Archipelago » qemu

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@settitle QEMU Emulator User Documentation

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@sp 7

@center @titlefont{QEMU Emulator}

@sp 1

@center @titlefont{User Documentation}

@sp 3

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@ifnottex

@node Top

@top

@menu

* Introduction::

* Installation::

* QEMU PC System emulator::

* QEMU System emulator for non PC targets::

* QEMU Linux User space emulator::

* compilation:: Compilation from the sources

* Index::

@end menu

@end ifnottex

@contents

@node Introduction

@chapter Introduction

@menu

* intro_features:: Features

@end menu

@node intro_features

@section Features

QEMU is a FAST! processor emulator using dynamic translation to

achieve good emulation speed.

QEMU has two operating modes:

@itemize @minus

@item 

Full system emulation. In this mode, QEMU emulates a full system (for

example a PC), including one or several processors and various

peripherals. It can be used to launch different Operating Systems

without rebooting the PC or to debug system code.

@item 

User mode emulation (Linux host only). In this mode, QEMU can launch

Linux processes compiled for one CPU on another CPU. It can be used to

launch the Wine Windows API emulator (@url{http://www.winehq.org}) or

to ease cross-compilation and cross-debugging.

@end itemize

QEMU can run without an host kernel driver and yet gives acceptable

performance. 

For system emulation, the following hardware targets are supported:

@itemize

@item PC (x86 or x86_64 processor)

@item ISA PC (old style PC without PCI bus)

@item PREP (PowerPC processor)

@item G3 BW PowerMac (PowerPC processor)

@item Mac99 PowerMac (PowerPC processor, in progress)

@item Sun4m (32-bit Sparc processor)

@item Sun4u (64-bit Sparc processor, in progress)

@item Malta board (32-bit MIPS processor)

@item ARM Integrator/CP (ARM926E or 1026E processor)

@item ARM Versatile baseboard (ARM926E)

@end itemize

For user emulation, x86, PowerPC, ARM, MIPS, Sparc32/64 and ColdFire(m68k) CPUs are supported.

@node Installation

@chapter Installation

If you want to compile QEMU yourself, see @ref{compilation}.

@menu

* install_linux::   Linux

* install_windows:: Windows

* install_mac::     Macintosh

@end menu

@node install_linux

@section Linux

If a precompiled package is available for your distribution - you just

have to install it. Otherwise, see @ref{compilation}.

@node install_windows

@section Windows

Download the experimental binary installer at

@url{http://www.free.oszoo.org/@/download.html}.

@node install_mac

@section Mac OS X

Download the experimental binary installer at

@url{http://www.free.oszoo.org/@/download.html}.

@node QEMU PC System emulator

@chapter QEMU PC System emulator

@menu

* pcsys_introduction:: Introduction

* pcsys_quickstart::   Quick Start

* sec_invocation::     Invocation

* pcsys_keys::         Keys

* pcsys_monitor::      QEMU Monitor

* disk_images::        Disk Images

* pcsys_network::      Network emulation

* direct_linux_boot::  Direct Linux Boot

* pcsys_usb::          USB emulation

* gdb_usage::          GDB usage

* pcsys_os_specific::  Target OS specific information

@end menu

@node pcsys_introduction

@section Introduction

@c man begin DESCRIPTION

The QEMU PC System emulator simulates the

following peripherals:

@itemize @minus

@item 

i440FX host PCI bridge and PIIX3 PCI to ISA bridge

@item

Cirrus CLGD 5446 PCI VGA card or dummy VGA card with Bochs VESA

extensions (hardware level, including all non standard modes).

@item

PS/2 mouse and keyboard

@item 

2 PCI IDE interfaces with hard disk and CD-ROM support

@item

Floppy disk

@item 

NE2000 PCI network adapters

@item

Serial ports

@item

Creative SoundBlaster 16 sound card

@item

ENSONIQ AudioPCI ES1370 sound card

@item

Adlib(OPL2) - Yamaha YM3812 compatible chip

@item

PCI UHCI USB controller and a virtual USB hub.

@end itemize

SMP is supported with up to 255 CPUs.

Note that adlib is only available when QEMU was configured with

-enable-adlib

QEMU uses the PC BIOS from the Bochs project and the Plex86/Bochs LGPL

VGA BIOS.

QEMU uses YM3812 emulation by Tatsuyuki Satoh.

@c man end

@node pcsys_quickstart

@section Quick Start

Download and uncompress the linux image (@file{linux.img}) and type:

@example

qemu linux.img

@end example

Linux should boot and give you a prompt.

@node sec_invocation

@section Invocation

@example

@c man begin SYNOPSIS

usage: qemu [options] [disk_image]

@c man end

@end example

@c man begin OPTIONS

@var{disk_image} is a raw hard disk image for IDE hard disk 0.

General options:

@table @option

@item -M machine

Select the emulated machine (@code{-M ?} for list)

@item -fda file

@item -fdb file

Use @var{file} as floppy disk 0/1 image (@pxref{disk_images}). You can

use the host floppy by using @file{/dev/fd0} as filename (@pxref{host_drives}).

@item -hda file

@item -hdb file

@item -hdc file

@item -hdd file

Use @var{file} as hard disk 0, 1, 2 or 3 image (@pxref{disk_images}).

@item -cdrom file

Use @var{file} as CD-ROM image (you cannot use @option{-hdc} and and

@option{-cdrom} at the same time). You can use the host CD-ROM by

using @file{/dev/cdrom} as filename (@pxref{host_drives}).

@item -boot [a|c|d|n]

Boot on floppy (a), hard disk (c), CD-ROM (d), or Etherboot (n). Hard disk boot

is the default.

@item -snapshot

Write to temporary files instead of disk image files. In this case,

the raw disk image you use is not written back. You can however force

the write back by pressing @key{C-a s} (@pxref{disk_images}).

@item -no-fd-bootchk

Disable boot signature checking for floppy disks in Bochs BIOS. It may

be needed to boot from old floppy disks.

@item -m megs

Set virtual RAM size to @var{megs} megabytes. Default is 128 MB.

@item -smp n

Simulate an SMP system with @var{n} CPUs. On the PC target, up to 255

CPUs are supported.

@item -nographic

Normally, QEMU uses SDL to display the VGA output. With this option,

you can totally disable graphical output so that QEMU is a simple

command line application. The emulated serial port is redirected on

the console. Therefore, you can still use QEMU to debug a Linux kernel

with a serial console.

@item -vnc display

Normally, QEMU uses SDL to display the VGA output.  With this option,

you can have QEMU listen on VNC display @var{display} and redirect the VGA

display over the VNC session.  It is very useful to enable the usb

tablet device when using this option (option @option{-usbdevice

tablet}). When using the VNC display, you must use the @option{-k}

option to set the keyboard layout if you are not using en-us.

@var{display} may be in the form @var{interface:d}, in which case connections

will only be allowed from @var{interface} on display @var{d}. Optionally,

@var{interface} can be omitted.  @var{display} can also be in the form

@var{unix:path} where @var{path} is the location of a unix socket to listen for

connections on.

@item -k language

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

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}.

@item -audio-help

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

parameters.

@item -soundhw card1,card2,... or -soundhw all

Enable audio and selected sound hardware. Use ? to print all

available sound hardware.

@example

qemu -soundhw sb16,adlib hda

qemu -soundhw es1370 hda

qemu -soundhw all hda

qemu -soundhw ?

@end example

@item -localtime

Set the real time clock to local time (the default is to UTC

time). This option is needed to have correct date in MS-DOS or

Windows.

@item -full-screen

Start in full screen.

@item -pidfile file

Store the QEMU process PID in @var{file}. It is useful if you launch QEMU

from a script.

@item -daemonize

Daemonize the QEMU process after initialization.  QEMU will not detach from

standard IO until it is ready to receive connections on any of its devices.

This option is a useful way for external programs to launch QEMU without having

to cope with initialization race conditions.

@item -win2k-hack

Use it when installing Windows 2000 to avoid a disk full bug. After

Windows 2000 is installed, you no longer need this option (this option

slows down the IDE transfers).

@item -option-rom file

Load the contents of file as an option ROM.  This option is useful to load

things like EtherBoot.

@end table

USB options:

@table @option

@item -usb

Enable the USB driver (will be the default soon)

@item -usbdevice devname

Add the USB device @var{devname}. @xref{usb_devices}.

@end table

Network options:

@table @option

@item -net nic[,vlan=n][,macaddr=addr][,model=type]

Create a new Network Interface Card and connect it to VLAN @var{n} (@var{n}

= 0 is the default). The NIC is currently an NE2000 on the PC

target. Optionally, the MAC address can be changed. If no

@option{-net} option is specified, a single NIC is created.

Qemu can emulate several different models of network card.  Valid values for

@var{type} are @code{ne2k_pci}, @code{ne2k_isa}, @code{rtl8139},

@code{smc91c111} and @code{lance}.  Not all devices are supported on all

targets.

@item -net user[,vlan=n][,hostname=name]

Use the user mode network stack which requires no administrator

priviledge to run.  @option{hostname=name} can be used to specify the client

hostname reported by the builtin DHCP server.

@item -net tap[,vlan=n][,fd=h][,ifname=name][,script=file]

Connect the host TAP network interface @var{name} to VLAN @var{n} and

use the network script @var{file} to configure it. The default

network script is @file{/etc/qemu-ifup}. If @var{name} is not

provided, the OS automatically provides one.  @option{fd=h} can be

used to specify the handle of an already opened host TAP interface. Example:

@example

qemu linux.img -net nic -net tap

@end example

More complicated example (two NICs, each one connected to a TAP device)

@example

qemu linux.img -net nic,vlan=0 -net tap,vlan=0,ifname=tap0 \

               -net nic,vlan=1 -net tap,vlan=1,ifname=tap1

@end example

@item -net socket[,vlan=n][,fd=h][,listen=[host]:port][,connect=host:port]

Connect the VLAN @var{n} to a remote VLAN in another QEMU virtual

machine using a TCP socket connection. If @option{listen} is

specified, QEMU waits for incoming connections on @var{port}

(@var{host} is optional). @option{connect} is used to connect to

another QEMU instance using the @option{listen} option. @option{fd=h}

specifies an already opened TCP socket.

Example:

@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

@end example

@item -net socket[,vlan=n][,fd=h][,mcast=maddr:port]

Create a VLAN @var{n} shared with another QEMU virtual

machines using a UDP multicast socket, effectively making a bus for 

every QEMU with same multicast address @var{maddr} and @var{port}.

NOTES:

@enumerate

@item 

Several QEMU can be running on different hosts and share same bus (assuming 

correct multicast setup for these hosts).

@item

mcast support is compatible with User Mode Linux (argument @option{eth@var{N}=mcast}), see

@url{http://user-mode-linux.sf.net}.

@item Use @option{fd=h} to specify an already opened UDP multicast socket.

@end enumerate

Example:

@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

@end example

Example (User Mode Linux compat.):

@example

# 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

@end example

@item -net none

Indicate that no network devices should be configured. It is used to

override the default configuration (@option{-net nic -net user}) which

is activated if no @option{-net} options are provided.

@item -tftp prefix

When using the user mode network stack, activate a built-in TFTP

server. All filenames beginning with @var{prefix} can be downloaded

from the host to the guest using a TFTP client. The TFTP client on the

guest must be configured in binary mode (use the command @code{bin} of

the Unix TFTP client). The host IP address on the guest is as usual

10.0.2.2.

@item -smb dir

When using the user mode network stack, activate a built-in SMB

server so that Windows OSes can access to the host files in @file{dir}

transparently.

In the guest Windows OS, the line:

@example

10.0.2.4 smbserver

@end example

must be added in the file @file{C:\WINDOWS\LMHOSTS} (for windows 9x/Me)

or @file{C:\WINNT\SYSTEM32\DRIVERS\ETC\LMHOSTS} (Windows NT/2000).

Then @file{dir} can be accessed in @file{\\smbserver\qemu}.

Note that a SAMBA server must be installed on the host OS in

@file{/usr/sbin/smbd}. QEMU was tested successfully with smbd version

2.2.7a from the Red Hat 9 and version 3.0.10-1.fc3 from Fedora Core 3.

@item -redir [tcp|udp]:host-port:[guest-host]:guest-port

When using the user mode network stack, redirect incoming TCP or UDP

connections to the host port @var{host-port} to the guest

@var{guest-host} on guest port @var{guest-port}. If @var{guest-host}

is not specified, its value is 10.0.2.15 (default address given by the

built-in DHCP server).

For example, to redirect host X11 connection from screen 1 to guest

screen 0, use the following:

@example

# on the host

qemu -redir tcp:6001::6000 [...]

# this host xterm should open in the guest X11 server

xterm -display :1

@end example

To redirect telnet connections from host port 5555 to telnet port on

the guest, use the following:

@example

# on the host

qemu -redir tcp:5555::23 [...]

telnet localhost 5555

@end example

Then when you use on the host @code{telnet localhost 5555}, you

connect to the guest telnet server.

@end table

Linux boot specific: When using these options, you can use a given

Linux kernel without installing it in the disk image. It can be useful

for easier testing of various kernels.

@table @option

@item -kernel bzImage 

Use @var{bzImage} as kernel image.

@item -append cmdline 

Use @var{cmdline} as kernel command line

@item -initrd file

Use @var{file} as initial ram disk.

@end table

Debug/Expert options:

@table @option

@item -serial dev

Redirect the virtual serial port to host character device

@var{dev}. The default device is @code{vc} in graphical mode and

@code{stdio} in non graphical mode.

This option can be used several times to simulate up to 4 serials

ports.

Use @code{-serial none} to disable all serial ports.

Available character devices are:

@table @code

@item vc

Virtual console

@item pty

[Linux only] Pseudo TTY (a new PTY is automatically allocated)

@item none

No device is allocated.

@item null

void device

@item /dev/XXX

[Linux only] Use host tty, e.g. @file{/dev/ttyS0}. The host serial port

parameters are set according to the emulated ones.

@item /dev/parportN

[Linux only, parallel port only] Use host parallel port

@var{N}. Currently only SPP parallel port features can be used.

@item file:filename

Write output to filename. No character can be read.

@item stdio

[Unix only] standard input/output

@item pipe:filename

name pipe @var{filename}

@item COMn

[Windows only] Use host serial port @var{n}

@item udp:[remote_host]:remote_port[@@[src_ip]:src_port]

This implements UDP Net Console.  When @var{remote_host} or @var{src_ip} are not specified they default to @code{0.0.0.0}.  When not using a specifed @var{src_port} a random port is automatically chosen.

If you just want a simple readonly console you can use @code{netcat} or

@code{nc}, by starting qemu with: @code{-serial udp::4555} and nc as:

@code{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 @code{-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.

@table @code

@item Qemu Options:

-serial udp::4555@@:4556

@item netcat options:

-u -P 4555 -L 0.0.0.0:4556 -t -p 5555 -I -T

@item telnet options:

localhost 5555

@end table

@item tcp:[host]:port[,server][,nowait]

The TCP Net Console has two modes of operation.  It can send the serial

I/O to a location or wait for a connection from a location.  By default

the TCP Net Console is sent to @var{host} at the @var{port}.  If you use

the @var{server} option QEMU will wait for a client socket application

to connect to the port before continuing, unless the @code{nowait}

option was specified. If @var{host} is omitted, 0.0.0.0 is assumed. Only

one TCP connection at a time is accepted. You can use @code{telnet} to

connect to the corresponding character device.

@table @code

@item Example to send tcp console to 192.168.0.2 port 4444

-serial tcp:192.168.0.2:4444

@item Example to listen and wait on port 4444 for connection

-serial tcp::4444,server

@item Example to not wait and listen on ip 192.168.0.100 port 4444

-serial tcp:192.168.0.100:4444,server,nowait

@end table

@item telnet:host:port[,server][,nowait]

The telnet protocol is used instead of raw tcp sockets.  The options

work the same as if you had specified @code{-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.

@item unix:path[,server][,nowait]

A unix domain socket is used instead of a tcp socket.  The option works the

same as if you had specified @code{-serial tcp} except the unix domain socket

@var{path} is used for connections.

@end table

@item -parallel dev

Redirect the virtual parallel port to host device @var{dev} (same

devices as the serial port). On Linux hosts, @file{/dev/parportN} can

be used to use hardware devices connected on the corresponding host

parallel port.

This option can be used several times to simulate up to 3 parallel

ports.

Use @code{-parallel none} to disable all parallel ports.

@item -monitor dev

Redirect the monitor to host device @var{dev} (same devices as the

serial port).

The default device is @code{vc} in graphical mode and @code{stdio} in

non graphical mode.

@item -s

Wait gdb connection to port 1234 (@pxref{gdb_usage}). 

@item -p port

Change gdb connection port.

@item -S

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

@item -d             

Output log in /tmp/qemu.log

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

Force hard disk 0 physical geometry (1 <= @var{c} <= 16383, 1 <=

@var{h} <= 16, 1 <= @var{s} <= 63) and optionally force the BIOS

translation mode (@var{t}=none, lba or auto). Usually QEMU can guess

all thoses parameters. This option is useful for old MS-DOS disk

images.

@item -L path

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

@item -std-vga

Simulate a standard VGA card with Bochs VBE extensions (default is

Cirrus Logic GD5446 PCI VGA). If your guest OS supports the VESA 2.0

VBE extensions (e.g. Windows XP) and if you want to use high

resolution modes (>= 1280x1024x16) then you should use this option.

@item -no-acpi

Disable ACPI (Advanced Configuration and Power Interface) support. Use

it if your guest OS complains about ACPI problems (PC target machine

only).

@item -no-reboot

Exit instead of rebooting.

@item -loadvm file

Start right away with a saved state (@code{loadvm} in monitor)

@item -semihosting

Enable "Angel" semihosting interface (ARM target machines only).

Note that this allows guest direct access to the host filesystem,

so should only be used with trusted guest OS.

@end table

@c man end

@node pcsys_keys

@section Keys

@c man begin OPTIONS

During the graphical emulation, you can use the following keys:

@table @key

@item Ctrl-Alt-f

Toggle full screen

@item Ctrl-Alt-n

Switch to virtual console 'n'. Standard console mappings are:

@table @emph

@item 1

Target system display

@item 2

Monitor

@item 3

Serial port

@end table

@item Ctrl-Alt

Toggle mouse and keyboard grab.

@end table

In the virtual consoles, you can use @key{Ctrl-Up}, @key{Ctrl-Down},

@key{Ctrl-PageUp} and @key{Ctrl-PageDown} to move in the back log.

During emulation, if you are using the @option{-nographic} option, use

@key{Ctrl-a h} to get terminal commands:

@table @key

@item Ctrl-a h

Print this help

@item Ctrl-a x    

Exit emulator

@item Ctrl-a s    

Save disk data back to file (if -snapshot)

@item Ctrl-a b

Send break (magic sysrq in Linux)

@item Ctrl-a c

Switch between console and monitor

@item Ctrl-a Ctrl-a

Send Ctrl-a

@end table

@c man end

@ignore

@c man begin SEEALSO

The HTML documentation of QEMU for more precise information and Linux

user mode emulator invocation.

@c man end

@c man begin AUTHOR

Fabrice Bellard

@c man end

@end ignore

@node pcsys_monitor

@section QEMU Monitor

The QEMU monitor is used to give complex commands to the QEMU

emulator. You can use it to:

@itemize @minus

@item

Remove or insert removable medias images

(such as CD-ROM or floppies)

@item 

Freeze/unfreeze the Virtual Machine (VM) and save or restore its state

from a disk file.

@item Inspect the VM state without an external debugger.

@end itemize

@subsection Commands

The following commands are available:

@table @option

@item help or ? [cmd]

Show the help for all commands or just for command @var{cmd}.

@item commit  

Commit changes to the disk images (if -snapshot is used)

@item info subcommand 

show various information about the system state

@table @option

@item info network

show the various VLANs and the associated devices

@item info block

show the block devices

@item info registers

show the cpu registers

@item info history

show the command line history

@item info pci

show emulated PCI device

@item info usb

show USB devices plugged on the virtual USB hub

@item info usbhost

show all USB host devices

@item info capture

show information about active capturing

@item info snapshots

show list of VM snapshots

@item info mice

show which guest mouse is receiving events

@end table

@item q or quit

Quit the emulator.

@item eject [-f] device

Eject a removable media (use -f to force it).

@item change device filename

Change a removable media.

@item screendump filename

Save screen into PPM image @var{filename}.

@item mouse_move dx dy [dz]

Move the active mouse to the specified coordinates @var{dx} @var{dy}

with optional scroll axis @var{dz}.

@item mouse_button val

Change the active mouse button state @var{val} (1=L, 2=M, 4=R).

@item mouse_set index

Set which mouse device receives events at given @var{index}, index

can be obtained with

@example

info mice

@end example

@item wavcapture filename [frequency [bits [channels]]]

Capture audio into @var{filename}. Using sample rate @var{frequency}

bits per sample @var{bits} and number of channels @var{channels}.

Defaults:

@itemize @minus

@item Sample rate = 44100 Hz - CD quality

@item Bits = 16

@item Number of channels = 2 - Stereo

@end itemize

@item stopcapture index

Stop capture with a given @var{index}, index can be obtained with

@example

info capture

@end example

@item log item1[,...]

Activate logging of the specified items to @file{/tmp/qemu.log}.

@item savevm [tag|id]

Create a snapshot of the whole virtual machine. If @var{tag} is

provided, it is used as human readable identifier. If there is already

a snapshot with the same tag or ID, it is replaced. More info at

@ref{vm_snapshots}.

@item loadvm tag|id

Set the whole virtual machine to the snapshot identified by the tag

@var{tag} or the unique snapshot ID @var{id}.

@item delvm tag|id

Delete the snapshot identified by @var{tag} or @var{id}.

@item stop

Stop emulation.

@item c or cont

Resume emulation.

@item gdbserver [port]

Start gdbserver session (default port=1234)

@item x/fmt addr

Virtual memory dump starting at @var{addr}.

@item xp /fmt addr

Physical memory dump starting at @var{addr}.

@var{fmt} is a format which tells the command how to format the

data. Its syntax is: @option{/@{count@}@{format@}@{size@}}

@table @var

@item count 

is the number of items to be dumped.

@item format

can be x (hexa), d (signed decimal), u (unsigned decimal), o (octal),

c (char) or i (asm instruction).

@item size

can be b (8 bits), h (16 bits), w (32 bits) or g (64 bits). On x86,

@code{h} or @code{w} can be specified with the @code{i} format to

respectively select 16 or 32 bit code instruction size.

@end table

Examples: 

@itemize

@item

Dump 10 instructions at the current instruction pointer:

@example 

(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

@end example

@item

Dump 80 16 bit values at the start of the video memory.

@smallexample 

(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

@end smallexample

@end itemize

@item p or print/fmt expr

Print expression value. Only the @var{format} part of @var{fmt} is

used.

@item sendkey keys

Send @var{keys} to the emulator. Use @code{-} to press several keys

simultaneously. Example:

@example

sendkey ctrl-alt-f1

@end example

This command is useful to send keys that your graphical user interface

intercepts at low level, such as @code{ctrl-alt-f1} in X Window.

@item system_reset

Reset the system.

@item usb_add devname

Add the USB device @var{devname}.  For details of available devices see

@ref{usb_devices}

@item usb_del devname

Remove the USB device @var{devname} from the QEMU virtual USB

hub. @var{devname} has the syntax @code{bus.addr}. Use the monitor

command @code{info usb} to see the devices you can remove.

@end table

@subsection Integer expressions

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 @emph{$}.

@node disk_images

@section Disk Images

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.

@menu

* disk_images_quickstart::    Quick start for disk image creation

* disk_images_snapshot_mode:: Snapshot mode

* vm_snapshots::              VM snapshots

* qemu_img_invocation::       qemu-img Invocation

* host_drives::               Using host drives

* disk_images_fat_images::    Virtual FAT disk images

@end menu

@node disk_images_quickstart

@subsection Quick start for disk image creation

You can create a disk image with the command:

@example

qemu-img create myimage.img mysize

@end example

where @var{myimage.img} is the disk image filename and @var{mysize} is its

size in kilobytes. You can add an @code{M} suffix to give the size in

megabytes and a @code{G} suffix for gigabytes.

See @ref{qemu_img_invocation} for more information.

@node disk_images_snapshot_mode

@subsection Snapshot mode

If you use the option @option{-snapshot}, all disk images are