Archipelago » qemu

\input texinfo @c -*- texinfo -*-

@c %**start of header

@setfilename qemu-doc.info

@settitle QEMU CPU Emulator User Documentation

@exampleindent 0

@paragraphindent 0

@c %**end of header

@iftex

@titlepage

@sp 7

@center @titlefont{QEMU CPU Emulator}

@sp 1

@center @titlefont{User Documentation}

@sp 3

@end titlepage

@end iftex

@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, and Sparc32/64 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.

@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.

@item -boot [a|c|d]

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

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

you can have QEMU listen on VNC display d 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}).

@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 or with some X11 servers). You don't 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 -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).

@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 succesfully 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 device @var{dev}. Available

devices are:

@table @code

@item vc

Virtual console

@item pty

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

[Unix only] name pipe @var{filename}

@end table

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.

@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.

@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 -std-vga

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

Cirrus Logic GD5446 PCI VGA)

@item -loadvm file

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

@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 emulatior

@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

@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 log item1[,...]

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

@item savevm filename

Save the whole virtual machine state to @var{filename}.

@item loadvm filename

Restore the whole virtual machine state from @var{filename}.

@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.

@menu

* disk_images_quickstart::    Quick start for disk image creation

* disk_images_snapshot_mode:: Snapshot mode

* qemu_img_invocation::       qemu-img Invocation

* 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

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 qemu_img_invocation

@subsection @code{qemu-img} Invocation

@include qemu-img.texi

@node disk_images_fat_images

@subsection Virtual FAT disk images

QEMU can automatically create a virtual FAT disk image from a

directory tree. In order to use it, just type:

@example 

qemu linux.img -hdb fat:/my_directory

@end example

Then you access access to all the files in the @file{/my_directory}

directory without having to copy them in a disk image or to export

them via SAMBA or NFS. The default access is @emph{read-only}.

Floppies can be emulated with the @code{:floppy:} option:

@example 

qemu linux.img -fda fat:floppy:/my_directory

@end example

A read/write support is available for testing (beta stage) with the

@code{:rw:} option:

@example 

qemu linux.img -fda fat:floppy:rw:/my_directory

@end example

What you should @emph{never} do:

@itemize

@item use non-ASCII filenames ;

@item use "-snapshot" together with ":rw:" ;

@item expect it to work when loadvm'ing ;

@item write to the FAT directory on the host system while accessing it with the guest system.

@end itemize

@node pcsys_network

@section Network emulation

QEMU can simulate several networks cards (NE2000 boards 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 priviledged user mode

network stack can replace the TAP device to have a basic network

connection.

@subsection VLANs

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).

@subsection Using TAP network interfaces

This is the standard way to connect QEMU to a real network. QEMU adds

a virtual network device on your host (called @code{tapN}), and you

can then configure it as if it was a real ethernet card.

As an example, you can download the @file{linux-test-xxx.tar.gz}

archive and copy the script @file{qemu-ifup} in @file{/etc} and

configure properly @code{sudo} so that the command @code{ifconfig}

contained in @file{qemu-ifup} can be executed as root. You must verify

that your host kernel supports the TAP network interfaces: the

device @file{/dev/net/tun} must be present.

See @ref{direct_linux_boot} to have an example of network use with a

Linux distribution and @ref{sec_invocation} to have examples of

command lines using the TAP network interfaces.

@subsection Using the user mode network stack

By using the option @option{-net user} (default configuration if no

@option{-net} option is specified), QEMU uses a completely user mode

network stack (you don't need root priviledge to use the virtual

network). The virtual network configuration is the following:

@example

         QEMU VLAN      <------>  Firewall/DHCP server <-----> Internet

                           |          (10.0.2.2)

                           |

                           ---->  DNS server (10.0.2.3)

                           |     

                           ---->  SMB server (10.0.2.4)

@end example

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 @code{ping} is not supported reliably to the internet as it

would require root priviledges. 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 @option{-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.

@subsection Connecting VLANs between QEMU instances

Using the @option{-net socket} option, it is possible to make VLANs

that span several QEMU instances. See @ref{sec_invocation} to have a

basic example.

@node direct_linux_boot

@section Direct Linux Boot

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 QEMU network configuration is also explained.

@enumerate

@item

Download the archive @file{linux-test-xxx.tar.gz} containing a Linux

kernel and a disk image. 

@item Optional: If you want network support (for example to launch X11 examples), you

must copy the script @file{qemu-ifup} in @file{/etc} and configure

properly @code{sudo} so that the command @code{ifconfig} contained in

@file{qemu-ifup} can be executed as root. You must verify that your host

kernel supports the TUN/TAP network interfaces: the device

@file{/dev/net/tun} must be present.

When network is enabled, there is a virtual network connection between

the host kernel and the emulated kernel. The emulated kernel is seen

from the host kernel at IP address 172.20.0.2 and the host kernel is

seen from the emulated kernel at IP address 172.20.0.1.

@item Launch @code{qemu.sh}. You should have the following output:

@smallexample

> ./qemu.sh 

Connected to host network interface: tun0

Linux version 2.4.21 (bellard@@voyager.localdomain) (gcc version 3.2.2 20030222 @/(Red Hat @/Linux 3.2.2-5)) #5 Tue Nov 11 18:18:53 CET 2003

BIOS-provided physical RAM map:

 BIOS-e801: 0000000000000000 - 000000000009f000 (usable)