow_mem=size of KVM shadow MMU in bytes\n"
" dump-guest-core=on|off include guest memory in a core dump (default=on)\n"
" mem-merge=on|off controls memory merge support (default: on)\n"
" igd-passthru=on|off controls IGD GFX passthrough support (default=off)\n"
" aes-key-wrap=on|off controls support for AES key wrapping (default=on)\n"
" dea-key-wrap=on|off controls support for DEA key wrapping (default=on)\n"
" suppress-vmdesc=on|off disables self-describing migration (default=off)\n"
" nvdimm=on|off controls NVDIMM support (default=off)\n"
" enforce-config-section=on|off enforce configuration section migration (default=off)\n"
" s390-squash-mcss=on|off (deprecated) controls support for squashing into default css (default=off)\n",
QEMU_ARCH_ALL)
STEXI
@item -machine [type=]@var{name}[,prop=@var{value}[,...]]
@findex -machine
Select the emulated machine by @var{name}. Use @code{-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:
@table @option
@item accel=@var{accels1}[:@var{accels2}[:...]]
This is used to enable an accelerator. Depending on the target architecture,
kvm, xen, hax, hvf, 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.
@item kernel_irqchip=on|off
Controls in-kernel irqchip support for the chosen accelerator when available.
@item gfx_passthru=on|off
Enables IGD GFX passthrough support for the chosen machine when available.
@item 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.
@item kvm_shadow_mem=size
Defines the size of the KVM shadow MMU.
@item dump-guest-core=on|off
Include guest memory in a core dump. The default is on.
@item mem-merge=on|off
Enables or disables memory merge support. This feature, when supported by
the host, de-duplicates identical memory pages among VMs instances
(enabled by default).
@item 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.
@item 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.
@item nvdimm=on|off
Enables or disables NVDIMM support. The default is off.
@item s390-squash-mcss=on|off
Enables or disables squashing subchannels into the default css.
The default is off.
NOTE: This property is deprecated and will be removed in future releases.
The ``s390-squash-mcss=on`` property has been obsoleted by allowing the
cssid to be chosen freely. Instead of squashing subchannels into the
default channel subsystem image for guests that do not support multiple
channel subsystems, all devices can be put into the default channel
subsystem image.
@item enforce-config-section=on|off
If @option{enforce-config-section} is set to @var{on}, force migration
code to send configuration section even if the machine-type sets the
@option{migration.send-configuration} property to @var{off}.
NOTE: this parameter is deprecated. Please use @option{-global}
@option{migration.send-configuration}=@var{on|off} instead.
@end table
ETEXI
HXCOMM Deprecated by -machine
DEF("M", HAS_ARG, QEMU_OPTION_M, "", QEMU_ARCH_ALL)
DEF("cpu", HAS_ARG, QEMU_OPTION_cpu,
"-cpu cpu select CPU ('-cpu help' for list)\n", QEMU_ARCH_ALL)
STEXI
@item -cpu @var{model}
@findex -cpu
Select CPU model (@code{-cpu help} for list and additional feature selection)
ETEXI
DEF("accel", HAS_ARG, QEMU_OPTION_accel,
"-accel [accel=]accelerator[,thread=single|multi]\n"
" select accelerator (kvm, xen, hax, hvf, whpx or tcg; use 'help' for a list)\n"
" thread=single|multi (enable multi-threaded TCG)", QEMU_ARCH_ALL)
STEXI
@item -accel @var{name}[,prop=@var{value}[,...]]
@findex -accel
This is used to enable an accelerator. Depending on the target architecture,
kvm, xen, hax, hvf, 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.
@table @option
@item thread=single|multi
Controls number of TCG threads. When the TCG is multi-threaded there will be one
thread per vCPU therefor taking advantage of additional host cores. The default
is to enable multi-threading where both the back-end and front-ends support it and
no incompatible TCG features have been enabled (e.g. icount/replay).
@end table
ETEXI
DEF("smp", HAS_ARG, QEMU_OPTION_smp,
"-smp [cpus=]n[,maxcpus=cpus][,cores=cores][,threads=threads][,sockets=sockets]\n"
" set the number of CPUs to 'n' [default=1]\n"
" maxcpus= maximum number of total cpus, including\n"
" offline CPUs for hotplug, etc\n"
" cores= number of CPU cores on one socket\n"
" threads= number of threads on one CPU core\n"
" sockets= number of discrete sockets in the system\n",
QEMU_ARCH_ALL)
STEXI
@item -smp [cpus=]@var{n}[,cores=@var{cores}][,threads=@var{threads}][,sockets=@var{sockets}][,maxcpus=@var{maxcpus}]
@findex -smp
Simulate an SMP system with @var{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 @var{cores} per socket, the number
of @var{threads} per cores and the total number of @var{sockets} can be
specified. Missing values will be computed. If any on the three values is
given, the total number of CPUs @var{n} can be omitted. @var{maxcpus}
specifies the maximum number of hotpluggable CPUs.
ETEXI
DEF("numa", HAS_ARG, QEMU_OPTION_numa,
"-numa node[,mem=size][,cpus=firstcpu[-lastcpu]][,nodeid=node]\n"
"-numa node[,memdev=id][,cpus=firstcpu[-lastcpu]][,nodeid=node]\n"
"-numa dist,src=source,dst=destination,val=distance\n"
"-numa cpu,node-id=node[,socket-id=x][,core-id=y][,thread-id=z]\n",
QEMU_ARCH_ALL)
STEXI
@item -numa node[,mem=@var{size}][,cpus=@var{firstcpu}[-@var{lastcpu}]][,nodeid=@var{node}]
@itemx -numa node[,memdev=@var{id}][,cpus=@var{firstcpu}[-@var{lastcpu}]][,nodeid=@var{node}]
@itemx -numa dist,src=@var{source},dst=@var{destination},val=@var{distance}
@itemx -numa cpu,node-id=@var{node}[,socket-id=@var{x}][,core-id=@var{y}][,thread-id=@var{z}]
@findex -numa
Define a NUMA node and assign RAM and VCPUs to it.
Set the NUMA distance from a source node to a destination node.
Legacy VCPU assignment uses @samp{cpus} option where
@var{firstcpu} and @var{lastcpu} are CPU indexes. Each
@samp{cpus} option represent a contiguous range of CPU indexes
(or a single VCPU if @var{lastcpu} is omitted). A non-contiguous
set of VCPUs can be represented by providing multiple @samp{cpus}
options. If @samp{cpus} is omitted on all nodes, VCPUs are automatically
split between them.
For example, the following option assigns VCPUs 0, 1, 2 and 5 to
a NUMA node:
@example
-numa node,cpus=0-2,cpus=5
@end example
@samp{cpu} option is a new alternative to @samp{cpus} option
which uses @samp{socket-id|core-id|thread-id} properties to assign
CPU objects to a @var{node} using topology layout properties of CPU.
The set of properties is machine specific, and depends on used
machine type/@samp{smp} options. It could be queried with
@samp{hotpluggable-cpus} monitor command.
@samp{node-id} property specifies @var{node} to which CPU object
will be assigned, it's required for @var{node} to be declared
with @samp{node} option before it's used with @samp{cpu} option.
For example:
@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
@end example
@samp{mem} assigns a given RAM amount to a node. @samp{memdev}
assigns RAM from a given memory backend device to a node. If
@samp{mem} and @samp{memdev} are omitted in all nodes, RAM is
split equally between them.
@samp{mem} and @samp{memdev} are mutually exclusive. Furthermore,
if one node uses @samp{memdev}, all of them have to use it.
@var{source} and @var{destination} are NUMA node IDs.
@var{distance} is the NUMA distance from @var{source} to @var{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 -@option{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 @option{-m},
@option{-smp} options to allocate RAM and VCPUs respectively.
ETEXI
DEF("add-fd", HAS_ARG, QEMU_OPTION_add_fd,
"-add-fd fd=fd,set=set[,opaque=opaque]\n"
" Add 'fd' to fd 'set'\n", QEMU_ARCH_ALL)
STEXI
@item -add-fd fd=@var{fd},set=@var{set}[,opaque=@var{opaque}]
@findex -add-fd
Add a file descriptor to an fd set. Valid options are:
@table @option
@item fd=@var{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.
@item set=@var{set}
This option defines the ID of the fd set to add the file descriptor to.
@item opaque=@var{opaque}
This option defines a free-form string that can be used to describe @var{fd}.
@end table
You can open an image using pre-opened file descriptors from an fd set:
@example
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
@end example
ETEXI
DEF("set", HAS_ARG, QEMU_OPTION_set,
"-set group.id.arg=value\n"
" set <arg> parameter for item <id> of type <group>\n"
" i.e. -set drive.$id.file=/path/to/image\n", QEMU_ARCH_ALL)
STEXI
@item -set @var{group}.@var{id}.@var{arg}=@var{value}
@findex -set
Set parameter @var{arg} for item @var{id} of type @var{group}
ETEXI
DEF("global", HAS_ARG, QEMU_OPTION_global,
"-global driver.property=value\n"
"-global driver=driver,property=property,value=value\n"
" set a global default for a driver property\n",
QEMU_ARCH_ALL)
STEXI
@item -global @var{driver}.@var{prop}=@var{value}
@itemx -global driver=@var{driver},property=@var{property},value=@var{value}
@findex -global
Set default value of @var{driver}'s property @var{prop} to @var{value}, e.g.:
@example
qemu-system-i386 -global ide-hd.physical_block_size=4096 disk-image.img
@end example
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 -@option{device}.
-global @var{driver}.@var{prop}=@var{value} is shorthand for -global
driver=@var{driver},property=@var{prop},value=@var{value}. The
longhand syntax works even when @var{driver} contains a dot.
ETEXI
DEF("boot", HAS_ARG, QEMU_OPTION_boot,
"-boot [order=drives][,once=drives][,menu=on|off]\n"
" [,splash=sp_name][,splash-time=sp_time][,reboot-timeout=rb_time][,strict=on|off]\n"
" 'drives': floppy (a), hard disk (c), CD-ROM (d), network (n)\n"
" 'sp_name': the file's name that would be passed to bios as logo picture, if menu=on\n"
" 'sp_time': the period that splash picture last if menu=on, unit is ms\n"
" 'rb_timeout': the timeout before guest reboot when boot failed, unit is ms\n",
QEMU_ARCH_ALL)
STEXI
@item -boot [order=@var{drives}][,once=@var{drives}][,menu=on|off][,splash=@var{sp_name}][,splash-time=@var{sp_time}][,reboot-timeout=@var{rb_timeout}][,strict=on|off]
@findex -boot
Specify boot order @var{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
@option{once}. Note that the @option{order} or @option{once} parameter
should not be used together with the @option{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 @option{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=@var{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 @var{rb_timeout} ms
when boot failed, then reboot. If @var{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 @option{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.
@example
# 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
@end example
Note: The legacy format '-boot @var{drives}' is still supported but its
use is discouraged as it may be removed from future versions.
ETEXI
DEF("m", HAS_ARG, QEMU_OPTION_m,
"-m [size=]megs[,slots=n,maxmem=size]\n"
" configure guest RAM\n"
" size: initial amount of guest memory\n"
" slots: number of hotplug slots (default: none)\n"
" maxmem: maximum amount of guest memory (default: none)\n"
"NOTE: Some architectures might enforce a specific granularity\n",
QEMU_ARCH_ALL)
STEXI
@item -m [size=]@var{megs}[,slots=n,maxmem=size]
@findex -m
Sets guest startup RAM size to @var{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 @var{slots}, @var{maxmem}
could be used to set amount of hotpluggable memory slots and maximum amount of
memory. Note that @var{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:
@example
qemu-system-x86_64 -m 1G,slots=3,maxmem=4G
@end example
If @var{slots} and @var{maxmem} are not specified, memory hotplug won't
be enabled and the guest startup RAM will never increase.
ETEXI
DEF("mem-path", HAS_ARG, QEMU_OPTION_mempath,
"-mem-path FILE provide backing storage for guest RAM\n", QEMU_ARCH_ALL)
STEXI
@item -mem-path @var{path}
@findex -mem-path
Allocate guest RAM from a temporarily created file in @var{path}.
ETEXI
DEF("mem-prealloc", 0, QEMU_OPTION_mem_prealloc,
"-mem-prealloc preallocate guest memory (use with -mem-path)\n",
QEMU_ARCH_ALL)
STEXI
@item -mem-prealloc
@findex -mem-prealloc
Preallocate memory when using -mem-path.
ETEXI
DEF("k", HAS_ARG, QEMU_OPTION_k,
"-k language use keyboard layout (for example 'fr' for French)\n",
QEMU_ARCH_ALL)
STEXI
@item -k @var{language}
@findex -k
Use keyboard layout @var{language} (for example @code{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:
@example
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
@end example
The default is @code{en-us}.
ETEXI
DEF("audio-help", 0, QEMU_OPTION_audio_help,
"-audio-help print list of audio drivers and their options\n",
QEMU_ARCH_ALL)
STEXI
@item -audio-help
@findex -audio-help
Will show the audio subsystem help: list of drivers, tunable
parameters.
ETEXI
DEF("soundhw", HAS_ARG, QEMU_OPTION_soundhw,
"-soundhw c1,... enable audio support\n"
" and only specified sound cards (comma separated list)\n"
" use '-soundhw help' to get the list of supported cards\n"
" use '-soundhw all' to enable all of them\n", QEMU_ARCH_ALL)
STEXI
@item -soundhw @var{card1}[,@var{card2},...] or -soundhw all
@findex -soundhw
Enable audio and selected sound hardware. Use 'help' to print all
available sound hardware.
@example
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
@end example
Note that Linux's i810_audio OSS kernel (for AC97) module might
require manually specifying clocking.
@example
modprobe i810_audio clocking=48000
@end example
ETEXI
DEF("balloon", HAS_ARG, QEMU_OPTION_balloon,
"-balloon virtio[,addr=str]\n"
" enable virtio balloon device (deprecated)\n", QEMU_ARCH_ALL)
STEXI
@item -balloon virtio[,addr=@var{addr}]
@findex -balloon
Enable virtio balloon device, optionally with PCI address @var{addr}. This
option is deprecated, use @option{--device virtio-balloon} instead.
ETEXI
DEF("device", HAS_ARG, QEMU_OPTION_device,
"-device driver[,prop[=value][,...]]\n"
" add device (based on driver)\n"
" prop=value,... sets driver properties\n"
" use '-device help' to print all possible drivers\n"
" use '-device driver,help' to print all possible properties\n",
QEMU_ARCH_ALL)
STEXI
@item -device @var{driver}[,@var{prop}[=@var{value}][,...]]
@findex -device
Add device @var{driver}. @var{prop}=@var{value} sets driver
properties. Valid properties depend on the driver. To get help on
possible drivers and properties, use @code{-device help} and
@code{-device @var{driver},help}.
Some drivers are:
@item -device ipmi-bmc-sim,id=@var{id}[,slave_addr=@var{val}][,sdrfile=@var{file}][,furareasize=@var{val}][,furdatafile=@var{file}]
Add an IPMI BMC. This is a simulation of a hardware management
interface processor that normally sits on a system. It provides
a watchdog and the ability to reset and power control the system.
You need to connect this to an IPMI interface to make it useful
The IPMI slave address to use for the BMC. The default is 0x20.
This address is the BMC's address on the I2C network of management
controllers. If you don't know what this means, it is safe to ignore
it.
@table @option
@item bmc=@var{id}
The BMC to connect to, one of ipmi-bmc-sim or ipmi-bmc-extern above.
@item slave_addr=@var{val}
Define slave address to use for the BMC. The default is 0x20.
@item sdrfile=@var{file}
file containing raw Sensor Data Records (SDR) data. The default is none.
@item fruareasize=@var{val}
size of a Field Replaceable Unit (FRU) area. The default is 1024.
@item frudatafile=@var{file}
file containing raw Field Replaceable Unit (FRU) inventory data. The default is none.
@end table
@item -device ipmi-bmc-extern,id=@var{id},chardev=@var{id}[,slave_addr=@var{val}]
Add a connection to an external IPMI BMC simulator. Instead of
locally emulating the BMC like the above item, instead connect
to an external entity that provides the IPMI services.
A connection is made to an external BMC simulator. If you do this, it
is strongly recommended that you use the "reconnect=" chardev option
to reconnect to the simulator if the connection is lost. Note that if
this is not used carefully, it can be a security issue, as the
interface has the ability to send resets, NMIs, and power off the VM.
It's best if QEMU makes a connection to an external simulator running
on a secure port on localhost, so neither the simulator nor QEMU is
exposed to any outside network.
See the "lanserv/README.vm" file in the OpenIPMI library for more
details on the external interface.
@item -device isa-ipmi-kcs,bmc=@var{id}[,ioport=@var{val}][,irq=@var{val}]
Add a KCS IPMI interafce on the ISA bus. This also adds a
corresponding ACPI and SMBIOS entries, if appropriate.
@table @option
@item bmc=@var{id}
The BMC to connect to, one of ipmi-bmc-sim or ipmi-bmc-extern above.
@item ioport=@var{val}
Define the I/O address of the interface. The default is 0xca0 for KCS.
@item irq=@var{val}
Define the interrupt to use. The default is 5. To disable interrupts,
set this to 0.
@end table
@item -device isa-ipmi-bt,bmc=@var{id}[,ioport=@var{val}][,irq=@var{val}]
Like the KCS interface, but defines a BT interface. The default port is
0xe4 and the default interrupt is 5.
ETEXI
DEF("name", HAS_ARG, QEMU_OPTION_name,
"-name string1[,process=string2][,debug-threads=on|off]\n"
" set the name of the guest\n"
" string1 sets the window title and string2 the process name (on Linux)\n"
" When debug-threads is enabled, individual threads are given a separate name (on Linux)\n"
" NOTE: The thread names are for debugging and not a stable API.\n",
QEMU_ARCH_ALL)
STEXI
@item -name @var{name}
@findex -name
Sets the @var{name} of the guest.
This name will be displayed in the SDL window caption.
The @var{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.
ETEXI
DEF("uuid", HAS_ARG, QEMU_OPTION_uuid,
"-uuid %08x-%04x-%04x-%04x-%012x\n"
" specify machine UUID\n", QEMU_ARCH_ALL)
STEXI
@item -uuid @var{uuid}
@findex -uuid
Set system UUID.
ETEXI
STEXI
@end table
ETEXI
DEFHEADING()
DEFHEADING(Block device options:)
STEXI
@table @option
ETEXI
DEF("fda", HAS_ARG, QEMU_OPTION_fda,
"-fda/-fdb file use 'file' as floppy disk 0/1 image\n", QEMU_ARCH_ALL)
DEF("fdb", HAS_ARG, QEMU_OPTION_fdb, "", QEMU_ARCH_ALL)
STEXI
@item -fda @var{file}
@itemx -fdb @var{file}
@findex -fda
@findex -fdb
Use @var{file} as floppy disk 0/1 image (@pxref{disk_images}).
ETEXI
DEF("hda", HAS_ARG, QEMU_OPTION_hda,
"-hda/-hdb file use 'file' as IDE hard disk 0/1 image\n", QEMU_ARCH_ALL)
DEF("hdb", HAS_ARG, QEMU_OPTION_hdb, "", QEMU_ARCH_ALL)
DEF("hdc", HAS_ARG, QEMU_OPTION_hdc,
"-hdc/-hdd file use 'file' as IDE hard disk 2/3 image\n", QEMU_ARCH_ALL)
DEF("hdd", HAS_ARG, QEMU_OPTION_hdd, "", QEMU_ARCH_ALL)
STEXI
@item -hda @var{file}
@itemx -hdb @var{file}
@itemx -hdc @var{file}
@itemx -hdd @var{file}
@findex -hda
@findex -hdb
@findex -hdc
@findex -hdd
Use @var{file} as hard disk 0, 1, 2 or 3 image (@pxref{disk_images}).
ETEXI
DEF("cdrom", HAS_ARG, QEMU_OPTION_cdrom,
"-cdrom file use 'file' as IDE cdrom image (cdrom is ide1 master)\n",
QEMU_ARCH_ALL)
STEXI
@item -cdrom @var{file}
@findex -cdrom
Use @var{file} as CD-ROM image (you cannot use @option{-hdc} and
@option{-cdrom} at the same time). You can use the host CD-ROM by
using @file{/dev/cdrom} as filename (@pxref{host_drives}).
ETEXI
DEF("blockdev", HAS_ARG, QEMU_OPTION_blockdev,
"-blockdev [driver=]driver[,node-name=N][,discard=ignore|unmap]\n"
" [,cache.direct=on|off][,cache.no-flush=on|off]\n"
" [,read-only=on|off][,detect-zeroes=on|off|unmap]\n"
" [,driver specific parameters...]\n"
" configure a block backend\n", QEMU_ARCH_ALL)
STEXI
@item -blockdev @var{option}[,@var{option}[,@var{option}[,...]]]
@findex -blockdev
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. @code{file}) can be
given in two ways. Either you specify the node name of an already existing node
(file=@var{node-name}), or you define a new node inline, adding options
for the referenced node after a dot (file.filename=@var{path},file.aio=native).
A block driver node created with @option{-blockdev} can be used for a guest
device by specifying its node name for the @code{drive} property in a
@option{-device} argument that defines a block device.
@table @option
@item Valid options for any block driver node:
@table @code
@item driver
Specifies the block driver to use for the given node.
@item node-name
This defines the name of the block driver node by which it will be referenced
later. The name must be unique, i.e. it must not match the name of a different
block driver node, or (if you use @option{-drive} as well) the ID of a drive.
If no node name is specified, it is automatically generated. The generated node
name is not intended to be predictable and changes between QEMU invocations.
For the top level, an explicit node name must be specified.
@item read-only
Open the node read-only. Guest write attempts will fail.
@item cache.direct
The host page cache can be avoided with @option{cache.direct=on}. This will
attempt to do disk IO directly to the guest's memory. QEMU may still perform an
internal copy of the data.
@item cache.no-flush
In case you don't care about data integrity over host failures, you can use
@option{cache.no-flush=on}. This option tells QEMU that it never needs to write
any data to the disk but can instead keep things in cache. If anything goes
wrong, like your host losing power, the disk storage getting disconnected
accidentally, etc. your image will most probably be rendered unusable.
@item discard=@var{discard}
@var{discard} is one of "ignore" (or "off") or "unmap" (or "on") and controls
whether @code{discard} (also known as @code{trim} or @code{unmap}) requests are
ignored or passed to the filesystem. Some machine types may not support
discard requests.
@item detect-zeroes=@var{detect-zeroes}
@var{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 @var{discard} is set
to "unmap" to allow a zero write to be converted to an @code{unmap} operation.
@end table
@item Driver-specific options for @code{file}
This is the protocol-level block driver for accessing regular files.
@table @code
@item filename
The path to the image file in the local filesystem
@item aio
Specifies the AIO backend (threads/native, default: threads)
@item locking
Specifies whether the image file is protected with Linux OFD / POSIX locks. The
default is to use the Linux Open File Descriptor API if available, otherwise no
lock is applied. (auto/on/off, default: auto)
@end table
Example:
@example
-blockdev driver=file,node-name=disk,filename=disk.img
@end example
@item Driver-specific options for @code{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 @code{file}.
@table @code
@item file
Reference to or definition of the data source block driver node
(e.g. a @code{file} driver node)
@end table
Example 1:
@example
-blockdev driver=file,node-name=disk_file,filename=disk.img
-blockdev driver=raw,node-name=disk,file=disk_file
@end example
Example 2:
@example
-blockdev driver=raw,node-name=disk,file.driver=file,file.filename=disk.img
@end example
@item Driver-specific options for @code{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 @code{file}.
@table @code
@item file
Reference to or definition of the data source block driver node
(e.g. a @code{file} driver node)
@item backing
Reference to or definition of the backing file block device (default is taken
from the image file). It is allowed to pass an empty string here in order to
disable the default backing file.
@item lazy-refcounts
Whether to enable the lazy refcounts feature (on/off; default is taken from the
image file)
@item cache-size
The maximum total size of the L2 table and refcount block caches in bytes
(default: 1048576 bytes or 8 clusters, whichever is larger)
@item l2-cache-size
The maximum size of the L2 table cache in bytes
(default: 4/5 of the total cache size)
@item refcount-cache-size
The maximum size of the refcount block cache in bytes
(default: 1/5 of the total cache size)
@item cache-clean-interval
Clean unused entries in the L2 and refcount caches. The interval is in seconds.
The default value is 0 and it disables this feature.
@item 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)
@item 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)
@item 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)
@item 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 @code{blockdev-add}.
@end table
Example 1:
@example
-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
@end example
Example 2:
@example
-blockdev driver=qcow2,node-name=disk,file.driver=http,file.filename=http://example.com/image.qcow2
@end example
@item Driver-specific options for other drivers
Please refer to the QAPI documentation of the @code{blockdev-add} QMP command.
@end table
ETEXI
DEF("drive", HAS_ARG, QEMU_OPTION_drive,
"-drive [file=file][,if=type][,bus=n][,unit=m][,media=d][,index=i]\n"
" [,cyls=c,heads=h,secs=s[,trans=t]][,snapshot=on|off]\n"
" [,cache=writethrough|writeback|none|directsync|unsafe][,format=f]\n"
" [,serial=s][,addr=A][,rerror=ignore|stop|report]\n"
" [,werror=ignore|stop|report|enospc][,id=name][,aio=threads|native]\n"
" [,readonly=on|off][,copy-on-read=on|off]\n"
" [,discard=ignore|unmap][,detect-zeroes=on|off|unmap]\n"
" [[,bps=b]|[[,bps_rd=r][,bps_wr=w]]]\n"
" [[,iops=i]|[[,iops_rd=r][,iops_wr=w]]]\n"
" [[,bps_max=bm]|[[,bps_rd_max=rm][,bps_wr_max=wm]]]\n"
" [[,iops_max=im]|[[,iops_rd_max=irm][,iops_wr_max=iwm]]]\n"
" [[,iops_size=is]]\n"
" [[,group=g]]\n"
" use 'file' as a drive image\n", QEMU_ARCH_ALL)
STEXI
@item -drive @var{option}[,@var{option}[,@var{option}[,...]]]
@findex -drive
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
@option{-blockdev} and @option{-device} options.
@option{-drive} accepts all options that are accepted by @option{-blockdev}. In
addition, it knows the following options:
@table @option
@item file=@var{file}
This option defines which disk image (@pxref{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.
@item if=@var{interface}
This option defines on which type on interface the drive is connected.
Available types are: ide, scsi, sd, mtd, floppy, pflash, virtio, none.
@item bus=@var{bus},unit=@var{unit}
These options define where is connected the drive by defining the bus number and
the unit id.
@item index=@var{index}
This option defines where is connected the drive by using an index in the list
of available connectors of a given interface type.
@item media=@var{media}
This option defines the type of the media: disk or cdrom.
@item cyls=@var{c},heads=@var{h},secs=@var{s}[,trans=@var{t}]
Force disk physical geometry and the optional BIOS translation (trans=none or
lba). These parameters are deprecated, use the corresponding parameters
of @code{-device} instead.
@item snapshot=@var{snapshot}
@var{snapshot} is "on" or "off" and controls snapshot mode for the given drive
(see @option{-snapshot}).
@item cache=@var{cache}
@var{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 @option{cache.direct} and @option{cache.no-flush}
options (as in @option{-blockdev}), and additionally @option{cache.writeback},
which provides a default for the @option{write-cache} option of block guest
devices (as in @option{-device}). The modes correspond to the following
settings:
@c Our texi2pod.pl script doesn't support @multitable, so fall back to using
@c plain ASCII art (well, UTF-8 art really). This looks okay both in the manpage
@c and the HTML output.
@example
@ │ 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
@end example
The default mode is @option{cache=writeback}.
@item aio=@var{aio}
@var{aio} is "threads", or "native" and selects between pthread based disk I/O and native Linux AIO.
@item format=@var{format}
Specify which disk @var{format} will be used rather than detecting
the format. Can be used to specify format=raw to avoid interpreting
an untrusted format header.
@item serial=@var{serial}
This option specifies the serial number to assign to the device. This
parameter is deprecated, use the corresponding parameter of @code{-device}
instead.
@item addr=@var{addr}
Specify the controller's PCI address (if=virtio only). This parameter is
deprecated, use the corresponding parameter of @code{-device} instead.
@item werror=@var{action},rerror=@var{action}
Specify which @var{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 @option{werror=enospc} and @option{rerror=report}.
@item copy-on-read=@var{copy-on-read}
@var{copy-on-read} is "on" or "off" and enables whether to copy read backing
file sectors into the image file.
@item bps=@var{b},bps_rd=@var{r},bps_wr=@var{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.
@item bps_max=@var{bm},bps_rd_max=@var{rm},bps_wr_max=@var{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.
@item iops=@var{i},iops_rd=@var{r},iops_wr=@var{w}
Specify request rate limits in requests per second, either for all request
types or for reads or writes only.
@item iops_max=@var{bm},iops_rd_max=@var{rm},iops_wr_max=@var{wm}
Specify bursts in requests per second, either for all request types or for reads
or writes only. Bursts allow the guest I/O to spike above the limit
temporarily.
@item iops_size=@var{is}
Let every @var{is} bytes of a request count as a new request for iops
throttling purposes. Use this option to prevent guests from circumventing iops
limits by sending fewer but larger requests.
@item group=@var{g}
Join a throttling quota group with given name @var{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.
@end table
By default, the @option{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 @option{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 @option{-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 @option{-cdrom} you can use:
@example
qemu-system-i386 -drive file=file,index=2,media=cdrom
@end example
Instead of @option{-hda}, @option{-hdb}, @option{-hdc}, @option{-hdd}, you can
use:
@example
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
@end example
You can open an image using pre-opened file descriptors from an fd set:
@example
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
@end example
You can connect a CDROM to the slave of ide0:
@example
qemu-system-i386 -drive file=file,if=ide,index=1,media=cdrom
@end example
If you don't specify the "file=" argument, you define an empty drive:
@example
qemu-system-i386 -drive if=ide,index=1,media=cdrom
@end example
Instead of @option{-fda}, @option{-fdb}, you can use:
@example
qemu-system-i386 -drive file=file,index=0,if=floppy
qemu-system-i386 -drive file=file,index=1,if=floppy
@end example
By default, @var{interface} is "ide" and @var{index} is automatically
incremented:
@example
qemu-system-i386 -drive file=a -drive file=b"
@end example
is interpreted like:
@example
qemu-system-i386 -hda a -hdb b
@end example
ETEXI
DEF("mtdblock", HAS_ARG, QEMU_OPTION_mtdblock,
"-mtdblock file use 'file' as on-board Flash memory image\n",
QEMU_ARCH_ALL)
STEXI
@item -mtdblock @var{file}
@findex -mtdblock
Use @var{file} as on-board Flash memory image.
ETEXI