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Block driver documentation is available in qemu-doc.html. It would be convenient to have documentation for formats, protocols, and filter drivers in a man page. Extract the relevant part of qemu-doc.html into a new file called docs/qemu-block-drivers.texi. This file can also be built as a stand-alone document (man, html, etc). Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>pull/69/head
Stefan Hajnoczi
9 years ago
committed by
Kevin Wolf
Kevin Wolf
3 changed files with 810 additions and 781 deletions
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@c man begin SYNOPSIS |
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QEMU block driver reference manual |
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@c man end |
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|
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@c man begin DESCRIPTION |
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|
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@node disk_images_formats |
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@subsection Disk image file formats |
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|
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QEMU supports many image file formats that can be used with VMs as well as with |
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any of the tools (like @code{qemu-img}). This includes the preferred formats |
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raw and qcow2 as well as formats that are supported for compatibility with |
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older QEMU versions or other hypervisors. |
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|
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Depending on the image format, different options can be passed to |
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@code{qemu-img create} and @code{qemu-img convert} using the @code{-o} option. |
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This section describes each format and the options that are supported for it. |
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|
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@table @option |
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@item raw |
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|
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Raw disk image format. This format has the advantage of |
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being simple and easily exportable to all other emulators. If your |
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file system supports @emph{holes} (for example in ext2 or ext3 on |
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Linux or NTFS on Windows), then only the written sectors will reserve |
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space. Use @code{qemu-img info} to know the real size used by the |
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image or @code{ls -ls} on Unix/Linux. |
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|
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Supported options: |
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@table @code |
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@item preallocation |
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Preallocation mode (allowed values: @code{off}, @code{falloc}, @code{full}). |
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@code{falloc} mode preallocates space for image by calling posix_fallocate(). |
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@code{full} mode preallocates space for image by writing zeros to underlying |
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storage. |
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@end table |
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|
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@item qcow2 |
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QEMU image format, the most versatile format. Use it to have smaller |
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images (useful if your filesystem does not supports holes, for example |
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on Windows), zlib based compression and support of multiple VM |
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snapshots. |
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|
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Supported options: |
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@table @code |
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@item compat |
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Determines the qcow2 version to use. @code{compat=0.10} uses the |
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traditional image format that can be read by any QEMU since 0.10. |
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@code{compat=1.1} enables image format extensions that only QEMU 1.1 and |
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newer understand (this is the default). Amongst others, this includes |
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zero clusters, which allow efficient copy-on-read for sparse images. |
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|
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@item backing_file |
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File name of a base image (see @option{create} subcommand) |
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@item backing_fmt |
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Image format of the base image |
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@item encryption |
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This option is deprecated and equivalent to @code{encrypt.format=aes} |
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|
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@item encrypt.format |
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|
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If this is set to @code{luks}, it requests that the qcow2 payload (not |
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qcow2 header) be encrypted using the LUKS format. The passphrase to |
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use to unlock the LUKS key slot is given by the @code{encrypt.key-secret} |
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parameter. LUKS encryption parameters can be tuned with the other |
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@code{encrypt.*} parameters. |
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|
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If this is set to @code{aes}, the image is encrypted with 128-bit AES-CBC. |
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The encryption key is given by the @code{encrypt.key-secret} parameter. |
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This encryption format is considered to be flawed by modern cryptography |
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standards, suffering from a number of design problems: |
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|
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@itemize @minus |
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@item The AES-CBC cipher is used with predictable initialization vectors based |
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on the sector number. This makes it vulnerable to chosen plaintext attacks |
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which can reveal the existence of encrypted data. |
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@item The user passphrase is directly used as the encryption key. A poorly |
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chosen or short passphrase will compromise the security of the encryption. |
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@item In the event of the passphrase being compromised there is no way to |
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change the passphrase to protect data in any qcow images. The files must |
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be cloned, using a different encryption passphrase in the new file. The |
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original file must then be securely erased using a program like shred, |
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though even this is ineffective with many modern storage technologies. |
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@end itemize |
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|
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The use of this is no longer supported in system emulators. Support only |
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remains in the command line utilities, for the purposes of data liberation |
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and interoperability with old versions of QEMU. The @code{luks} format |
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should be used instead. |
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|
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@item encrypt.key-secret |
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|
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Provides the ID of a @code{secret} object that contains the passphrase |
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(@code{encrypt.format=luks}) or encryption key (@code{encrypt.format=aes}). |
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|
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@item encrypt.cipher-alg |
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|
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Name of the cipher algorithm and key length. Currently defaults |
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to @code{aes-256}. Only used when @code{encrypt.format=luks}. |
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|
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@item encrypt.cipher-mode |
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|
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Name of the encryption mode to use. Currently defaults to @code{xts}. |
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Only used when @code{encrypt.format=luks}. |
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|
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@item encrypt.ivgen-alg |
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|
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Name of the initialization vector generator algorithm. Currently defaults |
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to @code{plain64}. Only used when @code{encrypt.format=luks}. |
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|
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@item encrypt.ivgen-hash-alg |
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|
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Name of the hash algorithm to use with the initialization vector generator |
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(if required). Defaults to @code{sha256}. Only used when @code{encrypt.format=luks}. |
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|
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@item encrypt.hash-alg |
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|
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Name of the hash algorithm to use for PBKDF algorithm |
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Defaults to @code{sha256}. Only used when @code{encrypt.format=luks}. |
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|
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@item encrypt.iter-time |
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|
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Amount of time, in milliseconds, to use for PBKDF algorithm per key slot. |
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Defaults to @code{2000}. Only used when @code{encrypt.format=luks}. |
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|
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@item cluster_size |
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Changes the qcow2 cluster size (must be between 512 and 2M). Smaller cluster |
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sizes can improve the image file size whereas larger cluster sizes generally |
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provide better performance. |
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|
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@item preallocation |
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Preallocation mode (allowed values: @code{off}, @code{metadata}, @code{falloc}, |
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@code{full}). An image with preallocated metadata is initially larger but can |
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improve performance when the image needs to grow. @code{falloc} and @code{full} |
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preallocations are like the same options of @code{raw} format, but sets up |
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metadata also. |
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|
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@item lazy_refcounts |
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If this option is set to @code{on}, reference count updates are postponed with |
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the goal of avoiding metadata I/O and improving performance. This is |
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particularly interesting with @option{cache=writethrough} which doesn't batch |
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metadata updates. The tradeoff is that after a host crash, the reference count |
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tables must be rebuilt, i.e. on the next open an (automatic) @code{qemu-img |
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check -r all} is required, which may take some time. |
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|
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This option can only be enabled if @code{compat=1.1} is specified. |
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|
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@item nocow |
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If this option is set to @code{on}, it will turn off COW of the file. It's only |
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valid on btrfs, no effect on other file systems. |
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|
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Btrfs has low performance when hosting a VM image file, even more when the guest |
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on the VM also using btrfs as file system. Turning off COW is a way to mitigate |
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this bad performance. Generally there are two ways to turn off COW on btrfs: |
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a) Disable it by mounting with nodatacow, then all newly created files will be |
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NOCOW. b) For an empty file, add the NOCOW file attribute. That's what this option |
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does. |
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|
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Note: this option is only valid to new or empty files. If there is an existing |
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file which is COW and has data blocks already, it couldn't be changed to NOCOW |
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by setting @code{nocow=on}. One can issue @code{lsattr filename} to check if |
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the NOCOW flag is set or not (Capital 'C' is NOCOW flag). |
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|
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@end table |
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|
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@item qed |
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Old QEMU image format with support for backing files and compact image files |
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(when your filesystem or transport medium does not support holes). |
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|
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When converting QED images to qcow2, you might want to consider using the |
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@code{lazy_refcounts=on} option to get a more QED-like behaviour. |
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|
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Supported options: |
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@table @code |
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@item backing_file |
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File name of a base image (see @option{create} subcommand). |
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@item backing_fmt |
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Image file format of backing file (optional). Useful if the format cannot be |
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autodetected because it has no header, like some vhd/vpc files. |
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@item cluster_size |
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Changes the cluster size (must be power-of-2 between 4K and 64K). Smaller |
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cluster sizes can improve the image file size whereas larger cluster sizes |
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generally provide better performance. |
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@item table_size |
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Changes the number of clusters per L1/L2 table (must be power-of-2 between 1 |
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and 16). There is normally no need to change this value but this option can be |
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used for performance benchmarking. |
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@end table |
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|
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@item qcow |
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Old QEMU image format with support for backing files, compact image files, |
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encryption and compression. |
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|
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Supported options: |
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@table @code |
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@item backing_file |
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File name of a base image (see @option{create} subcommand) |
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@item encryption |
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This option is deprecated and equivalent to @code{encrypt.format=aes} |
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|
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@item encrypt.format |
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If this is set to @code{aes}, the image is encrypted with 128-bit AES-CBC. |
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The encryption key is given by the @code{encrypt.key-secret} parameter. |
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This encryption format is considered to be flawed by modern cryptography |
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standards, suffering from a number of design problems enumerated previously |
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against the @code{qcow2} image format. |
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|
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The use of this is no longer supported in system emulators. Support only |
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remains in the command line utilities, for the purposes of data liberation |
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and interoperability with old versions of QEMU. |
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|
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Users requiring native encryption should use the @code{qcow2} format |
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instead with @code{encrypt.format=luks}. |
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|
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@item encrypt.key-secret |
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|
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Provides the ID of a @code{secret} object that contains the encryption |
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key (@code{encrypt.format=aes}). |
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|
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@end table |
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|
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@item luks |
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|
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LUKS v1 encryption format, compatible with Linux dm-crypt/cryptsetup |
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|
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Supported options: |
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@table @code |
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|
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@item key-secret |
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|
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Provides the ID of a @code{secret} object that contains the passphrase. |
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|
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@item cipher-alg |
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|
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Name of the cipher algorithm and key length. Currently defaults |
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to @code{aes-256}. |
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|
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@item cipher-mode |
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|
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Name of the encryption mode to use. Currently defaults to @code{xts}. |
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|
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@item ivgen-alg |
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|
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Name of the initialization vector generator algorithm. Currently defaults |
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to @code{plain64}. |
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|
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@item ivgen-hash-alg |
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|
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Name of the hash algorithm to use with the initialization vector generator |
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(if required). Defaults to @code{sha256}. |
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|
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@item hash-alg |
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|
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Name of the hash algorithm to use for PBKDF algorithm |
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Defaults to @code{sha256}. |
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|
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@item iter-time |
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|
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Amount of time, in milliseconds, to use for PBKDF algorithm per key slot. |
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Defaults to @code{2000}. |
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|
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@end table |
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|
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@item vdi |
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VirtualBox 1.1 compatible image format. |
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Supported options: |
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@table @code |
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@item static |
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If this option is set to @code{on}, the image is created with metadata |
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preallocation. |
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@end table |
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|
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@item vmdk |
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VMware 3 and 4 compatible image format. |
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|
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Supported options: |
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@table @code |
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@item backing_file |
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File name of a base image (see @option{create} subcommand). |
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@item compat6 |
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Create a VMDK version 6 image (instead of version 4) |
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@item hwversion |
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Specify vmdk virtual hardware version. Compat6 flag cannot be enabled |
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if hwversion is specified. |
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@item subformat |
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Specifies which VMDK subformat to use. Valid options are |
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@code{monolithicSparse} (default), |
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@code{monolithicFlat}, |
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@code{twoGbMaxExtentSparse}, |
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@code{twoGbMaxExtentFlat} and |
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@code{streamOptimized}. |
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@end table |
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|
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@item vpc |
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VirtualPC compatible image format (VHD). |
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Supported options: |
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@table @code |
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@item subformat |
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Specifies which VHD subformat to use. Valid options are |
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@code{dynamic} (default) and @code{fixed}. |
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@end table |
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|
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@item VHDX |
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Hyper-V compatible image format (VHDX). |
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Supported options: |
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@table @code |
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@item subformat |
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Specifies which VHDX subformat to use. Valid options are |
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@code{dynamic} (default) and @code{fixed}. |
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@item block_state_zero |
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Force use of payload blocks of type 'ZERO'. Can be set to @code{on} (default) |
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or @code{off}. When set to @code{off}, new blocks will be created as |
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@code{PAYLOAD_BLOCK_NOT_PRESENT}, which means parsers are free to return |
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arbitrary data for those blocks. Do not set to @code{off} when using |
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@code{qemu-img convert} with @code{subformat=dynamic}. |
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@item block_size |
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Block size; min 1 MB, max 256 MB. 0 means auto-calculate based on image size. |
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@item log_size |
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Log size; min 1 MB. |
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@end table |
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@end table |
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|
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@subsubsection Read-only formats |
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More disk image file formats are supported in a read-only mode. |
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@table @option |
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@item bochs |
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Bochs images of @code{growing} type. |
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@item cloop |
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Linux Compressed Loop image, useful only to reuse directly compressed |
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CD-ROM images present for example in the Knoppix CD-ROMs. |
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@item dmg |
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Apple disk image. |
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@item parallels |
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Parallels disk image format. |
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@end table |
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|
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|
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@node host_drives |
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@subsection Using host drives |
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|
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In addition to disk image files, QEMU can directly access host |
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devices. We describe here the usage for QEMU version >= 0.8.3. |
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|
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@subsubsection Linux |
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|
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On Linux, you can directly use the host device filename instead of a |
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disk image filename provided you have enough privileges to access |
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it. For example, use @file{/dev/cdrom} to access to the CDROM. |
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|
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@table @code |
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@item CD |
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You can specify a CDROM device even if no CDROM is loaded. QEMU has |
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specific code to detect CDROM insertion or removal. CDROM ejection by |
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the guest OS is supported. Currently only data CDs are supported. |
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@item Floppy |
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You can specify a floppy device even if no floppy is loaded. Floppy |
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removal is currently not detected accurately (if you change floppy |
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without doing floppy access while the floppy is not loaded, the guest |
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OS will think that the same floppy is loaded). |
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Use of the host's floppy device is deprecated, and support for it will |
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be removed in a future release. |
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@item Hard disks |
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Hard disks can be used. Normally you must specify the whole disk |
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(@file{/dev/hdb} instead of @file{/dev/hdb1}) so that the guest OS can |
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see it as a partitioned disk. WARNING: unless you know what you do, it |
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is better to only make READ-ONLY accesses to the hard disk otherwise |
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you may corrupt your host data (use the @option{-snapshot} command |
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line option or modify the device permissions accordingly). |
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@end table |
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|
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@subsubsection Windows |
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|
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@table @code |
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@item CD |
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The preferred syntax is the drive letter (e.g. @file{d:}). The |
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alternate syntax @file{\\.\d:} is supported. @file{/dev/cdrom} is |
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supported as an alias to the first CDROM drive. |
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|
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Currently there is no specific code to handle removable media, so it |
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is better to use the @code{change} or @code{eject} monitor commands to |
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change or eject media. |
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@item Hard disks |
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Hard disks can be used with the syntax: @file{\\.\PhysicalDrive@var{N}} |
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where @var{N} is the drive number (0 is the first hard disk). |
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|
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WARNING: unless you know what you do, it is better to only make |
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READ-ONLY accesses to the hard disk otherwise you may corrupt your |
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host data (use the @option{-snapshot} command line so that the |
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modifications are written in a temporary file). |
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@end table |
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|
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|
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@subsubsection Mac OS X |
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|
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@file{/dev/cdrom} is an alias to the first CDROM. |
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|
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Currently there is no specific code to handle removable media, so it |
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is better to use the @code{change} or @code{eject} monitor commands to |
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change or eject media. |
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|
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@node disk_images_fat_images |
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@subsection Virtual FAT disk images |
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|
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QEMU can automatically create a virtual FAT disk image from a |
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directory tree. In order to use it, just type: |
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|
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@example |
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qemu-system-i386 linux.img -hdb fat:/my_directory |
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@end example |
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|
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Then you access access to all the files in the @file{/my_directory} |
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directory without having to copy them in a disk image or to export |
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them via SAMBA or NFS. The default access is @emph{read-only}. |
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|
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Floppies can be emulated with the @code{:floppy:} option: |
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|
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@example |
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qemu-system-i386 linux.img -fda fat:floppy:/my_directory |
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@end example |
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|
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A read/write support is available for testing (beta stage) with the |
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@code{:rw:} option: |
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|
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@example |
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qemu-system-i386 linux.img -fda fat:floppy:rw:/my_directory |
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@end example |
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|
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What you should @emph{never} do: |
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@itemize |
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@item use non-ASCII filenames ; |
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@item use "-snapshot" together with ":rw:" ; |
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@item expect it to work when loadvm'ing ; |
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@item write to the FAT directory on the host system while accessing it with the guest system. |
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@end itemize |
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|
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@node disk_images_nbd |
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@subsection NBD access |
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|
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QEMU can access directly to block device exported using the Network Block Device |
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protocol. |
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|
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@example |
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qemu-system-i386 linux.img -hdb nbd://my_nbd_server.mydomain.org:1024/ |
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@end example |
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|
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If the NBD server is located on the same host, you can use an unix socket instead |
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of an inet socket: |
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|
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@example |
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qemu-system-i386 linux.img -hdb nbd+unix://?socket=/tmp/my_socket |
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@end example |
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|
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In this case, the block device must be exported using qemu-nbd: |
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|
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@example |
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qemu-nbd --socket=/tmp/my_socket my_disk.qcow2 |
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@end example |
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|
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The use of qemu-nbd allows sharing of a disk between several guests: |
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@example |
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qemu-nbd --socket=/tmp/my_socket --share=2 my_disk.qcow2 |
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@end example |
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|
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@noindent |
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and then you can use it with two guests: |
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@example |
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qemu-system-i386 linux1.img -hdb nbd+unix://?socket=/tmp/my_socket |
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qemu-system-i386 linux2.img -hdb nbd+unix://?socket=/tmp/my_socket |
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@end example |
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|
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If the nbd-server uses named exports (supported since NBD 2.9.18, or with QEMU's |
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own embedded NBD server), you must specify an export name in the URI: |
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@example |
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qemu-system-i386 -cdrom nbd://localhost/debian-500-ppc-netinst |
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qemu-system-i386 -cdrom nbd://localhost/openSUSE-11.1-ppc-netinst |
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@end example |
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|
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The URI syntax for NBD is supported since QEMU 1.3. An alternative syntax is |
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also available. Here are some example of the older syntax: |
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@example |
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qemu-system-i386 linux.img -hdb nbd:my_nbd_server.mydomain.org:1024 |
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qemu-system-i386 linux2.img -hdb nbd:unix:/tmp/my_socket |
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qemu-system-i386 -cdrom nbd:localhost:10809:exportname=debian-500-ppc-netinst |
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@end example |
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|
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@node disk_images_sheepdog |
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@subsection Sheepdog disk images |
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|
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Sheepdog is a distributed storage system for QEMU. It provides highly |
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available block level storage volumes that can be attached to |
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QEMU-based virtual machines. |
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|
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You can create a Sheepdog disk image with the command: |
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@example |
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qemu-img create sheepdog:///@var{image} @var{size} |
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@end example |
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where @var{image} is the Sheepdog image name and @var{size} is its |
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size. |
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|
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To import the existing @var{filename} to Sheepdog, you can use a |
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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. |
|||
|
|||
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} |
|||
@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[:<uuid>'] where <uuid> is the UUID of the |
|||
virtual machine. If the UUID is not specified qemu will use |
|||
'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 a user space distributed file system. |
|||
|
|||
You can boot from the GlusterFS disk image with the command: |
|||
@example |
|||
URI: |
|||
qemu-system-x86_64 -drive file=gluster[+@var{type}]://[@var{host}[:@var{port}]]/@var{volume}/@var{path} |
|||
[?socket=...][,file.debug=9][,file.logfile=...] |
|||
|
|||
JSON: |
|||
qemu-system-x86_64 'json:@{"driver":"qcow2", |
|||
"file":@{"driver":"gluster", |
|||
"volume":"testvol","path":"a.img","debug":9,"logfile":"...", |
|||
"server":[@{"type":"tcp","host":"...","port":"..."@}, |
|||
@{"type":"unix","socket":"..."@}]@}@}' |
|||
@end example |
|||
|
|||
@var{gluster} is the protocol. |
|||
|
|||
@var{type} specifies the transport type used to connect to gluster |
|||
management daemon (glusterd). Valid transport types are |
|||
tcp and unix. In the URI form, if a transport type isn't specified, |
|||
then tcp type is assumed. |
|||
|
|||
@var{host} specifies the server where the volume file specification for |
|||
the given volume resides. This can be either a hostname or an ipv4 address. |
|||
If transport type is unix, then @var{host} field should not be specified. |
|||
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, it defaults to port 24007. If the transport type is unix, |
|||
then @var{port} should not be specified. |
|||
|
|||
@var{volume} is the name of the gluster volume which contains the disk image. |
|||
|
|||
@var{path} is the path to the actual disk image that resides on gluster volume. |
|||
|
|||
@var{debug} is the logging level of the gluster protocol driver. Debug levels |
|||
are 0-9, with 9 being the most verbose, and 0 representing no debugging output. |
|||
The default level is 4. The current logging levels defined in the gluster source |
|||
are 0 - None, 1 - Emergency, 2 - Alert, 3 - Critical, 4 - Error, 5 - Warning, |
|||
6 - Notice, 7 - Info, 8 - Debug, 9 - Trace |
|||
|
|||
@var{logfile} is a commandline option to mention log file path which helps in |
|||
logging to the specified file and also help in persisting the gfapi logs. The |
|||
default is stderr. |
|||
|
|||
|
|||
|
|||
|
|||
You can create a GlusterFS disk image with the command: |
|||
@example |
|||
qemu-img create gluster://@var{host}/@var{volume}/@var{path} @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 |
|||
qemu-system-x86_64 -drive file=gluster://1.2.3.4/testvol/a.img,file.debug=9,file.logfile=/var/log/qemu-gluster.log |
|||
qemu-system-x86_64 'json:@{"driver":"qcow2", |
|||
"file":@{"driver":"gluster", |
|||
"volume":"testvol","path":"a.img", |
|||
"debug":9,"logfile":"/var/log/qemu-gluster.log", |
|||
"server":[@{"type":"tcp","host":"1.2.3.4","port":24007@}, |
|||
@{"type":"unix","socket":"/var/run/glusterd.socket"@}]@}@}' |
|||
qemu-system-x86_64 -drive driver=qcow2,file.driver=gluster,file.volume=testvol,file.path=/path/a.img, |
|||
file.debug=9,file.logfile=/var/log/qemu-gluster.log, |
|||
file.server.0.type=tcp,file.server.0.host=1.2.3.4,file.server.0.port=24007, |
|||
file.server.1.type=unix,file.server.1.socket=/var/run/glusterd.socket |
|||
@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. |
|||
|
|||
@c man end |
|||
|
|||
@ignore |
|||
|
|||
@setfilename qemu-block-drivers |
|||
@settitle QEMU block drivers reference |
|||
|
|||
@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 and the QEMU Project developers |
|||
@c man end |
|||
|
|||
@end ignore |
|||
Loading…
Reference in new issue