Archipelago » qemu

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@settitle QEMU Emulator User Documentation

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@iftex

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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 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. In this mode, QEMU can launch

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/Sun4c/Sun4d (32-bit Sparc processor)

@item Sun4u/Sun4v (64-bit Sparc processor, in progress)

@item Malta board (32-bit and 64-bit MIPS processors)

@item MIPS Magnum (64-bit MIPS processor)

@item ARM Integrator/CP (ARM)

@item ARM Versatile baseboard (ARM)

@item ARM RealView Emulation baseboard (ARM)

@item Spitz, Akita, Borzoi, Terrier and Tosa PDAs (PXA270 processor)

@item Luminary Micro LM3S811EVB (ARM Cortex-M3)

@item Luminary Micro LM3S6965EVB (ARM Cortex-M3)

@item Freescale MCF5208EVB (ColdFire V2).

@item Arnewsh MCF5206 evaluation board (ColdFire V2).

@item Palm Tungsten|E PDA (OMAP310 processor)

@item N800 and N810 tablets (OMAP2420 processor)

@item MusicPal (MV88W8618 ARM processor)

@item Gumstix "Connex" and "Verdex" motherboards (PXA255/270).

@item Siemens SX1 smartphone (OMAP310 processor)

@end itemize

For user emulation, x86, PowerPC, ARM, 32-bit 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

* vnc_security::       VNC security

* 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

PCI/ISA PCI network adapters

@item

Serial ports

@item

Creative SoundBlaster 16 sound card

@item

ENSONIQ AudioPCI ES1370 sound card

@item

Intel 82801AA AC97 Audio compatible sound card

@item

Adlib(OPL2) - Yamaha YM3812 compatible chip

@item

Gravis Ultrasound GF1 sound card

@item

CS4231A compatible sound card

@item

PCI UHCI USB controller and a virtual USB hub.

@end itemize

SMP is supported with up to 255 CPUs.

Note that adlib, ac97, 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 @url{http://www.deinmeister.de/gusemu/})

by Tibor "TS" Sch?tz.

CS4231A is the chip used in Windows Sound System and GUSMAX products

@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] [@var{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 @var{machine}

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

@item -fda @var{file}

@item -fdb @var{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 @var{file}

@item -hdb @var{file}

@item -hdc @var{file}

@item -hdd @var{file}

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

@item -cdrom @var{file}

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

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

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

@item -drive @var{option}[,@var{option}[,@var{option}[,...]]]

Define a new drive. Valid options are:

@table @code

@item file=@var{file}

This option defines which disk image (@pxref{disk_images}) to use with

this drive. If the filename contains comma, you must double it

(for instance, "file=my,,file" to use file "my,file").

@item if=@var{interface}

This option defines on which type on interface the drive is connected.

Available types are: ide, scsi, sd, mtd, floppy, pflash, virtio.

@item bus=@var{bus},unit=@var{unit}

These options define where is connected the drive by defining the bus number and

the unit id.

@item index=@var{index}

This option defines where is connected the drive by using an index in the list

of available connectors of a given interface type.

@item media=@var{media}

This option defines the type of the media: disk or cdrom.

@item cyls=@var{c},heads=@var{h},secs=@var{s}[,trans=@var{t}]

These options have the same definition as they have in @option{-hdachs}.

@item snapshot=@var{snapshot}

@var{snapshot} is "on" or "off" and allows to enable snapshot for given drive (see @option{-snapshot}).

@item cache=@var{cache}

@var{cache} is "none", "writeback", or "writethrough" and controls how the host cache is used to access block data.

@item format=@var{format}

Specify which disk @var{format} will be used rather than detecting

the format.  Can be used to specifiy format=raw to avoid interpreting

an untrusted format header.

@end table

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.  When using the @option{-snapshot} option, writeback caching is

used by default.

The host page can be avoided entirely with @option{cache=none}.  This will

attempt to do disk IO directly to the guests memory.  QEMU may still perform

an internal copy of the data.

Some block drivers perform badly with @option{cache=writethrough}, most notably,

qcow2.  If performance is more important than correctness,

@option{cache=writeback} should be used with qcow2.  By default, if no explicit

caching is specified for a qcow2 disk image, @option{cache=writeback} will be

used.  For all other disk types, @option{cache=writethrough} is the default.

Instead of @option{-cdrom} you can use:

@example

qemu -drive file=file,index=2,media=cdrom

@end example

Instead of @option{-hda}, @option{-hdb}, @option{-hdc}, @option{-hdd}, you can

use:

@example

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

@end example

You can connect a CDROM to the slave of ide0:

@example

qemu -drive file=file,if=ide,index=1,media=cdrom

@end example

If you don't specify the "file=" argument, you define an empty drive:

@example

qemu -drive if=ide,index=1,media=cdrom

@end example

You can connect a SCSI disk with unit ID 6 on the bus #0:

@example

qemu -drive file=file,if=scsi,bus=0,unit=6

@end example

Instead of @option{-fda}, @option{-fdb}, you can use:

@example

qemu -drive file=file,index=0,if=floppy

qemu -drive file=file,index=1,if=floppy

@end example

By default, @var{interface} is "ide" and @var{index} is automatically

incremented:

@example

qemu -drive file=a -drive file=b"

@end example

is interpreted like:

@example

qemu -hda a -hdb b

@end example

@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 @var{megs}

Set virtual RAM size to @var{megs} megabytes. Default is 128 MiB.  Optionally,

a suffix of ``M'' or ``G'' can be used to signify a value in megabytes or

gigabytes respectively.

@item -cpu @var{model}

Select CPU model (-cpu ? for list and additional feature selection)

@item -smp @var{n}

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

CPUs are supported. On Sparc32 target, Linux limits the number of usable CPUs

to 4.

@item -audio-help

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

parameters.

@item -soundhw @var{card1}[,@var{card2},...] or -soundhw all

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

available sound hardware.

@example

qemu -soundhw sb16,adlib disk.img

qemu -soundhw es1370 disk.img

qemu -soundhw ac97 disk.img

qemu -soundhw all disk.img

qemu -soundhw ?

@end example

Note that Linux's i810_audio OSS kernel (for AC97) module might

require manually specifying clocking.

@example

modprobe i810_audio clocking=48000

@end example

@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 -startdate @var{date}

Set the initial date of the real time clock. Valid formats for

@var{date} are: @code{now} or @code{2006-06-17T16:01:21} or

@code{2006-06-17}. The default value is @code{now}.

@item -pidfile @var{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 @var{file}

Load the contents of @var{file} as an option ROM.

This option is useful to load things like EtherBoot.

@item -name @var{name}

Sets the @var{name} of the guest.

This name will be displayed in the SDL window caption.

The @var{name} will also be used for the VNC server.

@end table

Display options:

@table @option

@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 -curses

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

QEMU can display the VGA output when in text mode using a 

curses/ncurses interface.  Nothing is displayed in graphical mode.

@item -no-frame

Do not use decorations for SDL windows and start them using the whole

available screen space. This makes the using QEMU in a dedicated desktop

workspace more convenient.

@item -no-quit

Disable SDL window close capability.

@item -full-screen

Start in full screen.

@item -vnc @var{display}[,@var{option}[,@var{option}[,...]]]

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}

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

syntax for the @var{display} is

@table @code

@item @var{host}:@var{d}

TCP connections will only be allowed from @var{host} on display @var{d}.

By convention the TCP port is 5900+@var{d}. Optionally, @var{host} can

be omitted in which case the server will accept connections from any host.

@item @code{unix}:@var{path}

Connections will be allowed over UNIX domain sockets where @var{path} is the

location of a unix socket to listen for connections on.

@item none

VNC is initialized but not started. The monitor @code{change} command

can be used to later start the VNC server.

@end table

Following the @var{display} value there may be one or more @var{option} flags

separated by commas. Valid options are

@table @code

@item reverse

Connect to a listening VNC client via a ``reverse'' connection. The

client is specified by the @var{display}. For reverse network

connections (@var{host}:@var{d},@code{reverse}), the @var{d} argument

is a TCP port number, not a display number.

@item password

Require that password based authentication is used for client connections.

The password must be set separately using the @code{change} command in the

@ref{pcsys_monitor}

@item tls

Require that client use TLS when communicating with the VNC server. This

uses anonymous TLS credentials so is susceptible to a man-in-the-middle

attack. It is recommended that this option be combined with either the

@var{x509} or @var{x509verify} options.

@item x509=@var{/path/to/certificate/dir}

Valid if @option{tls} is specified. Require that x509 credentials are used

for negotiating the TLS session. The server will send its x509 certificate

to the client. It is recommended that a password be set on the VNC server

to provide authentication of the client when this is used. The path following

this option specifies where the x509 certificates are to be loaded from.

See the @ref{vnc_security} section for details on generating certificates.

@item x509verify=@var{/path/to/certificate/dir}

Valid if @option{tls} is specified. Require that x509 credentials are used

for negotiating the TLS session. The server will send its x509 certificate

to the client, and request that the client send its own x509 certificate.

The server will validate the client's certificate against the CA certificate,

and reject clients when validation fails. If the certificate authority is

trusted, this is a sufficient authentication mechanism. You may still wish

to set a password on the VNC server as a second authentication layer. The

path following this option specifies where the x509 certificates are to

be loaded from. See the @ref{vnc_security} section for details on generating

certificates.

@end table

@item -k @var{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}.

@end table

USB options:

@table @option

@item -usb

Enable the USB driver (will be the default soon)

@item -usbdevice @var{devname}

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

@table @code

@item mouse

Virtual Mouse. This will override the PS/2 mouse emulation when activated.

@item tablet

Pointer device that uses absolute coordinates (like a touchscreen). This

means qemu is able to report the mouse position without having to grab the

mouse. Also overrides the PS/2 mouse emulation when activated.

@item disk:[format=@var{format}]:file

Mass storage device based on file. The optional @var{format} argument

will be used rather than detecting the format. Can be used to specifiy

format=raw to avoid interpreting an untrusted format header.

@item host:bus.addr

Pass through the host device identified by bus.addr (Linux only).

@item host:vendor_id:product_id

Pass through the host device identified by vendor_id:product_id (Linux only).

@item serial:[vendorid=@var{vendor_id}][,productid=@var{product_id}]:@var{dev}

Serial converter to host character device @var{dev}, see @code{-serial} for the

available devices.

@item braille

Braille device.  This will use BrlAPI to display the braille output on a real

or fake device.

@item net:options

Network adapter that supports CDC ethernet and RNDIS protocols.

@end table

@end table

Network options:

@table @option

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

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

= 0 is the default). The NIC is an ne2k_pci by default 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{i82551}, @code{i82557b}, @code{i82559er},

@code{ne2k_pci}, @code{ne2k_isa}, @code{pcnet}, @code{rtl8139},

@code{e1000}, @code{smc91c111}, @code{lance} and @code{mcf_fec}.

Not all devices are supported on all targets.  Use -net nic,model=?

for a list of available devices for your target.

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

Use the user mode network stack which requires no administrator

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

hostname reported by the builtin DHCP server.

@item -net tap[,vlan=@var{n}][,fd=@var{h}][,ifname=@var{name}][,script=@var{file}][,downscript=@var{dfile}]

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

the network script @var{file} to configure it and the network script 

@var{dfile} to deconfigure it. If @var{name} is not provided, the OS 

automatically provides one. @option{fd}=@var{h} can be used to specify

the handle of an already opened host TAP interface. The default network 

configure script is @file{/etc/qemu-ifup} and the default network 

deconfigure script is @file{/etc/qemu-ifdown}. Use @option{script=no} 

or @option{downscript=no} to disable script execution. 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=@var{n}][,fd=@var{h}][,listen=[@var{host}]:@var{port}][,connect=@var{host}:@var{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}=@var{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=@var{n}][,fd=@var{h}][,mcast=@var{maddr}:@var{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 vde[,vlan=@var{n}][,sock=@var{socketpath}][,port=@var{n}][,group=@var{groupname}][,mode=@var{octalmode}]

Connect VLAN @var{n} to PORT @var{n} of a vde switch running on host and

listening for incoming connections on @var{socketpath}. Use GROUP @var{groupname}

and MODE @var{octalmode} to change default ownership and permissions for

communication port. This option is available only if QEMU has been compiled

with vde support enabled.

Example:

@example

# launch vde switch

vde_switch -F -sock /tmp/myswitch

# launch QEMU instance

qemu linux.img -net nic -net vde,sock=/tmp/myswitch

@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 @var{dir}

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

server. The files in @var{dir} will be exposed as the root of a TFTP server.

The TFTP client on the guest must be configured in binary mode (use the command

@code{bin} of the Unix TFTP client). The host IP address on the guest is as

usual 10.0.2.2.

@item -bootp @var{file}

When using the user mode network stack, broadcast @var{file} as the BOOTP

filename.  In conjunction with @option{-tftp}, this can be used to network boot

a guest from a local directory.

Example (using pxelinux):

@example

qemu -hda linux.img -boot n -tftp /path/to/tftp/files -bootp /pxelinux.0

@end example

@item -smb @var{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{@var{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{@var{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]:@var{host-port}:[@var{guest-host}]:@var{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

Bluetooth(R) options:

@table @option

@item -bt hci[...]

Defines the function of the corresponding Bluetooth HCI.  -bt options

are matched with the HCIs present in the chosen machine type.  For

example when emulating a machine with only one HCI built into it, only

the first @code{-bt hci[...]} option is valid and defines the HCI's

logic.  The Transport Layer is decided by the machine type.  Currently

the machines @code{n800} and @code{n810} have one HCI and all other

machines have none.

@anchor{bt-hcis}

The following three types are recognized:

@table @code

@item -bt hci,null

(default) The corresponding Bluetooth HCI assumes no internal logic

and will not respond to any HCI commands or emit events.

@item -bt hci,host[:@var{id}]

(@code{bluez} only) The corresponding HCI passes commands / events

to / from the physical HCI identified by the name @var{id} (default:

@code{hci0}) on the computer running QEMU.  Only available on @code{bluez}

capable systems like Linux.

@item -bt hci[,vlan=@var{n}]

Add a virtual, standard HCI that will participate in the Bluetooth

scatternet @var{n} (default @code{0}).  Similarly to @option{-net}

VLANs, devices inside a bluetooth network @var{n} can only communicate

with other devices in the same network (scatternet).

@end table

@item -bt vhci[,vlan=@var{n}]

(Linux-host only) Create a HCI in scatternet @var{n} (default 0) attached

to the host bluetooth stack instead of to the emulated target.  This

allows the host and target machines to participate in a common scatternet

and communicate.  Requires the Linux @code{vhci} driver installed.  Can

be used as following:

@example

qemu [...OPTIONS...] -bt hci,vlan=5 -bt vhci,vlan=5

@end example

@item -bt device:@var{dev}[,vlan=@var{n}]

Emulate a bluetooth device @var{dev} and place it in network @var{n}

(default @code{0}).  QEMU can only emulate one type of bluetooth devices

currently:

@table @code

@item keyboard

Virtual wireless keyboard implementing the HIDP bluetooth profile.

@end table

@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 @var{bzImage}

Use @var{bzImage} as kernel image.

@item -append @var{cmdline}

Use @var{cmdline} as kernel command line

@item -initrd @var{file}

Use @var{file} as initial ram disk.

@end table

Debug/Expert options:

@table @option

@item -serial @var{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[:WxH]

Virtual console. Optionally, a width and height can be given in pixel with

@example

vc:800x600

@end example

It is also possible to specify width or height in characters:

@example

vc:80Cx24C

@end example

@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/parport@var{N}

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

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

@item file:@var{filename}

Write output to @var{filename}. No character can be read.

@item stdio

[Unix only] standard input/output

@item pipe:@var{filename}

name pipe @var{filename}

@item COM@var{n}

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

@item udp:[@var{remote_host}]:@var{remote_port}[@@[@var{src_ip}]:@var{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 specified @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:[@var{host}]:@var{port}[,@var{server}][,nowait][,nodelay]

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.  The @code{nodelay} option disables the Nagle buffering

algorithm.  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:@var{host}:@var{port}[,server][,nowait][,nodelay]

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:@var{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.

@item mon:@var{dev_string}

This is a special option to allow the monitor to be multiplexed onto

another serial port.  The monitor is accessed with key sequence of

@key{Control-a} and then pressing @key{c}. See monitor access

@ref{pcsys_keys} in the -nographic section for more keys.

@var{dev_string} should be any one of the serial devices specified

above.  An example to multiplex the monitor onto a telnet server

listening on port 4444 would be:

@table @code

@item -serial mon:telnet::4444,server,nowait

@end table

@item braille

Braille device.  This will use BrlAPI to display the braille output on a real

or fake device.

@end table

@item -parallel @var{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 @var{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 -echr numeric_ascii_value

Change the escape character used for switching to the monitor when using

monitor and serial sharing.  The default is @code{0x01} when using the

@code{-nographic} option.  @code{0x01} is equal to pressing

@code{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.

@table @code

@item -echr 0x14

@item -echr 20

@end table

@item -s

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

@item -p @var{port}

Change gdb connection port.  @var{port} can be either a decimal number

to specify a TCP port, or a host device (same devices as the serial 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 @var{c},@var{h},@var{s},[,@var{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 those 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 -vga @var{type}

Select type of VGA card to emulate. Valid values for @var{type} are

@table @code

@item cirrus

Cirrus Logic GD5446 Video card. All Windows versions starting from

Windows 95 should recognize and use this graphic card. For optimal

performances, use 16 bit color depth in the guest and the host OS.

(This one is the default)

@item std

Standard VGA card with Bochs VBE extensions.  If your guest OS

supports the VESA 2.0 VBE extensions (e.g. Windows XP) and if you want

to use high resolution modes (>= 1280x1024x16) then you should use

this option.

@item vmware

VMWare SVGA-II compatible adapter. Use it if you have sufficiently

recent XFree86/XOrg server or Windows guest with a driver for this

card.

@end table

@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 -no-shutdown

Don't exit QEMU on guest shutdown, but instead only stop the emulation.

This allows for instance switching to monitor to commit changes to the

disk image.

@item -loadvm file

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

@item -semihosting

Enable semihosting syscall emulation (ARM and M68K target machines only).

On ARM this implements the "Angel" interface.

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.

@item -icount [N|auto]

Enable virtual instruction counter.  The virtual cpu will execute one

instruction every 2^N ns of virtual time.  If @code{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.

@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 t

toggle console timestamps

@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 media 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 ? [@var{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 @var{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] @var{device}

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

@item change @var{device} @var{setting}

Change the configuration of a device.

@table @option

@item change @var{diskdevice} @var{filename}

Change the medium for a removable disk device to point to @var{filename}. eg

@example

(qemu) change ide1-cd0 /path/to/some.iso

@end example

@item change vnc @var{display},@var{options}

Change the configuration of the VNC server. The valid syntax for @var{display}

and @var{options} are described at @ref{sec_invocation}. eg

@example

(qemu) change vnc localhost:1

@end example

@item change vnc password [@var{password}]

Change the password associated with the VNC server. If the new password is not

supplied, the monitor will prompt for it to be entered. VNC passwords are only

significant up to 8 letters. eg

@example

(qemu) change vnc password

Password: ********

@end example

@end table

@item screendump @var{filename}

Save screen into PPM image @var{filename}.

@item mouse_move @var{dx} @var{dy} [@var{dz}]

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

with optional scroll axis @var{dz}.

@item mouse_button @var{val}

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

@item mouse_set @var{index}

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

can be obtained with

@example

info mice

@end example

@item wavcapture @var{filename} [@var{frequency} [@var{bits} [@var{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 @var{index}

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

@example

info capture

@end example

@item log @var{item1}[,...]

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

@item savevm [@var{tag}|@var{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 @var{tag}|@var{id}

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

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

@item delvm @var{tag}|@var{id}

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

@item stop

Stop emulation.

@item c or cont

Resume emulation.

@item gdbserver [@var{port}]

Start gdbserver session (default @var{port}=1234)

@item x/fmt @var{addr}

Virtual memory dump starting at @var{addr}.

@item xp /@var{fmt} @var{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 (hex), 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/@var{fmt} @var{expr}

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

used.

@item sendkey @var{keys}

Send @var{keys} to the emulator. @var{keys} could be the name of the

key or @code{#} followed by the raw value in either decimal or hexadecimal

format. 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 boot_set @var{bootdevicelist}

Define new values for the boot device list. Those values will override

the values specified on the command line through the @code{-boot} option.

The values that can be specified here depend on the machine type, but are

the same that can be specified in the @code{-boot} command line option.

@item usb_add @var{devname}

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

@ref{usb_devices}

@item usb_del @var{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

* qemu_nbd_invocation::       qemu-nbd Invocation

* host_drives::               Using host drives

* disk_images_fat_images::    Virtual FAT disk images

* disk_images_nbd::           NBD access

@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

considered as read only. When sectors in written, they are written in

a temporary file created in @file{/tmp}. You can however force the

write back to the raw disk images by using the @code{commit} monitor

command (or @key{C-a s} in the serial console).

@node vm_snapshots

@subsection VM snapshots

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 @code{qcow2} disk image

format. Normally this device is the first virtual hard drive.

Use the monitor command @code{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 @code{loadvm} to restore a VM snapshot and @code{delvm} to remove

a VM snapshot. @code{info snapshots} lists the available snapshots

with their associated information:

@example

(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

@end example

A VM snapshot is made of a VM state info (its size is shown in

@code{info snapshots}) and a snapshot of every writable disk image.

The VM state info is stored in the first @code{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 @code{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) @code{-snapshot} option

(@ref{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:

@itemize

@item

They cannot cope with removable devices if they are removed or

inserted after a snapshot is done.

@item

A few device drivers still have incomplete snapshot support so their

state is not saved or restored properly (in particular USB).

@end itemize

@node qemu_img_invocation

@subsection @code{qemu-img} Invocation

@include qemu-img.texi

@node qemu_nbd_invocation

@subsection @code{qemu-nbd} Invocation

@include qemu-nbd.texi

@node host_drives

@subsection Using host drives

In addition to disk image files, QEMU can directly access host

devices. We describe here the usage for QEMU version >= 0.8.3.

@subsubsection Linux

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 @file{/dev/cdrom} to access to the CDROM or

@file{/dev/fd0} for the floppy.

@table @code

@item CD

You can specify a CDROM device even if no CDROM is loaded. QEMU has

specific code to detect CDROM insertion or removal. CDROM ejection by

the guest OS is supported. Currently only data CDs are supported.

@item Floppy

You can specify a floppy device even if no floppy is loaded. Floppy

removal is currently not detected accurately (if you change floppy

without doing floppy access while the floppy is not loaded, the guest

OS will think that the same floppy is loaded).

@item Hard disks

Hard disks can be used. Normally you must specify the whole disk

(@file{/dev/hdb} instead of @file{/dev/hdb1}) so that the guest OS can

see it as a partitioned disk. WARNING: 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 @option{-snapshot} command

line option or modify the device permissions accordingly).

@end table

@subsubsection Windows

@table @code

@item CD

The preferred syntax is the drive letter (e.g. @file{d:}). The

alternate syntax @file{\\.\d:} is supported. @file{/dev/cdrom} is

supported as an alias to the first CDROM drive.

Currently there is no specific code to handle removable media, so it

is better to use the @code{change} or @code{eject} monitor commands to

change or eject media.

@item Hard disks

Hard disks can be used with the syntax: @file{\\.\PhysicalDrive@var{N}}

where @var{N} is the drive number (0 is the first hard disk).

WARNING: 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 @option{-snapshot} command line so that the

modifications are written in a temporary file).

@end table

@subsubsection Mac OS X

@file{/dev/cdrom} is an alias to the first CDROM.

Currently there is no specific code to handle removable media, so it