# Module libvirt-domain-snapshot from libvirt

Provides APIs for the management of domain snapshots Copyright (C) 2006-2014 Red Hat, Inc. This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this library. If not, see http://www.gnu.org/licenses/.

## Table of Contents

### Types

    typedef struct _virDomainSnapshot virDomainSnapshot
    typedef enum virDomainSnapshotCreateFlags
    typedef enum virDomainSnapshotDeleteFlags
    typedef enum virDomainSnapshotListFlags
    typedef virDomainSnapshot * virDomainSnapshotPtr
    typedef enum virDomainSnapshotRevertFlags
    typedef enum virDomainSnapshotXMLFlags

### Functions

    int	virDomainHasCurrentSnapshot	(virDomainPtr domain,
    					 unsigned int flags)
    int	virDomainListAllSnapshots	(virDomainPtr domain,
    					 virDomainSnapshotPtr ** snaps,
    					 unsigned int flags)
    int	virDomainRevertToSnapshot	(virDomainSnapshotPtr snapshot,
    					 unsigned int flags)
    virDomainSnapshotPtr	virDomainSnapshotCreateXML	(virDomainPtr domain,
    							 const char * xmlDesc,
    							 unsigned int flags)
    virDomainSnapshotPtr	virDomainSnapshotCurrent	(virDomainPtr domain,
    							 unsigned int flags)
    int	virDomainSnapshotDelete		(virDomainSnapshotPtr snapshot,
    					 unsigned int flags)
    int	virDomainSnapshotFree		(virDomainSnapshotPtr snapshot)
    virConnectPtr	virDomainSnapshotGetConnect	(virDomainSnapshotPtr snapshot)
    virDomainPtr	virDomainSnapshotGetDomain	(virDomainSnapshotPtr snapshot)
    const char *	virDomainSnapshotGetName	(virDomainSnapshotPtr snapshot)
    virDomainSnapshotPtr	virDomainSnapshotGetParent	(virDomainSnapshotPtr snapshot,
    							 unsigned int flags)
    char *	virDomainSnapshotGetXMLDesc	(virDomainSnapshotPtr snapshot,
    					 unsigned int flags)
    int	virDomainSnapshotHasMetadata	(virDomainSnapshotPtr snapshot,
    					 unsigned int flags)
    int	virDomainSnapshotIsCurrent	(virDomainSnapshotPtr snapshot,
    					 unsigned int flags)
    int	virDomainSnapshotListAllChildren	(virDomainSnapshotPtr snapshot,
    						 virDomainSnapshotPtr ** snaps,
    						 unsigned int flags)
    int	virDomainSnapshotListChildrenNames	(virDomainSnapshotPtr snapshot,
    						 char ** names,
    						 int nameslen,
    						 unsigned int flags)
    int	virDomainSnapshotListNames	(virDomainPtr domain,
    					 char ** names,
    					 int nameslen,
    					 unsigned int flags)
    virDomainSnapshotPtr	virDomainSnapshotLookupByName	(virDomainPtr domain,
    							 const char * name,
    							 unsigned int flags)
    int	virDomainSnapshotNum		(virDomainPtr domain,
    					 unsigned int flags)
    int	virDomainSnapshotNumChildren	(virDomainSnapshotPtr snapshot,
    					 unsigned int flags)
    int	virDomainSnapshotRef		(virDomainSnapshotPtr snapshot)

## Description

### Types

### `virDomainSnapshot`

    struct virDomainSnapshot {

The content of this structure is not made public by the API

    }

### `virDomainSnapshotCreateFlags`

    enum virDomainSnapshotCreateFlags {

VIR_DOMAIN_SNAPSHOT_CREATE_REDEFINE | = | 1 (0x1; 1 << 0) | Restore or alter metadata
VIR_DOMAIN_SNAPSHOT_CREATE_CURRENT | = | 2 (0x2; 1 << 1) | With redefine, make snapshot current
VIR_DOMAIN_SNAPSHOT_CREATE_NO_METADATA | = | 4 (0x4; 1 << 2) | Make snapshot without remembering it
VIR_DOMAIN_SNAPSHOT_CREATE_HALT | = | 8 (0x8; 1 << 3) | Stop running guest after snapshot
VIR_DOMAIN_SNAPSHOT_CREATE_DISK_ONLY | = | 16 (0x10; 1 << 4) | disk snapshot, not full system
VIR_DOMAIN_SNAPSHOT_CREATE_REUSE_EXT | = | 32 (0x20; 1 << 5) | reuse any existing external files
VIR_DOMAIN_SNAPSHOT_CREATE_QUIESCE | = | 64 (0x40; 1 << 6) | use guest agent to quiesce all mounted file systems within the domain
VIR_DOMAIN_SNAPSHOT_CREATE_ATOMIC | = | 128 (0x80; 1 << 7) | atomically avoid partial changes
VIR_DOMAIN_SNAPSHOT_CREATE_LIVE | = | 256 (0x100; 1 << 8) | create the snapshot while the guest is running
VIR_DOMAIN_SNAPSHOT_CREATE_VALIDATE | = | 512 (0x200; 1 << 9) | validate the XML against the schema

    }

### `virDomainSnapshotDeleteFlags`

    enum virDomainSnapshotDeleteFlags {

VIR_DOMAIN_SNAPSHOT_DELETE_CHILDREN | = | 1 (0x1; 1 << 0) | Also delete children
VIR_DOMAIN_SNAPSHOT_DELETE_METADATA_ONLY | = | 2 (0x2; 1 << 1) | Delete just metadata
VIR_DOMAIN_SNAPSHOT_DELETE_CHILDREN_ONLY | = | 4 (0x4; 1 << 2) | Delete just children

    }

### `virDomainSnapshotListFlags`

    enum virDomainSnapshotListFlags {

VIR_DOMAIN_SNAPSHOT_LIST_DESCENDANTS | = | 1 (0x1; 1 << 0) | List all descendants, not just children, when listing a snapshot For historical reasons, groups do not use contiguous bits.
VIR_DOMAIN_SNAPSHOT_LIST_ROOTS | = | 1 (0x1; 1 << 0) | Filter by snapshots with no parents, when listing a domain
VIR_DOMAIN_SNAPSHOT_LIST_METADATA | = | 2 (0x2; 1 << 1) | Filter by snapshots which have metadata
VIR_DOMAIN_SNAPSHOT_LIST_LEAVES | = | 4 (0x4; 1 << 2) | Filter by snapshots with no children
VIR_DOMAIN_SNAPSHOT_LIST_NO_LEAVES | = | 8 (0x8; 1 << 3) | Filter by snapshots that have children
VIR_DOMAIN_SNAPSHOT_LIST_NO_METADATA | = | 16 (0x10; 1 << 4) | Filter by snapshots with no metadata
VIR_DOMAIN_SNAPSHOT_LIST_INACTIVE | = | 32 (0x20; 1 << 5) | Filter by snapshots taken while guest was shut off
VIR_DOMAIN_SNAPSHOT_LIST_ACTIVE | = | 64 (0x40; 1 << 6) | Filter by snapshots taken while guest was active, and with memory state
VIR_DOMAIN_SNAPSHOT_LIST_DISK_ONLY | = | 128 (0x80; 1 << 7) | Filter by snapshots taken while guest was active, but without memory state
VIR_DOMAIN_SNAPSHOT_LIST_INTERNAL | = | 256 (0x100; 1 << 8) | Filter by snapshots stored internal to disk images
VIR_DOMAIN_SNAPSHOT_LIST_EXTERNAL | = | 512 (0x200; 1 << 9) | Filter by snapshots that use files external to disk images
VIR_DOMAIN_SNAPSHOT_LIST_TOPOLOGICAL | = | 1024 (0x400; 1 << 10) | Ensure parents occur before children in the resulting list

    }

### `virDomainSnapshotRevertFlags`

    enum virDomainSnapshotRevertFlags {

VIR_DOMAIN_SNAPSHOT_REVERT_RUNNING | = | 1 (0x1; 1 << 0) | Run after revert
VIR_DOMAIN_SNAPSHOT_REVERT_PAUSED | = | 2 (0x2; 1 << 1) | Pause after revert
VIR_DOMAIN_SNAPSHOT_REVERT_FORCE | = | 4 (0x4; 1 << 2) | Allow risky reverts

    }

### `virDomainSnapshotXMLFlags`

    enum virDomainSnapshotXMLFlags {

VIR_DOMAIN_SNAPSHOT_XML_SECURE | = | VIR_DOMAIN_XML_SECURE | dump security sensitive information too

    }

### Functions

### `virDomainHasCurrentSnapshot`

    int	virDomainHasCurrentSnapshot	(virDomainPtr domain,
    					 unsigned int flags)

Determine if the domain has a current snapshot.

domain
  pointer to the domain object
flags
  extra flags; not used yet, so callers should always pass 0
Returns
  1 if such snapshot exists, 0 if it doesn't, -1 on error.

### `virDomainListAllSnapshots`

    int	virDomainListAllSnapshots	(virDomainPtr domain,
    					 virDomainSnapshotPtr ** snaps,
    					 unsigned int flags)

Collect the list of domain snapshots for the given domain and allocate an array to store those objects. This API solves the race inherent in virDomainSnapshotListNames().

If @flags contains VIR_DOMAIN_SNAPSHOT_LIST_TOPOLOGICAL and @snaps is non-NULL, and no other connection is modifying snapshots, then it is guaranteed that for any snapshot in the resulting list, no snapshots later in the list can be reached by a sequence of virDomainSnapshotGetParent() starting from that earlier snapshot; otherwise, the order of snapshots in the resulting list is unspecified.

By default, this command covers all snapshots. It is also possible to limit things to just snapshots with no parents, when @flags includes VIR_DOMAIN_SNAPSHOT_LIST_ROOTS. Additional filters are provided in groups listed below. Within a group, bits are mutually exclusive, where all possible snapshots are described by exactly one bit from the group. Some hypervisors might reject particular flags where it cannot make a distinction for filtering. If the set of filter flags selected forms an impossible combination, the hypervisor may return either 0 or an error.

The first group of @flags is VIR_DOMAIN_SNAPSHOT_LIST_LEAVES and VIR_DOMAIN_SNAPSHOT_LIST_NO_LEAVES, to filter based on snapshots that have no further children (a leaf snapshot).

The next group of @flags is VIR_DOMAIN_SNAPSHOT_LIST_METADATA and VIR_DOMAIN_SNAPSHOT_LIST_NO_METADATA, for filtering snapshots based on whether they have metadata that would prevent the removal of the last reference to a domain.

The next group of @flags is VIR_DOMAIN_SNAPSHOT_LIST_INACTIVE, VIR_DOMAIN_SNAPSHOT_LIST_ACTIVE, and VIR_DOMAIN_SNAPSHOT_LIST_DISK_ONLY, for filtering snapshots based on what domain state is tracked by the snapshot.

The next group of @flags is VIR_DOMAIN_SNAPSHOT_LIST_INTERNAL and VIR_DOMAIN_SNAPSHOT_LIST_EXTERNAL, for filtering snapshots based on whether the snapshot is stored inside the disk images or as additional files.

domain
  a domain object
snaps
  pointer to variable to store the array containing snapshot objects or NULL if the list is not required (just returns number of snapshots)
flags
  bitwise-OR of supported virDomainSnapshotListFlags
Returns
  the number of domain snapshots found or -1 and sets @snaps to NULL in case of error. On success, the array stored into @snaps is guaranteed to have an extra allocated element set to NULL but not included in the return count, to make iteration easier. The caller is responsible for calling virDomainSnapshotFree() on each array element, then calling free() on @snaps.

### `virDomainRevertToSnapshot`

    int	virDomainRevertToSnapshot	(virDomainSnapshotPtr snapshot,
    					 unsigned int flags)

Revert the domain to a given snapshot.

Normally, the domain will revert to the same state the domain was in while the snapshot was taken (whether inactive, running, or paused), except that disk snapshots default to reverting to inactive state. Including VIR_DOMAIN_SNAPSHOT_REVERT_RUNNING in @flags overrides the snapshot state to guarantee a running domain after the revert; or including VIR_DOMAIN_SNAPSHOT_REVERT_PAUSED in @flags guarantees a paused domain after the revert. These two flags are mutually exclusive. While a persistent domain does not need either flag, it is not possible to revert a transient domain into an inactive state, so transient domains require the use of one of these two flags.

Reverting to any snapshot discards all configuration changes made since the last snapshot. Additionally, reverting to a snapshot from a running domain is a form of data loss, since it discards whatever is in the guest's RAM at the time. Since the very nature of keeping snapshots implies the intent to roll back state, no additional confirmation is normally required for these lossy effects.

However, there are two particular situations where reverting will be refused by default, and where @flags must include VIR_DOMAIN_SNAPSHOT_REVERT_FORCE to acknowledge the risks. 1) Any attempt to revert to a snapshot that lacks the metadata to perform ABI compatibility checks (generally the case for snapshots that lack a full <domain> when listed by virDomainSnapshotGetXMLDesc(), such as those created prior to libvirt 0.9.5). 2) Any attempt to revert a running domain to an active state that requires starting a new hypervisor instance rather than reusing the existing hypervisor (since this would terminate all connections to the domain, such as such as VNC or Spice graphics) - this condition arises from active snapshots that are provably ABI incompatible, as well as from inactive snapshots with a @flags request to start the domain after the revert.

snapshot
  a domain snapshot object
flags
  bitwise-OR of virDomainSnapshotRevertFlags
Returns
  0 if the creation is successful, -1 on error.

### `virDomainSnapshotCreateXML`

    virDomainSnapshotPtr	virDomainSnapshotCreateXML	(virDomainPtr domain,
    							 const char * xmlDesc,
    							 unsigned int flags)

Creates a new snapshot of a domain based on the snapshot xml contained in xmlDesc, with a top-level element <domainsnapshot>.

If @flags is 0, the domain can be active, in which case the snapshot will be a full system snapshot (capturing both disk state, and runtime VM state such as RAM contents), where reverting to the snapshot is the same as resuming from hibernation (TCP connections may have timed out, but everything else picks up where it left off); or the domain can be inactive, in which case the snapshot includes just the disk state prior to booting. The newly created snapshot becomes current (see virDomainSnapshotCurrent()), and is a child of any previous current snapshot.

If @flags includes VIR_DOMAIN_SNAPSHOT_CREATE_VALIDATE, then @xmlDesc is validated against the <domainsnapshot> XML schema.

If @flags includes VIR_DOMAIN_SNAPSHOT_CREATE_REDEFINE, then this is a request to reinstate snapshot metadata that was previously captured from virDomainSnapshotGetXMLDesc() before removing that metadata, rather than creating a new snapshot. This can be used to recreate a snapshot hierarchy on a destination, then remove it on the source, in order to allow migration (since migration normally fails if snapshot metadata still remains on the source machine). Note that while original creation can omit a number of elements from @xmlDesc (and libvirt will supply sane defaults based on the domain state at that point in time), a redefinition must supply more elements (as the domain may have changed in the meantime, so that libvirt no longer has a way to resupply correct defaults). When redefining snapshot metadata, the domain's current snapshot will not be altered unless the VIR_DOMAIN_SNAPSHOT_CREATE_CURRENT flag is also present. It is an error to request the VIR_DOMAIN_SNAPSHOT_CREATE_CURRENT flag without VIR_DOMAIN_SNAPSHOT_CREATE_REDEFINE. On some hypervisors, redefining an existing snapshot can be used to alter host-specific portions of the domain XML to be used during revert (such as backing filenames associated with disk devices), but must not alter guest-visible layout. When redefining a snapshot name that does not exist, the hypervisor may validate that reverting to the snapshot appears to be possible (for example, disk images have snapshot contents by the requested name). Not all hypervisors support these flags.

If @flags includes VIR_DOMAIN_SNAPSHOT_CREATE_NO_METADATA, then the domain's disk images are modified according to @xmlDesc, but libvirt does not track any metadata (similar to immediately calling virDomainSnapshotDelete() with VIR_DOMAIN_SNAPSHOT_DELETE_METADATA_ONLY). This flag is incompatible with VIR_DOMAIN_SNAPSHOT_CREATE_REDEFINE.

If @flags includes VIR_DOMAIN_SNAPSHOT_CREATE_HALT, then the domain will be inactive after the snapshot completes, regardless of whether it was active before; otherwise, a running domain will still be running after the snapshot. This flag is invalid on transient domains, and is incompatible with VIR_DOMAIN_SNAPSHOT_CREATE_REDEFINE.

If @flags includes VIR_DOMAIN_SNAPSHOT_CREATE_LIVE, then the domain is not paused while creating the snapshot. This increases the size of the memory dump file, but reduces downtime of the guest while taking the snapshot. Some hypervisors only support this flag during external snapshots.

If @flags includes VIR_DOMAIN_SNAPSHOT_CREATE_DISK_ONLY, then the snapshot will be limited to the disks described in @xmlDesc, and no VM state will be saved. For an active guest, the disk image may be inconsistent (as if power had been pulled), and specifying this with the VIR_DOMAIN_SNAPSHOT_CREATE_HALT flag risks data loss.

If @flags includes VIR_DOMAIN_SNAPSHOT_CREATE_QUIESCE, then the libvirt will attempt to use guest agent to freeze and thaw all file systems in use within domain OS. However, if the guest agent is not present, an error is thrown. Moreover, this flag requires VIR_DOMAIN_SNAPSHOT_CREATE_DISK_ONLY to be passed as well.

By default, if the snapshot involves external files, and any of the destination files already exist as a non-empty regular file, the snapshot is rejected to avoid losing contents of those files. However, if @flags includes VIR_DOMAIN_SNAPSHOT_CREATE_REUSE_EXT, then the destination files must be pre-created manually with the correct image format and metadata including backing store path (this allows a management app to pre-create files with relative backing file names, rather than the default of creating with absolute backing file names). Note that only the file specified in the snapshot XML is inserted as a snapshot thus setting incorrect metadata in the pre-created image may lead to the VM being unable to start or other block jobs may fail.

Be aware that although libvirt prefers to report errors up front with no other effect, some hypervisors have certain types of failures where the overall command can easily fail even though the guest configuration was partially altered (for example, if a disk snapshot request for two disks fails on the second disk, but the first disk alteration cannot be rolled back). If this API call fails, it is therefore normally necessary to follow up with virDomainGetXMLDesc() and check each disk to determine if any partial changes occurred. However, if @flags contains VIR_DOMAIN_SNAPSHOT_CREATE_ATOMIC, then libvirt guarantees that this command will not alter any disks unless the entire set of changes can be done atomically, making failure recovery simpler (note that it is still possible to fail after disks have changed, but only in the much rarer cases of running out of memory or disk space).

Some hypervisors may prevent this operation if there is a current block copy operation; in that case, use virDomainBlockJobAbort() to stop the block copy first.

virDomainSnapshotFree should be used to free the resources after the snapshot object is no longer needed.

domain
  a domain object
xmlDesc
  string containing an XML description of the domain snapshot
flags
  bitwise-OR of virDomainSnapshotCreateFlags
Returns
  an (opaque) new virDomainSnapshotPtr on success or NULL on failure.

### `virDomainSnapshotCurrent`

    virDomainSnapshotPtr	virDomainSnapshotCurrent	(virDomainPtr domain,
    							 unsigned int flags)

Get the current snapshot for a domain, if any.

virDomainSnapshotFree should be used to free the resources after the snapshot object is no longer needed.

domain
  a domain object
flags
  extra flags; not used yet, so callers should always pass 0
Returns
  a domain snapshot object or NULL in case of failure. If the current domain snapshot cannot be found, then the VIR_ERR_NO_DOMAIN_SNAPSHOT error is raised.

### `virDomainSnapshotDelete`

    int	virDomainSnapshotDelete		(virDomainSnapshotPtr snapshot,
    					 unsigned int flags)

Delete the snapshot.

If @flags is 0, then just this snapshot is deleted, and changes from this snapshot are automatically merged into children snapshots. If @flags includes VIR_DOMAIN_SNAPSHOT_DELETE_CHILDREN, then this snapshot and any descendant snapshots are deleted. If @flags includes VIR_DOMAIN_SNAPSHOT_DELETE_CHILDREN_ONLY, then any descendant snapshots are deleted, but this snapshot remains. These two flags are mutually exclusive.

If @flags includes VIR_DOMAIN_SNAPSHOT_DELETE_METADATA_ONLY, then any snapshot metadata tracked by libvirt is removed while keeping the snapshot contents intact; if a hypervisor does not require any libvirt metadata to track snapshots, then this flag is silently ignored.

snapshot
  a domain snapshot object
flags
  bitwise-OR of supported virDomainSnapshotDeleteFlags
Returns
  0 if the selected snapshot(s) were successfully deleted, -1 on error.

### `virDomainSnapshotFree`

    int	virDomainSnapshotFree		(virDomainSnapshotPtr snapshot)

Free the domain snapshot object. The snapshot itself is not modified. The data structure is freed and should not be used thereafter.

snapshot
  a domain snapshot object
Returns
  0 in case of success and -1 in case of failure.

### `virDomainSnapshotGetConnect`

    virConnectPtr	virDomainSnapshotGetConnect	(virDomainSnapshotPtr snapshot)

Provides the connection pointer associated with a snapshot. The reference counter on the connection is not increased by this call.

snapshot
  a snapshot object
Returns
  the connection or NULL.

### `virDomainSnapshotGetDomain`

    virDomainPtr	virDomainSnapshotGetDomain	(virDomainSnapshotPtr snapshot)

Provides the domain pointer associated with a snapshot. The reference counter on the domain is not increased by this call.

snapshot
  a snapshot object
Returns
  the domain or NULL.

### `virDomainSnapshotGetName`

    const char *	virDomainSnapshotGetName	(virDomainSnapshotPtr snapshot)

Get the public name for that snapshot

snapshot
  a snapshot object
Returns
  a pointer to the name or NULL, the string need not be deallocated as its lifetime will be the same as the snapshot object.

### `virDomainSnapshotGetParent`

    virDomainSnapshotPtr	virDomainSnapshotGetParent	(virDomainSnapshotPtr snapshot,
    							 unsigned int flags)

Get the parent snapshot for @snapshot, if any.

virDomainSnapshotFree should be used to free the resources after the snapshot object is no longer needed.

snapshot
  a snapshot object
flags
  extra flags; not used yet, so callers should always pass 0
Returns
  a domain snapshot object or NULL in case of failure. If the given snapshot is a root (no parent), then the VIR_ERR_NO_DOMAIN_SNAPSHOT error is raised.

### `virDomainSnapshotGetXMLDesc`

    char *	virDomainSnapshotGetXMLDesc	(virDomainSnapshotPtr snapshot,
    					 unsigned int flags)

Provide an XML description of the domain snapshot, with a top-level element of <domainsnapshot>.

No security-sensitive data will be included unless @flags contains VIR_DOMAIN_SNAPSHOT_XML_SECURE; this flag is rejected on read-only connections.

snapshot
  a domain snapshot object
flags
  bitwise-OR of supported virDomainSnapshotXMLFlags
Returns
  a 0 terminated UTF-8 encoded XML instance or NULL in case of error. The caller must free() the returned value.

### `virDomainSnapshotHasMetadata`

    int	virDomainSnapshotHasMetadata	(virDomainSnapshotPtr snapshot,
    					 unsigned int flags)

Determine if the given snapshot is associated with libvirt metadata that would prevent the deletion of the domain.

snapshot
  a snapshot object
flags
  extra flags; not used yet, so callers should always pass 0
Returns
  1 if the snapshot has metadata, 0 if the snapshot exists without help from libvirt, or -1 on error.

### `virDomainSnapshotIsCurrent`

    int	virDomainSnapshotIsCurrent	(virDomainSnapshotPtr snapshot,
    					 unsigned int flags)

Determine if the given snapshot is the domain's current snapshot. See also virDomainHasCurrentSnapshot().

snapshot
  a snapshot object
flags
  extra flags; not used yet, so callers should always pass 0
Returns
  1 if current, 0 if not current, or -1 on error.

### `virDomainSnapshotListAllChildren`

    int	virDomainSnapshotListAllChildren	(virDomainSnapshotPtr snapshot,
    						 virDomainSnapshotPtr ** snaps,
    						 unsigned int flags)

Collect the list of domain snapshots that are children of the given snapshot, and allocate an array to store those objects. This API solves the race inherent in virDomainSnapshotListChildrenNames().

If @flags lacks VIR_DOMAIN_SNAPSHOT_LIST_DESCENDANTS or contains VIR_DOMAIN_SNAPSHOT_LIST_TOPOLOGICAL, @snaps is non-NULL, and no other connection is modifying snapshots, then it is guaranteed that for any snapshot in the resulting list, no snapshots later in the list can be reached by a sequence of virDomainSnapshotGetParent() starting from that earlier snapshot; otherwise, the order of snapshots in the resulting list is unspecified.

By default, this command covers only direct children. It is also possible to expand things to cover all descendants, when @flags includes VIR_DOMAIN_SNAPSHOT_LIST_DESCENDANTS. Additional filters are provided via the remaining @flags values as documented in virDomainListAllSnapshots(), with the exception that VIR_DOMAIN_SNAPSHOT_LIST_ROOTS is not supported (in fact, VIR_DOMAIN_SNAPSHOT_LIST_DESCENDANTS has the same bit value but opposite semantics of widening rather than narrowing the listing).

snapshot
  a domain snapshot object
snaps
  pointer to variable to store the array containing snapshot objects or NULL if the list is not required (just returns number of snapshots)
flags
  bitwise-OR of supported virDomainSnapshotListFlags
Returns
  the number of domain snapshots found or -1 and sets @snaps to NULL in case of error. On success, the array stored into @snaps is guaranteed to have an extra allocated element set to NULL but not included in the return count, to make iteration easier. The caller is responsible for calling virDomainSnapshotFree() on each array element, then calling free() on @snaps.

### `virDomainSnapshotListChildrenNames`

    int	virDomainSnapshotListChildrenNames	(virDomainSnapshotPtr snapshot,
    						 char ** names,
    						 int nameslen,
    						 unsigned int flags)

Collect the list of domain snapshots that are children of the given snapshot, and store their names in @names. The value to use for @nameslen can be determined by virDomainSnapshotNumChildren() with the same @flags.

If @flags lacks VIR_DOMAIN_SNAPSHOT_LIST_DESCENDANTS or contains VIR_DOMAIN_SNAPSHOT_LIST_TOPOLOGICAL, and no other connection is modifying snapshots, then it is guaranteed that for any snapshot in the resulting list, no snapshots later in the list can be reached by a sequence of virDomainSnapshotGetParent() starting from that earlier snapshot; otherwise, the order of snapshots in the resulting list is unspecified.

By default, this command covers only direct children. It is also possible to expand things to cover all descendants, when @flags includes VIR_DOMAIN_SNAPSHOT_LIST_DESCENDANTS. Additional filters are provided via the same @flags values as documented in virDomainSnapshotListAllChildren().

Note that this command is inherently racy: another connection can define a new snapshot between a call to virDomainSnapshotNumChildren() and this call. You are only guaranteed that all currently defined snapshots were listed if the return is less than @nameslen. Likewise, you should be prepared for virDomainSnapshotLookupByName() to fail when converting a name from this call into a snapshot object, if another connection deletes the snapshot in the meantime. For more control over the results, see virDomainSnapshotListAllChildren().

snapshot
  a domain snapshot object
names
  array to collect the list of names of snapshots
nameslen
  size of @names
flags
  bitwise-OR of supported virDomainSnapshotListFlags
Returns
  the number of domain snapshots found or -1 in case of error. The caller is responsible to call free() for each member of the array.

### `virDomainSnapshotListNames`

    int	virDomainSnapshotListNames	(virDomainPtr domain,
    					 char ** names,
    					 int nameslen,
    					 unsigned int flags)

Collect the list of domain snapshots for the given domain, and store their names in @names. The value to use for @nameslen can be determined by virDomainSnapshotNum() with the same @flags.

If @flags contains VIR_DOMAIN_SNAPSHOT_LIST_TOPOLOGICAL, and no other connection is modifying snapshots, then it is guaranteed that for any snapshot in the resulting list, no snapshots later in the list can be reached by a sequence of virDomainSnapshotGetParent() starting from that earlier snapshot; otherwise, the order of snapshots in the resulting list is unspecified.

By default, this command covers all snapshots. It is also possible to limit things to just snapshots with no parents, when @flags includes VIR_DOMAIN_SNAPSHOT_LIST_ROOTS. Additional filters are provided via the same @flags values as documented in virDomainListAllSnapshots().

Note that this command is inherently racy: another connection can define a new snapshot between a call to virDomainSnapshotNum() and this call. You are only guaranteed that all currently defined snapshots were listed if the return is less than @nameslen. Likewise, you should be prepared for virDomainSnapshotLookupByName() to fail when converting a name from this call into a snapshot object, if another connection deletes the snapshot in the meantime. For more control over the results, see virDomainListAllSnapshots().

domain
  a domain object
names
  array to collect the list of names of snapshots
nameslen
  size of @names
flags
  bitwise-OR of supported virDomainSnapshotListFlags
Returns
  the number of domain snapshots found or -1 in case of error. The caller is responsible to call free() for each member of the array.

### `virDomainSnapshotLookupByName`

    virDomainSnapshotPtr	virDomainSnapshotLookupByName	(virDomainPtr domain,
    							 const char * name,
    							 unsigned int flags)

Try to lookup a domain snapshot based on its name.

domain
  a domain object
name
  name for the domain snapshot
flags
  extra flags; not used yet, so callers should always pass 0
Returns
  a domain snapshot object or NULL in case of failure. If the domain snapshot cannot be found, then the VIR_ERR_NO_DOMAIN_SNAPSHOT error is raised.

### `virDomainSnapshotNum`

    int	virDomainSnapshotNum		(virDomainPtr domain,
    					 unsigned int flags)

Provides the number of domain snapshots for this domain.

This function will accept VIR_DOMAIN_SNAPSHOT_LIST_TOPOLOGICAL in @flags only if virDomainSnapshotListNames() can honor it, although the flag has no other effect here.

By default, this command covers all snapshots. It is also possible to limit things to just snapshots with no parents, when @flags includes VIR_DOMAIN_SNAPSHOT_LIST_ROOTS. Additional filters are provided via the same @flags values as documented in virDomainListAllSnapshots().

domain
  a domain object
flags
  bitwise-OR of supported virDomainSnapshotListFlags
Returns
  the number of domain snapshots found or -1 in case of error.

### `virDomainSnapshotNumChildren`

    int	virDomainSnapshotNumChildren	(virDomainSnapshotPtr snapshot,
    					 unsigned int flags)

Provides the number of child snapshots for this domain snapshot.

This function will accept VIR_DOMAIN_SNAPSHOT_LIST_TOPOLOGICAL in @flags only if virDomainSnapshotListChildrenNames() can honor it, although the flag has no other effect here.

By default, this command covers only direct children. It is also possible to expand things to cover all descendants, when @flags includes VIR_DOMAIN_SNAPSHOT_LIST_DESCENDANTS. Additional filters are provided via the same @flags values as documented in virDomainSnapshotListAllChildren().

snapshot
  a domain snapshot object
flags
  bitwise-OR of supported virDomainSnapshotListFlags
Returns
  the number of domain snapshots found or -1 in case of error.

### `virDomainSnapshotRef`

    int	virDomainSnapshotRef		(virDomainSnapshotPtr snapshot)

Increment the reference count on the snapshot. For each additional call to this method, there shall be a corresponding call to virDomainSnapshotFree to release the reference count, once the caller no longer needs the reference to this object.

This method is typically useful for applications where multiple threads are using a connection, and it is required that the connection and domain remain open until all threads have finished using the snapshot. ie, each new thread using a snapshot would increment the reference count.

snapshot
  the snapshot to hold a reference on
Returns
  0 in case of success and -1 in case of failure.