File:  [Qemu by Fabrice Bellard] / qemu / qemu-doc.texi
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CVS tags: qemu0080, HEAD
qemu 0.8.0

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

@settitle QEMU CPU Emulator User Documentation
@sp 7
@center @titlefont{QEMU CPU Emulator User Documentation}
@sp 3
@end titlepage
@end iftex

@chapter Introduction

@section Features

QEMU is a FAST! processor emulator using dynamic translation to
achieve good emulation speed.

QEMU has two operating modes:

@itemize @minus

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.

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{}) or
to ease cross-compilation and cross-debugging.

@end itemize

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

For system emulation, the following hardware targets are supported:
@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 (ARM1026E processor)
@end itemize

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

@chapter Installation

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

@section Linux

If a precompiled package is available for your distribution - you just
have to install it. Otherwise, see @ref{compilation}.

@section Windows

Download the experimental binary installer at

@section Mac OS X

Download the experimental binary installer at

@chapter QEMU PC System emulator

@section Introduction

@c man begin DESCRIPTION

The QEMU PC System emulator simulates the
following peripherals:

@itemize @minus
i440FX host PCI bridge and PIIX3 PCI to ISA bridge
Cirrus CLGD 5446 PCI VGA card or dummy VGA card with Bochs VESA
extensions (hardware level, including all non standard modes).
PS/2 mouse and keyboard
2 PCI IDE interfaces with hard disk and CD-ROM support
Floppy disk
NE2000 PCI network adapters
Serial ports
Creative SoundBlaster 16 sound card
ENSONIQ AudioPCI ES1370 sound card
Adlib(OPL2) - Yamaha YM3812 compatible chip
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

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

QEMU uses YM3812 emulation by Tatsuyuki Satoh.

@c man end

@section Quick Start

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

qemu linux.img
@end example

Linux should boot and give you a prompt.

@node sec_invocation
@section Invocation

@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 (@xref{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 (@xref{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} (@xref{disk_images}). 

@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 -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:
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

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

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

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

@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}. See the monitor command
@code{usb_add} to have more information.
@end table

Network options:

@table @option

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

@item -net user[,vlan=n]
Use the user mode network stack which requires no administrator
priviledge to run. This is the default if no @option{-net} option is

@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:

qemu linux.img -net nic -net tap
@end example

More complicated example (two NICs, each one connected to a TAP device)
qemu linux.img -net nic,vlan=0 -net tap,vlan=0,ifname=tap0 \
               -net nic,vlan=1 -net tap,vlan=1,ifname=tap1
@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.

# 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=
@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}.
Several QEMU can be running on different hosts and share same bus (assuming 
correct multicast setup for these hosts).
mcast support is compatible with User Mode Linux (argument @option{eth@var{N}=mcast}), see
@item Use @option{fd=h} to specify an already opened UDP multicast socket.
@end enumerate

# launch one QEMU instance
qemu linux.img -net nic,macaddr=52:54:00:12:34:56 -net socket,mcast=
# launch another QEMU instance on same "bus"
qemu linux.img -net nic,macaddr=52:54:00:12:34:57 -net socket,mcast=
# launch yet another QEMU instance on same "bus"
qemu linux.img -net nic,macaddr=52:54:00:12:34:58 -net socket,mcast=
@end example

Example (User Mode Linux compat.):
# launch QEMU instance (note mcast address selected is UML's default)
qemu linux.img -net nic,macaddr=52:54:00:12:34:56 -net socket,mcast=
# 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 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

@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}

In the guest Windows OS, the line:
@example 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 (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:

# 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:

# 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

@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

@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 (@xref{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

@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

@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
@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


@setfilename qemu 
@settitle QEMU System Emulator

@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

@end ignore

@section QEMU Monitor

The QEMU monitor is used to give complex commands to the QEMU
emulator. You can use it to:

@itemize @minus

Remove or insert removable medias images
(such as CD-ROM or floppies)

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

Dump 10 instructions at the current instruction pointer:
(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

Dump 80 16 bit values at the start of the video memory.
(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 example
@end itemize

@item p or print/fmt expr

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

@item sendkey keys

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

Plug the USB device devname to the QEMU virtual USB hub. @var{devname}
is either a virtual device name (for example @code{mouse}) or a host
USB device identifier. Host USB device identifiers have the following
syntax: @code{host:bus.addr} or @code{host:vendor_id:product_id}.

@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.

@subsection Quick start for disk image creation

You can create a disk image with the command:
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.

@xref{qemu_img_invocation} for more information.

@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

@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:

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:

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:

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

What you should @emph{never} do:
@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

@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

@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:


         QEMU VLAN      <------>  Firewall/DHCP server <-----> Internet
                           |          (
                           ---->  DNS server (
                           ---->  SMB server (
@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

In order to check that the user mode network is working, you can ping
the address 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 (

When using the built-in TFTP server, the router is also the TFTP

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.

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 and the host kernel is
seen from the emulated kernel at IP address

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

> ./ 
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)
 BIOS-e801: 0000000000100000 - 0000000002000000 (usable)
32MB LOWMEM available.
On node 0 totalpages: 8192
zone(0): 4096 pages.
zone(1): 4096 pages.
zone(2): 0 pages.
Kernel command line: root=/dev/hda sb=0x220,5,1,5 ide2=noprobe ide3=noprobe ide4=noprobe ide5=noprobe console=ttyS0
ide_setup: ide2=noprobe
ide_setup: ide3=noprobe
ide_setup: ide4=noprobe
ide_setup: ide5=noprobe
Initializing CPU#0
Detected 2399.621 MHz processor.
Console: colour EGA 80x25
Calibrating delay loop... 4744.80 BogoMIPS
Memory: 28872k/32768k available (1210k kernel code, 3508k reserved, 266k data, 64k init, 0k highmem)
Dentry cache hash table entries: 4096 (order: 3, 32768 bytes)
Inode cache hash table entries: 2048 (order: 2, 16384 bytes)
Mount cache hash table entries: 512 (order: 0, 4096 bytes)
Buffer-cache hash table entries: 1024 (order: 0, 4096 bytes)
Page-cache hash table entries: 8192 (order: 3, 32768 bytes)
CPU: Intel Pentium Pro stepping 03
Checking 'hlt' instruction... OK.
POSIX conformance testing by UNIFIX
Linux NET4.0 for Linux 2.4
Based upon Swansea University Computer Society NET3.039
Initializing RT netlink socket
apm: BIOS not found.
Starting kswapd
Journalled Block Device driver loaded
Detected PS/2 Mouse Port.
pty: 256 Unix98 ptys configured
Serial driver version 5.05c (2001-07-08) with no serial options enabled
ttyS00 at 0x03f8 (irq = 4) is a 16450
ne.c:v1.10 9/23/94 Donald Becker (
Last modified Nov 1, 2000 by Paul Gortmaker
NE*000 ethercard probe at 0x300: 52 54 00 12 34 56
eth0: NE2000 found at 0x300, using IRQ 9.
RAMDISK driver initialized: 16 RAM disks of 4096K size 1024 blocksize
Uniform Multi-Platform E-IDE driver Revision: 7.00beta4-2.4
ide: Assuming 50MHz system bus speed for PIO modes; override with idebus=xx
ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
hda: attached ide-disk driver.
hda: 20480 sectors (10 MB) w/256KiB Cache, CHS=20/16/63
Partition check:
Soundblaster audio driver Copyright (C) by Hannu Savolainen 1993-1996
NET4: Linux TCP/IP 1.0 for NET4.0
IP Protocols: ICMP, UDP, TCP, IGMP
IP: routing cache hash table of 512 buckets, 4Kbytes
TCP: Hash tables configured (established 2048 bind 4096)
NET4: Unix domain sockets 1.0/SMP for Linux NET4.0.
EXT2-fs warning: mounting unchecked fs, running e2fsck is recommended
VFS: Mounted root (ext2 filesystem).
Freeing unused kernel memory: 64k freed
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
QEMU Linux test distribution (based on Redhat 9)
Type 'exit' to halt the system
@end example

Then you can play with the kernel inside the virtual serial console. You
can launch @code{ls} for example. Type @key{Ctrl-a h} to have an help
about the keys you can type inside the virtual serial console. In
particular, use @key{Ctrl-a x} to exit QEMU and use @key{Ctrl-a b} as
the Magic SysRq key.

If the network is enabled, launch the script @file{/etc/linuxrc} in the
emulator (don't forget the leading dot):
. /etc/linuxrc
@end example

Then enable X11 connections on your PC from the emulated Linux: 
xhost +
@end example

You can now launch @file{xterm} or @file{xlogo} and verify that you have
a real Virtual Linux system !

@end enumerate

A 2.5.74 kernel is also included in the archive. Just
replace the bzImage in to try it.

In order to exit cleanly from qemu, you can do a @emph{shutdown} inside
qemu. qemu will automatically exit when the Linux shutdown is done.

You can boot slightly faster by disabling the probe of non present IDE
interfaces. To do so, add the following options on the kernel command
ide1=noprobe ide2=noprobe ide3=noprobe ide4=noprobe ide5=noprobe
@end example

The example disk image is a modified version of the one made by Kevin
Lawton for the plex86 Project (@url{}).

@end enumerate

@section USB emulation

QEMU emulates a PCI UHCI USB controller and a 8 port USB hub connected
to it. You can virtually plug to the hub virtual USB devices or real
host USB devices (experimental, works only on Linux hosts).

@subsection Using virtual USB devices

A virtual USB mouse device is available for testing in QEMU.

You can try it with the following monitor commands:

# add the mouse device
(qemu) usb_add mouse 

# show the virtual USB devices plugged on the QEMU Virtual USB hub
(qemu) info usb
  Device 0.3, speed 12 Mb/s

# after some time you can try to remove the mouse
(qemu) usb_del 0.3
@end example

The option @option{-usbdevice} is similar to the monitor command

@subsection Using host USB devices on a Linux host

WARNING: this is an experimental feature. QEMU will slow down when
using it. USB devices requiring real time streaming (i.e. USB Video
Cameras) are not supported yet.

@item If you use an early Linux 2.4 kernel, verify that no Linux driver 
is actually using the USB device. A simple way to do that is simply to
disable the corresponding kernel module by renaming it from @file{mydriver.o}
to @file{mydriver.o.disabled}.

@item Verify that @file{/proc/bus/usb} is working (most Linux distributions should enable it by default). You should see something like that:
ls /proc/bus/usb
001  devices  drivers
@end example

@item Since only root can access to the USB devices directly, you can either launch QEMU as root or change the permissions of the USB devices you want to use. For testing, the following suffices:
chown -R myuid /proc/bus/usb
@end example

@item Launch QEMU and do in the monitor:
info usbhost
  Device 1.2, speed 480 Mb/s
    Class 00: USB device 1234:5678, USB DISK
@end example
You should see the list of the devices you can use (Never try to use
hubs, it won't work).

@item Add the device in QEMU by using:
usb_add host:1234:5678
@end example

Normally the guest OS should report that a new USB device is
plugged. You can use the option @option{-usbdevice} to do the same.

@item Now you can try to use the host USB device in QEMU.

@end enumerate

When relaunching QEMU, you may have to unplug and plug again the USB
device to make it work again (this is a bug).

@node gdb_usage
@section GDB usage

QEMU has a primitive support to work with gdb, so that you can do
'Ctrl-C' while the virtual machine is running and inspect its state.

In order to use gdb, launch qemu with the '-s' option. It will wait for a
gdb connection:
> qemu -s -kernel arch/i386/boot/bzImage -hda root-2.4.20.img -append "root=/dev/hda"
Connected to host network interface: tun0
Waiting gdb connection on port 1234
@end example

Then launch gdb on the 'vmlinux' executable:
> gdb vmlinux
@end example

In gdb, connect to QEMU:
(gdb) target remote localhost:1234
@end example

Then you can use gdb normally. For example, type 'c' to launch the kernel:
(gdb) c
@end example

Here are some useful tips in order to use gdb on system code:

Use @code{info reg} to display all the CPU registers.
Use @code{x/10i $eip} to display the code at the PC position.
Use @code{set architecture i8086} to dump 16 bit code. Then use
@code{x/10i $cs*16+*eip} to dump the code at the PC position.
@end enumerate

@section Target OS specific information

@subsection Linux

To have access to SVGA graphic modes under X11, use the @code{vesa} or
the @code{cirrus} X11 driver. For optimal performances, use 16 bit
color depth in the guest and the host OS.

When using a 2.6 guest Linux kernel, you should add the option
@code{clock=pit} on the kernel command line because the 2.6 Linux
kernels make very strict real time clock checks by default that QEMU
cannot simulate exactly.

When using a 2.6 guest Linux kernel, verify that the 4G/4G patch is
not activated because QEMU is slower with this patch. The QEMU
Accelerator Module is also much slower in this case. Earlier Fedora
Core 3 Linux kernel (< 2.6.9-1.724_FC3) were known to incorporte this
patch by default. Newer kernels don't have it.

@subsection Windows

If you have a slow host, using Windows 95 is better as it gives the
best speed. Windows 2000 is also a good choice.

@subsubsection SVGA graphic modes support

QEMU emulates a Cirrus Logic GD5446 Video
card. All Windows versions starting from Windows 95 should recognize
and use this graphic card. For optimal performances, use 16 bit color
depth in the guest and the host OS.

@subsubsection CPU usage reduction

Windows 9x does not correctly use the CPU HLT
instruction. The result is that it takes host CPU cycles even when
idle. You can install the utility from
@url{} to solve this
problem. Note that no such tool is needed for NT, 2000 or XP.

@subsubsection Windows 2000 disk full problem

Windows 2000 has a bug which gives a disk full problem during its
installation. When installing it, use the @option{-win2k-hack} QEMU
option to enable a specific workaround. After Windows 2000 is
installed, you no longer need this option (this option slows down the
IDE transfers).

@subsubsection Windows 2000 shutdown

Windows 2000 cannot automatically shutdown in QEMU although Windows 98
can. It comes from the fact that Windows 2000 does not automatically
use the APM driver provided by the BIOS.

In order to correct that, do the following (thanks to Struan
Bartlett): go to the Control Panel => Add/Remove Hardware & Next =>
Add/Troubleshoot a device => Add a new device & Next => No, select the
hardware from a list & Next => NT Apm/Legacy Support & Next => Next
(again) a few times. Now the driver is installed and Windows 2000 now
correctly instructs QEMU to shutdown at the appropriate moment. 

@subsubsection Share a directory between Unix and Windows

See @ref{sec_invocation} about the help of the option @option{-smb}.

@subsubsection Windows XP security problems

Some releases of Windows XP install correctly but give a security
error when booting:
A problem is preventing Windows from accurately checking the
license for this computer. Error code: 0x800703e6.
@end example
The only known workaround is to boot in Safe mode
without networking support. 

Future QEMU releases are likely to correct this bug.

@subsection MS-DOS and FreeDOS

@subsubsection CPU usage reduction

DOS does not correctly use the CPU HLT instruction. The result is that
it takes host CPU cycles even when idle. You can install the utility
from @url{} to solve this

@chapter QEMU System emulator for non PC targets

QEMU is a generic emulator and it emulates many non PC
machines. Most of the options are similar to the PC emulator. The
differences are mentionned in the following sections.

@section QEMU PowerPC System emulator

Use the executable @file{qemu-system-ppc} to simulate a complete PREP
or PowerMac PowerPC system.

QEMU emulates the following PowerMac peripherals:

@itemize @minus
UniNorth PCI Bridge 
PCI VGA compatible card with VESA Bochs Extensions
2 PMAC IDE interfaces with hard disk and CD-ROM support
NE2000 PCI adapters
Non Volatile RAM
VIA-CUDA with ADB keyboard and mouse.
@end itemize

QEMU emulates the following PREP peripherals:

@itemize @minus
PCI Bridge
PCI VGA compatible card with VESA Bochs Extensions
2 IDE interfaces with hard disk and CD-ROM support
Floppy disk
NE2000 network adapters
Serial port
PREP Non Volatile RAM
PC compatible keyboard and mouse.
@end itemize

QEMU uses the Open Hack'Ware Open Firmware Compatible BIOS available at

@c man begin OPTIONS

The following options are specific to the PowerPC emulation:

@table @option

@item -g WxH[xDEPTH]  

Set the initial VGA graphic mode. The default is 800x600x15.

@end table

@c man end 

More information is available at

@section Sparc32 System emulator invocation

Use the executable @file{qemu-system-sparc} to simulate a JavaStation
(sun4m architecture). The emulation is somewhat complete.

QEMU emulates the following sun4m peripherals:

@itemize @minus
TCX Frame buffer
Lance (Am7990) Ethernet
Non Volatile RAM M48T08
Slave I/O: timers, interrupt controllers, Zilog serial ports, keyboard
and power/reset logic
ESP SCSI controller with hard disk and CD-ROM support
Floppy drive
@end itemize

The number of peripherals is fixed in the architecture.

QEMU uses the Proll, a PROM replacement available at
@url{}. The required
QEMU-specific patches are included with the sources.

A sample Linux 2.6 series kernel and ram disk image are available on
the QEMU web site. Please note that currently neither Linux 2.4
series, NetBSD, nor OpenBSD kernels work.

@c man begin OPTIONS

The following options are specific to the Sparc emulation:

@table @option

@item -g WxH

Set the initial TCX graphic mode. The default is 1024x768.

@end table

@c man end 

@section Sparc64 System emulator invocation

Use the executable @file{qemu-system-sparc64} to simulate a Sun4u machine.
The emulator is not usable for anything yet.

QEMU emulates the following sun4u peripherals:

@itemize @minus
UltraSparc IIi APB PCI Bridge 
PCI VGA compatible card with VESA Bochs Extensions
Non Volatile RAM M48T59
PC-compatible serial ports
@end itemize

@section MIPS System emulator invocation

Use the executable @file{qemu-system-mips} to simulate a MIPS machine.
The emulator is able to boot a Linux kernel and to run a Linux Debian
installation from NFS. The following devices are emulated:

@itemize @minus
PC style serial port
NE2000 network card
@end itemize

More information is available in the QEMU mailing-list archive.

@section ARM System emulator invocation

Use the executable @file{qemu-system-arm} to simulate a ARM
machine. The ARM Integrator/CP board is emulated with the following

@itemize @minus
Two PL011 UARTs
SMC 91c111 Ethernet adapter
@end itemize

A Linux 2.6 test image is available on the QEMU web site. More
information is available in the QEMU mailing-list archive.

@chapter QEMU Linux User space emulator 

@section Quick Start

In order to launch a Linux process, QEMU needs the process executable
itself and all the target (x86) dynamic libraries used by it. 


@item On x86, you can just try to launch any process by using the native

qemu-i386 -L / /bin/ls
@end example

@code{-L /} tells that the x86 dynamic linker must be searched with a
@file{/} prefix.

@item Since QEMU is also a linux process, you can launch qemu with qemu (NOTE: you can only do that if you compiled QEMU from the sources):

qemu-i386 -L / qemu-i386 -L / /bin/ls
@end example

@item On non x86 CPUs, you need first to download at least an x86 glibc
(@file{qemu-runtime-i386-XXX-.tar.gz} on the QEMU web page). Ensure that
@code{LD_LIBRARY_PATH} is not set:

@end example

Then you can launch the precompiled @file{ls} x86 executable:

qemu-i386 tests/i386/ls
@end example
You can look at @file{} so that
QEMU is automatically launched by the Linux kernel when you try to
launch x86 executables. It requires the @code{binfmt_misc} module in the
Linux kernel.

@item The x86 version of QEMU is also included. You can try weird things such as:
qemu-i386 /usr/local/qemu-i386/bin/qemu-i386 /usr/local/qemu-i386/bin/ls-i386
@end example

@end itemize

@section Wine launch


@item Ensure that you have a working QEMU with the x86 glibc
distribution (see previous section). In order to verify it, you must be
able to do:

qemu-i386 /usr/local/qemu-i386/bin/ls-i386
@end example

@item Download the binary x86 Wine install
(@file{qemu-XXX-i386-wine.tar.gz} on the QEMU web page). 

@item Configure Wine on your account. Look at the provided script
@file{/usr/local/qemu-i386/bin/}. Your previous
@code{$@{HOME@}/.wine} directory is saved to @code{$@{HOME@}/}.

@item Then you can try the example @file{putty.exe}:

qemu-i386 /usr/local/qemu-i386/wine/bin/wine /usr/local/qemu-i386/wine/c/Program\ Files/putty.exe
@end example

@end itemize

@section Command line options

usage: qemu-i386 [-h] [-d] [-L path] [-s size] program [arguments...]
@end example

@table @option
@item -h
Print the help
@item -L path   
Set the x86 elf interpreter prefix (default=/usr/local/qemu-i386)
@item -s size
Set the x86 stack size in bytes (default=524288)
@end table

Debug options:

@table @option
@item -d
Activate log (logfile=/tmp/qemu.log)
@item -p pagesize
Act as if the host page size was 'pagesize' bytes
@end table

@node compilation
@chapter Compilation from the sources

@section Linux/Unix

@subsection Compilation

First you must decompress the sources:
cd /tmp
tar zxvf qemu-x.y.z.tar.gz
cd qemu-x.y.z
@end example

Then you configure QEMU and build it (usually no options are needed):
@end example

Then type as root user:
make install
@end example
to install QEMU in @file{/usr/local}.

@subsection Tested tool versions

In order to compile QEMU succesfully, it is very important that you
have the right tools. The most important one is gcc. I cannot guaranty
that QEMU works if you do not use a tested gcc version. Look at
'configure' and 'Makefile' if you want to make a different gcc
version work.

host      gcc      binutils      glibc    linux       distribution
x86       3.2      2.13.2        2.1.3    2.4.18
          2.96   2.2.5    2.4.18      Red Hat 7.3
          3.2.2  2.3.2    2.4.20      Red Hat 9

PowerPC   3.3 [4]  2.3.1    2.4.20briq

Alpha     3.3 [1]   2.2.5    2.2.20 [2]  Debian 3.0

Sparc32   2.95.4   2.2.5    2.4.18      Debian 3.0

ARM       2.95.4   2.2.5    2.4.9 [3]   Debian 3.0

[1] On Alpha, QEMU needs the gcc 'visibility' attribute only available
    for gcc version >= 3.3.
[2] Linux >= 2.4.20 is necessary for precise exception support
[3] 2.4.9-ac10-rmk2-np1-cerf2

[4] gcc 2.95.x generates invalid code when using too many register
variables. You must use gcc 3.x on PowerPC.
@end example

@section Windows

@item Install the current versions of MSYS and MinGW from
@url{}. You can find detailed installation
instructions in the download section and the FAQ.

@item Download 
the MinGW development library of SDL 1.2.x
(@file{SDL-devel-1.2.x-mingw32.tar.gz}) from
@url{}. Unpack it in a temporary place, and
unpack the archive @file{i386-mingw32msvc.tar.gz} in the MinGW tool
directory. Edit the @file{sdl-config} script so that it gives the
correct SDL directory when invoked.

@item Extract the current version of QEMU.
@item Start the MSYS shell (file @file{msys.bat}).

@item Change to the QEMU directory. Launch @file{./configure} and 
@file{make}.  If you have problems using SDL, verify that
@file{sdl-config} can be launched from the MSYS command line.

@item You can install QEMU in @file{Program Files/Qemu} by typing 
@file{make install}. Don't forget to copy @file{SDL.dll} in
@file{Program Files/Qemu}.

@end itemize

@section Cross compilation for Windows with Linux

Install the MinGW cross compilation tools available at

Install the Win32 version of SDL (@url{}) by
unpacking @file{i386-mingw32msvc.tar.gz}. Set up the PATH environment
variable so that @file{i386-mingw32msvc-sdl-config} can be launched by
the QEMU configuration script.

Configure QEMU for Windows cross compilation:
./configure --enable-mingw32
@end example
If necessary, you can change the cross-prefix according to the prefix
choosen for the MinGW tools with --cross-prefix. You can also use
--prefix to set the Win32 install path.

@item You can install QEMU in the installation directory by typing 
@file{make install}. Don't forget to copy @file{SDL.dll} in the
installation directory. 

@end itemize

Note: Currently, Wine does not seem able to launch
QEMU for Win32.

@section Mac OS X

The Mac OS X patches are not fully merged in QEMU, so you should look
at the QEMU mailing list archive to have all the necessary