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.
* 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
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).
+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.
@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.
+newer understand (this is the default). 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.
+If this option is set to @code{on}, the image is encrypted with 128-bit AES-CBC.
+
+The use of encryption in qcow and qcow2 images is considered to be flawed by
+modern cryptography standards, suffering from a number of design problems:
+
+@itemize @minus
+@item The AES-CBC cipher is used with predictable initialization vectors based
+on the sector number. This makes it vulnerable to chosen plaintext attacks
+which can reveal the existence of encrypted data.
+@item The user passphrase is directly used as the encryption key. A poorly
+chosen or short passphrase will compromise the security of the encryption.
+@item In the event of the passphrase being compromised there is no way to
+change the passphrase to protect data in any qcow images. The files must
+be cloned, using a different encryption passphrase in the new file. The
+original file must then be securely erased using a program like shred,
+though even this is ineffective with many modern storage technologies.
+@end itemize
-Encryption uses the AES format which is very secure (128 bit keys). Use
-a long password (16 characters) to get maximum protection.
+Use of qcow / qcow2 encryption is thus strongly discouraged. Users are
+recommended to use an alternative encryption technology such as the
+Linux dm-crypt / LUKS system.
@item cluster_size
Changes the qcow2 cluster size (must be between 512 and 2M). Smaller cluster
This option can only be enabled if @code{compat=1.1} is specified.
+@item nocow
+If this option is set to @code{on}, it will turn off COW of the file. It's only
+valid on btrfs, no effect on other file systems.
+
+Btrfs has low performance when hosting a VM image file, even more when the guest
+on the VM also using btrfs as file system. Turning off COW is a way to mitigate
+this bad performance. Generally there are two ways to turn off COW on btrfs:
+a) Disable it by mounting with nodatacow, then all newly created files will be
+NOCOW. b) For an empty file, add the NOCOW file attribute. That's what this option
+does.
+
+Note: this option is only valid to new or empty files. If there is an existing
+file which is COW and has data blocks already, it couldn't be changed to NOCOW
+by setting @code{nocow=on}. One can issue @code{lsattr filename} to check if
+the NOCOW flag is set or not (Capital 'C' is NOCOW flag).
+
@end table
@item qed
Specifies which VHD subformat to use. Valid options are
@code{dynamic} (default) and @code{fixed}.
@end table
+
+@item VHDX
+Hyper-V compatible image format (VHDX).
+Supported options:
+@table @code
+@item subformat
+Specifies which VHDX subformat to use. Valid options are
+@code{dynamic} (default) and @code{fixed}.
+@item block_state_zero
+Force use of payload blocks of type 'ZERO'.
+@item block_size
+Block size; min 1 MB, max 256 MB. 0 means auto-calculate based on image size.
+@item log_size
+Log size; min 1 MB.
+@end table
@end table
@subsubsection Read-only formats
qemu-nbd --socket=/tmp/my_socket my_disk.qcow2
@end example
-The use of qemu-nbd allows to share a disk between several guests:
+The use of qemu-nbd allows sharing of a disk between several guests:
@example
qemu-nbd --socket=/tmp/my_socket --share=2 my_disk.qcow2
@end example
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 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).
+Note that ICMP traffic in general does not work with user mode networking.
+@code{ping}, aka. ICMP echo, to the local router (10.0.2.2) shall work,
+however. If you're using QEMU on Linux >= 3.0, it can use unprivileged ICMP
+ping sockets to allow @code{ping} to the Internet. The host admin has to set
+the ping_group_range in order to grant access to those sockets. To allow ping
+for GID 100 (usually users group):
+
+@example
+echo 100 100 > /proc/sys/net/ipv4/ping_group_range
+@end example
When using the built-in TFTP server, the router is also the TFTP
server.
@item -g @var{W}x@var{H}[x@var{DEPTH}]
-Set the initial VGA graphic mode. The default is 800x600x15.
+Set the initial VGA graphic mode. The default is 800x600x32.
@item -prom-env @var{string}
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
+TCX or cgthree Frame buffer
@item
Lance (Am7990) Ethernet
@item
A sample Linux 2.6 series kernel and ram disk image are available on
the QEMU web site. There are still issues with NetBSD and OpenBSD, but
-some kernel versions work. Please note that currently Solaris kernels
+some kernel versions work. Please note that currently older Solaris kernels
don't work probably due to interface issues between OpenBIOS and
Solaris.
@item -g @var{W}x@var{H}x[x@var{DEPTH}]
-Set the initial TCX graphic mode. The default is 1024x768x8, currently
-the only other possible mode is 1024x768x24.
+Set the initial graphics mode. For TCX, the default is 1024x768x8 with the
+option of 1024x768x24. For cgthree, the default is 1024x768x8 with the option
+of 1152x900x8 for people who wish to use OBP.
@item -prom-env @var{string}
-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}
projects / lisovros / qemu_apohw.git / blobdiff