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
+QEMU uses the PC BIOS from the Seabios project and the Plex86/Bochs LGPL
VGA BIOS.
QEMU uses YM3812 emulation by Tatsuyuki Satoh.
* 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
+* disk_images_ssh:: Secure Shell (ssh) disk images
@end menu
@node disk_images_quickstart
@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
You can create a Sheepdog disk image with the command:
@example
-qemu-img create sheepdog:@var{image} @var{size}
+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}
+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}
+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}
+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}
+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}
+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.
+You can use an unix socket instead of an inet socket:
+
+@example
+qemu-system-i386 sheepdog+unix:///@var{image}?socket=@var{path}
+@end example
+
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}
+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
qemu-system-x86_64 -drive file=gluster+rdma://1.2.3.4:24007/testvol/a.img
@end example
+@node disk_images_ssh
+@subsection Secure Shell (ssh) disk images
+
+You can access disk images located on a remote ssh server
+by using the ssh protocol:
+
+@example
+qemu-system-x86_64 -drive file=ssh://[@var{user}@@]@var{server}[:@var{port}]/@var{path}[?host_key_check=@var{host_key_check}]
+@end example
+
+Alternative syntax using properties:
+
+@example
+qemu-system-x86_64 -drive file.driver=ssh[,file.user=@var{user}],file.host=@var{server}[,file.port=@var{port}],file.path=@var{path}[,file.host_key_check=@var{host_key_check}]
+@end example
+
+@var{ssh} is the protocol.
+
+@var{user} is the remote user. If not specified, then the local
+username is tried.
+
+@var{server} specifies the remote ssh server. Any ssh server can be
+used, but it must implement the sftp-server protocol. Most Unix/Linux
+systems should work without requiring any extra configuration.
+
+@var{port} is the port number on which sshd is listening. By default
+the standard ssh port (22) is used.
+
+@var{path} is the path to the disk image.
+
+The optional @var{host_key_check} parameter controls how the remote
+host's key is checked. The default is @code{yes} which means to use
+the local @file{.ssh/known_hosts} file. Setting this to @code{no}
+turns off known-hosts checking. Or you can check that the host key
+matches a specific fingerprint:
+@code{host_key_check=md5:78:45:8e:14:57:4f:d5:45:83:0a:0e:f3:49:82:c9:c8}
+(@code{sha1:} can also be used as a prefix, but note that OpenSSH
+tools only use MD5 to print fingerprints).
+
+Currently authentication must be done using ssh-agent. Other
+authentication methods may be supported in future.
+
+Note: Many ssh servers do not support an @code{fsync}-style operation.
+The ssh driver cannot guarantee that disk flush requests are
+obeyed, and this causes a risk of disk corruption if the remote
+server or network goes down during writes. The driver will
+print a warning when @code{fsync} is not supported:
+
+warning: ssh server @code{ssh.example.com:22} does not support fsync
+
+With sufficiently new versions of libssh2 and OpenSSH, @code{fsync} is
+supported.
+
@node pcsys_network
@section Network emulation
The emulation is somewhat complete. SMP up to 16 CPUs is supported,
but Linux limits the number of usable CPUs to 4.
-It's also possible to simulate a SPARCstation 2 (sun4c architecture),
-SPARCserver 1000, or SPARCcenter 2000 (sun4d architecture), but these
-emulators are not usable yet.
-
-QEMU emulates the following sun4m/sun4c/sun4d peripherals:
+QEMU emulates the following sun4m peripherals:
@itemize @minus
@item
-IOMMU or IO-UNITs
+IOMMU
@item
TCX Frame buffer
@item
-prom-env 'boot-device=sd(0,2,0):d' -prom-env 'boot-args=linux single'
@end example
-@item -M [SS-4|SS-5|SS-10|SS-20|SS-600MP|LX|Voyager|SPARCClassic] [|SPARCbook|SS-2|SS-1000|SS-2000]
+@item -M [SS-4|SS-5|SS-10|SS-20|SS-600MP|LX|Voyager|SPARCClassic] [|SPARCbook]
Set the emulated machine type. Default is SS-5.
Set the x86 stack size in bytes (default=524288)
@item -cpu model
Select CPU model (-cpu help for list and additional feature selection)
-@item -ignore-environment
-Start with an empty environment. Without this option,
-the initial environment is a copy of the caller's environment.
@item -E @var{var}=@var{value}
Set environment @var{var} to @var{value}.
@item -U @var{var}
Debug options:
@table @option
-@item -d
-Activate log (logfile=/tmp/qemu.log)
+@item -d item1,...
+Activate logging of the specified items (use '-d help' for a list of log items)
@item -p pagesize
Act as if the host page size was 'pagesize' bytes
@item -g port
Debug options:
@table @option
-@item -d
-Activate log (logfile=/tmp/qemu.log)
+@item -d item1,...
+Activate logging of the specified items (use '-d help' for a list of log items)
@item -p pagesize
Act as if the host page size was 'pagesize' bytes
@item -singlestep
projects / qemu.git / blobdiff