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IMedium Interface Reference

The IMedium interface represents virtual storage for a machine's hard disks, CD/DVD or floppy drives. More...

Inheritance diagram for IMedium:

Public Member Functions

void setIds (in boolean setImageId, in wstringUUID imageId, in boolean setParentId, in wstringUUID parentId)
 Changes the UUID and parent UUID for a hard disk medium. More...
 
void refreshState ([retval] out MediumState state)
 If the current medium state (see MediumState) is one of "Created", "Inaccessible" or "LockedRead", then this performs an accessibility check on the medium and sets the value of the state attribute accordingly; that value is also returned for convenience. More...
 
void getSnapshotIds (in wstringUUID machineId, [retval] out wstringUUID[] snapshotIds)
 Returns an array of UUIDs of all snapshots of the given machine where this medium is attached to. More...
 
void lockRead ([retval] out IToken token)
 Locks this medium for reading. More...
 
void lockWrite ([retval] out IToken token)
 Locks this medium for writing. More...
 
void close ()
 Closes this medium. More...
 
void getProperty (in wstring name, [retval] out wstring value)
 Returns the value of the custom medium property with the given name. More...
 
void setProperty (in wstring name, in wstring value)
 Sets the value of the custom medium property with the given name. More...
 
void getProperties (in wstring names, out wstring[] returnNames, [retval] out wstring[] returnValues)
 Returns values for a group of properties in one call. More...
 
void setProperties (in wstring[] names, in wstring[] values)
 Sets values for a group of properties in one call. More...
 
void createBaseStorage (in long long logicalSize, in MediumVariant[] variant, [retval] out IProgress progress)
 Starts creating a hard disk storage unit (fixed/dynamic, according to the variant flags) in in the background. More...
 
void deleteStorage ([retval] out IProgress progress)
 Starts deleting the storage unit of this medium. More...
 
void createDiffStorage (in IMedium target, in MediumVariant[] variant, [retval] out IProgress progress)
 Starts creating an empty differencing storage unit based on this medium in the format and at the location defined by the target argument. More...
 
void mergeTo (in IMedium target, [retval] out IProgress progress)
 Starts merging the contents of this medium and all intermediate differencing media in the chain to the given target medium. More...
 
void cloneTo (in IMedium target, in MediumVariant[] variant, in IMedium parent, [retval] out IProgress progress)
 Starts creating a clone of this medium in the format and at the location defined by the target argument. More...
 
void cloneToBase (in IMedium target, in MediumVariant[] variant, [retval] out IProgress progress)
 Starts creating a clone of this medium in the format and at the location defined by the target argument. More...
 
void setLocation (in wstring location, [retval] out IProgress progress)
 Changes the location of this medium. More...
 
void compact ([retval] out IProgress progress)
 Starts compacting of this medium. More...
 
void resize (in long long logicalSize, [retval] out IProgress progress)
 Starts resizing this medium. More...
 
void reset ([retval] out IProgress progress)
 Starts erasing the contents of this differencing medium. More...
 
void changeEncryption (in wstring currentPassword, in wstring cipher, in wstring newPassword, in wstring newPasswordId, [retval] out IProgress progress)
 Starts encryption of this medium. More...
 
void getEncryptionSettings (out wstring cipher, [retval] out wstring passwordId)
 Returns the encryption settings for this medium. More...
 
void checkEncryptionPassword (in wstring password)
 Checks whether the supplied password is correct for the medium. More...
 

Public Attributes

readonly attribute wstringUUID id
 UUID of the medium. More...
 
attribute wstring description
 Optional description of the medium. More...
 
readonly attribute MediumState state
 Returns the current medium state, which is the last state set by the accessibility check performed by refreshState. More...
 
readonly attribute MediumVariant[] variant
 Returns the storage format variant information for this medium as an array of the flags described at MediumVariant. More...
 
readonly attribute wstring location
 Location of the storage unit holding medium data. More...
 
readonly attribute wstring name
 Name of the storage unit holding medium data. More...
 
readonly attribute DeviceType deviceType
 Kind of device (DVD/Floppy/HardDisk) which is applicable to this medium. More...
 
readonly attribute boolean hostDrive
 True if this corresponds to a drive on the host. More...
 
readonly attribute long long size
 Physical size of the storage unit used to hold medium data (in bytes). More...
 
readonly attribute wstring format
 Storage format of this medium. More...
 
readonly attribute IMediumFormat mediumFormat
 Storage medium format object corresponding to this medium. More...
 
attribute MediumType type
 Type (role) of this medium. More...
 
readonly attribute MediumType[] allowedTypes
 Returns which medium types can selected for this medium. More...
 
readonly attribute IMedium parent
 Parent of this medium (the medium this medium is directly based on). More...
 
readonly attribute IMedium[] children
 Children of this medium (all differencing media directly based on this medium). More...
 
readonly attribute IMedium base
 Base medium of this medium. More...
 
readonly attribute boolean readOnly
 Returns true if this medium is read-only and false otherwise. More...
 
readonly attribute long long logicalSize
 Logical size of this medium (in bytes), as reported to the guest OS running inside the virtual machine this medium is attached to. More...
 
attribute boolean autoReset
 Whether this differencing medium will be automatically reset each time a virtual machine it is attached to is powered up. More...
 
readonly attribute wstring lastAccessError
 Text message that represents the result of the last accessibility check performed by refreshState. More...
 
readonly attribute wstringUUID[] machineIds
 Array of UUIDs of all machines this medium is attached to. More...
 

Detailed Description

The IMedium interface represents virtual storage for a machine's hard disks, CD/DVD or floppy drives.

It will typically represent a disk image on the host, for example a VDI or VMDK file representing a virtual hard disk, or an ISO or RAW file representing virtual removable media, but can also point to a network location (e.g. for iSCSI targets).

Instances of IMedium are connected to virtual machines by way of medium attachments, which link the storage medium to a particular device slot of a storage controller of the virtual machine. In the VirtualBox API, virtual storage is therefore always represented by the following chain of object links:

  Existing media are opened using @link IVirtualBox::openMedium IVirtualBox::openMedium@endlink<b></b>;
  new hard disk media can be created with the VirtualBox API using the
  @link IVirtualBox::createMedium IVirtualBox::createMedium@endlink<b></b> method. Differencing hard
  disks (see below) are usually implicitly created by VirtualBox as
  needed, but may also be created explicitly using @link #createDiffStorage createDiffStorage@endlink<b></b>.
  VirtualBox cannot create CD/DVD or floppy images (ISO and RAW files); these
  should be created with external tools and then opened from within VirtualBox.

  Only for CD/DVDs and floppies, an IMedium instance can also represent a host
  drive. In that case the @link #id id@endlink<b></b> attribute contains the UUID of
  one of the drives in @link IHost::DVDDrives IHost::DVDDrives@endlink<b></b> or @link IHost::floppyDrives IHost::floppyDrives@endlink<b></b>.

  <h3>Media registries</h3>

  When a medium has been opened or created using one of the aforementioned
  APIs, it becomes "known" to VirtualBox. Known media can be attached
  to virtual machines and re-found through @link IVirtualBox::openMedium IVirtualBox::openMedium@endlink<b></b>.
  They also appear in the global
  @link IVirtualBox::hardDisks IVirtualBox::hardDisks@endlink<b></b>,
  @link IVirtualBox::DVDImages IVirtualBox::DVDImages@endlink<b></b> and
  @link IVirtualBox::floppyImages IVirtualBox::floppyImages@endlink<b></b> arrays.

  Prior to VirtualBox 4.0, opening a medium added it to a global media registry
  in the VirtualBox.xml file, which was shared between all machines and made
  transporting machines and their media from one host to another difficult.

  Starting with VirtualBox 4.0, media are only added to a registry when they are
  <i>attached</i> to a machine using @link IMachine::attachDevice IMachine::attachDevice@endlink<b></b>. For
  backwards compatibility, which registry a medium is added to depends on which
  VirtualBox version created a machine:
  See @link IVirtualBox::openMedium IVirtualBox::openMedium@endlink<b></b> for more information.

  Media are removed from media registries by the @link IMedium::close IMedium::close@endlink<b></b>,
  @link #deleteStorage deleteStorage@endlink<b></b> and @link #mergeTo mergeTo@endlink<b></b> methods.

  <h3>Accessibility checks</h3>

  VirtualBox defers media accessibility checks until the @link #refreshState refreshState@endlink<b></b>
  method is called explicitly on a medium. This is done to make the VirtualBox object
  ready for serving requests as fast as possible and let the end-user
  application decide if it needs to check media accessibility right away or not.

  As a result, when VirtualBox starts up (e.g. the VirtualBox
  object gets created for the first time), all known media are in the
  "Inaccessible" state, but the value of the @link #lastAccessError lastAccessError@endlink<b></b>
  attribute is an empty string because no actual accessibility check has
  been made yet.

  After calling @link #refreshState refreshState@endlink<b></b>, a medium is considered
  <i>accessible</i> if its storage unit can be read. In that case, the
  @link #state state@endlink<b></b> attribute has a value of "Created". If the storage
  unit cannot be read (for example, because it is located on a disconnected
  network resource, or was accidentally deleted outside VirtualBox),
  the medium is considered <i>inaccessible</i>, which is indicated by the
  "Inaccessible" state. The exact reason why the medium is inaccessible can be
  obtained by reading the @link #lastAccessError lastAccessError@endlink<b></b> attribute.

  <h3>Medium types</h3>

  There are five types of medium behavior which are stored in the
  @link #type type@endlink<b></b> attribute (see @link ::MediumType MediumType@endlink<b></b>) and
  which define the medium's behavior with attachments and snapshots.

  All media can be also divided in two groups: <i>base</i> media and
  <i>differencing</i> media. A base medium contains all sectors of the
  medium data in its own storage and therefore can be used independently.
  In contrast, a differencing medium is a "delta" to some other medium and
  contains only those sectors which differ from that other medium, which is
  then called a <i>parent</i>. The differencing medium is said to be
  <i>linked to</i> that parent. The parent may be itself a differencing
  medium, thus forming a chain of linked media. The last element in that
  chain must always be a base medium. Note that several differencing
  media may be linked to the same parent medium.

  Differencing media can be distinguished from base media by querying the
  @link #parent parent@endlink<b></b> attribute: base media do not have parents they would
  depend on, so the value of this attribute is always @c null for them.
  Using this attribute, it is possible to walk up the medium tree (from the
  child medium to its parent). It is also possible to walk down the tree
  using the @link #children children@endlink<b></b> attribute.

  Note that the type of all differencing media is "normal"; all other
  values are meaningless for them. Base media may be of any type.

  <h3>Automatic composition of the file name part</h3>

  Another extension to the @link IMedium::location IMedium::location@endlink<b></b> attribute is that
  there is a possibility to cause VirtualBox to compose a unique value for
  the file name part of the location using the UUID of the hard disk. This
  applies only to hard disks in @link ::MediumState_NotCreated MediumState_NotCreated@endlink<b></b> state,
  e.g. before the storage unit is created, and works as follows. You set the
  value of the @link IMedium::location IMedium::location@endlink<b></b> attribute to a location
  specification which only contains the path specification but not the file
  name part and ends with either a forward slash or a backslash character.
  In response, VirtualBox will generate a new UUID for the hard disk and
  compose the file name using the following pattern:
        <path>/{<uuid>}.<ext>
      

where <path> is the supplied path specification, <uuid> is the newly generated UUID and <ext> is the default extension for the storage format of this hard disk. After that, you may call any of the methods that create a new hard disk storage unit and they will use the generated UUID and file name.

Interface ID:
{4AFE423B-43E0-E9D0-82E8-CEB307940DDA}

Member Function Documentation

void IMedium::setIds ( in boolean  setImageId,
in wstringUUID  imageId,
in boolean  setParentId,
in wstringUUID  parentId 
)

Changes the UUID and parent UUID for a hard disk medium.

Parameters
setImageIdSelect whether a new image UUID is set or not.
imageIdNew UUID for the image. If an empty string is passed, then a new UUID is automatically created, provided that setImageId is true. Specifying a zero UUID is not allowed.
setParentIdSelect whether a new parent UUID is set or not.
parentIdNew parent UUID for the image. If an empty string is passed, then a new UUID is automatically created, provided setParentId is true. A zero UUID is valid.
void IMedium::refreshState ( [retval] out MediumState  state)

If the current medium state (see MediumState) is one of "Created", "Inaccessible" or "LockedRead", then this performs an accessibility check on the medium and sets the value of the state attribute accordingly; that value is also returned for convenience.

For all other state values, this does not perform a refresh but returns the state only.

The refresh, if performed, may take a long time (several seconds or even minutes, depending on the storage unit location and format) because it performs an accessibility check of the storage unit. This check may cause a significant delay if the storage unit of the given medium is, for example, a file located on a network share which is not currently accessible due to connectivity problems. In that case, the call will not return until a timeout interval defined by the host OS for this operation expires. For this reason, it is recommended to never read this attribute on the main UI thread to avoid making the UI unresponsive.

If the last known state of the medium is "Created" and the accessibility check fails, then the state would be set to "Inaccessible", and lastAccessError may be used to get more details about the failure. If the state of the medium is "LockedRead", then it remains the same, and a non-empty value of lastAccessError will indicate a failed accessibility check in this case.

Note that not all medium states are applicable to all medium types.

Parameters
stateNew medium state.
void IMedium::getSnapshotIds ( in wstringUUID  machineId,
[retval] out wstringUUID[]  snapshotIds 
)

Returns an array of UUIDs of all snapshots of the given machine where this medium is attached to.

If the medium is attached to the machine in the current state, then the first element in the array will always be the ID of the queried machine (i.e. the value equal to the machineId argument), followed by snapshot IDs (if any).

If the medium is not attached to the machine in the current state, then the array will contain only snapshot IDs.

The returned array may be null if this medium is not attached to the given machine at all, neither in the current state nor in one of the snapshots.

Parameters
machineIdUUID of the machine to query.
snapshotIdsArray of snapshot UUIDs of the given machine using this medium.
void IMedium::lockRead ( [retval] out IToken  token)

Locks this medium for reading.

A read lock is shared: many clients can simultaneously lock the same medium for reading unless it is already locked for writing (see lockWrite) in which case an error is returned.

When the medium is locked for reading, it cannot be modified from within VirtualBox. This means that any method that changes the properties of this medium or contents of the storage unit will return an error (unless explicitly stated otherwise). That includes an attempt to start a virtual machine that wants to write to the the medium.

When the virtual machine is started up, it locks for reading all media it uses in read-only mode. If some medium cannot be locked for reading, the startup procedure will fail. A medium is typically locked for reading while it is used by a running virtual machine but has a depending differencing image that receives the actual write operations. This way one base medium can have multiple child differencing images which can be written to simultaneously. Read-only media such as DVD and floppy images are also locked for reading only (so they can be in use by multiple machines simultaneously).

A medium is also locked for reading when it is the source of a write operation such as cloneTo or mergeTo.

The medium locked for reading must be unlocked by abandoning the returned token object, see IToken. Calls to lockRead can be nested and the lock is actually released when all callers have abandoned the token.

This method sets the medium state (see state) to "LockedRead" on success. The medium's previous state must be one of "Created", "Inaccessible" or "LockedRead".

Locking an inaccessible medium is not an error; this method performs a logical lock that prevents modifications of this medium through the VirtualBox API, not a physical file-system lock of the underlying storage unit.

This method returns the current state of the medium before the operation.

Parameters
tokenToken object, when this is released (reference count reaches 0) then the lock count is decreased. The lock is released when the lock count reaches 0.
Expected result codes:
VBOX_E_INVALID_OBJECT_STATE Invalid medium state (e.g. not created, locked, inaccessible, creating, deleting).
void IMedium::lockWrite ( [retval] out IToken  token)

Locks this medium for writing.

A write lock, as opposed to lockRead, is exclusive: there may be only one client holding a write lock, and there may be no read locks while the write lock is held. As a result, read-locking fails if a write lock is held, and write-locking fails if either a read or another write lock is held.

When a medium is locked for writing, it cannot be modified from within VirtualBox, and it is not guaranteed that the values of its properties are up-to-date. Any method that changes the properties of this medium or contents of the storage unit will return an error (unless explicitly stated otherwise).

When a virtual machine is started up, it locks for writing all media it uses to write data to. If any medium could not be locked for writing, the startup procedure will fail. If a medium has differencing images, then while the machine is running, only the last ("leaf") differencing image is locked for writing, whereas its parents are locked for reading only.

A medium is also locked for writing when it is the target of a write operation such as cloneTo or mergeTo.

The medium locked for writing must be unlocked by abandoning the returned token object, see IToken. Write locks cannot be nested.

This method sets the medium state (see state) to "LockedWrite" on success. The medium's previous state must be either "Created" or "Inaccessible".

Locking an inaccessible medium is not an error; this method performs a logical lock that prevents modifications of this medium through the VirtualBox API, not a physical file-system lock of the underlying storage unit.

Parameters
tokenToken object, when this is released (reference count reaches 0) then the lock is released.
Expected result codes:
VBOX_E_INVALID_OBJECT_STATE Invalid medium state (e.g. not created, locked, inaccessible, creating, deleting).
void IMedium::close ( )

Closes this medium.

The medium must not be attached to any known virtual machine and must not have any known child media, otherwise the operation will fail.

When the medium is successfully closed, it is removed from the list of registered media, but its storage unit is not deleted. In particular, this means that this medium can later be opened again using the IVirtualBox::openMedium call.

Note that after this method successfully returns, the given medium object becomes uninitialized. This means that any attempt to call any of its methods or attributes will fail with the "Object not ready" (E_ACCESSDENIED) error.

Expected result codes:
VBOX_E_INVALID_OBJECT_STATE Invalid medium state (other than not created, created or inaccessible).
VBOX_E_OBJECT_IN_USE Medium attached to virtual machine.
VBOX_E_FILE_ERROR Settings file not accessible.
VBOX_E_XML_ERROR Could not parse the settings file.
void IMedium::getProperty ( in wstring  name,
[retval] out wstring  value 
)

Returns the value of the custom medium property with the given name.

The list of all properties supported by the given medium format can be obtained with IMediumFormat::describeProperties.

Parameters
nameName of the property to get.
valueCurrent property value.
Expected result codes:
VBOX_E_OBJECT_NOT_FOUND Requested property does not exist (not supported by the format).
E_INVALIDARG name is null or empty.
Note
If this method returns an empty string in value, the requested property is supported but currently not assigned any value.
void IMedium::setProperty ( in wstring  name,
in wstring  value 
)

Sets the value of the custom medium property with the given name.

The list of all properties supported by the given medium format can be obtained with IMediumFormat::describeProperties.

Parameters
nameName of the property to set.
valueProperty value to set.
Expected result codes:
VBOX_E_OBJECT_NOT_FOUND Requested property does not exist (not supported by the format).
E_INVALIDARG name is null or empty.
Note
Setting the property value to null or an empty string is equivalent to deleting the existing value. A default value (if it is defined for this property) will be used by the format backend in this case.
void IMedium::getProperties ( in wstring  names,
out wstring[]  returnNames,
[retval] out wstring[]  returnValues 
)

Returns values for a group of properties in one call.

The names of the properties to get are specified using the names argument which is a list of comma-separated property names or an empty string if all properties are to be returned.

    The list of all properties supported by the given medium format can
    be obtained with @link IMediumFormat::describeProperties IMediumFormat::describeProperties@endlink<b></b>.

    The method returns two arrays, the array of property names corresponding
    to the @a names argument and the current values of these properties.
    Both arrays have the same number of elements with each element at the
    given index in the first array corresponds to an element at the same
    index in the second array.

    For properties that do not have assigned values, an empty string is
    returned at the appropriate index in the @a returnValues array.
Parameters
namesNames of properties to get.
returnNamesNames of returned properties.
returnValuesValues of returned properties.
Note
Currently the value of this argument is ignored and the method always returns all existing properties.
void IMedium::setProperties ( in wstring[]  names,
in wstring[]  values 
)

Sets values for a group of properties in one call.

The names of the properties to set are passed in the names array along with the new values for them in the values array. Both arrays have the same number of elements with each element at the given index in the first array corresponding to an element at the same index in the second array.

If there is at least one property name in names that is not valid, the method will fail before changing the values of any other properties from the names array.

Using this method over setProperty is preferred if you need to set several properties at once since it is more efficient.

The list of all properties supported by the given medium format can be obtained with IMediumFormat::describeProperties.

Setting the property value to null or an empty string is equivalent to deleting the existing value. A default value (if it is defined for this property) will be used by the format backend in this case.

Parameters
namesNames of properties to set.
valuesValues of properties to set.
void IMedium::createBaseStorage ( in long long  logicalSize,
in MediumVariant[]  variant,
[retval] out IProgress  progress 
)

Starts creating a hard disk storage unit (fixed/dynamic, according to the variant flags) in in the background.

The previous storage unit created for this object, if any, must first be deleted using deleteStorage, otherwise the operation will fail.

Before the operation starts, the medium is placed in MediumState_Creating state. If the create operation fails, the medium will be placed back in MediumState_NotCreated state.

After the returned progress object reports that the operation has successfully completed, the medium state will be set to MediumState_Created, the medium will be remembered by this VirtualBox installation and may be attached to virtual machines.

Parameters
logicalSizeMaximum logical size of the medium in bytes.
variantExact image variant which should be created (as a combination of MediumVariant flags).
progressProgress object to track the operation completion.
Expected result codes:
VBOX_E_NOT_SUPPORTED The variant of storage creation operation is not supported. See IMediumFormat::capabilities.
void IMedium::deleteStorage ( [retval] out IProgress  progress)

Starts deleting the storage unit of this medium.

The medium must not be attached to any known virtual machine and must not have any known child media, otherwise the operation will fail. It will also fail if there is no storage unit to delete or if deletion is already in progress, or if the medium is being in use (locked for read or for write) or inaccessible. Therefore, the only valid state for this operation to succeed is MediumState_Created.

Before the operation starts, the medium is placed in MediumState_Deleting state and gets removed from the list of remembered hard disks (media registry). If the delete operation fails, the medium will be remembered again and placed back to MediumState_Created state.

After the returned progress object reports that the operation is complete, the medium state will be set to MediumState_NotCreated and you will be able to use one of the storage creation methods to create it again.

Parameters
progressProgress object to track the operation completion.
Expected result codes:
VBOX_E_OBJECT_IN_USE Medium is attached to a virtual machine.
VBOX_E_NOT_SUPPORTED Storage deletion is not allowed because neither of storage creation operations are supported. See IMediumFormat::capabilities.
Note
If the deletion operation fails, it is not guaranteed that the storage unit still exists. You may check the IMedium::state value to answer this question.
See also
close
void IMedium::createDiffStorage ( in IMedium  target,
in MediumVariant[]  variant,
[retval] out IProgress  progress 
)

Starts creating an empty differencing storage unit based on this medium in the format and at the location defined by the target argument.

The target medium must be in MediumState_NotCreated state (i.e. must not have an existing storage unit). Upon successful completion, this operation will set the type of the target medium to MediumType_Normal and create a storage unit necessary to represent the differencing medium data in the given format (according to the storage format of the target object).

After the returned progress object reports that the operation is successfully complete, the target medium gets remembered by this VirtualBox installation and may be attached to virtual machines.

Parameters
targetTarget medium.
variantExact image variant which should be created (as a combination of MediumVariant flags).
progressProgress object to track the operation completion.
Expected result codes:
VBOX_E_OBJECT_IN_USE Medium not in NotCreated state.
Note
The medium will be set to MediumState_LockedRead state for the duration of this operation.
void IMedium::mergeTo ( in IMedium  target,
[retval] out IProgress  progress 
)

Starts merging the contents of this medium and all intermediate differencing media in the chain to the given target medium.

The target medium must be either a descendant of this medium or its ancestor (otherwise this method will immediately return a failure). It follows that there are two logical directions of the merge operation: from ancestor to descendant (forward merge) and from descendant to ancestor (backward merge). Let us consider the following medium chain:

Base <- Diff_1 <- Diff_2
    Here, calling this method on the <tt>Base</tt> medium object with
    <tt>Diff_2</tt> as an argument will be a forward merge; calling it on
    <tt>Diff_2</tt> with <tt>Base</tt> as an argument will be a backward
    merge. Note that in both cases the contents of the resulting medium
    will be the same, the only difference is the medium object that takes
    the result of the merge operation. In case of the forward merge in the
    above example, the result will be written to <tt>Diff_2</tt>; in case of
    the backward merge, the result will be written to <tt>Base</tt>. In
    other words, the result of the operation is always stored in the target
    medium.

    Upon successful operation completion, the storage units of all media in
    the chain between this (source) medium and the target medium, including
    the source medium itself, will be automatically deleted and the
    relevant medium objects (including this medium) will become
    uninitialized. This means that any attempt to call any of
    their methods or attributes will fail with the
    <tt>"Object not ready" (E_ACCESSDENIED)</tt> error. Applied to the above
    example, the forward merge of <tt>Base</tt> to <tt>Diff_2</tt> will
    delete and uninitialize both <tt>Base</tt> and <tt>Diff_1</tt> media.
    Note that <tt>Diff_2</tt> in this case will become a base medium
    itself since it will no longer be based on any other medium.

    Considering the above, all of the following conditions must be met in
    order for the merge operation to succeed:
  • Neither this (source) medium nor any intermediate differencing medium in the chain between it and the target medium is attached to any virtual machine.
  • Neither the source medium nor the target medium is an MediumType_Immutable medium.
  • The part of the medium tree from the source medium to the target medium is a linear chain, i.e. all medium in this chain have exactly one child which is the next medium in this chain. The only exception from this rule is the target medium in the forward merge operation; it is allowed to have any number of child media because the merge operation will not change its logical contents (as it is seen by the guest OS or by children).
  • None of the involved media are in MediumState_LockedRead or MediumState_LockedWrite state.
Parameters
targetTarget medium.
progressProgress object to track the operation completion.
Note
This (source) medium and all intermediates will be placed to MediumState_Deleting state and the target medium will be placed to MediumState_LockedWrite state and for the duration of this operation.
void IMedium::cloneTo ( in IMedium  target,
in MediumVariant[]  variant,
in IMedium  parent,
[retval] out IProgress  progress 
)

Starts creating a clone of this medium in the format and at the location defined by the target argument.

The target medium must be either in MediumState_NotCreated state (i.e. must not have an existing storage unit) or in MediumState_Created state (i.e. created and not locked, and big enough to hold the data or else the copy will be partial). Upon successful completion, the cloned medium will contain exactly the same sector data as the medium being cloned, except that in the first case a new UUID for the clone will be randomly generated, and in the second case the UUID will remain unchanged.

The parent argument defines which medium will be the parent of the clone. Passing a null reference indicates that the clone will be a base image, i.e. completely independent. It is possible to specify an arbitrary medium for this parameter, including the parent of the medium which is being cloned. Even cloning to a child of the source medium is possible. Note that when cloning to an existing image, the parent argument is ignored.

After the returned progress object reports that the operation is successfully complete, the target medium gets remembered by this VirtualBox installation and may be attached to virtual machines.

Parameters
targetTarget medium.
variantExact image variant which should be created (as a combination of MediumVariant flags).
parentParent of the cloned medium.
progressProgress object to track the operation completion.
Expected result codes:
E_NOTIMPL The specified cloning variant is not supported at the moment.
Note
This medium will be placed to MediumState_LockedRead state for the duration of this operation.
void IMedium::cloneToBase ( in IMedium  target,
in MediumVariant[]  variant,
[retval] out IProgress  progress 
)

Starts creating a clone of this medium in the format and at the location defined by the target argument.

The target medium must be either in MediumState_NotCreated state (i.e. must not have an existing storage unit) or in MediumState_Created state (i.e. created and not locked, and big enough to hold the data or else the copy will be partial). Upon successful completion, the cloned medium will contain exactly the same sector data as the medium being cloned, except that in the first case a new UUID for the clone will be randomly generated, and in the second case the UUID will remain unchanged.

The parent argument defines which medium will be the parent of the clone. In this case the clone will be a base image, i.e. completely independent. It is possible to specify an arbitrary medium for this parameter, including the parent of the medium which is being cloned. Even cloning to a child of the source medium is possible. Note that when cloning to an existing image, the parent argument is ignored.

After the returned progress object reports that the operation is successfully complete, the target medium gets remembered by this VirtualBox installation and may be attached to virtual machines.

Parameters
targetTarget medium.
variantMediumVariant flags).
progressProgress object to track the operation completion.
Expected result codes:
E_NOTIMPL The specified cloning variant is not supported at the moment.
Note
This medium will be placed to MediumState_LockedRead state for the duration of this operation.
void IMedium::setLocation ( in wstring  location,
[retval] out IProgress  progress 
)

Changes the location of this medium.

Some medium types may support changing the storage unit location by simply changing the value of the associated property. In this case the operation is performed immediately, and progress is returning a null reference. Otherwise on success there is a progress object returned, which signals progress and completion of the operation. This distinction is necessary because for some formats the operation is very fast, while for others it can be very slow (moving the image file by copying all data), and in the former case it'd be a waste of resources to create a progress object which will immediately signal completion.

When setting a location for a medium which corresponds to a/several regular file(s) in the host's file system, the given file name may be either relative to the VirtualBox home folder or absolute. Note that if the given location specification does not contain the file extension part then a proper default extension will be automatically appended by the implementation depending on the medium type.

Parameters
locationNew location.
progressProgress object to track the operation completion.
Expected result codes:
E_NOTIMPL The operation is not implemented yet.
VBOX_E_NOT_SUPPORTED Medium format does not support changing the location.
void IMedium::compact ( [retval] out IProgress  progress)

Starts compacting of this medium.

This means that the medium is transformed into a possibly more compact storage representation. This potentially creates temporary images, which can require a substantial amount of additional disk space.

This medium will be placed to MediumState_LockedWrite state and all its parent media (if any) will be placed to MediumState_LockedRead state for the duration of this operation.

Please note that the results can be either returned straight away, or later as the result of the background operation via the object returned via the progress parameter.

Parameters
progressProgress object to track the operation completion.
Expected result codes:
VBOX_E_NOT_SUPPORTED Medium format does not support compacting (but potentially needs it).
void IMedium::resize ( in long long  logicalSize,
[retval] out IProgress  progress 
)

Starts resizing this medium.

This means that the nominal size of the medium is set to the new value. Both increasing and decreasing the size is possible, and there are no safety checks, since VirtualBox does not make any assumptions about the medium contents.

Resizing usually needs additional disk space, and possibly also some temporary disk space. Note that resize does not create a full temporary copy of the medium, so the additional disk space requirement is usually much lower than using the clone operation.

This medium will be placed to MediumState_LockedWrite state for the duration of this operation.

Please note that the results can be either returned straight away, or later as the result of the background operation via the object returned via the progress parameter.

Parameters
logicalSizeNew nominal capacity of the medium in bytes.
progressProgress object to track the operation completion.
Expected result codes:
VBOX_E_NOT_SUPPORTED Medium format does not support resizing.
void IMedium::reset ( [retval] out IProgress  progress)

Starts erasing the contents of this differencing medium.

This operation will reset the differencing medium to its initial state when it does not contain any sector data and any read operation is redirected to its parent medium. This automatically gets called during VM power-up for every medium whose autoReset attribute is true.

The medium will be write-locked for the duration of this operation (see lockWrite).

Parameters
progressProgress object to track the operation completion.
Expected result codes:
VBOX_E_NOT_SUPPORTED This is not a differencing medium.
VBOX_E_INVALID_OBJECT_STATE Medium is not in MediumState_Created or MediumState_Inaccessible state.
void IMedium::changeEncryption ( in wstring  currentPassword,
in wstring  cipher,
in wstring  newPassword,
in wstring  newPasswordId,
[retval] out IProgress  progress 
)

Starts encryption of this medium.

This means that the stored data in the medium is encrypted.

This medium will be placed to MediumState_LockedWrite state.

Please note that the results can be either returned straight away, or later as the result of the background operation via the object returned via the progress parameter.

Parameters
currentPasswordThe current password the medium is protected with. Use an empty string to indicate that the medium isn't encrypted.
cipherThe cipher to use for encryption. An empty string indicates no encryption for the result.
newPasswordThe new password the medium should be protected with. An empty password and password ID will result in the medium being encrypted with the current password.
newPasswordIdThe ID of the new password when unlocking the medium.
progressProgress object to track the operation completion.
Expected result codes:
VBOX_E_NOT_SUPPORTED Encryption is not supported for this medium because it is attached to more than one VM or has children.
void IMedium::getEncryptionSettings ( out wstring  cipher,
[retval] out wstring  passwordId 
)

Returns the encryption settings for this medium.

Parameters
cipherThe cipher used for encryption.
passwordIdThe ID of the password when unlocking the medium.
Expected result codes:
VBOX_E_NOT_SUPPORTED Encryption is not configured for this medium.
void IMedium::checkEncryptionPassword ( in wstring  password)

Checks whether the supplied password is correct for the medium.

Parameters
passwordThe password to check.
Expected result codes:
VBOX_E_NOT_SUPPORTED Encryption is not configured for this medium.
VBOX_E_PASSWORD_INCORRECT The given password is incorrect.

Member Data Documentation

readonly attribute wstringUUID IMedium::id

UUID of the medium.

For a newly created medium, this value is a randomly generated UUID.

Note
For media in one of MediumState_NotCreated, MediumState_Creating or MediumState_Deleting states, the value of this property is undefined and will most likely be an empty UUID.
attribute wstring IMedium::description

Optional description of the medium.

For a newly created medium the value of this attribute is an empty string.

Medium types that don't support this attribute will return E_NOTIMPL in attempt to get or set this attribute's value.

Note
For some storage types, reading this attribute may return an outdated (last known) value when state is MediumState_Inaccessible or MediumState_LockedWrite because the value of this attribute is stored within the storage unit itself. Also note that changing the attribute value is not possible in such case, as well as when the medium is the MediumState_LockedRead state.
readonly attribute MediumState IMedium::state

Returns the current medium state, which is the last state set by the accessibility check performed by refreshState.

If that method has not yet been called on the medium, the state is "Inaccessible"; as opposed to truly inaccessible media, the value of lastAccessError will be an empty string in that case.

Note
As of version 3.1, this no longer performs an accessibility check automatically; call refreshState for that.
readonly attribute MediumVariant [] IMedium::variant

Returns the storage format variant information for this medium as an array of the flags described at MediumVariant.

Before refreshState is called this method returns an undefined value.

readonly attribute wstring IMedium::location

Location of the storage unit holding medium data.

The format of the location string is medium type specific. For medium types using regular files in a host's file system, the location string is the full file name.

readonly attribute wstring IMedium::name

Name of the storage unit holding medium data.

The returned string is a short version of the location attribute that is suitable for representing the medium in situations where the full location specification is too long (such as lists and comboboxes in GUI frontends). This string is also used by frontends to sort the media list alphabetically when needed.

For example, for locations that are regular files in the host's file system, the value of this attribute is just the file name (+ extension), without the path specification.

Note that as opposed to the location attribute, the name attribute will not necessary be unique for a list of media of the given type and format.

readonly attribute DeviceType IMedium::deviceType

Kind of device (DVD/Floppy/HardDisk) which is applicable to this medium.

readonly attribute boolean IMedium::hostDrive

True if this corresponds to a drive on the host.

readonly attribute long long IMedium::size

Physical size of the storage unit used to hold medium data (in bytes).

Note
For media whose state is MediumState_Inaccessible, the value of this property is the last known size. For MediumState_NotCreated media, the returned value is zero.
readonly attribute wstring IMedium::format

Storage format of this medium.

The value of this attribute is a string that specifies a backend used to store medium data. The storage format is defined when you create a new medium or automatically detected when you open an existing medium, and cannot be changed later.

The list of all storage formats supported by this VirtualBox installation can be obtained using ISystemProperties::mediumFormats.

readonly attribute IMediumFormat IMedium::mediumFormat

Storage medium format object corresponding to this medium.

The value of this attribute is a reference to the medium format object that specifies the backend properties used to store medium data. The storage format is defined when you create a new medium or automatically detected when you open an existing medium, and cannot be changed later.

Note
null is returned if there is no associated medium format object. This can e.g. happen for medium objects representing host drives and other special medium objects.
attribute MediumType IMedium::type

Type (role) of this medium.

The following constraints apply when changing the value of this attribute:

  • If a medium is attached to a virtual machine (either in the current state or in one of the snapshots), its type cannot be changed.
  • As long as the medium has children, its type cannot be set to MediumType_Writethrough.
  • The type of all differencing media is MediumType_Normal and cannot be changed.
    The type of a newly created or opened medium is set to
    @link ::MediumType_Normal MediumType_Normal@endlink<b></b>, except for DVD and floppy media,
    which have a type of @link ::MediumType_Writethrough MediumType_Writethrough@endlink<b></b>.
readonly attribute MediumType [] IMedium::allowedTypes

Returns which medium types can selected for this medium.

Expected result codes:
E_NOTIMPL This attribute is not implemented at the moment.
readonly attribute IMedium IMedium::parent

Parent of this medium (the medium this medium is directly based on).

Only differencing media have parents. For base (non-differencing) media, null is returned.

readonly attribute IMedium [] IMedium::children

Children of this medium (all differencing media directly based on this medium).

A null array is returned if this medium does not have any children.

readonly attribute IMedium IMedium::base

Base medium of this medium.

If this is a differencing medium, its base medium is the medium the given medium branch starts from. For all other types of media, this property returns the medium object itself (i.e. the same object this property is read on).

readonly attribute boolean IMedium::readOnly

Returns true if this medium is read-only and false otherwise.

A medium is considered to be read-only when its contents cannot be modified without breaking the integrity of other parties that depend on this medium such as its child media or snapshots of virtual machines where this medium is attached to these machines. If there are no children and no such snapshots then there is no dependency and the medium is not read-only.

The value of this attribute can be used to determine the kind of the attachment that will take place when attaching this medium to a virtual machine. If the value is false then the medium will be attached directly. If the value is true then the medium will be attached indirectly by creating a new differencing child medium for that. See the interface description for more information.

Note that all Immutable media are always read-only while all Writethrough media are always not.

Note
The read-only condition represented by this attribute is related to the medium type and usage, not to the current medium state and not to the read-only state of the storage unit.
readonly attribute long long IMedium::logicalSize

Logical size of this medium (in bytes), as reported to the guest OS running inside the virtual machine this medium is attached to.

The logical size is defined when the medium is created and cannot be changed later.

Note
For media whose state is state is MediumState_Inaccessible, the value of this property is the last known logical size. For MediumState_NotCreated media, the returned value is zero.
attribute boolean IMedium::autoReset

Whether this differencing medium will be automatically reset each time a virtual machine it is attached to is powered up.

This attribute is automatically set to true for the last differencing image of an "immutable" medium (see MediumType).

See reset for more information about resetting differencing media.

Expected result codes:
VBOX_E_NOT_SUPPORTED This is not a differencing medium (when changing the attribute value).
Note
Reading this property on a base (non-differencing) medium will always false. Changing the value of this property in this case is not supported.
readonly attribute wstring IMedium::lastAccessError

Text message that represents the result of the last accessibility check performed by refreshState.

An empty string is returned if the last accessibility check was successful or has not yet been called. As a result, if state is "Inaccessible" and this attribute is empty, then refreshState has yet to be called; this is the default value of media after VirtualBox initialization. A non-empty string indicates a failure and should normally describe a reason of the failure (for example, a file read error).

readonly attribute wstringUUID [] IMedium::machineIds

Array of UUIDs of all machines this medium is attached to.

A null array is returned if this medium is not attached to any machine or to any machine's snapshot.

Note
The returned array will include a machine even if this medium is not attached to that machine in the current state but attached to it in one of the machine's snapshots. See getSnapshotIds for details.