QEMU is a FAST! processor emulator using dynamic translation to achieve good emulation speed.
QEMU can run without an host kernel driver and yet gives acceptable performance.
For system emulation, the following hardware targets are supported:
For user emulation, x86 (32 and 64 bit), PowerPC (32 and 64 bit), ARM, MIPS (32 bit only), Sparc (32 and 64 bit), Alpha, ColdFire(m68k), CRISv32 and MicroBlaze CPUs are supported.
If you want to compile QEMU yourself, see compilation.
If a precompiled package is available for your distribution - you just have to install it. Otherwise, see compilation.
Download the experimental binary installer at http://www.free.oszoo.org/download.html. TODO (no longer available)
Download the experimental binary installer at http://www.free.oszoo.org/download.html. TODO (no longer available)
The QEMU PC System emulator simulates the following peripherals:
SMP is supported with up to 255 CPUs.
Note that adlib, gus and cs4231a are only available when QEMU was configured with –audio-card-list option containing the name(s) of required card(s).
QEMU uses the PC BIOS from the Bochs 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 dos.img -soundhw gus -parallel none
Alternatively:
qemu dos.img -device gus,irq=5
Or some other unclaimed IRQ.
CS4231A is the chip used in Windows Sound System and GUSMAX products
Download and uncompress the linux image (linux.img) and type:
qemu linux.img
Linux should boot and give you a prompt.
usage: qemu [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:
-machine ? to list
available machines. Supported machine properties are:
Special files such as iSCSI devices can be specified using protocol
specific URLs. See the section for "Device URL Syntax" for more information.
By default, writethrough caching is used for all block device. 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 when the data has been reported as written by the storage subsystem.
Writeback caching will report data writes as completed as soon as the data is present in the host page cache. This is safe as long as you trust your host. If your host crashes or loses power, then the guest may experience data corruption.
The host page cache can be avoided entirely with cache=none. This will attempt to do disk IO directly to the guests memory. QEMU may still perform an internal copy of the data.
The host page cache can be avoided while only sending write notifications to the guest when the data has been reported as written by the storage subsystem using cache=directsync.
Some block drivers perform badly with cache=writethrough, most notably, qcow2. If performance is more important than correctness, cache=writeback should be used with qcow2.
In case you don't care about data integrity over host failures, use cache=unsafe. This option tells qemu that it never needs to write any data to the disk but can instead keeps things in cache. If anything goes wrong, like your host losing power, the disk storage getting disconnected accidently, etc. you're image will most probably be rendered unusable. When using the -snapshot option, unsafe caching is always used.
Instead of -cdrom you can use:
qemu -drive file=file,index=2,media=cdrom
Instead of -hda, -hdb, -hdc, -hdd, you can use:
qemu -drive file=file,index=0,media=disk
qemu -drive file=file,index=1,media=disk
qemu -drive file=file,index=2,media=disk
qemu -drive file=file,index=3,media=disk
You can connect a CDROM to the slave of ide0:
qemu -drive file=file,if=ide,index=1,media=cdrom
If you don't specify the "file=" argument, you define an empty drive:
qemu -drive if=ide,index=1,media=cdrom
You can connect a SCSI disk with unit ID 6 on the bus #0:
qemu -drive file=file,if=scsi,bus=0,unit=6
Instead of -fda, -fdb, you can use:
qemu -drive file=file,index=0,if=floppy
qemu -drive file=file,index=1,if=floppy
By default, interface is "ide" and index is automatically incremented:
qemu -drive file=a -drive file=b"
is interpreted like:
qemu -hda a -hdb b
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.
# try to boot from network first, then from hard disk
qemu -boot order=nc
# boot from CD-ROM first, switch back to default order after reboot
qemu -boot once=d
# boot with a splash picture for 5 seconds.
qemu -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.
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
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.
qemu -soundhw sb16,adlib disk.img
qemu -soundhw es1370 disk.img
qemu -soundhw ac97 disk.img
qemu -soundhw hda disk.img
qemu -soundhw all disk.img
qemu -soundhw ?
Note that Linux's i810_audio OSS kernel (for AC97) module might require manually specifying clocking.
modprobe i810_audio clocking=48000
format=raw to avoid interpreting an untrusted format header.
-serial for the
available devices.
-device ? and
-device driver,?.
File system options:
-fsdev option is used along with -device driver "virtio-9p-pci".
Virtual File system pass-through options:
Display options:
change command
can be used to later start the VNC server.
Following the display value there may be one or more option flags separated by commas. Valid options are
reverse), the d argument
is a TCP port number, not a display number.
change command in the
pcsys_monitor
C=GB,O=ACME,L=Boston,CN=bob. For SASL party, the ACL check is
made against the username, which depending on the SASL plugin, may
include a realm component, eg bob or bob@EXAMPLE.COM.
When the acl flag is set, the initial access list will be
empty, with a deny policy. Thus no one will be allowed to
use the VNC server until the ACLs have been loaded. This can be
achieved using the acl monitor command.
i386 target only:
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=?
for a list of available devices for your target.
bin of the Unix TFTP client).
Example (using pxelinux):
qemu -hda linux.img -boot n -net user,tftp=/path/to/tftp/files,bootfile=/pxelinux.0
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.
For example, to redirect host X11 connection from screen 1 to guest screen 0, use the following:
# on the host
qemu -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 -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.
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.
qemu linux.img -net nic -net tap
More complicated example (two NICs, each one connected to a TAP device)
qemu linux.img -net nic,vlan=0 -net tap,vlan=0,ifname=tap0 \
-net nic,vlan=1 -net tap,vlan=1,ifname=tap1
Example:
# launch a first QEMU instance
qemu 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 linux.img -net nic,macaddr=52:54:00:12:34:57 \
-net socket,connect=127.0.0.1:1234
Example:
# launch one QEMU instance
qemu 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 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 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 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 linux.img -net nic,macaddr=52:54:00:12:34:56 \
-net socket,mcast=239.192.168.1:1102,localaddr=1.2.3.4
Example:
# launch vde switch
vde_switch -F -sock /tmp/myswitch
# launch QEMU instance
qemu linux.img -net nic -net vde,sock=/tmp/myswitch
Character device options:
The general form of a character device option is:
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. The key sequence of <Control-a> and <c> will rotate the input focus between attached front-ends. Specify mux=on to enable this mode.
Options to each backend are described below.
server specifies that the socket shall be a listening socket.
nowait specifies that QEMU should not block waiting for a client to connect to a listening socket.
telnet specifies that traffic on the socket should interpret telnet escape sequences.
TCP and unix socket options are given below:
0.0.0.0.
port for a listening socket specifies the local port to be bound. For a connecting socket specifies the port on the remote host to connect to. port can be given as either a port number or a service name. port is required.
to is only relevant to listening sockets. If it is specified, and port cannot be bound, QEMU will attempt to bind to subsequent ports up to and including to until it succeeds. to must be specified as a port number.
ipv4 and ipv6 specify that either IPv4 or IPv6 must be used. If neither is specified the socket may use either protocol.
nodelay disables the Nagle algorithm.
host specifies the remote host to connect to. If not specified it
defaults to localhost.
port specifies the port on the remote host to connect to. port is required.
localaddr specifies the local address to bind to. If not specified it
defaults to 0.0.0.0.
localport specifies the local port to bind to. If not specified any available local port will be used.
ipv4 and ipv6 specify that either IPv4 or IPv6 must be used.
If neither is specified the device may use either protocol.
width and height specify the width and height respectively of the console, in pixels.
cols and rows specify that the console be sized to fit a text
console with the given dimensions.
path specifies the path of the file to be opened. This file will be
created if it does not already exist, and overwritten if it does. path
is required.
On Windows, a single duplex pipe will be created at \.pipe\path.
On other hosts, 2 pipes will be created called path.in and path.out. Data written to path.in will be received by the guest. Data written by the guest can be read from path.out. QEMU will not create these fifos, and requires them to be present.
path forms part of the pipe path as described above. path is
required.
console is only available on Windows hosts.
serial is only available on Windows hosts.
path specifies the name of the serial device to open.
pty is not available on Windows hosts.
signal controls if signals are enabled on the terminal, that includes exiting QEMU with the key sequence <Control-c>. This option is enabled by default, use signal=off to disable it.
stdio is not available on Windows hosts.
tty is only available on Linux, Sun, FreeBSD, NetBSD, OpenBSD and DragonFlyBSD hosts.
path specifies the path to the tty. path is required.
Connect to a local parallel port.
path specifies the path to the parallel port device. path is
required.
debug debug level for spicevmc
name name of spice channel to connect to
Connect to a spice virtual machine channel, such as vdiport.
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.
Syntax for specifying iSCSI LUNs is “iscsi://<target-ip>[:<port>]/<target-iqn>/<lun>”
Example (without authentication):
qemu -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 --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 --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.
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 --drive file=nbd:192.0.2.1:30000
Example for Unix Domain Sockets
qemu --drive file=nbd:unix:/tmp/nbd-socket
Syntax for specifying a sheepdog device
“sheepdog:<vdiname>:<snapid>”
“sheepdog:<vdiname>:<tag>”
“sheepdog:<host>:<port>:<vdiname>”
“sheepdog:<host>:<port>:<vdiname>:<snapid>”
“sheepdog:<host>:<port>:<vdiname>:<tag>”
Example
qemu --drive file=sheepdog:192.0.2.1:30000:MyVirtualMachine
See also http://http://www.osrg.net/sheepdog/.
-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:
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.
0). Similarly to -net
VLANs, devices inside a bluetooth network n can only communicate
with other devices in the same network (scatternet).
vhci driver installed. Can
be used as following:
qemu [...OPTIONS...] -bt hci,vlan=5 -bt vhci,vlan=5
0). QEMU can only emulate one type of bluetooth devices
currently:
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.
Use file1 and file2 as modules and pass arg=foo as parameter to the first module.
Debug/Expert options:
vc in graphical mode and
stdio in non graphical mode.
This option can be used several times to simulate up to 4 serial ports.
Use -serial none to disable all serial ports.
Available character devices are:
vc:800x600
It is also possible to specify width or height in characters:
vc:80Cx24C
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:netcat options:telnet options:nowait
option was specified. The nodelay option disables the Nagle buffering
algorithm. 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 4444Example to listen and wait on port 4444 for connectionExample to not wait and listen on ip 192.168.0.100 port 4444-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.
-serial tcp except the unix domain socket
path is used for connections.
-serial mon:telnet::4444,server,nowaitThis option can be used several times to simulate up to 3 parallel ports.
Use -parallel none to disable all parallel ports.
vc in graphical mode and stdio in
non graphical mode.
vc in graphical mode and stdio in
non graphical mode.
(gdb) target remote | exec qemu -gdb stdio ...
loadvm in monitor)
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 to use 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, even prevent it from
progressing during suspension, you can set clock to vm instead.
Enable driftfix (i386 targets only) if you experience time drift problems,
specifically with Windows' ACPI HAL. This option will try to figure out how
many timer interrupts were not processed by the Windows guest and will
re-inject them.
auto is specified
then the virtual cpu speed will be automatically adjusted to keep virtual
time within a few seconds of real time.
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.
The model is the model of hardware watchdog to emulate. Choices
for model are: ib700 (iBASE 700) which is a very simple ISA
watchdog with a single timer, or i6300esb (Intel 6300ESB I/O
controller hub) which is a much more featureful PCI-based dual-timer
watchdog. Choose a model for which your guest has drivers.
Use -watchdog ? to list available hardware models. Only one
watchdog can be enabled for a guest.
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 ib7000x01 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 20This option is maintained for backward compatibility.
Please use -device virtconsole for the new way of invocation.
-nodefconfig
option will prevent QEMU from loading these configuration files at startup.
This option is only available if QEMU has been compiled with the simple tracing backend.
During the graphical emulation, you can use special key combinations to change
modes. The default key mappings are shown below, but if you use -alt-grab
then the modifier is Ctrl-Alt-Shift (instead of Ctrl-Alt) and if you use
-ctrl-grab then the modifier is the right Ctrl key (instead of Ctrl-Alt):
In the virtual consoles, you can use <Ctrl-Up>, <Ctrl-Down>, <Ctrl-PageUp> and <Ctrl-PageDown> to move in the back log.
During emulation, if you are using the -nographic option, use <Ctrl-a h> to get terminal commands:
The QEMU monitor is used to give complex commands to the QEMU emulator. You can use it to:
The following commands are available:
(qemu) change ide1-cd0 /path/to/some.iso
format is optional.
(qemu) change vnc localhost:1
(qemu) change vnc password
Password: ********
fmt is a format which tells the command how to format the data. Its syntax is: /{count}{format}{size}
h or w can be specified with the i format to
respectively select 16 or 32 bit code instruction size.
Examples:
(qemu) x/10i $eip
0x90107063: ret
0x90107064: sti
0x90107065: lea 0x0(%esi,1),%esi
0x90107069: lea 0x0(%edi,1),%edi
0x90107070: ret
0x90107071: jmp 0x90107080
0x90107073: nop
0x90107074: nop
0x90107075: nop
0x90107076: nop
(qemu) xp/80hx 0xb8000
0x000b8000: 0x0b50 0x0b6c 0x0b65 0x0b78 0x0b38 0x0b36 0x0b2f 0x0b42
0x000b8010: 0x0b6f 0x0b63 0x0b68 0x0b73 0x0b20 0x0b56 0x0b47 0x0b41
0x000b8020: 0x0b42 0x0b69 0x0b6f 0x0b73 0x0b20 0x0b63 0x0b75 0x0b72
0x000b8030: 0x0b72 0x0b65 0x0b6e 0x0b74 0x0b2d 0x0b63 0x0b76 0x0b73
0x000b8040: 0x0b20 0x0b30 0x0b35 0x0b20 0x0b4e 0x0b6f 0x0b76 0x0b20
0x000b8050: 0x0b32 0x0b30 0x0b30 0x0b33 0x0720 0x0720 0x0720 0x0720
0x000b8060: 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720
0x000b8070: 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720
0x000b8080: 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720
0x000b8090: 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720 0x0720
# followed by the raw value in either decimal or hexadecimal
format. Use - to press several keys simultaneously. Example:
sendkey ctrl-alt-f1
This command is useful to send keys that your graphical user interface
intercepts at low level, such as ctrl-alt-f1 in X Window.
bus.addr. Use the monitor
command info usb to see the devices you can remove.
info mice
Defaults:
info capture
-boot option.
The values that can be specified here depend on the machine type, but are
the same that can be specified in the -boot command line option.
allow|denydeny.
allow|deny [index]*@EXAMPLE.COM to
allow all users in the EXAMPLE.COM kerberos realm. The match will
normally be appended to the end of the ACL, but can be inserted
earlier in the list if the optional index parameter is supplied.
deny.
getfd command. This is only needed if the file descriptor was never
used by another monitor command.
The monitor understands integers expressions for every integer argument. You can use register names to get the value of specifics CPU registers by prefixing them with $.
Since version 0.6.1, QEMU supports many disk image formats, including growable disk images (their size increase as non empty sectors are written), compressed and encrypted disk images. Version 0.8.3 added the new qcow2 disk image format which is essential to support VM snapshots.
You can create a disk image with the command:
qemu-img create myimage.img mysize
where myimage.img is the disk image filename and mysize is its
size in kilobytes. You can add an M suffix to give the size in
megabytes and a G suffix for gigabytes.
See qemu_img_invocation for more information.
If you use the option -snapshot, all disk images are
considered as read only. When sectors in written, they are written in
a temporary file created in /tmp. You can however force the
write back to the raw disk images by using the commit monitor
command (or <C-a s> in the serial console).
VM snapshots are snapshots of the complete virtual machine including
CPU state, RAM, device state and the content of all the writable
disks. In order to use VM snapshots, you must have at least one non
removable and writable block device using the qcow2 disk image
format. Normally this device is the first virtual hard drive.
Use the monitor command savevm to create a new VM snapshot or
replace an existing one. A human readable name can be assigned to each
snapshot in addition to its numerical ID.
Use loadvm to restore a VM snapshot and delvm to remove
a VM snapshot. info snapshots lists the available snapshots
with their associated information:
(qemu) info snapshots Snapshot devices: hda Snapshot list (from hda): ID TAG VM SIZE DATE VM CLOCK 1 start 41M 2006-08-06 12:38:02 00:00:14.954 2 40M 2006-08-06 12:43:29 00:00:18.633 3 msys 40M 2006-08-06 12:44:04 00:00:23.514
A VM snapshot is made of a VM state info (its size is shown in
info snapshots) and a snapshot of every writable disk image.
The VM state info is stored in the first qcow2 non removable
and writable block device. The disk image snapshots are stored in
every disk image. The size of a snapshot in a disk image is difficult
to evaluate and is not shown by info snapshots because the
associated disk sectors are shared among all the snapshots to save
disk space (otherwise each snapshot would need a full copy of all the
disk images).
When using the (unrelated) -snapshot option
(disk_images_snapshot_mode), you can always make VM snapshots,
but they are deleted as soon as you exit QEMU.
VM snapshots currently have the following known limitations:
qemu-img Invocationusage: qemu-img command [command options]
The following commands are supported:
Command parameters:
k or K
(kilobyte, 1024) M (megabyte, 1024k) and G (gigabyte, 1024M)
and T (terabyte, 1024G) are supported. b is ignored.
-o ? for an overview of the options supported
by the used format or see the format descriptions below for details.
k for kilobytes.
Parameters to snapshot subcommand:
Command description:
Only the formats qcow2, qed and vdi support
consistency checks.
If the option backing_file is specified, then the image will record
only the differences from backing_file. No size needs to be specified in
this case. backing_file will never be modified unless you use the
commit monitor command (or qemu-img commit).
The size can also be specified using the size option with -o,
it doesn't need to be specified separately in this case.
-c
option) or use any format specific options like encryption (-o option).
Only the formats qcow and qcow2 support compression. The
compression is read-only. It means that if a compressed sector is
rewritten, then it is rewritten as uncompressed data.
Image conversion is also useful to get smaller image when using a
growable format such as qcow or cow: the empty sectors
are detected and suppressed from the destination image.
You can use the backing_file option to force the output image to be
created as a copy on write image of the specified base image; the
backing_file should have the same content as the input's base image,
however the path, image format, etc may differ.
qcow2 and
qed support changing the backing file.
The backing file is changed to backing_file and (if the image format of filename supports this) the backing file format is changed to backing_fmt.
There are two different modes in which rebase can operate:
In order to achieve this, any clusters that differ between backing_file and the old backing file of filename are merged into filename before actually changing the backing file.
Note that the safe mode is an expensive operation, comparable to converting
an image. It only works if the old backing file still exists.
-u is specified. In this mode, only the
backing file name and format of filename is changed without any checks
on the file contents. The user must take care of specifying the correct new
backing file, or the guest-visible content of the image will be corrupted.
This mode is useful for renaming or moving the backing file to somewhere else. It can be used without an accessible old backing file, i.e. you can use it to fix an image whose backing file has already been moved/renamed.
Before using this command to shrink a disk image, you MUST use file system and partitioning tools inside the VM to reduce allocated file systems and partition sizes accordingly. Failure to do so will result in data loss!
After using this command to grow a disk image, you must use file system and partitioning tools inside the VM to actually begin using the new space on the device.
Supported image file formats:
qemu-img info to know the real size used by the
image or ls -ls on Unix/Linux.
Supported options:
backing_filebacking_fmtencryptionon, the image is encrypted.
Encryption uses the AES format which is very secure (128 bit keys). Use
a long password (16 characters) to get maximum protection.
cluster_sizepreallocationSupported options:
backing_fileencryptionon, the image is encrypted.
Supported options:
backing_fmtcompat6qemu-nbd Invocationusage: qemu-nbd [OPTION]... filename
Export Qemu disk image using NBD protocol.
In addition to disk image files, QEMU can directly access host devices. We describe here the usage for QEMU version >= 0.8.3.
On Linux, you can directly use the host device filename instead of a disk image filename provided you have enough privileges to access it. For example, use /dev/cdrom to access to the CDROM or /dev/fd0 for the floppy.
CDFloppyHard disksCDCurrently there is no specific code to handle removable media, so it
is better to use the change or eject monitor commands to
change or eject media.
Hard disksWARNING: unless you know what you do, it is better to only make READ-ONLY accesses to the hard disk otherwise you may corrupt your host data (use the -snapshot command line so that the modifications are written in a temporary file).
/dev/cdrom is an alias to the first CDROM.
Currently there is no specific code to handle removable media, so it
is better to use the change or eject monitor commands to
change or eject media.
QEMU can automatically create a virtual FAT disk image from a directory tree. In order to use it, just type:
qemu linux.img -hdb fat:/my_directory
Then you access access to all the files in the /my_directory directory without having to copy them in a disk image or to export them via SAMBA or NFS. The default access is read-only.
Floppies can be emulated with the :floppy: option:
qemu linux.img -fda fat:floppy:/my_directory
A read/write support is available for testing (beta stage) with the
:rw: option:
qemu linux.img -fda fat:floppy:rw:/my_directory
What you should never do:
QEMU can access directly to block device exported using the Network Block Device protocol.
qemu linux.img -hdb nbd:my_nbd_server.mydomain.org:1024
If the NBD server is located on the same host, you can use an unix socket instead of an inet socket:
qemu linux.img -hdb nbd:unix:/tmp/my_socket
In this case, the block device must be exported using qemu-nbd:
qemu-nbd --socket=/tmp/my_socket my_disk.qcow2
The use of qemu-nbd allows to share a disk between several guests:
qemu-nbd --socket=/tmp/my_socket --share=2 my_disk.qcow2
and then you can use it with two guests:
qemu linux1.img -hdb nbd:unix:/tmp/my_socket qemu linux2.img -hdb nbd:unix:/tmp/my_socket
If the nbd-server uses named exports (since NBD 2.9.18), you must use the "exportname" option:
qemu -cdrom nbd:localhost:exportname=debian-500-ppc-netinst qemu -cdrom nbd:localhost:exportname=openSUSE-11.1-ppc-netinst
Sheepdog is a distributed storage system for QEMU. It provides highly available block level storage volumes that can be attached to QEMU-based virtual machines.
You can create a Sheepdog disk image with the command:
qemu-img create sheepdog:image size
where image is the Sheepdog image name and size is its size.
To import the existing filename to Sheepdog, you can use a convert command.
qemu-img convert filename sheepdog:image
You can boot from the Sheepdog disk image with the command:
qemu sheepdog:image
You can also create a snapshot of the Sheepdog image like qcow2.
qemu-img snapshot -c tag sheepdog:image
where tag is a tag name of the newly created snapshot.
To boot from the Sheepdog snapshot, specify the tag name of the snapshot.
qemu sheepdog:image:tag
You can create a cloned image from the existing snapshot.
qemu-img create -b sheepdog:base:tag sheepdog:image
where base is a image name of the source snapshot and tag is its tag name.
If the Sheepdog daemon doesn't run on the local host, you need to specify one of the Sheepdog servers to connect to.
qemu-img create sheepdog:hostname:port:image size qemu sheepdog:hostname:port:image
iSCSI is a popular protocol used to access SCSI devices across a computer network.
There are two different ways iSCSI devices can be used by QEMU.
The first method is to mount the iSCSI LUN on the host, and make it appear as any other ordinary SCSI device on the host and then to access this device as a /dev/sd device from QEMU. How to do this differs between host OSes.
The second method involves using the iSCSI initiator that is built into QEMU. This provides a mechanism that works the same way regardless of which host OS you are running QEMU on. This section will describe this second method of using iSCSI together with QEMU.
In QEMU, iSCSI devices are described using special iSCSI URLs
URL syntax: iscsi://[<username>[%<password>]@]<host>[:<port>]/<target-iqn-name>/<lun>
Username and password are optional and only used if your target is set up using CHAP authentication for access control. Alternatively the username and password can also be set via environment variables to have these not show up in the process list
export LIBISCSI_CHAP_USERNAME=<username> export LIBISCSI_CHAP_PASSWORD=<password> iscsi://<host>/<target-iqn-name>/<lun>
Howto set up a simple iSCSI target on loopback and accessing it via QEMU:
This example shows how to set up an iSCSI target with one CDROM and one DISK
using the Linux STGT software target. This target is available on Red Hat based
systems as the package 'scsi-target-utils'.
tgtd --iscsi portal=127.0.0.1:3260
tgtadm --lld iscsi --op new --mode target --tid 1 -T iqn.qemu.test
tgtadm --lld iscsi --mode logicalunit --op new --tid 1 --lun 1 \
-b /IMAGES/disk.img --device-type=disk
tgtadm --lld iscsi --mode logicalunit --op new --tid 1 --lun 2 \
-b /IMAGES/cd.iso --device-type=cd
tgtadm --lld iscsi --op bind --mode target --tid 1 -I ALL
qemu-system-i386 -boot d -drive file=iscsi://127.0.0.1/iqn.qemu.test/1 \
-cdrom iscsi://127.0.0.1/iqn.qemu.test/2
QEMU can simulate several network cards (PCI or ISA cards on the PC target) and can connect them to an arbitrary number of Virtual Local Area Networks (VLANs). Host TAP devices can be connected to any QEMU VLAN. VLAN can be connected between separate instances of QEMU to simulate large networks. For simpler usage, a non privileged user mode network stack can replace the TAP device to have a basic network connection.
QEMU simulates several VLANs. A VLAN can be symbolised as a virtual connection between several network devices. These devices can be for example QEMU virtual Ethernet cards or virtual Host ethernet devices (TAP devices).
This is the standard way to connect QEMU to a real network. QEMU adds
a virtual network device on your host (called tapN), and you
can then configure it as if it was a real ethernet card.
As an example, you can download the linux-test-xxx.tar.gz
archive and copy the script qemu-ifup in /etc and
configure properly sudo so that the command ifconfig
contained in qemu-ifup can be executed as root. You must verify
that your host kernel supports the TAP network interfaces: the
device /dev/net/tun must be present.
See sec_invocation to have examples of command lines using the TAP network interfaces.
There is a virtual ethernet driver for Windows 2000/XP systems, called TAP-Win32. But it is not included in standard QEMU for Windows, so you will need to get it separately. It is part of OpenVPN package, so download OpenVPN from : http://openvpn.net/.
By using the option -net user (default configuration if no -net option is specified), QEMU uses a completely user mode network stack (you don't need root privilege to use the virtual network). The virtual network configuration is the following:
QEMU VLAN <------> Firewall/DHCP server <-----> Internet
| (10.0.2.2)
|
----> DNS server (10.0.2.3)
|
----> SMB server (10.0.2.4)
The QEMU VM behaves as if it was behind a firewall which blocks all incoming connections. You can use a DHCP client to automatically configure the network in the QEMU VM. The DHCP server assign addresses to the hosts starting from 10.0.2.15.
In order to check that the user mode network is working, you can ping the address 10.0.2.2 and verify that you got an address in the range 10.0.2.x from the QEMU virtual DHCP server.
Note that ping is not supported reliably to the internet as it
would require root privileges. It means you can only ping the local
router (10.0.2.2).
When using the built-in TFTP server, the router is also the TFTP server.
When using the -redir option, TCP or UDP connections can be redirected from the host to the guest. It allows for example to redirect X11, telnet or SSH connections.
Using the -net socket option, it is possible to make VLANs that span several QEMU instances. See sec_invocation to have a basic example.
With KVM enabled on a Linux host, a shared memory device is available. Guests map a POSIX shared memory region into the guest as a PCI device that enables zero-copy communication to the application level of the guests. The basic syntax is:
qemu -device ivshmem,size=<size in format accepted by -m>[,shm=<shm name>]
If desired, interrupts can be sent between guest VMs accessing the same shared memory region. Interrupt support requires using a shared memory server and using a chardev socket to connect to it. The code for the shared memory server is qemu.git/contrib/ivshmem-server. An example syntax when using the shared memory server is:
qemu -device ivshmem,size=<size in format accepted by -m>[,chardev=<id>]
[,msi=on][,ioeventfd=on][,vectors=n][,role=peer|master]
qemu -chardev socket,path=<path>,id=<id>
When using the server, the guest will be assigned a VM ID (>=0) that allows guests using the same server to communicate via interrupts. Guests can read their VM ID from a device register (see example code). Since receiving the shared memory region from the server is asynchronous, there is a (small) chance the guest may boot before the shared memory is attached. To allow an application to ensure shared memory is attached, the VM ID register will return -1 (an invalid VM ID) until the memory is attached. Once the shared memory is attached, the VM ID will return the guest's valid VM ID. With these semantics, the guest application can check to ensure the shared memory is attached to the guest before proceeding.
The role argument can be set to either master or peer and will affect how the shared memory is migrated. With role=master, the guest will copy the shared memory on migration to the destination host. With role=peer, the guest will not be able to migrate with the device attached. With the peer case, the device should be detached and then reattached after migration using the PCI hotplug support.
This section explains how to launch a Linux kernel inside QEMU without having to make a full bootable image. It is very useful for fast Linux kernel testing.
The syntax is:
qemu -kernel arch/i386/boot/bzImage -hda root-2.4.20.img -append "root=/dev/hda"
Use -kernel to provide the Linux kernel image and -append to give the kernel command line arguments. The -initrd option can be used to provide an INITRD image.
When using the direct Linux boot, a disk image for the first hard disk hda is required because its boot sector is used to launch the Linux kernel.
If you do not need graphical output, you can disable it and redirect the virtual serial port and the QEMU monitor to the console with the -nographic option. The typical command line is:
qemu -kernel arch/i386/boot/bzImage -hda root-2.4.20.img \
-append "root=/dev/hda console=ttyS0" -nographic
Use <Ctrl-a c> to switch between the serial console and the monitor (see pcsys_keys).
QEMU emulates a PCI UHCI USB controller. You can virtually plug virtual USB devices or real host USB devices (experimental, works only on Linux hosts). Qemu will automatically create and connect virtual USB hubs as necessary to connect multiple USB devices.
USB devices can be connected with the -usbdevice commandline option
or the usb_add monitor command. Available devices are:
mousetabletdisk:filehost:bus.addrhost:vendor_id:product_idwacom-tablettablet
above but it can be used with the tslib library because in addition to touch
coordinates it reports touch pressure.
keyboardserial:[vendorid=vendor_id][,product_id=product_id]:dev-serial option. The vendorid and productid options can be
used to override the default 0403:6001. For instance,
usb_add serial:productid=FA00:tcp:192.168.0.2:4444
will connect to tcp port 4444 of ip 192.168.0.2, and plug that to the virtual
serial converter, faking a Matrix Orbital LCD Display (USB ID 0403:FA00).
braillenet:options-net nic,options (see description).
For instance, user-mode networking can be used with
qemu [...OPTIONS...] -net user,vlan=0 -usbdevice net:vlan=0
Currently this cannot be used in machines that support PCI NICs.
bt[:hci-type]-bt hci,vlan=0.
This USB device implements the USB Transport Layer of HCI. Example
usage:
qemu [...OPTIONS...] -usbdevice bt:hci,vlan=3 -bt device:keyboard,vlan=3
WARNING: this is an experimental feature. QEMU will slow down when using it. USB devices requiring real time streaming (i.e. USB Video Cameras) are not supported yet.
ls /proc/bus/usb
001 devices drivers
chown -R myuid /proc/bus/usb
info usbhost
Device 1.2, speed 480 Mb/s
Class 00: USB device 1234:5678, USB DISK
You should see the list of the devices you can use (Never try to use hubs, it won't work).
usb_add host:1234:5678
Normally the guest OS should report that a new USB device is plugged. You can use the option -usbdevice to do the same.
When relaunching QEMU, you may have to unplug and plug again the USB device to make it work again (this is a bug).
The VNC server capability provides access to the graphical console of the guest VM across the network. This has a number of security considerations depending on the deployment scenarios.
The simplest VNC server setup does not include any form of authentication. For this setup it is recommended to restrict it to listen on a UNIX domain socket only. For example
qemu [...OPTIONS...] -vnc unix:/home/joebloggs/.qemu-myvm-vnc
This ensures that only users on local box with read/write access to that path can access the VNC server. To securely access the VNC server from a remote machine, a combination of netcat+ssh can be used to provide a secure tunnel.
The VNC protocol has limited support for password based authentication. Since
the protocol limits passwords to 8 characters it should not be considered
to provide high security. The password can be fairly easily brute-forced by
a client making repeat connections. For this reason, a VNC server using password
authentication should be restricted to only listen on the loopback interface
or UNIX domain sockets. Password authentication is requested with the password
option, and then once QEMU is running the password is set with the monitor. Until
the monitor is used to set the password all clients will be rejected.
qemu [...OPTIONS...] -vnc :1,password -monitor stdio (qemu) change vnc password Password: ******** (qemu)
The QEMU VNC server also implements the VeNCrypt extension allowing use of TLS for encryption of the session, and x509 certificates for authentication. The use of x509 certificates is strongly recommended, because TLS on its own is susceptible to man-in-the-middle attacks. Basic x509 certificate support provides a secure session, but no authentication. This allows any client to connect, and provides an encrypted session.
qemu [...OPTIONS...] -vnc :1,tls,x509=/etc/pki/qemu -monitor stdio
In the above example /etc/pki/qemu should contain at least three files,
ca-cert.pem, server-cert.pem and server-key.pem. Unprivileged
users will want to use a private directory, for example $HOME/.pki/qemu.
NB the server-key.pem file should be protected with file mode 0600 to
only be readable by the user owning it.
Certificates can also provide a means to authenticate the client connecting. The server will request that the client provide a certificate, which it will then validate against the CA certificate. This is a good choice if deploying in an environment with a private internal certificate authority.
qemu [...OPTIONS...] -vnc :1,tls,x509verify=/etc/pki/qemu -monitor stdio
Finally, the previous method can be combined with VNC password authentication to provide two layers of authentication for clients.
qemu [...OPTIONS...] -vnc :1,password,tls,x509verify=/etc/pki/qemu -monitor stdio (qemu) change vnc password Password: ******** (qemu)
The SASL authentication method is a VNC extension, that provides an easily extendable, pluggable authentication method. This allows for integration with a wide range of authentication mechanisms, such as PAM, GSSAPI/Kerberos, LDAP, SQL databases, one-time keys and more. The strength of the authentication depends on the exact mechanism configured. If the chosen mechanism also provides a SSF layer, then it will encrypt the datastream as well.
Refer to the later docs on how to choose the exact SASL mechanism used for authentication, but assuming use of one supporting SSF, then QEMU can be launched with:
qemu [...OPTIONS...] -vnc :1,sasl -monitor stdio
If the desired SASL authentication mechanism does not supported SSF layers, then it is strongly advised to run it in combination with TLS and x509 certificates. This provides securely encrypted data stream, avoiding risk of compromising of the security credentials. This can be enabled, by combining the 'sasl' option with the aforementioned TLS + x509 options:
qemu [...OPTIONS...] -vnc :1,tls,x509,sasl -monitor stdio
The GNU TLS packages provides a command called certtool which can
be used to generate certificates and keys in PEM format. At a minimum it
is necessary to setup a certificate authority, and issue certificates to
each server. If using certificates for authentication, then each client
will also need to be issued a certificate. The recommendation is for the
server to keep its certificates in either /etc/pki/qemu or for
unprivileged users in $HOME/.pki/qemu.
This step only needs to be performed once per organization / organizational unit. First the CA needs a private key. This key must be kept VERY secret and secure. If this key is compromised the entire trust chain of the certificates issued with it is lost.
# certtool --generate-privkey > ca-key.pem
A CA needs to have a public certificate. For simplicity it can be a self-signed certificate, or one issue by a commercial certificate issuing authority. To generate a self-signed certificate requires one core piece of information, the name of the organization.
# cat > ca.info <<EOF
cn = Name of your organization
ca
cert_signing_key
EOF
# certtool --generate-self-signed \
--load-privkey ca-key.pem
--template ca.info \
--outfile ca-cert.pem
The ca-cert.pem file should be copied to all servers and clients wishing to utilize
TLS support in the VNC server. The ca-key.pem must not be disclosed/copied at all.
Each server (or host) needs to be issued with a key and certificate. When connecting the certificate is sent to the client which validates it against the CA certificate. The core piece of information for a server certificate is the hostname. This should be the fully qualified hostname that the client will connect with, since the client will typically also verify the hostname in the certificate. On the host holding the secure CA private key:
# cat > server.info <<EOF
organization = Name of your organization
cn = server.foo.example.com
tls_www_server
encryption_key
signing_key
EOF
# certtool --generate-privkey > server-key.pem
# certtool --generate-certificate \
--load-ca-certificate ca-cert.pem \
--load-ca-privkey ca-key.pem \
--load-privkey server server-key.pem \
--template server.info \
--outfile server-cert.pem
The server-key.pem and server-cert.pem files should now be securely copied
to the server for which they were generated. The server-key.pem is security
sensitive and should be kept protected with file mode 0600 to prevent disclosure.
If the QEMU VNC server is to use the x509verify option to validate client
certificates as its authentication mechanism, each client also needs to be issued
a certificate. The client certificate contains enough metadata to uniquely identify
the client, typically organization, state, city, building, etc. On the host holding
the secure CA private key:
# cat > client.info <<EOF
country = GB
state = London
locality = London
organiazation = Name of your organization
cn = client.foo.example.com
tls_www_client
encryption_key
signing_key
EOF
# certtool --generate-privkey > client-key.pem
# certtool --generate-certificate \
--load-ca-certificate ca-cert.pem \
--load-ca-privkey ca-key.pem \
--load-privkey client-key.pem \
--template client.info \
--outfile client-cert.pem
The client-key.pem and client-cert.pem files should now be securely
copied to the client for which they were generated.
The following documentation assumes use of the Cyrus SASL implementation on a Linux host, but the principals should apply to any other SASL impl. When SASL is enabled, the mechanism configuration will be loaded from system default SASL service config /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.
The default configuration might contain
mech_list: digest-md5 sasldb_path: /etc/qemu/passwd.db
This says to use the 'Digest MD5' mechanism, which is similar to the HTTP Digest-MD5 mechanism. The list of valid usernames & passwords is maintained in the /etc/qemu/passwd.db file, and can be updated using the saslpasswd2 command. While this mechanism is easy to configure and use, it is not considered secure by modern standards, so only suitable for developers / ad-hoc testing.
A more serious deployment might use Kerberos, which is done with the 'gssapi' mechanism
mech_list: gssapi keytab: /etc/qemu/krb5.tab
For this to work the administrator of your KDC must generate a Kerberos principal for the server, with a name of 'qemu/somehost.example.com@EXAMPLE.COM' replacing 'somehost.example.com' with the fully qualified host name of the machine running QEMU, and 'EXAMPLE.COM' with the Kerberos Realm.
Other configurations will be left as an exercise for the reader. It should be noted that only Digest-MD5 and GSSAPI provides a SSF layer for data encryption. For all other mechanisms, VNC should always be configured to use TLS and x509 certificates to protect security credentials from snooping.
QEMU has a primitive support to work with gdb, so that you can do 'Ctrl-C' while the virtual machine is running and inspect its state.
In order to use gdb, launch qemu with the '-s' option. It will wait for a gdb connection:
> qemu -s -kernel arch/i386/boot/bzImage -hda root-2.4.20.img \
-append "root=/dev/hda"
Connected to host network interface: tun0
Waiting gdb connection on port 1234
Then launch gdb on the 'vmlinux' executable:
> gdb vmlinux
In gdb, connect to QEMU:
(gdb) target remote localhost:1234
Then you can use gdb normally. For example, type 'c' to launch the kernel:
(gdb) c
Here are some useful tips in order to use gdb on system code:
info reg to display all the CPU registers.
x/10i $eip to display the code at the PC position.
set architecture i8086 to dump 16 bit code. Then use
x/10i $cs*16+$eip to dump the code at the PC position.
Advanced debugging options:
The default single stepping behavior is step with the IRQs and timer service routines off. It is set this way because when gdb executes a single step it expects to advance beyond the current instruction. With the IRQs and and timer service routines on, a single step might jump into the one of the interrupt or exception vectors instead of executing the current instruction. This means you may hit the same breakpoint a number of times before executing the instruction gdb wants to have executed. Because there are rare circumstances where you want to single step into an interrupt vector the behavior can be controlled from GDB. There are three commands you can query and set the single step behavior:
maintenance packet qqemu.sstepbits (gdb) maintenance packet qqemu.sstepbits
sending: "qqemu.sstepbits"
received: "ENABLE=1,NOIRQ=2,NOTIMER=4"
maintenance packet qqemu.sstep (gdb) maintenance packet qqemu.sstep
sending: "qqemu.sstep"
received: "0x7"
maintenance packet Qqemu.sstep=HEX_VALUE (gdb) maintenance packet Qqemu.sstep=0x5
sending: "qemu.sstep=0x5"
received: "OK"
To have access to SVGA graphic modes under X11, use the vesa or
the cirrus X11 driver. For optimal performances, use 16 bit
color depth in the guest and the host OS.
When using a 2.6 guest Linux kernel, you should add the option
clock=pit on the kernel command line because the 2.6 Linux
kernels make very strict real time clock checks by default that QEMU
cannot simulate exactly.
When using a 2.6 guest Linux kernel, verify that the 4G/4G patch is not activated because QEMU is slower with this patch. The QEMU Accelerator Module is also much slower in this case. Earlier Fedora Core 3 Linux kernel (< 2.6.9-1.724_FC3) were known to incorporate this patch by default. Newer kernels don't have it.
If you have a slow host, using Windows 95 is better as it gives the best speed. Windows 2000 is also a good choice.
QEMU emulates a 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.
If you are using Windows XP as guest OS and if you want to use high resolution modes which the Cirrus Logic BIOS does not support (i.e. >= 1280x1024x16), then you should use the VESA VBE virtual graphic card (option -std-vga).
Windows 9x does not correctly use the CPU HLT instruction. The result is that it takes host CPU cycles even when idle. You can install the utility from http://www.user.cityline.ru/~maxamn/amnhltm.zip to solve this problem. Note that no such tool is needed for NT, 2000 or XP.
Windows 2000 has a bug which gives a disk full problem during its installation. When installing it, use the -win2k-hack QEMU option to enable a specific workaround. After Windows 2000 is installed, you no longer need this option (this option slows down the IDE transfers).
Windows 2000 cannot automatically shutdown in QEMU although Windows 98 can. It comes from the fact that Windows 2000 does not automatically use the APM driver provided by the BIOS.
In order to correct that, do the following (thanks to Struan Bartlett): go to the Control Panel => Add/Remove Hardware & Next => Add/Troubleshoot a device => Add a new device & Next => No, select the hardware from a list & Next => NT Apm/Legacy Support & Next => Next (again) a few times. Now the driver is installed and Windows 2000 now correctly instructs QEMU to shutdown at the appropriate moment.
See sec_invocation about the help of the option -smb.
Some releases of Windows XP install correctly but give a security error when booting:
A problem is preventing Windows from accurately checking the license for this computer. Error code: 0x800703e6.
The workaround is to install a service pack for XP after a boot in safe mode. Then reboot, and the problem should go away. Since there is no network while in safe mode, its recommended to download the full installation of SP1 or SP2 and transfer that via an ISO or using the vvfat block device ("-hdb fat:directory_which_holds_the_SP").
DOS does not correctly use the CPU HLT instruction. The result is that it takes host CPU cycles even when idle. You can install the utility from http://www.vmware.com/software/dosidle210.zip to solve this problem.
QEMU is a generic emulator and it emulates many non PC machines. Most of the options are similar to the PC emulator. The differences are mentioned in the following sections.
Use the executable qemu-system-ppc to simulate a complete PREP or PowerMac PowerPC system.
QEMU emulates the following PowerMac peripherals:
QEMU emulates the following PREP peripherals:
QEMU uses the Open Hack'Ware Open Firmware Compatible BIOS available at http://perso.magic.fr/l_indien/OpenHackWare/index.htm.
Since version 0.9.1, QEMU uses OpenBIOS http://www.openbios.org/ for the g3beige and mac99 PowerMac machines. OpenBIOS is a free (GPL v2) portable firmware implementation. The goal is to implement a 100% IEEE 1275-1994 (referred to as Open Firmware) compliant firmware.
The following options are specific to the PowerPC emulation:
qemu-system-ppc -prom-env 'auto-boot?=false' \
-prom-env 'boot-device=hd:2,\yaboot' \
-prom-env 'boot-args=conf=hd:2,\yaboot.conf'
These variables are not used by Open Hack'Ware.
More information is available at http://perso.magic.fr/l_indien/qemu-ppc/.
Use the executable qemu-system-sparc to simulate the following Sun4m architecture machines:
The emulation is somewhat complete. SMP up to 16 CPUs is supported, but Linux limits the number of usable CPUs to 4.
It's also possible to simulate a SPARCstation 2 (sun4c architecture), SPARCserver 1000, or SPARCcenter 2000 (sun4d architecture), but these emulators are not usable yet.
QEMU emulates the following sun4m/sun4c/sun4d peripherals:
The number of peripherals is fixed in the architecture. Maximum memory size depends on the machine type, for SS-5 it is 256MB and for others 2047MB.
Since version 0.8.2, QEMU uses OpenBIOS http://www.openbios.org/. OpenBIOS is a free (GPL v2) portable firmware implementation. The goal is to implement a 100% IEEE 1275-1994 (referred to as Open Firmware) compliant firmware.
A sample Linux 2.6 series kernel and ram disk image are available on the QEMU web site. There are still issues with NetBSD and OpenBSD, but some kernel versions work. Please note that currently Solaris kernels don't work probably due to interface issues between OpenBIOS and Solaris.
The following options are specific to the Sparc32 emulation:
qemu-system-sparc -prom-env 'auto-boot?=false' \
-prom-env 'boot-device=sd(0,2,0):d' -prom-env 'boot-args=linux single'
Use the executable qemu-system-sparc64 to simulate a Sun4u (UltraSPARC PC-like machine), Sun4v (T1 PC-like machine), or generic Niagara (T1) machine. The emulator is not usable for anything yet, but it can launch some kernels.
QEMU emulates the following peripherals:
The following options are specific to the Sparc64 emulation:
qemu-system-sparc64 -prom-env 'auto-boot?=false'
Four executables cover simulation of 32 and 64-bit MIPS systems in both endian options, qemu-system-mips, qemu-system-mipsel qemu-system-mips64 and qemu-system-mips64el. Five different machine types are emulated:
The generic emulation is supported by Debian 'Etch' and is able to install Debian into a virtual disk image. The following devices are emulated:
The Malta emulation supports the following devices:
The ACER Pica emulation supports:
The mipssim pseudo board emulation provides an environment similar to what the proprietary MIPS emulator uses for running Linux. It supports:
The MIPS Magnum R4000 emulation supports:
Use the executable qemu-system-arm to simulate a ARM machine. The ARM Integrator/CP board is emulated with the following devices:
The ARM Versatile baseboard is emulated with the following devices:
Several variants of the ARM RealView baseboard are emulated, including the EB, PB-A8 and PBX-A9. Due to interactions with the bootloader, only certain Linux kernel configurations work out of the box on these boards.
Kernels for the PB-A8 board should have CONFIG_REALVIEW_HIGH_PHYS_OFFSET enabled in the kernel, and expect 512M RAM. Kernels for The PBX-A9 board should have CONFIG_SPARSEMEM enabled, CONFIG_REALVIEW_HIGH_PHYS_OFFSET disabled and expect 1024M RAM.
The following devices are emulated:
The XScale-based clamshell PDA models ("Spitz", "Akita", "Borzoi" and "Terrier") emulation includes the following peripherals:
The Palm Tungsten|E PDA (codename "Cheetah") emulation includes the following elements:
Nokia N800 and N810 internet tablets (known also as RX-34 and RX-44 / 48) emulation supports the following elements:
The Luminary Micro Stellaris LM3S811EVB emulation includes the following devices:
The Luminary Micro Stellaris LM3S6965EVB emulation includes the following devices:
The Freecom MusicPal internet radio emulation includes the following elements:
The Siemens SX1 models v1 and v2 (default) basic emulation. The emulation includes the following elements:
The "Syborg" Symbian Virtual Platform base model includes the following elements:
A Linux 2.6 test image is available on the QEMU web site. More information is available in the QEMU mailing-list archive.
The following options are specific to the ARM emulation:
On ARM this implements the "Angel" interface.
Note that this allows guest direct access to the host filesystem, so should only be used with trusted guest OS.
Use the executable qemu-system-m68k to simulate a ColdFire machine. The emulator is able to boot a uClinux kernel.
The M5208EVB emulation includes the following devices:
The AN5206 emulation includes the following devices:
The following options are specific to the ColdFire emulation:
On M68K this implements the "ColdFire GDB" interface used by libgloss.
Note that this allows guest direct access to the host filesystem, so should only be used with trusted guest OS.
Two executables cover simulation of both Xtensa endian options, qemu-system-xtensa and qemu-system-xtensaeb. Two different machine types are emulated:
The sim pseudo board emulation provides an environment similar to one provided by the proprietary Tensilica ISS. It supports:
The Avnet LX60/LX110/LX200 emulation supports:
The following options are specific to the Xtensa emulation:
Xtensa semihosting provides basic file IO calls, such as open/read/write/seek/select. Tensilica baremetal libc for ISS and linux platform "sim" use this interface.
Note that this allows guest direct access to the host filesystem, so should only be used with trusted guest OS.
The following OS are supported in user space emulation:
In order to launch a Linux process, QEMU needs the process executable itself and all the target (x86) dynamic libraries used by it.
qemu-i386 -L / /bin/ls
-L / tells that the x86 dynamic linker must be searched with a
/ prefix.
qemu-i386 -L / qemu-i386 -L / /bin/ls
LD_LIBRARY_PATH is not set:
unset LD_LIBRARY_PATH
Then you can launch the precompiled ls x86 executable:
qemu-i386 tests/i386/ls
You can look at scripts/qemu-binfmt-conf.sh so that
QEMU is automatically launched by the Linux kernel when you try to
launch x86 executables. It requires the binfmt_misc module in the
Linux kernel.
qemu-i386 /usr/local/qemu-i386/bin/qemu-i386 \
/usr/local/qemu-i386/bin/ls-i386
qemu-i386 /usr/local/qemu-i386/bin/ls-i386
${HOME}/.wine directory is saved to ${HOME}/.wine.org.
qemu-i386 /usr/local/qemu-i386/wine/bin/wine \
/usr/local/qemu-i386/wine/c/Program\ Files/putty.exe
usage: qemu-i386 [-h] [-d] [-L path] [-s size] [-cpu model] [-g port] [-B offset] [-R size] program [arguments...]
Debug options:
Environment variables:
qemu-arm is also capable of running ARM "Angel" semihosted ELF binaries (as implemented by the arm-elf and arm-eabi Newlib/GDB configurations), and arm-uclinux bFLT format binaries.
qemu-m68k is capable of running semihosted binaries using the BDM (m5xxx-ram-hosted.ld) or m68k-sim (sim.ld) syscall interfaces, and coldfire uClinux bFLT format binaries.
The binary format is detected automatically.
qemu-i386 TODO. qemu-x86_64 TODO.
qemu-mips TODO. qemu-mipsel TODO.
qemu-ppc64abi32 TODO. qemu-ppc64 TODO. qemu-ppc TODO.
qemu-sh4eb TODO. qemu-sh4 TODO.
qemu-sparc can execute Sparc32 binaries (Sparc32 CPU, 32 bit ABI).
qemu-sparc32plus can execute Sparc32 and SPARC32PLUS binaries (Sparc64 CPU, 32 bit ABI).
qemu-sparc64 can execute some Sparc64 (Sparc64 CPU, 64 bit ABI) and SPARC32PLUS binaries (Sparc64 CPU, 32 bit ABI).
[1] If you're host commpage can be executed by qemu.
In order to launch a Mac OS X/Darwin process, QEMU needs the process executable itself and all the target dynamic libraries used by it. If you don't have the FAT libraries (you're running Mac OS X/ppc) you'll need to obtain it from a Mac OS X CD or compile them by hand.
qemu-i386 /bin/ls
or to run the ppc version of the executable:
qemu-ppc /bin/ls
qemu-i386 -L /opt/x86_root/ /bin/ls
-L /opt/x86_root/ tells that the dynamic linker (dyld) path is in
/opt/x86_root/usr/bin/dyld.
usage: qemu-i386 [-h] [-d] [-L path] [-s size] program [arguments...]
Debug options:
In order to launch a BSD process, QEMU needs the process executable itself and all the target dynamic libraries used by it.
qemu-sparc64 /bin/ls
usage: qemu-sparc64 [-h] [-d] [-L path] [-s size] [-bsd type] program [arguments...]
Debug options:
First you must decompress the sources:
cd /tmp tar zxvf qemu-x.y.z.tar.gz cd qemu-x.y.z
Then you configure QEMU and build it (usually no options are needed):
./configure make
Then type as root user:
make install
to install QEMU in /usr/local.
PATH environment
variable so that sdl-config can be launched by
the QEMU configuration script.
PATH=/usr/i686-pc-mingw32/sys-root/mingw/bin:$PATH ./configure --cross-prefix='i686-pc-mingw32-'
The example assumes sdl-config is installed under /usr/i686-pc-mingw32/sys-root/mingw/bin and
MinGW cross compilation tools have names like i686-pc-mingw32-gcc and i686-pc-mingw32-strip.
We set the PATH environment variable to ensure the MinGW version of sdl-config is used and
use –cross-prefix to specify the name of the cross compiler.
You can also use –prefix to set the Win32 install path which defaults to c:/Program Files/Qemu.
Under Fedora Linux, you can run:
yum -y install mingw32-gcc mingw32-SDL mingw32-zlib
to get a suitable cross compilation environment.
make install. Don't forget to copy SDL.dll and zlib1.dll into the
installation directory.
Wine can be used to launch the resulting qemu.exe compiled for Win32.
The Mac OS X patches are not fully merged in QEMU, so you should look at the QEMU mailing list archive to have all the necessary information.
makemake allinstallinstall-docmake cleanmake distcleanmake dvimake htmlmake infomake pdfmake cscopemake defconfigtartarbinQEMU is a trademark of Fabrice Bellard.
QEMU is released under the GNU General Public License (TODO: add link). Parts of QEMU have specific licenses, see file LICENSE.
TODO (refer to file LICENSE, include it, include the GPL?)
This is the main index. Should we combine all keywords in one index? TODO
This index could be used for command line options and monitor functions.
-acpitable: sec_invocation-alt-grab: sec_invocation-append: sec_invocation-audio-help: sec_invocation-balloon: sec_invocation-bios: sec_invocation-boot: sec_invocation-bt: sec_invocation-cdrom: sec_invocation-chardev: sec_invocation-chroot: sec_invocation-clock: sec_invocation-cpu: sec_invocation-ctrl-grab: sec_invocation-D: sec_invocation-d: sec_invocation-daemonize: sec_invocation-debugcon: sec_invocation-device: sec_invocation-display: sec_invocation-drive: sec_invocation-echr: sec_invocation-enable-kvm: sec_invocation-fda: sec_invocation-fdb: sec_invocation-fsdev: sec_invocation-full-screen: sec_invocation-g: sec_invocation-gdb: sec_invocation-global: sec_invocation-h: sec_invocation-hda: sec_invocation-hdachs: sec_invocation-hdb: sec_invocation-hdc: sec_invocation-hdd: sec_invocation-icount: sec_invocation-incoming: sec_invocation-initrd: sec_invocation-k: sec_invocation-kernel: sec_invocation-L: sec_invocation-loadvm: sec_invocation-m: sec_invocation-machine: sec_invocation-mon: sec_invocation-monitor: sec_invocation-mtdblock: sec_invocation-name: sec_invocation-net: sec_invocation-no-acpi: sec_invocation-no-fd-bootchk: sec_invocation-no-frame: sec_invocation-no-hpet: sec_invocation-no-quit: sec_invocation-no-reboot: sec_invocation-no-shutdown: sec_invocation-nodefaults: sec_invocation-nodefconfig: sec_invocation-nographic: sec_invocation-numa: sec_invocation-old-param (ARM): sec_invocation-option-rom: sec_invocation-parallel: sec_invocation-pflash: sec_invocation-pidfile: sec_invocation-portrait: sec_invocation-prom-env: sec_invocation-qmp: sec_invocation-readconfig: sec_invocation-rotate: sec_invocation-rtc: sec_invocation-runas: sec_invocation-s: sec_invocation-S: sec_invocation-sd: sec_invocation-sdl: sec_invocation-semihosting: sec_invocation-serial: sec_invocation-set: sec_invocation-show-cursor: sec_invocation-singlestep: sec_invocation-smbios: sec_invocation-smp: sec_invocation-snapshot: sec_invocation-soundhw: sec_invocation-spice: sec_invocation-tb-size: sec_invocation-trace: sec_invocation-usb: sec_invocation-usbdevice: sec_invocation-uuid: sec_invocation-version: sec_invocation-vga: sec_invocation-virtfs: sec_invocation-virtfs_synth: sec_invocation-virtioconsole: sec_invocation-vnc: sec_invocation-watchdog: sec_invocation-win2k-hack: sec_invocation-writeconfig: sec_invocation-xen-attach: sec_invocation-xen-create: sec_invocation-xen-domid: sec_invocationacl_add: pcsys_monitoracl_policy: pcsys_monitoracl_remove: pcsys_monitoracl_reset: pcsys_monitoracl_show: pcsys_monitorballoon: pcsys_monitorblock_passwd: pcsys_monitorblock_resize: pcsys_monitorboot_set: pcsys_monitorchange: pcsys_monitorclient_migrate_info: pcsys_monitorclosefd: pcsys_monitorcommit: pcsys_monitorcont: pcsys_monitorcpu: pcsys_monitorcurses: sec_invocationdelvm: pcsys_monitordevice_add: pcsys_monitordevice_del: pcsys_monitordrive_add: pcsys_monitordrive_del: pcsys_monitoreject: pcsys_monitorexpire_password: pcsys_monitorgdbserver: pcsys_monitorgetfd: pcsys_monitorhelp: pcsys_monitorhost_net_add: pcsys_monitorhost_net_remove: pcsys_monitorhostfwd_add: pcsys_monitorhostfwd_remove: pcsys_monitorinfo: pcsys_monitorloadvm: pcsys_monitorlog: pcsys_monitorlogfile: pcsys_monitormce (x86): pcsys_monitormemsave: pcsys_monitormigrate: pcsys_monitormigrate_cancel: pcsys_monitormigrate_set_downtime: pcsys_monitormigrate_set_speed: pcsys_monitormouse_button: pcsys_monitormouse_move: pcsys_monitormouse_set: pcsys_monitornetdev_add: pcsys_monitornetdev_del: pcsys_monitornmi: pcsys_monitorpci_add: pcsys_monitorpci_del: pcsys_monitorpcie_aer_inject_error: pcsys_monitorpmemsave: pcsys_monitorprint: pcsys_monitorquit: pcsys_monitorsavevm: pcsys_monitorscreendump: pcsys_monitorsendkey: pcsys_monitorset_link: pcsys_monitorset_password: pcsys_monitorsinglestep: pcsys_monitorsnapshot_blkdev: pcsys_monitorstop: pcsys_monitorstopcapture: pcsys_monitorsum: pcsys_monitorsystem_powerdown: pcsys_monitorsystem_reset: pcsys_monitortrace-event: pcsys_monitortrace-file: pcsys_monitorusb_add: pcsys_monitorusb_del: pcsys_monitorwatchdog_action: pcsys_monitorwavcapture: pcsys_monitorx: pcsys_monitorxp: pcsys_monitorThis is a list of all keystrokes which have a special function in system emulation.
Ctrl-a ?: pcsys_keysCtrl-a a: pcsys_keysCtrl-a b: pcsys_keysCtrl-a c: pcsys_keysCtrl-a h: pcsys_keysCtrl-a s: pcsys_keysCtrl-a t: pcsys_keysCtrl-a x: pcsys_keysCtrl-Alt: pcsys_keysCtrl-Alt-+: pcsys_keysCtrl-Alt--: pcsys_keysCtrl-Alt-f: pcsys_keysCtrl-Alt-n: pcsys_keysCtrl-Alt-u: pcsys_keysCtrl-Down: pcsys_keysCtrl-PageDown: pcsys_keysCtrl-PageUp: pcsys_keysCtrl-Up: pcsys_keysThis index could be used for qdev device names and options.