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27 Commits

Author SHA1 Message Date
Eric Blake
7efe930ec3 backup: Prevent snapshots and checkpoints at same time
Earlier patches mentioned that the initial implementation will prevent
snapshots and checkpoints from being used on the same domain at once.
However, the actual restriction is done in this separate patch to make
it easier to lift that restriction via a revert, when we are finally
ready to tackle that integration in the future.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
2019-07-29 08:22:29 -05:00
Eric Blake
9943c42a22 backup: Document nuances between different state capture APIs
Now that various new API have been added or are coming soon, it is
worth a landing page that gives an overview of capturing various
pieces of guest state, and which APIs are best suited to which tasks.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
2019-07-26 16:48:58 -05:00
Eric Blake
48c656ca55 snapshot: Documentation and comment improvements
Changes noticed while copying to similar aspects of checkpoints.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
2019-07-24 17:03:34 -05:00
Peter Krempa
ac88a8cfad docs: schemas: Add 'seclabel' for external disk snapshot
Allow using seclabels the same way as disk images allow it. Currently
the snapshot code copies the seclabels from the original image if no
seclabel is provided. Also there's no code change required as the
snapshot XML parser actually uses parts of the disk parser thus
seclabels are already parsed and formatted and even applied thus this is
just a formalization of our support for this.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
2019-06-20 17:08:53 +02:00
Peter Krempa
c79ef73c37 docs: snapshot: Encourage people ot use disk 'target' to refer to disks
Change the example and add a recommendation to use disk target rather
than path.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
2019-06-20 17:08:53 +02:00
Eric Blake
1c6b6c0ba1 snapshot: Various doc tweaks
Since I was copying this text to form checkpoint XML and API
documentation, I might as well make improvements along the way. Most
of these changes are based on reviews of the checkpoint docs.

Among other things: grammar tweaks, point to a single source of
documentation rather than repeating verbosity, reword things for
easier legibility.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
2019-03-26 15:33:07 -05:00
Eric Blake
a6a25d5cb6 snapshot: More clarification about REDEFINE
Based on recent list questions about the proposed addition of
virDomainCheckpointCreateXML(REDEFINE), it is worth adding some
clarification to the existing snapshot redefine documentation that is
serving as the basis for checkpoints.

Normal snapshot creation requires very few elements from the user XML
(libvirt can pick sane defaults for items that are omitted, and many
fields, including <domain>, are documented as readonly output fields
ignored on input, produced by drivers that track it). But during
REDEFINE, the API wants the complete XML produced by an earlier
virDomainSnapshotGetXMLDesc; as the domain definition has likely
changed since the snapshot was first created, libvirt is unable to
recreate a <domain> sub-element that matches the original output
representing the domain state at the time the snapshot was first
created. In fact, reverting without a <domain> sub-element is risky
enough that we had to add a FORCE flag for virDomainSnapshotRevert().
In short, we only support omitting domain for qemu because of
backwards-compatibility to snapshots created before 0.9.5 started
capturing <domain>; even though there are other drivers like vbox that
do not output <domain> because they have other reliable ways to
revert.

And based on the confusion caused when omitting <domain> from snapshot
XML, the initial design for checkpoints in later patches will make
<domain> a mandatory element during its REDEFINE.

[Side note: the fact that <domain> can appear in <domainsnapshot> is a
reason we cannot add a new API for a bulk listing or redefine of all
snapshots of a single domain in one XML call (for example, a 1M
<domain> XML * 16 snapshots explodes into 16M in a bulk form, which
gets difficult to send over RPC). Perhaps we could add a flag to
request that the <domain> sub-element be omitted on output, but such
output is no longer suitable for sane REDEFINE input.]

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
2019-03-15 08:32:37 -05:00
Eric Blake
d152c727c6 snapshots: Avoid term 'checkpoint' for full system snapshot
Upcoming patches plan to introduce virDomainCheckpointPtr as a new
object for use in incremental backups, along with documentation on
how incremental backups differ from snapshots.  But first, we need
to rename any existing mention of a 'system checkpoint' to instead
be a 'full system snapshot', so that we aren't overloading
the term checkpoint.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>
2019-02-26 15:48:58 -06:00
Daniel P. Berrange
b1c81567c7 docs: switch to using HTML5 doctype declaration
The HTML5 doctype is simply

  <!DOCTYPE html>

no DTD is present because HTML5 is no longer defined as an
extension of SGML.

XSL has no way to natively output a doctype without a public
or system identifier, so we have to use an <xsl:text> hack
instead.

See also

  https://dev.w3.org/html5/html-author/#doctype-declaration

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
2017-08-02 17:00:11 +01:00
Daniel P. Berrange
4e42ff6b7e docs: switch to using 'id' attribute instead of 'name' for links
The 'name' attribute on <a...> elements is deprecated in favour
of the 'id' attribute which is allowed on any element. HTML5
drops 'name' support entirely.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
2017-08-02 17:00:11 +01:00
Jiri Denemark
5c2f01abcb qemu: Store save cookie in save images and snapshots
The following patches will add an actual content in the cookie and use
the data when restoring a domain.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Pavel Hrdina <phrdina@redhat.com>
2017-06-07 13:36:02 +02:00
Daniel P. Berrange
fb2236f9f7 Revert "syntax-check: Enforce <code> inside <dt> elements"
This reverts commit 1f29f3da06.

Assuming <dt> is always used to document symbols is way too
broad, requiring far too many exemptions to be marked to
avoid syntax check rules.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
2016-11-11 12:15:05 +00:00
Andrea Bolognani
1f29f3da06 syntax-check: Enforce <code> inside <dt> elements
Commit 61b070cf20 cleaned up a number of cases where the <dt>
element was used to document symbols, but the symbol itself was
not inside a <code> element.

To make sure we don't end up having to clean up again a few
months from now, introduce a syntax-check rule that can spot
such mistakes.

All existing exceptions are marked as such, with either file
or line granularity depending on the case.
2016-04-25 12:09:34 +02:00
Ján Tomko
755ec23cca Visually separate snapshot disk subelements
Create four smaller blocks of texts instead of one large one.
2015-04-13 14:05:23 +02:00
Peter Krempa
500f80a595 doc: Document that snapshot name of block-backed disk isn't autogenerated
Libvirt generates external snapshot target file names for file backed
storage but not for block backed storage. Document the limitation.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1032363
2014-07-14 09:26:26 +02:00
Peter Krempa
3cf074ee40 qemu: snapshot: Add support for external active snapshots on gluster
Add support for gluster backed images as sources for snapshots in the
qemu driver. This will also simplify adding further network backed
volumes as sources for snapshot in case qemu will support them.
2014-02-14 11:07:29 +01:00
Peter Krempa
7076b4b72c snapshot: Add support for specifying snapshot disk backing type
Add support for specifying various types when doing snapshots. This will
later allow to do snapshots on network backed volumes. Disks of type
'volume' are not supported by snapshots (yet).

Also amend the test suite to check parsing of the various new disk
types that can now be specified.
2014-01-29 12:56:35 +01:00
Daniel P. Berrange
f2f9742d4d Fix multiple formatting problems in HTML docs
The rule generating the HTML docs passing the --html flag
to xsltproc. This makes it use the legacy HTML parser, which
either ignores or tries to fix all sorts of broken XML tags.
There's no reason why we should be writing broken XML in
the first place, so removing --html and adding the XHTML
doctype to all files forces us to create good XML.

This adds the XHTML doc type and fixes many, many XML tag
problems it exposes.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
2013-05-03 15:56:15 +01:00
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