diff options
Diffstat (limited to 'docs/interop')
| -rw-r--r-- | docs/interop/index.rst | 3 | ||||
| -rw-r--r-- | docs/interop/live-block-operations.rst | 4 | ||||
| -rw-r--r-- | docs/interop/nbd.rst | 89 | ||||
| -rw-r--r-- | docs/interop/nbd.txt | 72 | ||||
| -rw-r--r-- | docs/interop/parallels.rst (renamed from docs/interop/parallels.txt) | 108 | ||||
| -rw-r--r-- | docs/interop/prl-xml.rst | 192 | ||||
| -rw-r--r-- | docs/interop/prl-xml.txt | 158 |
7 files changed, 344 insertions, 282 deletions
diff --git a/docs/interop/index.rst b/docs/interop/index.rst index ed65395bfb..999e44eae1 100644 --- a/docs/interop/index.rst +++ b/docs/interop/index.rst @@ -14,6 +14,9 @@ are useful for making QEMU interoperate with other software. dbus-vmstate dbus-display live-block-operations + nbd + parallels + prl-xml pr-helper qmp-spec qemu-ga diff --git a/docs/interop/live-block-operations.rst b/docs/interop/live-block-operations.rst index 691429c7af..6b549ede7c 100644 --- a/docs/interop/live-block-operations.rst +++ b/docs/interop/live-block-operations.rst @@ -931,8 +931,8 @@ Shutdown the guest, by issuing the ``quit`` QMP command:: } -Live disk backup --- ``blockdev-backup`` and the deprecated``drive-backup`` ---------------------------------------------------------------------------- +Live disk backup --- ``blockdev-backup`` and the deprecated ``drive-backup`` +---------------------------------------------------------------------------- The ``blockdev-backup`` (and the deprecated ``drive-backup``) allows you to create a point-in-time snapshot. diff --git a/docs/interop/nbd.rst b/docs/interop/nbd.rst new file mode 100644 index 0000000000..de079d31fd --- /dev/null +++ b/docs/interop/nbd.rst @@ -0,0 +1,89 @@ +QEMU NBD protocol support +========================= + +QEMU supports the NBD protocol, and has an internal NBD client (see +``block/nbd.c``), an internal NBD server (see ``blockdev-nbd.c``), and an +external NBD server tool (see ``qemu-nbd.c``). The common code is placed +in ``nbd/*``. + +The NBD protocol is specified here: +https://github.com/NetworkBlockDevice/nbd/blob/master/doc/proto.md + +The following paragraphs describe some specific properties of NBD +protocol realization in QEMU. + +Metadata namespaces +------------------- + +QEMU supports the ``base:allocation`` metadata context as defined in the +NBD protocol specification, and also defines an additional metadata +namespace ``qemu``. + +``qemu`` namespace +------------------ + +The ``qemu`` namespace currently contains two available metadata context +types. The first is related to exposing the contents of a dirty +bitmap alongside the associated disk contents. That metadata context +is named with the following form:: + + qemu:dirty-bitmap:<dirty-bitmap-export-name> + +Each dirty-bitmap metadata context defines only one flag for extents +in reply for ``NBD_CMD_BLOCK_STATUS``: + +bit 0: + ``NBD_STATE_DIRTY``, set when the extent is "dirty" + +The second is related to exposing the source of various extents within +the image, with a single metadata context named:: + + qemu:allocation-depth + +In the allocation depth context, the entire 32-bit value represents a +depth of which layer in a thin-provisioned backing chain provided the +data (0 for unallocated, 1 for the active layer, 2 for the first +backing layer, and so forth). + +For ``NBD_OPT_LIST_META_CONTEXT`` the following queries are supported +in addition to the specific ``qemu:allocation-depth`` and +``qemu:dirty-bitmap:<dirty-bitmap-export-name>``: + +``qemu:`` + returns list of all available metadata contexts in the namespace +``qemu:dirty-bitmap:`` + returns list of all available dirty-bitmap metadata contexts + +Features by version +------------------- + +The following list documents which qemu version first implemented +various features (both as a server exposing the feature, and as a +client taking advantage of the feature when present), to make it +easier to plan for cross-version interoperability. Note that in +several cases, the initial release containing a feature may require +additional patches from the corresponding stable branch to fix bugs in +the operation of that feature. + +2.6 + ``NBD_OPT_STARTTLS`` with TLS X.509 Certificates +2.8 + ``NBD_CMD_WRITE_ZEROES`` +2.10 + ``NBD_OPT_GO``, ``NBD_INFO_BLOCK`` +2.11 + ``NBD_OPT_STRUCTURED_REPLY`` +2.12 + ``NBD_CMD_BLOCK_STATUS`` for ``base:allocation`` +3.0 + ``NBD_OPT_STARTTLS`` with TLS Pre-Shared Keys (PSK), + ``NBD_CMD_BLOCK_STATUS`` for ``qemu:dirty-bitmap:``, ``NBD_CMD_CACHE`` +4.2 + ``NBD_FLAG_CAN_MULTI_CONN`` for shareable read-only exports, + ``NBD_CMD_FLAG_FAST_ZERO`` +5.2 + ``NBD_CMD_BLOCK_STATUS`` for ``qemu:allocation-depth`` +7.1 + ``NBD_FLAG_CAN_MULTI_CONN`` for shareable writable exports +8.2 + ``NBD_OPT_EXTENDED_HEADERS``, ``NBD_FLAG_BLOCK_STATUS_PAYLOAD`` diff --git a/docs/interop/nbd.txt b/docs/interop/nbd.txt deleted file mode 100644 index 18efb251de..0000000000 --- a/docs/interop/nbd.txt +++ /dev/null @@ -1,72 +0,0 @@ -QEMU supports the NBD protocol, and has an internal NBD client (see -block/nbd.c), an internal NBD server (see blockdev-nbd.c), and an -external NBD server tool (see qemu-nbd.c). The common code is placed -in nbd/*. - -The NBD protocol is specified here: -https://github.com/NetworkBlockDevice/nbd/blob/master/doc/proto.md - -The following paragraphs describe some specific properties of NBD -protocol realization in QEMU. - -= Metadata namespaces = - -QEMU supports the "base:allocation" metadata context as defined in the -NBD protocol specification, and also defines an additional metadata -namespace "qemu". - -== "qemu" namespace == - -The "qemu" namespace currently contains two available metadata context -types. The first is related to exposing the contents of a dirty -bitmap alongside the associated disk contents. That metadata context -is named with the following form: - - qemu:dirty-bitmap:<dirty-bitmap-export-name> - -Each dirty-bitmap metadata context defines only one flag for extents -in reply for NBD_CMD_BLOCK_STATUS: - - bit 0: NBD_STATE_DIRTY, set when the extent is "dirty" - -The second is related to exposing the source of various extents within -the image, with a single metadata context named: - - qemu:allocation-depth - -In the allocation depth context, the entire 32-bit value represents a -depth of which layer in a thin-provisioned backing chain provided the -data (0 for unallocated, 1 for the active layer, 2 for the first -backing layer, and so forth). - -For NBD_OPT_LIST_META_CONTEXT the following queries are supported -in addition to the specific "qemu:allocation-depth" and -"qemu:dirty-bitmap:<dirty-bitmap-export-name>": - -* "qemu:" - returns list of all available metadata contexts in the - namespace. -* "qemu:dirty-bitmap:" - returns list of all available dirty-bitmap - metadata contexts. - -= Features by version = - -The following list documents which qemu version first implemented -various features (both as a server exposing the feature, and as a -client taking advantage of the feature when present), to make it -easier to plan for cross-version interoperability. Note that in -several cases, the initial release containing a feature may require -additional patches from the corresponding stable branch to fix bugs in -the operation of that feature. - -* 2.6: NBD_OPT_STARTTLS with TLS X.509 Certificates -* 2.8: NBD_CMD_WRITE_ZEROES -* 2.10: NBD_OPT_GO, NBD_INFO_BLOCK -* 2.11: NBD_OPT_STRUCTURED_REPLY -* 2.12: NBD_CMD_BLOCK_STATUS for "base:allocation" -* 3.0: NBD_OPT_STARTTLS with TLS Pre-Shared Keys (PSK), -NBD_CMD_BLOCK_STATUS for "qemu:dirty-bitmap:", NBD_CMD_CACHE -* 4.2: NBD_FLAG_CAN_MULTI_CONN for shareable read-only exports, -NBD_CMD_FLAG_FAST_ZERO -* 5.2: NBD_CMD_BLOCK_STATUS for "qemu:allocation-depth" -* 7.1: NBD_FLAG_CAN_MULTI_CONN for shareable writable exports -* 8.2: NBD_OPT_EXTENDED_HEADERS, NBD_FLAG_BLOCK_STATUS_PAYLOAD diff --git a/docs/interop/parallels.txt b/docs/interop/parallels.rst index bb3fadf369..7b328a40c8 100644 --- a/docs/interop/parallels.txt +++ b/docs/interop/parallels.rst @@ -1,41 +1,46 @@ -= License = +Parallels Expandable Image File Format +====================================== -Copyright (c) 2015 Denis Lunev -Copyright (c) 2015 Vladimir Sementsov-Ogievskiy +.. + Copyright (c) 2015 Denis Lunev + Copyright (c) 2015 Vladimir Sementsov-Ogievskiy -This work is licensed under the terms of the GNU GPL, version 2 or later. -See the COPYING file in the top-level directory. + This work is licensed under the terms of the GNU GPL, version 2 or later. + See the COPYING file in the top-level directory. -= Parallels Expandable Image File Format = A Parallels expandable image file consists of three consecutive parts: - * header - * BAT - * data area + +* header +* BAT +* data area All numbers in a Parallels expandable image are stored in little-endian byte order. -== Definitions == - - Sector A 512-byte data chunk. +Definitions +----------- - Cluster A data chunk of the size specified in the image header. - Currently, the default size is 1MiB (2048 sectors). In previous - versions, cluster sizes of 63 sectors, 256 and 252 kilobytes were - used. +Sector + A 512-byte data chunk. - BAT Block Allocation Table, an entity that contains information for - guest-to-host I/O data address translation. +Cluster + A data chunk of the size specified in the image header. + Currently, the default size is 1MiB (2048 sectors). In previous + versions, cluster sizes of 63 sectors, 256 and 252 kilobytes were used. +BAT + Block Allocation Table, an entity that contains information for + guest-to-host I/O data address translation. -== Header == +Header +------ The header is placed at the start of an image and contains the following -fields: +fields:: -Bytes: + Bytes: 0 - 15: magic Must contain "WithoutFreeSpace" or "WithouFreSpacExt". @@ -103,44 +108,46 @@ Bytes: ext_off must meet the same requirements as cluster offsets defined by BAT entries (see below). - -== BAT == +BAT +--- BAT is placed immediately after the image header. In the file, BAT is a contiguous array of 32-bit unsigned little-endian integers with -(bat_entries * 4) bytes size. +``(bat_entries * 4)`` bytes size. Each BAT entry contains an offset from the start of the file to the -corresponding cluster. The offset set in clusters for "WithouFreSpacExt" images -and in sectors for "WithoutFreeSpace" images. +corresponding cluster. The offset set in clusters for ``WithouFreSpacExt`` +images and in sectors for ``WithoutFreeSpace`` images. If a BAT entry is zero, the corresponding cluster is not allocated and should be considered as filled with zeroes. Cluster offsets specified by BAT entries must meet the following requirements: - - the value must not be lower than data offset (provided by header.data_off - or calculated as specified above), - - the value must be lower than the desired file size, - - the value must be unique among all BAT entries, - - the result of (cluster offset - data offset) must be aligned to cluster - size. +- the value must not be lower than data offset (provided by ``header.data_off`` + or calculated as specified above) +- the value must be lower than the desired file size +- the value must be unique among all BAT entries +- the result of ``(cluster offset - data offset)`` must be aligned to + cluster size -== Data Area == +Data Area +--------- -The data area is an area from the data offset (provided by header.data_off or -calculated as specified above) to the end of the file. It represents a +The data area is an area from the data offset (provided by ``header.data_off`` +or calculated as specified above) to the end of the file. It represents a contiguous array of clusters. Most of them are allocated by the BAT, some may -be allocated by the ext_off field in the header while other may be allocated by -extensions. All clusters allocated by ext_off and extensions should meet the -same requirements as clusters specified by BAT entries. +be allocated by the ``ext_off`` field in the header while other may be +allocated by extensions. All clusters allocated by ``ext_off`` and extensions +should meet the same requirements as clusters specified by BAT entries. -== Format Extension == +Format Extension +---------------- The Format Extension is an area 1 cluster in size that provides additional format features. This cluster is addressed by the ext_off field in the header. -The format of the Format Extension area is the following: +The format of the Format Extension area is the following:: 0 - 7: magic Must be 0xAB234CEF23DCEA87 @@ -149,10 +156,10 @@ The format of the Format Extension area is the following: The MD5 checksum of the entire Header Extension cluster except the first 24 bytes. - The above are followed by feature sections or "extensions". The last - extension must be "End of features" (see below). +The above are followed by feature sections or "extensions". The last +extension must be "End of features" (see below). -Each feature section has the following format: +Each feature section has the following format:: 0 - 7: magic The identifier of the feature: @@ -183,16 +190,17 @@ Each feature section has the following format: variable: data (data_size bytes) - The above is followed by padding to the next 8 bytes boundary, then the - next extension starts. +The above is followed by padding to the next 8 bytes boundary, then the +next extension starts. - The last extension must be "End of features" with all the fields set to 0. +The last extension must be "End of features" with all the fields set to 0. -=== Dirty bitmaps feature === +Dirty bitmaps feature +--------------------- This feature provides a way of storing dirty bitmaps in the image. The fields -of its data area are: +of its data area are:: 0 - 7: size The bitmap size, should be equal to disk size in sectors. @@ -215,7 +223,7 @@ clusters inside the Parallels image file. The offsets of these clusters are saved in the L1 offset table specified by the feature extension. Each L1 table entry is a 64 bit integer as described below: -Given an offset in bytes into the bitmap data, corresponding L1 entry is +Given an offset in bytes into the bitmap data, corresponding L1 entry is:: l1_table[offset / cluster_size] @@ -227,6 +235,6 @@ are assumed to be 1. If an L1 table entry is not 0 or 1, it contains the corresponding cluster offset (in 512b sectors). Given an offset in bytes into the bitmap data the -offset in bytes into the image file can be obtained as follows: +offset in bytes into the image file can be obtained as follows:: offset = l1_table[offset / cluster_size] * 512 + (offset % cluster_size) diff --git a/docs/interop/prl-xml.rst b/docs/interop/prl-xml.rst new file mode 100644 index 0000000000..5bb63bb93a --- /dev/null +++ b/docs/interop/prl-xml.rst @@ -0,0 +1,192 @@ +Parallels Disk Format +===================== + +.. + Copyright (c) 2015-2017, Virtuozzo, Inc. + Authors: + 2015 Denis Lunev <den@openvz.org> + 2015 Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> + 2016-2017 Klim Kireev <klim.kireev@virtuozzo.com> + 2016-2017 Edgar Kaziakhmedov <edgar.kaziakhmedov@virtuozzo.com> + + This work is licensed under the terms of the GNU GPL, version 2 or later. + See the COPYING file in the top-level directory. + +This specification contains minimal information about Parallels Disk Format, +which is enough to properly work with QEMU. Nevertheless, Parallels Cloud Server +and Parallels Desktop are able to add some unspecified nodes to the xml and use +them, but they are for internal work and don't affect functionality. Also it +uses auxiliary xml ``Snapshot.xml``, which allows storage of optional snapshot +information, but this doesn't influence open/read/write functionality. QEMU and +other software should not use fields not covered in this document or the +``Snapshot.xml`` file, and must leave them as is. + +A Parallels disk consists of two parts: the set of snapshots and the disk +descriptor file, which stores information about all files and snapshots. + +Definitions +----------- + +Snapshot + a record of the contents captured at a particular time, capable + of storing current state. A snapshot has a UUID and a parent UUID. + +Snapshot image + an overlay representing the difference between this + snapshot and some earlier snapshot. + +Overlay + an image storing the different sectors between two captured states. + +Root image + a snapshot image with no parent, the root of the snapshot tree. + +Storage + the backing storage for a subset of the virtual disk. When + there is more than one storage in a Parallels disk then that + is referred to as a split image. In this case every storage + covers a specific address space area of the disk and has its + particular root image. Split images are not considered here + and are not supported. Each storage consists of disk + parameters and a list of images. The list of images always + contains a root image and may also contain overlays. The + root image can be an expandable Parallels image file or + plain. Overlays must be expandable. + +Description file + ``DiskDescriptor.xml`` stores information about disk parameters, + snapshots, and storages. + +Top Snapshot + The overlay between actual state and some previous snapshot. + It is not a snapshot in the classical sense because it + serves as the active image that the guest writes to. + +Sector + a 512-byte data chunk. + +Description file +---------------- + +All information is placed in a single XML element +``Parallels_disk_image``. +The element has only one attribute, ``Version``, which must be ``1.0``. + +The schema of ``DiskDescriptor.xml``:: + + <Parallels_disk_image Version="1.0"> + <Disk_Parameters> + ... + </Disk_Parameters> + <StorageData> + ... + </StorageData> + <Snapshots> + ... + </Snapshots> + </Parallels_disk_image> + +``Disk_Parameters`` element +^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The ``Disk_Parameters`` element describes the physical layout of the +virtual disk and some general settings. + +The ``Disk_Parameters`` element MUST contain the following child elements: + +* ``Disk_size`` - number of sectors in the disk, + desired size of the disk. +* ``Cylinders`` - number of the disk cylinders. +* ``Heads`` - number of the disk heads. +* ``Sectors`` - number of the disk sectors per cylinder + (sector size is 512 bytes) + Limitation: The product of the ``Heads``, ``Sectors`` and ``Cylinders`` + values MUST be equal to the value of the Disk_size parameter. +* ``Padding`` - must be 0. Parallels Cloud Server and Parallels Desktop may + use padding set to 1; however this case is not covered + by this specification. QEMU and other software should not open + such disks and should not create them. + +``StorageData`` element +^^^^^^^^^^^^^^^^^^^^^^^ + +This element of the file describes the root image and all snapshot images. + +The ``StorageData`` element consists of the ``Storage`` child element, +as shown below:: + + <StorageData> + <Storage> + ... + </Storage> + </StorageData> + +A ``Storage`` element has the following child elements: + +* ``Start`` - start sector of the storage, in case of non split storage + equals to 0. +* ``End`` - number of sector following the last sector, in case of non + split storage equals to ``Disk_size``. +* ``Blocksize`` - storage cluster size, number of sectors per one cluster. + The cluster size for each "Compressed" (see below) image in + a parallels disk must be equal to this field. Note: the cluster + size for a Parallels Expandable Image is in the ``tracks`` field of + its header (see :doc:`parallels`). +* Several ``Image`` child elements. + +Each ``Image`` element has the following child elements: + +* ``GUID`` - image identifier, UUID in curly brackets. + For instance, ``{12345678-9abc-def1-2345-6789abcdef12}.`` + The GUID is used by the Snapshots element to reference images + (see below) +* ``Type`` - image type of the element. It can be: + + * ``Plain`` for raw files. + * ``Compressed`` for expanding disks. + +* ``File`` - path to image file. The path can be relative to + ``DiskDescriptor.xml`` or absolute. + +``Snapshots`` element +^^^^^^^^^^^^^^^^^^^^^ + +The ``Snapshots`` element describes the snapshot relations with the snapshot tree. + +The element contains the set of ``Shot`` child elements, as shown below:: + + <Snapshots> + <TopGUID> ... </TopGUID> /* Optional child element */ + <Shot> + ... + </Shot> + <Shot> + ... + </Shot> + ... + </Snapshots> + +Each ``Shot`` element contains the following child elements: + +* ``GUID`` - an image GUID. +* ``ParentGUID`` - GUID of the image of the parent snapshot. + +The software may traverse snapshots from child to parent using the +``<ParentGUID>`` field as reference. The ``ParentGUID`` of the root +snapshot is ``{00000000-0000-0000-0000-000000000000}``. +There should be only one root snapshot. + +The Top snapshot could be +described via two ways: via the ``TopGUID`` child +element of the ``Snapshots`` element, or via the predefined GUID +``{5fbaabe3-6958-40ff-92a7-860e329aab41}``. If ``TopGUID`` is defined, +the predefined GUID is interpreted as a normal GUID. All snapshot images +(except the Top Snapshot) should be +opened read-only. + +There is another predefined GUID, +``BackupID = {704718e1-2314-44c8-9087-d78ed36b0f4e}``, which is used by +original and some third-party software for backup. QEMU and other +software may operate with images with ``GUID = BackupID`` as usual. +However, it is not recommended to use this +GUID for new disks. The Top snapshot cannot have this GUID. diff --git a/docs/interop/prl-xml.txt b/docs/interop/prl-xml.txt deleted file mode 100644 index cf9b3fba26..0000000000 --- a/docs/interop/prl-xml.txt +++ /dev/null @@ -1,158 +0,0 @@ -= License = - -Copyright (c) 2015-2017, Virtuozzo, Inc. -Authors: - 2015 Denis Lunev <den@openvz.org> - 2015 Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> - 2016-2017 Klim Kireev <klim.kireev@virtuozzo.com> - 2016-2017 Edgar Kaziakhmedov <edgar.kaziakhmedov@virtuozzo.com> - -This work is licensed under the terms of the GNU GPL, version 2 or later. -See the COPYING file in the top-level directory. - -This specification contains minimal information about Parallels Disk Format, -which is enough to proper work with QEMU. Nevertheless, Parallels Cloud Server -and Parallels Desktop are able to add some unspecified nodes to xml and use -them, but they are for internal work and don't affect functionality. Also it -uses auxiliary xml "Snapshot.xml", which allows to store optional snapshot -information, but it doesn't influence open/read/write functionality. QEMU and -other software should not use fields not covered in this document and -Snapshot.xml file and must leave them as is. - -= Parallels Disk Format = - -Parallels disk consists of two parts: the set of snapshots and the disk -descriptor file, which stores information about all files and snapshots. - -== Definitions == - Snapshot a record of the contents captured at a particular time, - capable of storing current state. A snapshot has UUID and - parent UUID. - - Snapshot image an overlay representing the difference between this - snapshot and some earlier snapshot. - - Overlay an image storing the different sectors between two captured - states. - - Root image snapshot image with no parent, the root of snapshot tree. - - Storage the backing storage for a subset of the virtual disk. When - there is more than one storage in a Parallels disk then that - is referred to as a split image. In this case every storage - covers specific address space area of the disk and has its - particular root image. Split images are not considered here - and are not supported. Each storage consists of disk - parameters and a list of images. The list of images always - contains a root image and may also contain overlays. The - root image can be an expandable Parallels image file or - plain. Overlays must be expandable. - - Description DiskDescriptor.xml stores information about disk parameters, - file snapshots, storages. - - Top The overlay between actual state and some previous snapshot. - Snapshot It is not a snapshot in the classical sense because it - serves as the active image that the guest writes to. - - Sector a 512-byte data chunk. - -== Description file == -All information is placed in a single XML element Parallels_disk_image. -The element has only one attribute "Version", that must be 1.0. -Schema of DiskDescriptor.xml: - -<Parallels_disk_image Version="1.0"> - <Disk_Parameters> - ... - </Disk_Parameters> - <StorageData> - ... - </StorageData> - <Snapshots> - ... - </Snapshots> -</Parallels_disk_image> - -== Disk_Parameters element == -The Disk_Parameters element describes the physical layout of the virtual disk -and some general settings. - -The Disk_Parameters element MUST contain the following child elements: - * Disk_size - number of sectors in the disk, - desired size of the disk. - * Cylinders - number of the disk cylinders. - * Heads - number of the disk heads. - * Sectors - number of the disk sectors per cylinder - (sector size is 512 bytes) - Limitation: Product of the Heads, Sectors and Cylinders - values MUST be equal to the value of the Disk_size parameter. - * Padding - must be 0. Parallels Cloud Server and Parallels Desktop may - use padding set to 1, however this case is not covered - by this spec, QEMU and other software should not open - such disks and should not create them. - -== StorageData element == -This element of the file describes the root image and all snapshot images. - -The StorageData element consists of the Storage child element, as shown below: -<StorageData> - <Storage> - ... - </Storage> -</StorageData> - -A Storage element has following child elements: - * Start - start sector of the storage, in case of non split storage - equals to 0. - * End - number of sector following the last sector, in case of non - split storage equals to Disk_size. - * Blocksize - storage cluster size, number of sectors per one cluster. - Cluster size for each "Compressed" (see below) image in - parallels disk must be equal to this field. Note: cluster - size for Parallels Expandable Image is in 'tracks' field of - its header (see docs/interop/parallels.txt). - * Several Image child elements. - -Each Image element has following child elements: - * GUID - image identifier, UUID in curly brackets. - For instance, {12345678-9abc-def1-2345-6789abcdef12}. - The GUID is used by the Snapshots element to reference images - (see below) - * Type - image type of the element. It can be: - "Plain" for raw files. - "Compressed" for expanding disks. - * File - path to image file. Path can be relative to DiskDescriptor.xml or - absolute. - -== Snapshots element == -The Snapshots element describes the snapshot relations with the snapshot tree. - -The element contains the set of Shot child elements, as shown below: -<Snapshots> - <TopGUID> ... </TopGUID> /* Optional child element */ - <Shot> - ... - </Shot> - <Shot> - ... - </Shot> - ... -</Snapshots> - -Each Shot element contains the following child elements: - * GUID - an image GUID. - * ParentGUID - GUID of the image of the parent snapshot. - -The software may traverse snapshots from child to parent using <ParentGUID> -field as reference. ParentGUID of root snapshot is -{00000000-0000-0000-0000-000000000000}. There should be only one root -snapshot. Top snapshot could be described via two ways: via TopGUID child -element of the Snapshots element or via predefined GUID -{5fbaabe3-6958-40ff-92a7-860e329aab41}. If TopGUID is defined, predefined GUID is -interpreted as usual GUID. All snapshot images (except Top Snapshot) should be -opened read-only. There is another predefined GUID, -BackupID = {704718e1-2314-44c8-9087-d78ed36b0f4e}, which is used by original and -some third-party software for backup, QEMU and other software may operate with -images with GUID = BackupID as usual, however, it is not recommended to use this -GUID for new disks. Top snapshot cannot have this GUID. |