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@settitle QEMU Emulator User Documentation

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@direntry

* QEMU: (qemu-doc).    The QEMU Emulator User Documentation.

@end direntry

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@iftex

@titlepage

@sp 7

@center @titlefont{QEMU 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 User space emulator::

* compilation:: Compilation from the sources

* License::

* 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

@cindex operating modes

@item

@cindex system emulation

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

@cindex user mode emulation

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 a host kernel driver and yet gives acceptable

performance.

For system emulation, the following hardware targets are supported:

@itemize

@cindex emulated target systems

@cindex supported target systems

@item PC (x86 or x86_64 processor)

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

@item PREP (PowerPC processor)

@item G3 Beige 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/Platform 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)

@item AXIS-Devboard88 (CRISv32 ETRAX-FS).

@item Petalogix Spartan 3aDSP1800 MMU ref design (MicroBlaze).

@item Avnet LX60/LX110/LX200 boards (Xtensa)

@end itemize

@cindex supported user mode targets

For user emulation, x86 (32 and 64 bit), PowerPC (32 and 64 bit),

ARM, MIPS (32 bit only), Sparc (32 and 64 bit),

Alpha, ColdFire(m68k), CRISv32 and MicroBlaze CPUs are supported.

@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

@cindex installation (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

@cindex installation (Windows)

Download the experimental binary installer at

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

TODO (no longer available)

@node install_mac

@section Mac OS X

Download the experimental binary installer at

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

TODO (no longer available)

@node QEMU PC System emulator

@chapter QEMU PC System emulator

@cindex system emulation (PC)

@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

* pcsys_other_devs::   Other Devices

* 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 and ISA 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

Intel HD Audio Controller and HDA codec

@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, 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" Schütz.

Note that, by default, GUS shares IRQ(7) with parallel ports and so

QEMU must be told to not have parallel ports to have working GUS.

@example

qemu-system-i386 dos.img -soundhw gus -parallel none

@end example

Alternatively:

@example

qemu-system-i386 dos.img -device gus,irq=5

@end example

Or some other unclaimed IRQ.

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

@c man end

@node pcsys_quickstart

@section Quick Start

@cindex quick start

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

@example

qemu-system-i386 linux.img

@end example

Linux should boot and give you a prompt.

@node sec_invocation

@section Invocation

@example

@c man begin SYNOPSIS

usage: qemu-system-i386 [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. Some

targets do not need a disk image.

@include qemu-options.texi

@c man end

@node pcsys_keys

@section Keys

@c man begin OPTIONS

During the graphical emulation, you can use special key combinations to change

modes. The default key mappings are shown below, but if you use @code{-alt-grab}

then the modifier is Ctrl-Alt-Shift (instead of Ctrl-Alt) and if you use

@code{-ctrl-grab} then the modifier is the right Ctrl key (instead of Ctrl-Alt):

@table @key

@item Ctrl-Alt-f

@kindex Ctrl-Alt-f

Toggle full screen

@item Ctrl-Alt-+

@kindex Ctrl-Alt-+

Enlarge the screen

@item Ctrl-Alt--

@kindex Ctrl-Alt--

Shrink the screen

@item Ctrl-Alt-u

@kindex Ctrl-Alt-u

Restore the screen's un-scaled dimensions

@item Ctrl-Alt-n

@kindex 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

@kindex Ctrl-Alt

Toggle mouse and keyboard grab.

@end table

@kindex Ctrl-Up

@kindex Ctrl-Down

@kindex Ctrl-PageUp

@kindex Ctrl-PageDown

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.

@kindex Ctrl-a h

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

@kindex Ctrl-a h

@item Ctrl-a ?

@kindex Ctrl-a ?

Print this help

@item Ctrl-a x

@kindex Ctrl-a x

Exit emulator

@item Ctrl-a s

@kindex Ctrl-a s

Save disk data back to file (if -snapshot)

@item Ctrl-a t

@kindex Ctrl-a t

Toggle console timestamps

@item Ctrl-a b

@kindex Ctrl-a b

Send break (magic sysrq in Linux)

@item Ctrl-a c

@kindex Ctrl-a c

Switch between console and monitor

@item Ctrl-a Ctrl-a

@kindex Ctrl-a 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

@cindex 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:

@include qemu-monitor.texi

@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

* disk_images_formats::       Disk image file formats

* host_drives::               Using host drives

* disk_images_fat_images::    Virtual FAT disk images

* disk_images_nbd::           NBD access

* disk_images_sheepdog::      Sheepdog disk images

* disk_images_iscsi::         iSCSI LUNs

* disk_images_gluster::       GlusterFS 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 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 disk_images_formats

@subsection Disk image file formats

QEMU supports many image file formats that can be used with VMs as well as with

any of the tools (like @code{qemu-img}). This includes the preferred formats

raw and qcow2 as well as formats that are supported for compatibility with

older QEMU versions or other hypervisors.

Depending on the image format, different options can be passed to

@code{qemu-img create} and @code{qemu-img convert} using the @code{-o} option.

This section describes each format and the options that are supported for it.

@table @option

@item raw

Raw disk image format. This format has the advantage of

being simple and easily exportable to all other emulators. If your

file system supports @emph{holes} (for example in ext2 or ext3 on

Linux or NTFS on Windows), then only the written sectors will reserve

space. Use @code{qemu-img info} to know the real size used by the

image or @code{ls -ls} on Unix/Linux.

@item qcow2

QEMU image format, the most versatile format. Use it to have smaller

images (useful if your filesystem does not supports holes, for example

on Windows), optional AES encryption, zlib based compression and

support of multiple VM snapshots.

Supported options:

@table @code

@item compat

Determines the qcow2 version to use. @code{compat=0.10} uses the traditional

image format that can be read by any QEMU since 0.10 (this is the default).

@code{compat=1.1} enables image format extensions that only QEMU 1.1 and

newer understand. Amongst others, this includes zero clusters, which allow

efficient copy-on-read for sparse images.

@item backing_file

File name of a base image (see @option{create} subcommand)

@item backing_fmt

Image format of the base image

@item encryption

If this option is set to @code{on}, the image is encrypted.

Encryption uses the AES format which is very secure (128 bit keys). Use

a long password (16 characters) to get maximum protection.

@item cluster_size

Changes the qcow2 cluster size (must be between 512 and 2M). Smaller cluster

sizes can improve the image file size whereas larger cluster sizes generally

provide better performance.

@item preallocation

Preallocation mode (allowed values: off, metadata). An image with preallocated

metadata is initially larger but can improve performance when the image needs

to grow.

@item lazy_refcounts

If this option is set to @code{on}, reference count updates are postponed with

the goal of avoiding metadata I/O and improving performance. This is

particularly interesting with @option{cache=writethrough} which doesn't batch

metadata updates. The tradeoff is that after a host crash, the reference count

tables must be rebuilt, i.e. on the next open an (automatic) @code{qemu-img

check -r all} is required, which may take some time.

This option can only be enabled if @code{compat=1.1} is specified.

@end table

@item qed

Old QEMU image format with support for backing files and compact image files

(when your filesystem or transport medium does not support holes).

When converting QED images to qcow2, you might want to consider using the

@code{lazy_refcounts=on} option to get a more QED-like behaviour.

Supported options:

@table @code

@item backing_file

File name of a base image (see @option{create} subcommand).

@item backing_fmt

Image file format of backing file (optional).  Useful if the format cannot be

autodetected because it has no header, like some vhd/vpc files.

@item cluster_size

Changes the cluster size (must be power-of-2 between 4K and 64K). Smaller

cluster sizes can improve the image file size whereas larger cluster sizes

generally provide better performance.

@item table_size

Changes the number of clusters per L1/L2 table (must be power-of-2 between 1

and 16).  There is normally no need to change this value but this option can be

used for performance benchmarking.

@end table

@item qcow

Old QEMU image format with support for backing files, compact image files,

encryption and compression.

Supported options:

@table @code

@item backing_file

File name of a base image (see @option{create} subcommand)

@item encryption

If this option is set to @code{on}, the image is encrypted.

@end table

@item cow

User Mode Linux Copy On Write image format. It is supported only for

compatibility with previous versions.

Supported options:

@table @code

@item backing_file

File name of a base image (see @option{create} subcommand)

@end table

@item vdi

VirtualBox 1.1 compatible image format.

Supported options:

@table @code

@item static

If this option is set to @code{on}, the image is created with metadata

preallocation.

@end table

@item vmdk

VMware 3 and 4 compatible image format.

Supported options:

@table @code

@item backing_file

File name of a base image (see @option{create} subcommand).

@item compat6

Create a VMDK version 6 image (instead of version 4)

@item subformat

Specifies which VMDK subformat to use. Valid options are

@code{monolithicSparse} (default),

@code{monolithicFlat},

@code{twoGbMaxExtentSparse},

@code{twoGbMaxExtentFlat} and

@code{streamOptimized}.

@end table

@item vpc

VirtualPC compatible image format (VHD).

Supported options:

@table @code

@item subformat

Specifies which VHD subformat to use. Valid options are

@code{dynamic} (default) and @code{fixed}.

@end table

@end table

@subsubsection Read-only formats

More disk image file formats are supported in a read-only mode.

@table @option

@item bochs

Bochs images of @code{growing} type.

@item cloop

Linux Compressed Loop image, useful only to reuse directly compressed

CD-ROM images present for example in the Knoppix CD-ROMs.

@item dmg

Apple disk image.

@item parallels

Parallels disk image format.

@end table

@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

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

change or eject media.

@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-system-i386 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-system-i386 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-system-i386 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 disk_images_nbd

@subsection NBD access

QEMU can access directly to block device exported using the Network Block Device

protocol.

@example

qemu-system-i386 linux.img -hdb nbd://my_nbd_server.mydomain.org:1024/

@end example

If the NBD server is located on the same host, you can use an unix socket instead

of an inet socket:

@example

qemu-system-i386 linux.img -hdb nbd+unix://?socket=/tmp/my_socket

@end example

In this case, the block device must be exported using qemu-nbd:

@example

qemu-nbd --socket=/tmp/my_socket my_disk.qcow2

@end example

The use of qemu-nbd allows to share a disk between several guests:

@example

qemu-nbd --socket=/tmp/my_socket --share=2 my_disk.qcow2

@end example

@noindent

and then you can use it with two guests:

@example

qemu-system-i386 linux1.img -hdb nbd+unix://?socket=/tmp/my_socket

qemu-system-i386 linux2.img -hdb nbd+unix://?socket=/tmp/my_socket

@end example

If the nbd-server uses named exports (supported since NBD 2.9.18, or with QEMU's

own embedded NBD server), you must specify an export name in the URI:

@example

qemu-system-i386 -cdrom nbd://localhost/debian-500-ppc-netinst

qemu-system-i386 -cdrom nbd://localhost/openSUSE-11.1-ppc-netinst

@end example

The URI syntax for NBD is supported since QEMU 1.3.  An alternative syntax is

also available.  Here are some example of the older syntax:

@example

qemu-system-i386 linux.img -hdb nbd:my_nbd_server.mydomain.org:1024

qemu-system-i386 linux2.img -hdb nbd:unix:/tmp/my_socket

qemu-system-i386 -cdrom nbd:localhost:10809:exportname=debian-500-ppc-netinst

@end example

@node disk_images_sheepdog

@subsection Sheepdog disk images

Sheepdog is a distributed storage system for QEMU.  It provides highly

available block level storage volumes that can be attached to

QEMU-based virtual machines.

You can create a Sheepdog disk image with the command:

@example

qemu-img create sheepdog:@var{image} @var{size}

@end example

where @var{image} is the Sheepdog image name and @var{size} is its

size.

To import the existing @var{filename} to Sheepdog, you can use a

convert command.

@example

qemu-img convert @var{filename} sheepdog:@var{image}

@end example

You can boot from the Sheepdog disk image with the command:

@example

qemu-system-i386 sheepdog:@var{image}

@end example

You can also create a snapshot of the Sheepdog image like qcow2.

@example

qemu-img snapshot -c @var{tag} sheepdog:@var{image}

@end example

where @var{tag} is a tag name of the newly created snapshot.

To boot from the Sheepdog snapshot, specify the tag name of the

snapshot.

@example

qemu-system-i386 sheepdog:@var{image}:@var{tag}

@end example

You can create a cloned image from the existing snapshot.

@example

qemu-img create -b sheepdog:@var{base}:@var{tag} sheepdog:@var{image}

@end example

where @var{base} is a image name of the source snapshot and @var{tag}

is its tag name.

If the Sheepdog daemon doesn't run on the local host, you need to

specify one of the Sheepdog servers to connect to.

@example

qemu-img create sheepdog:@var{hostname}:@var{port}:@var{image} @var{size}

qemu-system-i386 sheepdog:@var{hostname}:@var{port}:@var{image}

@end example

@node disk_images_iscsi

@subsection iSCSI LUNs

iSCSI is a popular protocol used to access SCSI devices across a computer

network.

There are two different ways iSCSI devices can be used by QEMU.

The first method is to mount the iSCSI LUN on the host, and make it appear as

any other ordinary SCSI device on the host and then to access this device as a

/dev/sd device from QEMU. How to do this differs between host OSes.

The second method involves using the iSCSI initiator that is built into

QEMU. This provides a mechanism that works the same way regardless of which

host OS you are running QEMU on. This section will describe this second method

of using iSCSI together with QEMU.

In QEMU, iSCSI devices are described using special iSCSI URLs

@example

URL syntax:

iscsi://[<username>[%<password>]@@]<host>[:<port>]/<target-iqn-name>/<lun>

@end example

Username and password are optional and only used if your target is set up

using CHAP authentication for access control.

Alternatively the username and password can also be set via environment

variables to have these not show up in the process list

@example

export LIBISCSI_CHAP_USERNAME=<username>

export LIBISCSI_CHAP_PASSWORD=<password>

iscsi://<host>/<target-iqn-name>/<lun>

@end example

Various session related parameters can be set via special options, either

in a configuration file provided via '-readconfig' or directly on the

command line.

If the initiator-name is not specified qemu will use a default name

of 'iqn.2008-11.org.linux-kvm[:<name>'] where <name> is the name of the

virtual machine.

@example

Setting a specific initiator name to use when logging in to the target

-iscsi initiator-name=iqn.qemu.test:my-initiator

@end example

@example

Controlling which type of header digest to negotiate with the target

-iscsi header-digest=CRC32C|CRC32C-NONE|NONE-CRC32C|NONE

@end example

These can also be set via a configuration file

@example

[iscsi]

  user = "CHAP username"

  password = "CHAP password"

  initiator-name = "iqn.qemu.test:my-initiator"

  # header digest is one of CRC32C|CRC32C-NONE|NONE-CRC32C|NONE

  header-digest = "CRC32C"

@end example

Setting the target name allows different options for different targets

@example

[iscsi "iqn.target.name"]

  user = "CHAP username"

  password = "CHAP password"

  initiator-name = "iqn.qemu.test:my-initiator"

  # header digest is one of CRC32C|CRC32C-NONE|NONE-CRC32C|NONE

  header-digest = "CRC32C"

@end example

Howto use a configuration file to set iSCSI configuration options:

@example

cat >iscsi.conf <<EOF

[iscsi]

  user = "me"

  password = "my password"

  initiator-name = "iqn.qemu.test:my-initiator"

  header-digest = "CRC32C"

EOF

qemu-system-i386 -drive file=iscsi://127.0.0.1/iqn.qemu.test/1 \

    -readconfig iscsi.conf

@end example

Howto set up a simple iSCSI target on loopback and accessing it via QEMU:

@example

This example shows how to set up an iSCSI target with one CDROM and one DISK

using the Linux STGT software target. This target is available on Red Hat based

systems as the package 'scsi-target-utils'.

tgtd --iscsi portal=127.0.0.1:3260

tgtadm --lld iscsi --op new --mode target --tid 1 -T iqn.qemu.test

tgtadm --lld iscsi --mode logicalunit --op new --tid 1 --lun 1 \

    -b /IMAGES/disk.img --device-type=disk

tgtadm --lld iscsi --mode logicalunit --op new --tid 1 --lun 2 \

    -b /IMAGES/cd.iso --device-type=cd

tgtadm --lld iscsi --op bind --mode target --tid 1 -I ALL

qemu-system-i386 -iscsi initiator-name=iqn.qemu.test:my-initiator \

    -boot d -drive file=iscsi://127.0.0.1/iqn.qemu.test/1 \

    -cdrom iscsi://127.0.0.1/iqn.qemu.test/2

@end example

@node disk_images_gluster

@subsection GlusterFS disk images

GlusterFS is an user space distributed file system.

You can boot from the GlusterFS disk image with the command:

@example

qemu-system-x86_64 -drive file=gluster[+@var{transport}]://[@var{server}[:@var{port}]]/@var{volname}/@var{image}[?socket=...]

@end example

@var{gluster} is the protocol.

@var{transport} specifies the transport type used to connect to gluster

management daemon (glusterd). Valid transport types are

tcp, unix and rdma. If a transport type isn't specified, then tcp

type is assumed.

@var{server} specifies the server where the volume file specification for

the given volume resides. This can be either hostname, ipv4 address

or ipv6 address. ipv6 address needs to be within square brackets [ ].

If transport type is unix, then @var{server} field should not be specifed.

Instead @var{socket} field needs to be populated with the path to unix domain

socket.

@var{port} is the port number on which glusterd is listening. This is optional

and if not specified, QEMU will send 0 which will make gluster to use the

default port. If the transport type is unix, then @var{port} should not be

specified.

@var{volname} is the name of the gluster volume which contains the disk image.

@var{image} is the path to the actual disk image that resides on gluster volume.

You can create a GlusterFS disk image with the command:

@example

qemu-img create gluster://@var{server}/@var{volname}/@var{image} @var{size}

@end example

Examples

@example

qemu-system-x86_64 -drive file=gluster://1.2.3.4/testvol/a.img

qemu-system-x86_64 -drive file=gluster+tcp://1.2.3.4/testvol/a.img

qemu-system-x86_64 -drive file=gluster+tcp://1.2.3.4:24007/testvol/dir/a.img

qemu-system-x86_64 -drive file=gluster+tcp://[1:2:3:4:5:6:7:8]/testvol/dir/a.img

qemu-system-x86_64 -drive file=gluster+tcp://[1:2:3:4:5:6:7:8]:24007/testvol/dir/a.img

qemu-system-x86_64 -drive file=gluster+tcp://server.domain.com:24007/testvol/dir/a.img

qemu-system-x86_64 -drive file=gluster+unix:///testvol/dir/a.img?socket=/tmp/glusterd.socket

qemu-system-x86_64 -drive file=gluster+rdma://1.2.3.4:24007/testvol/a.img

@end example

@node pcsys_network

@section Network emulation

QEMU can simulate several network cards (PCI or ISA cards on the PC

target) and can connect them to an arbitrary number of Virtual Local

Area Networks (VLANs). Host TAP devices can be connected to any QEMU

VLAN. VLAN can be connected between separate instances of QEMU to

simulate large networks. For simpler usage, a non privileged user mode

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

connection.

@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.

@subsubsection Linux host

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{sec_invocation} to have examples of command lines using the

TAP network interfaces.

@subsubsection Windows host

There is a virtual ethernet driver for Windows 2000/XP systems, called

TAP-Win32. But it is not included in standard QEMU for Windows,

so you will need to get it separately. It is part of OpenVPN package,

so download OpenVPN from : @url{http://openvpn.net/}.

@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 privilege 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 privileges. It means you can only ping the local

router (10.0.2.2).

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

server.

When using the @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 pcsys_other_devs

@section Other Devices

@subsection Inter-VM Shared Memory device

With KVM enabled on a Linux host, a shared memory device is available.  Guests

map a POSIX shared memory region into the guest as a PCI device that enables

zero-copy communication to the application level of the guests.  The basic

syntax is:

@example

qemu-system-i386 -device ivshmem,size=<size in format accepted by -m>[,shm=<shm name>]

@end example

If desired, interrupts can be sent between guest VMs accessing the same shared

memory region.  Interrupt support requires using a shared memory server and

using a chardev socket to connect to it.  The code for the shared memory server

is qemu.git/contrib/ivshmem-server.  An example syntax when using the shared

memory server is:

@example

qemu-system-i386 -device ivshmem,size=<size in format accepted by -m>[,chardev=<id>]

                 [,msi=on][,ioeventfd=on][,vectors=n][,role=peer|master]

qemu-system-i386 -chardev socket,path=<path>,id=<id>

@end example

When using the server, the guest will be assigned a VM ID (>=0) that allows guests

using the same server to communicate via interrupts.  Guests can read their

VM ID from a device register (see example code).  Since receiving the shared

memory region from the server is asynchronous, there is a (small) chance the

guest may boot before the shared memory is attached.  To allow an application

to ensure shared memory is attached, the VM ID register will return -1 (an

invalid VM ID) until the memory is attached.  Once the shared memory is

attached, the VM ID will return the guest's valid VM ID.  With these semantics,

the guest application can check to ensure the shared memory is attached to the

guest before proceeding.

The @option{role} argument can be set to either master or peer and will affect

how the shared memory is migrated.  With @option{role=master}, the guest will

copy the shared memory on migration to the destination host.  With

@option{role=peer}, the guest will not be able to migrate with the device attached.

With the @option{peer} case, the device should be detached and then reattached

after migration using the PCI hotplug support.

@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 syntax is:

@example

qemu-system-i386 -kernel arch/i386/boot/bzImage -hda root-2.4.20.img -append "root=/dev/hda"

@end example

Use @option{-kernel} to provide the Linux kernel image and

@option{-append} to give the kernel command line arguments. The

@option{-initrd} option can be used to provide an INITRD image.

When using the direct Linux boot, a disk image for the first hard disk

@file{hda} is required because its boot sector is used to launch the

Linux kernel.

If you do not need graphical output, you can disable it and redirect

the virtual serial port and the QEMU monitor to the console with the

@option{-nographic} option. The typical command line is:

@example

qemu-system-i386 -kernel arch/i386/boot/bzImage -hda root-2.4.20.img \

                 -append "root=/dev/hda console=ttyS0" -nographic

@end example

Use @key{Ctrl-a c} to switch between the serial console and the

monitor (@pxref{pcsys_keys}).

@node pcsys_usb

@section USB emulation

QEMU emulates a PCI UHCI USB controller. You can virtually plug

virtual USB devices or real host USB devices (experimental, works only

on Linux hosts).  QEMU will automatically create and connect virtual USB hubs

as necessary to connect multiple USB devices.

@menu

* usb_devices::

* host_usb_devices::

@end menu

@node usb_devices

@subsection Connecting USB devices

USB devices can be connected with the @option{-usbdevice} commandline option

or the @code{usb_add} monitor command.  Available devices are:

@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:@var{file}

Mass storage device based on @var{file} (@pxref{disk_images})

@item host:@var{bus.addr}

Pass through the host device identified by @var{bus.addr}

(Linux only)

@item host:@var{vendor_id:product_id}

Pass through the host device identified by @var{vendor_id:product_id}

(Linux only)

@item wacom-tablet

Virtual Wacom PenPartner tablet.  This device is similar to the @code{tablet}

above but it can be used with the tslib library because in addition to touch

coordinates it reports touch pressure.

@item keyboard

Standard USB keyboard.  Will override the PS/2 keyboard (if present).

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

Serial converter. This emulates an FTDI FT232BM chip connected to host character

device @var{dev}. The available character devices are the same as for the

@code{-serial} option. The @code{vendorid} and @code{productid} options can be

used to override the default 0403:6001. For instance,

@example

usb_add serial:productid=FA00:tcp:192.168.0.2:4444

@end example

will connect to tcp port 4444 of ip 192.168.0.2, and plug that to the virtual

serial converter, faking a Matrix Orbital LCD Display (USB ID 0403:FA00).

@item braille

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

or fake device.

@item net:@var{options}

Network adapter that supports CDC ethernet and RNDIS protocols.  @var{options}

specifies NIC options as with @code{-net nic,}@var{options} (see description).

For instance, user-mode networking can be used with

@example

qemu-system-i386 [...OPTIONS...] -net user,vlan=0 -usbdevice net:vlan=0

@end example

Currently this cannot be used in machines that support PCI NICs.

@item bt[:@var{hci-type}]

Bluetooth dongle whose type is specified in the same format as with

the @option{-bt hci} option, @pxref{bt-hcis,,allowed HCI types}.  If

no type is given, the HCI logic corresponds to @code{-bt hci,vlan=0}.

This USB device implements the USB Transport Layer of HCI.  Example

usage:

@example

qemu-system-i386 [...OPTIONS...] -usbdevice bt:hci,vlan=3 -bt device:keyboard,vlan=3

@end example

@end table

@node host_usb_devices

@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.

@enumerate

@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:

@example

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:

@example

chown -R myuid /proc/bus/usb

@end example

@item Launch QEMU and do in the monitor:

@example

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:

@example

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 vnc_security

@section VNC security

The VNC server capability provides access to the graphical console

of the guest VM across the network. This has a number of security

considerations depending on the deployment scenarios.

@menu

* vnc_sec_none::

* vnc_sec_password::

* vnc_sec_certificate::

* vnc_sec_certificate_verify::

* vnc_sec_certificate_pw::

* vnc_sec_sasl::

* vnc_sec_certificate_sasl::

* vnc_generate_cert::

* vnc_setup_sasl::

@end menu

@node vnc_sec_none

@subsection Without passwords

The simplest VNC server setup does not include any form of authentication.

For this setup it is recommended to restrict it to listen on a UNIX domain

socket only. For example

@example

qemu-system-i386 [...OPTIONS...] -vnc unix:/home/joebloggs/.qemu-myvm-vnc

@end example

This ensures that only users on local box with read/write access to that

path can access the VNC server. To securely access the VNC server from a

remote machine, a combination of netcat+ssh can be used to provide a secure

tunnel.

@node vnc_sec_password

@subsection With passwords

The VNC protocol has limited support for password based authentication. Since

the protocol limits passwords to 8 characters it should not be considered

to provide high security. The password can be fairly easily brute-forced by

a client making repeat connections. For this reason, a VNC server using password

authentication should be restricted to only listen on the loopback interface

or UNIX domain sockets. Password authentication is not supported when operating

in FIPS 140-2 compliance mode as it requires the use of the DES cipher. Password

authentication is requested with the @code{password} option, and then once QEMU

is running the password is set with the monitor. Until the monitor is used to

set the password all clients will be rejected.

@example

qemu-system-i386 [...OPTIONS...] -vnc :1,password -monitor stdio

(qemu) change vnc password

Password: ********

(qemu)

@end example

@node vnc_sec_certificate

@subsection With x509 certificates

The QEMU VNC server also implements the VeNCrypt extension allowing use of

TLS for encryption of the session, and x509 certificates for authentication.

The use of x509 certificates is strongly recommended, because TLS on its

own is susceptible to man-in-the-middle attacks. Basic x509 certificate

support provides a secure session, but no authentication. This allows any

client to connect, and provides an encrypted session.

@example

qemu-system-i386 [...OPTIONS...] -vnc :1,tls,x509=/etc/pki/qemu -monitor stdio

@end example

In the above example @code{/etc/pki/qemu} should contain at least three files,

@code{ca-cert.pem}, @code{server-cert.pem} and @code{server-key.pem}. Unprivileged

users will want to use a private directory, for example @code{$HOME/.pki/qemu}.

NB the @code{server-key.pem} file should be protected with file mode 0600 to

only be readable by the user owning it.

@node vnc_sec_certificate_verify

@subsection With x509 certificates and client verification

Certificates can also provide a means to authenticate the client connecting.

The server will request that the client provide a certificate, which it will

then validate against the CA certificate. This is a good choice if deploying

in an environment with a private internal certificate authority.

@example

qemu-system-i386 [...OPTIONS...] -vnc :1,tls,x509verify=/etc/pki/qemu -monitor stdio

@end example

@node vnc_sec_certificate_pw

@subsection With x509 certificates, client verification and passwords

Finally, the previous method can be combined with VNC password authentication

to provide two layers of authentication for clients.

@example

qemu-system-i386 [...OPTIONS...] -vnc :1,password,tls,x509verify=/etc/pki/qemu -monitor stdio

(qemu) change vnc password

Password: ********

(qemu)

@end example

@node vnc_sec_sasl

@subsection With SASL authentication

The SASL authentication method is a VNC extension, that provides an

easily extendable, pluggable authentication method. This allows for

integration with a wide range of authentication mechanisms, such as

PAM, GSSAPI/Kerberos, LDAP, SQL databases, one-time keys and more.

The strength of the authentication depends on the exact mechanism

configured. If the chosen mechanism also provides a SSF layer, then

it will encrypt the datastream as well.

Refer to the later docs on how to choose the exact SASL mechanism

used for authentication, but assuming use of one supporting SSF,

then QEMU can be launched with:

@example

qemu-system-i386 [...OPTIONS...] -vnc :1,sasl -monitor stdio

@end example

@node vnc_sec_certificate_sasl

@subsection With x509 certificates and SASL authentication

If the desired SASL authentication mechanism does not supported

SSF layers, then it is strongly advised to run it in combination

with TLS and x509 certificates. This provides securely encrypted

data stream, avoiding risk of compromising of the security

credentials. This can be enabled, by combining the 'sasl' option

with the aforementioned TLS + x509 options:

@example

qemu-system-i386 [...OPTIONS...] -vnc :1,tls,x509,sasl -monitor stdio

@end example

@node vnc_generate_cert

@subsection Generating certificates for VNC

The GNU TLS packages provides a command called @code{certtool} which can

be used to generate certificates and keys in PEM format. At a minimum it

is necessary to setup a certificate authority, and issue certificates to

each server. If using certificates for authentication, then each client

will also need to be issued a certificate. The recommendation is for the

server to keep its certificates in either @code{/etc/pki/qemu} or for

unprivileged users in @code{$HOME/.pki/qemu}.

@menu

* vnc_generate_ca::

* vnc_generate_server::

* vnc_generate_client::

@end menu

@node vnc_generate_ca

@subsubsection Setup the Certificate Authority

This step only needs to be performed once per organization / organizational

unit. First the CA needs a private key. This key must be kept VERY secret

and secure. If this key is compromised the entire trust chain of the certificates

issued with it is lost.

@example

# certtool --generate-privkey > ca-key.pem

@end example

A CA needs to have a public certificate. For simplicity it can be a self-signed

certificate, or one issue by a commercial certificate issuing authority. To

generate a self-signed certificate requires one core piece of information, the

name of the organization.

@example

# cat > ca.info <<EOF

cn = Name of your organization

ca

cert_signing_key

EOF

# certtool --generate-self-signed \

           --load-privkey ca-key.pem

           --template ca.info \

           --outfile ca-cert.pem

@end example

The @code{ca-cert.pem} file should be copied to all servers and clients wishing to utilize

TLS support in the VNC server. The @code{ca-key.pem} must not be disclosed/copied at all.

@node vnc_generate_server

@subsubsection Issuing server certificates

Each server (or host) needs to be issued with a key and certificate. When connecting

the certificate is sent to the client which validates it against the CA certificate.

The core piece of information for a server certificate is the hostname. This should

be the fully qualified hostname that the client will connect with, since the client

will typically also verify the hostname in the certificate. On the host holding the

secure CA private key:

@example

# cat > server.info <<EOF

organization = Name  of your organization

cn = server.foo.example.com

tls_www_server

encryption_key

signing_key

EOF

# certtool --generate-privkey > server-key.pem

# certtool --generate-certificate \

           --load-ca-certificate ca-cert.pem \

           --load-ca-privkey ca-key.pem \

           --load-privkey server server-key.pem \

           --template server.info \

           --outfile server-cert.pem

@end example

The @code{server-key.pem} and @code{server-cert.pem} files should now be securely copied

to the server for which they were generated. The @code{server-key.pem} is security

sensitive and should be kept protected with file mode 0600 to prevent disclosure.

@node vnc_generate_client

@subsubsection Issuing client certificates

If the QEMU VNC server is to use the @code{x509verify} option to validate client

certificates as its authentication mechanism, each client also needs to be issued

a certificate. The client certificate contains enough metadata to uniquely identify

the client, typically organization, state, city, building, etc. On the host holding

the secure CA private key:

@example

# cat > client.info <<EOF

country = GB

state = London

locality = London

organiazation = Name of your organization

cn = client.foo.example.com

tls_www_client

encryption_key

signing_key

EOF

# certtool --generate-privkey > client-key.pem

# certtool --generate-certificate \

           --load-ca-certificate ca-cert.pem \

           --load-ca-privkey ca-key.pem \

           --load-privkey client-key.pem \

           --template client.info \

           --outfile client-cert.pem

@end example

The @code{client-key.pem} and @code{client-cert.pem} files should now be securely

copied to the client for which they were generated.

@node vnc_setup_sasl

@subsection Configuring SASL mechanisms

The following documentation assumes use of the Cyrus SASL implementation on a

Linux host, but the principals should apply to any other SASL impl. When SASL

is enabled, the mechanism configuration will be loaded from system default

SASL service config /etc/sasl2/qemu.conf. If running QEMU as an

unprivileged user, an environment variable SASL_CONF_PATH can be used

to make it search alternate locations for the service config.

The default configuration might contain

@example

mech_list: digest-md5

sasldb_path: /etc/qemu/passwd.db

@end example

This says to use the 'Digest MD5' mechanism, which is similar to the HTTP

Digest-MD5 mechanism. The list of valid usernames & passwords is maintained

in the /etc/qemu/passwd.db file, and can be updated using the saslpasswd2

command. While this mechanism is easy to configure and use, it is not

considered secure by modern standards, so only suitable for developers /

ad-hoc testing.