Commit Graph

9 Commits

Author SHA1 Message Date
Christophe Fergeau
364554a01b docs: Fix closing tag in snapshot documentation
Commit cc6d19f3 added text containing "<code>snapshot<code>" to
formatsnapshot.html.in. The closing tag is missing '/' which causes
the documentation to misrender.
2013-05-01 20:03:12 +02:00
Christophe Fergeau
cc6d19f313 Improve /domainsnapshot/disks/disk@snapshot doc
The previous description was a bit confusing.
2013-04-25 21:57:19 +02:00
Eric Blake
4201a7ea1c snapshot: new XML for external system checkpoint
Each <domainsnapshot> can now contain an optional <memory>
element that describes how the VM state was handled, similar
to disk snapshots.  The new element will always appear in
output; for back-compat, an input that lacks the element will
assume 'no' or 'internal' according to the domain state.

Along with this change, it is now possible to pass <disks> in
the XML for an offline snapshot; this also needs to be wired up
in a future patch, to make it possible to choose internal vs.
external on a per-disk basis for each disk in an offline domain.
At that point, using the --disk-only flag for an offline domain
will be able to work.

For some examples below, remember that qemu supports the
following snapshot actions:

qemu-img: offline external and internal disk
savevm: online internal VM and disk
migrate: online external VM
transaction: online external disk

=====
<domainsnapshot>
  <memory snapshot='no'/>
  ...
</domainsnapshot>

implies that there is no VM state saved (mandatory for
offline and disk-only snapshots, not possible otherwise);
using qemu-img for offline domains and transaction for online.

=====
<domainsnapshot>
  <memory snapshot='internal'/>
  ...
</domainsnapshot>

state is saved inside one of the disks (as in qemu's 'savevm'
system checkpoint implementation).  If needed in the future,
we can also add an attribute pointing out _which_ disk saved
the internal state; maybe disk='vda'.

=====
<domainsnapshot>
  <memory snapshot='external' file='/path/to/state'/>
  ...
</domainsnapshot>

This is not wired up yet, but future patches will allow this to
control a combination of 'virsh save /path/to/state' plus disk
snapshots from the same point in time.

=====

So for 1.0.1 (and later, as needed), I plan to implement this table
of combinations, with '*' designating new code and '+' designating
existing code reached through new combinations of xml and/or the
existing DISK_ONLY flag:

domain  memory  disk   disk-only | result
-----------------------------------------
offline omit    omit   any       | memory=no disk=int, via qemu-img
offline no      omit   any       |+memory=no disk=int, via qemu-img
offline omit/no no     any       | invalid combination (nothing to snapshot)
offline omit/no int    any       |+memory=no disk=int, via qemu-img
offline omit/no ext    any       |*memory=no disk=ext, via qemu-img
offline int/ext any    any       | invalid combination (no memory to save)
online  omit    omit   off       | memory=int disk=int, via savevm
online  omit    omit   on        | memory=no disk=default, via transaction
online  omit    no/ext off       | unsupported for now
online  omit    no     on        | invalid combination (nothing to snapshot)
online  omit    ext    on        | memory=no disk=ext, via transaction
online  omit    int    off       |+memory=int disk=int, via savevm
online  omit    int    on        | unsupported for now
online  no      omit   any       |+memory=no disk=default, via transaction
online  no      no     any       | invalid combination (nothing to snapshot)
online  no      int    any       | unsupported for now
online  no      ext    any       |+memory=no disk=ext, via transaction
online  int/ext any    on        | invalid combination (disk-only vs. memory)
online  int     omit   off       |+memory=int disk=int, via savevm
online  int     no/ext off       | unsupported for now
online  int     int    off       |+memory=int disk=int, via savevm
online  ext     omit   off       |*memory=ext disk=default, via migrate+trans
online  ext     no     off       |+memory=ext disk=no, via migrate
online  ext     int    off       | unsupported for now
online  ext     ext    off       |*memory=ext disk=ext, via migrate+transaction

* docs/schemas/domainsnapshot.rng (memory): New RNG element.
* docs/formatsnapshot.html.in: Document it.
* src/conf/snapshot_conf.h (virDomainSnapshotDef): New fields.
* src/conf/domain_conf.c (virDomainSnapshotDefFree)
(virDomainSnapshotDefParseString, virDomainSnapshotDefFormat):
Manage new fields.
* tests/domainsnapshotxml2xmltest.c: New test.
* tests/domainsnapshotxml2xmlin/*.xml: Update existing tests.
* tests/domainsnapshotxml2xmlout/*.xml: Likewise.
2012-11-02 09:56:23 -06:00
Eric Blake
89b6284fd9 snapshot: also support disks by path
I got confused when 'virsh domblkinfo dom disk' required the
path to a disk (which can be ambiguous, since a single file
can back multiple disks), rather than the unambiguous target
device name that I was using in disk snapshots.  So, in true
developer fashion, I went for the best of both worlds - all
interfaces that operate on a disk (aka block) now accept
either the target name or the unambiguous path to the backing
file used by the disk.

* src/conf/domain_conf.h (virDomainDiskIndexByName): Add
parameter.
(virDomainDiskPathByName): New prototype.
* src/libvirt_private.syms (domain_conf.h): Export it.
* src/conf/domain_conf.c (virDomainDiskIndexByName): Also allow
searching by path, and decide whether ambiguity is okay.
(virDomainDiskPathByName): New function.
(virDomainDiskRemoveByName, virDomainSnapshotAlignDisks): Update
callers.
* src/qemu/qemu_driver.c (qemudDomainBlockPeek)
(qemuDomainAttachDeviceConfig, qemuDomainUpdateDeviceConfig)
(qemuDomainGetBlockInfo, qemuDiskPathToAlias): Likewise.
* src/qemu/qemu_process.c (qemuProcessFindDomainDiskByPath):
Likewise.
* src/libxl/libxl_driver.c (libxlDomainAttachDeviceDiskLive)
(libxlDomainDetachDeviceDiskLive, libxlDomainAttachDeviceConfig)
(libxlDomainUpdateDeviceConfig): Likewise.
* src/uml/uml_driver.c (umlDomainBlockPeek): Likewise.
* src/xen/xend_internal.c (xenDaemonDomainBlockPeek): Likewise.
* docs/formatsnapshot.html.in: Update documentation.
* tools/virsh.pod (domblkstat, domblkinfo): Likewise.
* docs/schemas/domaincommon.rng (diskTarget): Tighten pattern on
disk targets.
* docs/schemas/domainsnapshot.rng (disksnapshot): Update to match.
* tests/domainsnapshotxml2xmlin/disk_snapshot.xml: Update test.
2011-09-05 07:03:04 -06:00
Eric Blake
d6f6b2d194 snapshot: add <disks> to snapshot xml
Adds an optional element to <domainsnapshot>, which will be used
to give user control over external snapshot filenames on input,
and specify generated filenames on output.

For now, no driver accepts this element; that will come later.

<domainsnapshot>
  ...
  <disks>
    <disk name='vda' snapshot='no'/>
    <disk name='vdb' snapshot='internal'/>
    <disk name='vdc' snapshot='external'>
      <driver type='qcow2'/>
      <source file='/path/to/new'/>
    </disk>
  </disks>
  <domain>
    ...
    <devices>
      <disk ...>
        <driver name='qemu' type='raw'/>
        <target dev='vdc'/>
        <source file='/path/to/old'/>
      </disk>
    </devices>
  </domain>
</domainsnapshot>

* src/conf/domain_conf.h (_virDomainSnapshotDiskDef): New type.
(_virDomainSnapshotDef): Add new elements.
(virDomainSnapshotAlignDisks): New prototype.
* src/conf/domain_conf.c (virDomainSnapshotDiskDefClear)
(virDomainSnapshotDiskDefParseXML, disksorter)
(virDomainSnapshotAlignDisks): New functions.
(virDomainSnapshotDefParseString): Parse new fields.
(virDomainSnapshotDefFree): Clean them up.
(virDomainSnapshotDefFormat): Output them.
* src/libvirt_private.syms (domain_conf.h): Export new function.
* docs/schemas/domainsnapshot.rng (domainsnapshot, disksnapshot):
Add more xml.
* docs/formatsnapshot.html.in: Document it.
* tests/domainsnapshotxml2xmlin/disk_snapshot.xml: New test.
* tests/domainsnapshotxml2xmlout/disk_snapshot.xml: Update.
2011-09-05 07:03:04 -06:00
Eric Blake
5b30b08d66 snapshot: support extra state in snapshots
In order to distinguish disk snapshots from system checkpoints, a
new state value that is only valid for snapshots is helpful.

* include/libvirt/libvirt.h.in (VIR_DOMAIN_LAST): New placeholder.
* src/conf/domain_conf.h (virDomainSnapshotState): New enum mapping.
(VIR_DOMAIN_DISK_SNAPSHOT): New internal enum value.
* src/conf/domain_conf.c (virDomainState): Use placeholder.
(virDomainSnapshotState): Extend mapping by one for use in snapshot.
(virDomainSnapshotDefParseString, virDomainSnapshotDefFormat):
Handle new state.
(virDomainObjSetState, virDomainStateReasonToString)
(virDomainStateReasonFromString): Avoid compiler warnings.
* tools/virsh.c (vshDomainState, vshDomainStateReasonToString):
Likewise.
* src/libvirt_private.syms (domain_conf.h): Export new functions.
* docs/schemas/domainsnapshot.rng: Tighten state definition.
* docs/formatsnapshot.html.in: Document it.
* tests/domainsnapshotxml2xmlout/disk_snapshot.xml: New test.
2011-09-05 07:03:04 -06:00
Eric Blake
f609cb85ca snapshot: allow full domain xml in snapshot
Just like VM saved state images (virsh save), snapshots MUST
track the inactive domain xml to detect any ABI incompatibilities.

The indentation is not perfect, but functionality comes before form.

Later patches will actually supply a full domain; for now, this
wires up the storage to support one, but doesn't ever generate one
in dumpxml output.

Happily, libvirt.c was already rejecting use of VIR_DOMAIN_XML_SECURE
from read-only connections, even though before this patch, there was
no information to be secured by the use of that flag.

And while we're at it, mark the libvirt snapshot metadata files
as internal-use only.

* src/libvirt.c (virDomainSnapshotGetXMLDesc): Document flag.
* src/conf/domain_conf.h (_virDomainSnapshotDef): Add member.
(virDomainSnapshotDefParseString, virDomainSnapshotDefFormat):
Update signature.
* src/conf/domain_conf.c (virDomainSnapshotDefFree): Clean up.
(virDomainSnapshotDefParseString): Optionally parse domain.
(virDomainSnapshotDefFormat): Output full domain.
* src/esx/esx_driver.c (esxDomainSnapshotCreateXML)
(esxDomainSnapshotGetXMLDesc): Update callers.
* src/vbox/vbox_tmpl.c (vboxDomainSnapshotCreateXML)
(vboxDomainSnapshotGetXMLDesc): Likewise.
* src/qemu/qemu_driver.c (qemuDomainSnapshotCreateXML)
(qemuDomainSnapshotLoad, qemuDomainSnapshotGetXMLDesc)
(qemuDomainSnapshotWriteMetadata): Likewise.
* docs/formatsnapshot.html.in: Rework doc example.
Based on a patch by Philipp Hahn.
2011-09-03 08:09:35 -06:00
Eric Blake
af65695af0 snapshot: allow recreation of metadata
The first two flags are essential for being able to replicate
snapshot hierarchies across multiple hosts, which will come in
handy for supervised migrations.  It also allows a management app
to take a snapshot of a transient domain, save the metadata, stop
the domain, recreate a new transient domain by the same name,
redefine the snapshot, then revert to it.

This is not quite as convenient as leaving the metadata behind
after a domain is no longer around, but doing that has a few
problems: 1. the libvirt API can only delete snapshot metadata
if there is a valid domain handle to use to get to that snapshot
object - if stale data is left behind without a domain, there is
no way to request that the data be cleaned up. 2. creating a new
domain with the same name but different uuid than the older
domain where a snapshot existed cannot use the older snapshot
data; this risks confusing libvirt, and forbidding the stale
data is similar to the recent patch to forbid stale managed save.

The first two flags might be useful on hypervisors with no metadata,
but only for modifying the notion of the current snapshot;
however, I don't know how to do that for ESX or VBox.

The third flag is a convenience option, to combine a creation with
a delete metadata into one step.  It is trivial for hypervisors
with no metadata.

The qemu changes will be involved enough to warrant a separate patch.

* include/libvirt/libvirt.h.in
(VIR_DOMAIN_SNAPSHOT_CREATE_REDEFINE)
(VIR_DOMAIN_SNAPSHOT_CREATE_CURRENT)
(VIR_DOMAIN_SNAPSHOT_CREATE_NO_METADATA): New flags.
* src/libvirt.c (virDomainSnapshotCreateXML): Document them, and
enforce mutual exclusion.
* src/esx/esx_driver.c (esxDomainSnapshotCreateXML): Trivial
implementation.
* src/vbox/vbox_tmpl.c (vboxDomainSnapshotCreateXML): Likewise.
* docs/formatsnapshot.html.in: Document re-creation.
2011-09-02 17:44:42 -06:00
Chris Lalancette
86fe2ba6dc Website documentation for the snapshot XML.
Signed-off-by: Chris Lalancette <clalance@redhat.com>
2010-04-06 09:44:03 -04:00