Applications based on libvirt such as OpenStack need some public APIs about export/import of external snapshot during daily backup, snapshot recovery or system migration. virDomainSnapshotDiskExport, virDomainSnapshotVmstateExport and virDomainSnapshotImport are designed to satisfy such requirement. @flags: virDomainSnapshotExportImportFlags include, DATA_FULL: all data snapshot DATA_DELTA: delta data only /** * virDomainSnapshotDiskExport * @domain: the domain object to be exported snapshot * @id: top Overlays which to be exported * @base_id: RootBase of snapshot to be exported * @disk: block device of domain * @export_path: path of snapshots export * @flags: bitwise-OR of virDomainSnapshotExportImportFlags * * Import snapshot disk data to the pointed path. * * If @flags includes DATA_FULL, full backup snapshot will be exported. * * If @flags includes DATA_DELTA, incremental backup snapshot will be * exported. * * DATA_FULL and DATA_DELTA should not appear at the same time * * Returns 0 on success, or -1 on error */ int virDomainSnapshotDiskExport(virDomain *domain, virSnapshotId *id, virSnapshotId *base_id, virDevice *disk, char *export_path, unsigned int flags) Usage: export external snapshot disk file from virtual machine to the target path. /** * virDomainSnapshotVmstateExport * @domain: the domain object to be exported snapshot * @id: top Overlays which to be exported * @export_path: path of snapshots export * @flags: not used yet, so callers should always pass 0 * * Import snapshot vmstate data to the pointed path. * * If @flags includes DATA_FULL, full backup snapshot will be exported. * * If @flags includes DATA_DELTA, incremental backup snapshot will be * exported. * * DATA_FULL and DATA_DELTA should not appear at the same time * * Returns 0 on success, or -1 on error */ int virDomainSnapshotVmstateExport(virDomain *domain, virSnapshotId *id, char *export_path, unsigned int flags) Usage: dump vmstate file of snapshot and copy it to the target path. /** * virDomainSnapshotImport * @domain: the domain object to be exported snapshot * @xmlDesc: string containing an XML description of the domain * @flags: bitwise-OR of virDomainSnapshotExportImportFlags * * Import snapshot data to the pointed path. * * If @flags includes DATA_FULL, full backup snapshot will be exported. * * If @flags includes DATA_DELTA, incremental backup snapshot will be * exported. * * DATA_FULL and DATA_DELTA should not appear at the same time * * Returns 0 on success, or -1 on error */ int virDomainSnapshotImport(virDomain *domain, const char *xmlDesc, unsigned int flags) Usage: import .xml file of external snapshot and use it for recovering a virtual machine. Usecase: If users want to finish daily backup&recovery work by above APIs, the process should be, 1. call virDomainSnapshotDiskExport() to export pointed snapshot disk files to the traget path. ------------------- --------------------- | host A | | host B | | --------------- | | ----------------- | | | dom1 | | snapshot disk files | | backup folder | | | | base.img----------------------------------->base.img | | | | snap1.qcow2-------------------------------->snap1.qcow2 | | | | snap2.qcow2-------------------------------->snap2.qcow2 | | | --------------- | | ----------------- | ------------------- --------------------- virDomainSnapshotDiskSnapshot() 2. call virDomainSnapshotVmstateExport() to export vmstate data file to the target path. --------------- --------------------- | host A | | host B | | ----------- | | ----------------- | | | dom1 | | vmstate data files | | backup folder | | | | dumpxml-------------------------------->vmstate.xml | | | ----------- | | ----------------- | --------------- --------------------- virDomainSnapshotVmstateSnapshot() 3. when some error occured, or guest copy/migration, users copy snapshot disk files from host B to the target host and edit <source file> field of <disk> tag. Then users call virDomainSnapshotImport to recovery domain to the snapshot. a. copy snapshot disk files to the target host: ------------------------------- --------------------- | host A | snapshot | host B | | --------------------------- | disk | ----------------- | | | /var/lib/libvirt/images | | files | | backup folder | | | | base.img<-----------------------------------base.img | | | | snap1.qcow2<--------------------------------snap1.qcow2 | | | | snap2.qcow2<--------------------------------snap2.qcow2 | | | --------------------------- | | ----------------- | ------------------------------- --------------------- snapshot disk files transfer b. import vmstate data to recovery snapshot: --------------------- ------------------- | host B | | host A | | ----------------- | | --------------- | vmstate data | | backup folder | | | | dom1<-------------------------------vmstate.xml | | | | base.img | | | ----------------- | | | snap1.qcow2 | | --------------------- | | snap2.qcow2 | | | --------------- | ------------------- virDomainSnapshotImport()