import 15.2.5

[ceph.git] / ceph / doc / man / 8 / rbd.rst

:orphan:

===============================================
 rbd -- manage rados block device (RBD) images
===============================================

.. program:: rbd

Synopsis
========

| **rbd** [ -c *ceph.conf* ] [ -m *monaddr* ] [--cluster *cluster-name*]
  [ -p | --pool *pool* ] [ *command* ... ]


Description
===========

**rbd** is a utility for manipulating rados block device (RBD) images,
used by the Linux rbd driver and the rbd storage driver for QEMU/KVM.
RBD images are simple block devices that are striped over objects and
stored in a RADOS object store. The size of the objects the image is
striped over must be a power of two.


Options
=======

.. option:: -c ceph.conf, --conf ceph.conf

   Use ceph.conf configuration file instead of the default /etc/ceph/ceph.conf to
   determine monitor addresses during startup.

.. option:: -m monaddress[:port]

   Connect to specified monitor (instead of looking through ceph.conf).

.. option:: --cluster cluster-name

   Use different cluster name as compared to default cluster name *ceph*.

.. option:: -p pool-name, --pool pool-name

   Interact with the given pool. Required by most commands.

.. option:: --namespace namespace-name

   Use a pre-defined image namespace within a pool

.. option:: --no-progress

   Do not output progress information (goes to standard error by
   default for some commands).


Parameters
==========

.. option:: --image-format format-id

   Specifies which object layout to use. The default is 2.

   * format 1 - (deprecated) Use the original format for a new rbd image. This
     format is understood by all versions of librbd and the kernel rbd module,
     but does not support newer features like cloning.

   * format 2 - Use the second rbd format, which is supported by librbd since
     the Bobtail release and the kernel rbd module since kernel 3.10 (except
     for "fancy" striping, which is supported since kernel 4.17). This adds
     support for cloning and is more easily extensible to allow more
     features in the future.

.. option:: -s size-in-M/G/T, --size size-in-M/G/T

   Specifies the size of the new rbd image or the new size of the existing rbd
   image in M/G/T.  If no suffix is given, unit M is assumed.

.. option:: --object-size size-in-B/K/M

   Specifies the object size in B/K/M.  Object size will be rounded up the
   nearest power of two; if no suffix is given, unit B is assumed.  The default
   object size is 4M, smallest is 4K and maximum is 32M.

.. option:: --stripe-unit size-in-B/K/M

   Specifies the stripe unit size in B/K/M.  If no suffix is given, unit B is
   assumed.  See striping section (below) for more details.

.. option:: --stripe-count num

   Specifies the number of objects to stripe over before looping back
   to the first object.  See striping section (below) for more details.

.. option:: --snap snap

   Specifies the snapshot name for the specific operation.

.. option:: --id username

   Specifies the username (without the ``client.`` prefix) to use with the map command.

.. option:: --keyring filename

   Specifies a keyring file containing a secret for the specified user
   to use with the map command.  If not specified, the default keyring
   locations will be searched.

.. option:: --keyfile filename

   Specifies a file containing the secret key of ``--id user`` to use with the map command.
   This option is overridden by ``--keyring`` if the latter is also specified.

.. option:: --shared lock-tag

   Option for `lock add` that allows multiple clients to lock the
   same image if they use the same tag. The tag is an arbitrary
   string. This is useful for situations where an image must
   be open from more than one client at once, like during
   live migration of a virtual machine, or for use underneath
   a clustered file system.

.. option:: --format format

   Specifies output formatting (default: plain, json, xml)

.. option:: --pretty-format

   Make json or xml formatted output more human-readable.

.. option:: -o krbd-options, --options krbd-options

   Specifies which options to use when mapping or unmapping an image via the
   rbd kernel driver.  krbd-options is a comma-separated list of options
   (similar to mount(8) mount options).  See kernel rbd (krbd) options section
   below for more details.

.. option:: --read-only

   Map the image read-only.  Equivalent to -o ro.

.. option:: --image-feature feature-name

   Specifies which RBD format 2 feature should be enabled when creating
   an image. Multiple features can be enabled by repeating this option
   multiple times. The following features are supported:

   * layering: layering support
   * striping: striping v2 support
   * exclusive-lock: exclusive locking support
   * object-map: object map support (requires exclusive-lock)
   * fast-diff: fast diff calculations (requires object-map)
   * deep-flatten: snapshot flatten support
   * journaling: journaled IO support (requires exclusive-lock)
   * data-pool: erasure coded pool support

.. option:: --image-shared

   Specifies that the image will be used concurrently by multiple clients.
   This will disable features that are dependent upon exclusive ownership
   of the image.

.. option:: --whole-object

   Specifies that the diff should be limited to the extents of a full object
   instead of showing intra-object deltas. When the object map feature is
   enabled on an image, limiting the diff to the object extents will
   dramatically improve performance since the differences can be computed
   by examining the in-memory object map instead of querying RADOS for each
   object within the image.

.. option:: --limit

   Specifies the limit for the number of snapshots permitted.

Commands
========

.. TODO rst "option" directive seems to require --foo style options, parsing breaks on subcommands.. the args show up as bold too

:command:`bench` --io-type <read | write | readwrite | rw> [--io-size *size-in-B/K/M/G/T*] [--io-threads *num-ios-in-flight*] [--io-total *size-in-B/K/M/G/T*] [--io-pattern seq | rand] [--rw-mix-read *read proportion in readwrite*] *image-spec*
  Generate a series of IOs to the image and measure the IO throughput and
  latency.  If no suffix is given, unit B is assumed for both --io-size and
  --io-total.  Defaults are: --io-size 4096, --io-threads 16, --io-total 1G,
  --io-pattern seq, --rw-mix-read 50.

:command:`children` *snap-spec*
  List the clones of the image at the given snapshot. This checks
  every pool, and outputs the resulting poolname/imagename.

  This requires image format 2.

:command:`clone` [--object-size *size-in-B/K/M*] [--stripe-unit *size-in-B/K/M* --stripe-count *num*] [--image-feature *feature-name*] [--image-shared] *parent-snap-spec* *child-image-spec*
  Will create a clone (copy-on-write child) of the parent snapshot.
  Object size will be identical to that of the parent image unless
  specified. Size will be the same as the parent snapshot. The --stripe-unit
  and --stripe-count arguments are optional, but must be used together.

  The parent snapshot must be protected (see `rbd snap protect`).
  This requires image format 2.

:command:`config global get` *config-entity* *key*
  Get a global-level configuration override.

:command:`config global list` [--format plain | json | xml] [--pretty-format] *config-entity*
  List global-level configuration overrides.

:command:`config global set` *config-entity* *key* *value*
  Set a global-level configuration override.

:command:`config global remove` *config-entity* *key*
  Remove a global-level configuration override.

:command:`config image get` *image-spec* *key*
  Get an image-level configuration override.

:command:`config image list` [--format plain | json | xml] [--pretty-format] *image-spec*
  List image-level configuration overrides.

:command:`config image set` *image-spec* *key* *value*
  Set an image-level configuration override.

:command:`config image remove` *image-spec* *key*
  Remove an image-level configuration override.

:command:`config pool get` *pool-name* *key*
  Get a pool-level configuration override.

:command:`config pool list` [--format plain | json | xml] [--pretty-format] *pool-name*
  List pool-level configuration overrides.

:command:`config pool set` *pool-name* *key* *value*
  Set a pool-level configuration override.

:command:`config pool remove` *pool-name* *key*
  Remove a pool-level configuration override.

:command:`cp` (*src-image-spec* | *src-snap-spec*) *dest-image-spec*
  Copy the content of a src-image into the newly created dest-image.
  dest-image will have the same size, object size, and image format as src-image.

:command:`create` (-s | --size *size-in-M/G/T*) [--image-format *format-id*] [--object-size *size-in-B/K/M*] [--stripe-unit *size-in-B/K/M* --stripe-count *num*] [--thick-provision] [--no-progress] [--image-feature *feature-name*]... [--image-shared] *image-spec*
  Will create a new rbd image. You must also specify the size via --size.  The
  --stripe-unit and --stripe-count arguments are optional, but must be used together.
  If the --thick-provision is enabled, it will fully allocate storage for
  the image at creation time. It will take a long time to do.
  Note: thick provisioning requires zeroing the contents of the entire image.

:command:`deep cp` (*src-image-spec* | *src-snap-spec*) *dest-image-spec*
  Deep copy the content of a src-image into the newly created dest-image.
  Dest-image will have the same size, object size, image format, and snapshots as src-image.

:command:`device list` [-t | --device-type *device-type*] [--format plain | json | xml] --pretty-format
  Show the rbd images that are mapped via the rbd kernel module
  (default) or other supported device.

:command:`device map` [-t | --device-type *device-type*] [--read-only] [--exclusive] [-o | --options *device-options*] *image-spec* | *snap-spec*
  Map the specified image to a block device via the rbd kernel module
  (default) or other supported device (*nbd* on Linux or *ggate* on
  FreeBSD).

  The --options argument is a comma separated list of device type
  specific options (opt1,opt2=val,...).

:command:`device unmap` [-t | --device-type *device-type*] [-o | --options *device-options*] *image-spec* | *snap-spec* | *device-path*
  Unmap the block device that was mapped via the rbd kernel module
  (default) or other supported device.

  The --options argument is a comma separated list of device type
  specific options (opt1,opt2=val,...).

:command:`diff` [--from-snap *snap-name*] [--whole-object] *image-spec* | *snap-spec*
  Dump a list of byte extents in the image that have changed since the specified start
  snapshot, or since the image was created.  Each output line includes the starting offset
  (in bytes), the length of the region (in bytes), and either 'zero' or 'data' to indicate
  whether the region is known to be zeros or may contain other data.

:command:`du` [-p | --pool *pool-name*] [*image-spec* | *snap-spec*] [--merge-snapshots]
  Will calculate the provisioned and actual disk usage of all images and
  associated snapshots within the specified pool.  It can also be used against
  individual images and snapshots.

  If the RBD fast-diff feature is not enabled on images, this operation will
  require querying the OSDs for every potential object within the image.

  The --merge-snapshots will merge snapshots used space into their parent images.

:command:`export` [--export-format *format (1 or 2)*] (*image-spec* | *snap-spec*) [*dest-path*]
  Export image to dest path (use - for stdout).
  The --export-format accepts '1' or '2' currently. Format 2 allow us to export not only the content
  of image, but also the snapshots and other properties, such as image_order, features.

:command:`export-diff` [--from-snap *snap-name*] [--whole-object] (*image-spec* | *snap-spec*) *dest-path*
  Export an incremental diff for an image to dest path (use - for stdout).  If
  an initial snapshot is specified, only changes since that snapshot are included; otherwise,
  any regions of the image that contain data are included.  The end snapshot is specified
  using the standard --snap option or @snap syntax (see below).  The image diff format includes
  metadata about image size changes, and the start and end snapshots.  It efficiently represents
  discarded or 'zero' regions of the image.

:command:`feature disable` *image-spec* *feature-name*...
  Disable the specified feature on the specified image. Multiple features can
  be specified.

:command:`feature enable` *image-spec* *feature-name*...
  Enable the specified feature on the specified image. Multiple features can
  be specified.

:command:`flatten` *image-spec*
  If image is a clone, copy all shared blocks from the parent snapshot and
  make the child independent of the parent, severing the link between
  parent snap and child.  The parent snapshot can be unprotected and
  deleted if it has no further dependent clones.

  This requires image format 2.

:command:`group create` *group-spec*
  Create a group.

:command:`group image add` *group-spec* *image-spec*
  Add an image to a group.

:command:`group image list` *group-spec*
  List images in a group.

:command:`group image remove` *group-spec* *image-spec*
  Remove an image from a group.

:command:`group ls` [-p | --pool *pool-name*]
  List rbd groups.

:command:`group rename` *src-group-spec* *dest-group-spec*
  Rename a group.  Note: rename across pools is not supported.

:command:`group rm` *group-spec*
  Delete a group.

:command:`group snap create` *group-snap-spec*
  Make a snapshot of a group.

:command:`group snap list` *group-spec*
  List snapshots of a group.

:command:`group snap rm` *group-snap-spec*
  Remove a snapshot from a group.

:command:`group snap rename` *group-snap-spec* *snap-name*
  Rename group's snapshot.

:command:`group snap rollback` *group-snap-spec*
  Rollback group to snapshot.

:command:`image-meta get` *image-spec* *key*
  Get metadata value with the key.

:command:`image-meta list` *image-spec*
  Show metadata held on the image. The first column is the key
  and the second column is the value.

:command:`image-meta remove` *image-spec* *key*
  Remove metadata key with the value.

:command:`image-meta set` *image-spec* *key* *value*
  Set metadata key with the value. They will displayed in `image-meta list`.

:command:`import` [--export-format *format (1 or 2)*] [--image-format *format-id*] [--object-size *size-in-B/K/M*] [--stripe-unit *size-in-B/K/M* --stripe-count *num*] [--image-feature *feature-name*]... [--image-shared] *src-path* [*image-spec*]
  Create a new image and imports its data from path (use - for
  stdin).  The import operation will try to create sparse rbd images 
  if possible.  For import from stdin, the sparsification unit is
  the data block size of the destination image (object size).

  The --stripe-unit and --stripe-count arguments are optional, but must be
  used together.

  The --export-format accepts '1' or '2' currently. Format 2 allow us to import not only the content
  of image, but also the snapshots and other properties, such as image_order, features.

:command:`import-diff` *src-path* *image-spec*
  Import an incremental diff of an image and applies it to the current image.  If the diff
  was generated relative to a start snapshot, we verify that snapshot already exists before
  continuing.  If there was an end snapshot we verify it does not already exist before
  applying the changes, and create the snapshot when we are done.
  
:command:`info` *image-spec* | *snap-spec*
  Will dump information (such as size and object size) about a specific rbd image.
  If image is a clone, information about its parent is also displayed.
  If a snapshot is specified, whether it is protected is shown as well.

:command:`journal client disconnect` *journal-spec*
  Flag image journal client as disconnected.

:command:`journal export` [--verbose] [--no-error] *src-journal-spec* *path-name*
  Export image journal to path (use - for stdout). It can be make a backup
  of the image journal especially before attempting dangerous operations.

  Note that this command may not always work if the journal is badly corrupted.

:command:`journal import` [--verbose] [--no-error] *path-name* *dest-journal-spec*
  Import image journal from path (use - for stdin).

:command:`journal info` *journal-spec*
  Show information about image journal.

:command:`journal inspect` [--verbose] *journal-spec*
  Inspect and report image journal for structural errors.

:command:`journal reset` *journal-spec*
  Reset image journal.

:command:`journal status` *journal-spec*
  Show status of image journal.

:command:`lock add` [--shared *lock-tag*] *image-spec* *lock-id*
  Lock an image. The lock-id is an arbitrary name for the user's
  convenience. By default, this is an exclusive lock, meaning it
  will fail if the image is already locked. The --shared option
  changes this behavior. Note that locking does not affect
  any operation other than adding a lock. It does not
  protect an image from being deleted.

:command:`lock ls` *image-spec*
  Show locks held on the image. The first column is the locker
  to use with the `lock remove` command.

:command:`lock rm` *image-spec* *lock-id* *locker*
  Release a lock on an image. The lock id and locker are
  as output by lock ls.

:command:`ls` [-l | --long] [*pool-name*]
  Will list all rbd images listed in the rbd_directory object.  With
  -l, also show snapshots, and use longer-format output including
  size, parent (if clone), format, etc.

:command:`merge-diff` *first-diff-path* *second-diff-path* *merged-diff-path*
  Merge two continuous incremental diffs of an image into one single diff. The
  first diff's end snapshot must be equal with the second diff's start snapshot.
  The first diff could be - for stdin, and merged diff could be - for stdout, which
  enables multiple diff files to be merged using something like
  'rbd merge-diff first second - | rbd merge-diff - third result'. Note this command
  currently only support the source incremental diff with stripe_count == 1

:command:`migration abort` *image-spec*
  Cancel image migration. This step may be run after successful or
  failed migration prepare or migration execute steps and returns the
  image to its initial (before migration) state. All modifications to
  the destination image are lost.

:command:`migration commit` *image-spec*
  Commit image migration. This step is run after a successful migration
  prepare and migration execute steps and removes the source image data.

:command:`migration execute` *image-spec*
  Execute image migration. This step is run after a successful migration
  prepare step and copies image data to the destination.

:command:`migration prepare` [--order *order*] [--object-size *object-size*] [--image-feature *image-feature*] [--image-shared] [--stripe-unit *stripe-unit*] [--stripe-count *stripe-count*] [--data-pool *data-pool*] *src-image-spec* [*dest-image-spec*]
  Prepare image migration. This is the first step when migrating an
  image, i.e. changing the image location, format or other
  parameters that can't be changed dynamically. The destination can
  match the source, and in this case *dest-image-spec* can be omitted.
  After this step the source image is set as a parent of the
  destination image, and the image is accessible in copy-on-write mode
  by its destination spec.

:command:`mirror image demote` *image-spec*
  Demote a primary image to non-primary for RBD mirroring.

:command:`mirror image disable` [--force] *image-spec*
  Disable RBD mirroring for an image. If the mirroring is
  configured in ``image`` mode for the image's pool, then it
  can be explicitly disabled mirroring for each image within
  the pool.

:command:`mirror image enable` *image-spec* *mode*
  Enable RBD mirroring for an image. If the mirroring is
  configured in ``image`` mode for the image's pool, then it
  can be explicitly enabled mirroring for each image within
  the pool.

  The mirror image mode can either be ``journal`` (default) or
  ``snapshot``. The ``journal`` mode requires the RBD journaling
  feature.

:command:`mirror image promote` [--force] *image-spec*
  Promote a non-primary image to primary for RBD mirroring.

:command:`mirror image resync` *image-spec*
  Force resync to primary image for RBD mirroring.

:command:`mirror image status` *image-spec*
  Show RBD mirroring status for an image.

:command:`mirror pool demote` [*pool-name*]
  Demote all primary images within a pool to non-primary.
  Every mirroring enabled image will demoted in the pool.

:command:`mirror pool disable` [*pool-name*]
  Disable RBD mirroring by default within a pool. When mirroring
  is disabled on a pool in this way, mirroring will also be
  disabled on any images (within the pool) for which mirroring
  was enabled explicitly.

:command:`mirror pool enable` [*pool-name*] *mode*
  Enable RBD mirroring by default within a pool.
  The mirroring mode can either be ``pool`` or ``image``.
  If configured in ``pool`` mode, all images in the pool
  with the journaling feature enabled are mirrored.
  If configured in ``image`` mode, mirroring needs to be
  explicitly enabled (by ``mirror image enable`` command)
  on each image.

:command:`mirror pool info` [*pool-name*]
  Show information about the pool mirroring configuration.
  It includes mirroring mode, peer UUID, remote cluster name,
  and remote client name.

:command:`mirror pool peer add` [*pool-name*] *remote-cluster-spec*
  Add a mirroring peer to a pool.
  *remote-cluster-spec* is [*remote client name*\ @\ ]\ *remote cluster name*.

  The default for *remote client name* is "client.admin".

  This requires mirroring mode is enabled.

:command:`mirror pool peer remove` [*pool-name*] *uuid*
  Remove a mirroring peer from a pool. The peer uuid is available
  from ``mirror pool info`` command.

:command:`mirror pool peer set` [*pool-name*] *uuid* *key* *value*
  Update mirroring peer settings.
  The key can be either ``client`` or ``cluster``, and the value
  is corresponding to remote client name or remote cluster name.

:command:`mirror pool promote` [--force] [*pool-name*]
  Promote all non-primary images within a pool to primary.
  Every mirroring enabled image will promoted in the pool.

:command:`mirror pool status` [--verbose] [*pool-name*]
  Show status for all mirrored images in the pool.
  With --verbose, also show additionally output status
  details for every mirroring image in the pool.

:command:`mirror snapshot schedule add` [-p | --pool *pool*] [--namespace *namespace*] [--image *image*] *interval* [*start-time*]
  Add mirror snapshot schedule.

:command:`mirror snapshot schedule list` [-R | --recursive] [--format *format*] [--pretty-format] [-p | --pool *pool*] [--namespace *namespace*] [--image *image*]
  List mirror snapshot schedule.

:command:`mirror snapshot schedule remove` [-p | --pool *pool*] [--namespace *namespace*] [--image *image*] *interval* [*start-time*]
  Remove mirror snapshot schedule.

:command:`mirror snapshot schedule status` [-p | --pool *pool*] [--format *format*] [--pretty-format] [--namespace *namespace*] [--image *image*]
  Show mirror snapshot schedule status.

:command:`mv` *src-image-spec* *dest-image-spec*
  Rename an image.  Note: rename across pools is not supported.

:command:`namespace create` *pool-name*/*namespace-name*
  Create a new image namespace within the pool.

:command:`namespace list` *pool-name*
  List image namespaces defined within the pool.

:command:`namespace remove` *pool-name*/*namespace-name*
  Remove an empty image namespace from the pool.

:command:`object-map check` *image-spec* | *snap-spec*
  Verify the object map is correct.

:command:`object-map rebuild` *image-spec* | *snap-spec*
  Rebuild an invalid object map for the specified image. An image snapshot can be
  specified to rebuild an invalid object map for a snapshot.

:command:`pool init` [*pool-name*] [--force]
  Initialize pool for use by RBD. Newly created pools must initialized
  prior to use.

:command:`resize` (-s | --size *size-in-M/G/T*) [--allow-shrink] *image-spec*
  Resize rbd image. The size parameter also needs to be specified.
  The --allow-shrink option lets the size be reduced.
  
:command:`rm` *image-spec*
  Delete an rbd image (including all data blocks). If the image has
  snapshots, this fails and nothing is deleted.

:command:`snap create` *snap-spec*
  Create a new snapshot. Requires the snapshot name parameter specified.

:command:`snap limit clear` *image-spec*
  Remove any previously set limit on the number of snapshots allowed on
  an image.

:command:`snap limit set` [--limit] *limit* *image-spec*
  Set a limit for the number of snapshots allowed on an image.

:command:`snap ls` *image-spec*
  Dump the list of snapshots inside a specific image.

:command:`snap protect` *snap-spec*
  Protect a snapshot from deletion, so that clones can be made of it
  (see `rbd clone`).  Snapshots must be protected before clones are made;
  protection implies that there exist dependent cloned children that
  refer to this snapshot.  `rbd clone` will fail on a nonprotected
  snapshot.

  This requires image format 2.

:command:`snap purge` *image-spec*
  Remove all unprotected snapshots from an image.

:command:`snap rename` *src-snap-spec* *dest-snap-spec*
  Rename a snapshot. Note: rename across pools and images is not supported.

:command:`snap rm` [--force] *snap-spec*
  Remove the specified snapshot.

:command:`snap rollback` *snap-spec*
  Rollback image content to snapshot. This will iterate through the entire blocks
  array and update the data head content to the snapshotted version.

:command:`snap unprotect` *snap-spec*
  Unprotect a snapshot from deletion (undo `snap protect`).  If cloned
  children remain, `snap unprotect` fails.  (Note that clones may exist
  in different pools than the parent snapshot.)

  This requires image format 2.

:command:`sparsify` [--sparse-size *sparse-size*] *image-spec*
  Reclaim space for zeroed image extents. The default sparse size is
  4096 bytes and can be changed via --sparse-size option with the
  following restrictions: it should be power of two, not less than
  4096, and not larger than image object size.

:command:`status` *image-spec*
  Show the status of the image, including which clients have it open.

:command:`trash ls` [*pool-name*]
  List all entries from trash.

:command:`trash mv` *image-spec*
  Move an image to the trash. Images, even ones actively in-use by 
  clones, can be moved to the trash and deleted at a later time.

:command:`trash purge` [*pool-name*]
  Remove all expired images from trash.

:command:`trash restore` *image-id*  
  Restore an image from trash.

:command:`trash rm` *image-id* 
  Delete an image from trash. If image deferment time has not expired
  you can not removed it unless use force. But an actively in-use by clones 
  or has snapshots can not be removed.

:command:`trash purge schedule add` [-p | --pool *pool*] [--namespace *namespace*] *interval* [*start-time*]
  Add trash purge schedule.

:command:`trash purge schedule list` [-R | --recursive] [--format *format*] [--pretty-format] [-p | --pool *pool*] [--namespace *namespace*]
  List trash purge schedule.

:command:`trash purge schedule remove` [-p | --pool *pool*] [--namespace *namespace*] *interval* [*start-time*]
  Remove trash purge schedule.

:command:`trash purge schedule status` [-p | --pool *pool*] [--format *format*] [--pretty-format] [--namespace *namespace*]
  Show trash purge schedule status.

:command:`watch` *image-spec*
  Watch events on image.

Image, snap, group and journal specs
====================================

| *image-spec*      is [*pool-name*/[*namespace-name*/]]\ *image-name*
| *snap-spec*       is [*pool-name*/[*namespace-name*/]]\ *image-name*\ @\ *snap-name*
| *group-spec*      is [*pool-name*/[*namespace-name*/]]\ *group-name*
| *group-snap-spec* is [*pool-name*/[*namespace-name*/]]\ *group-name*\ @\ *snap-name*
| *journal-spec*    is [*pool-name*/[*namespace-name*/]]\ *journal-name*

The default for *pool-name* is "rbd" and *namespace-name* is "". If an image
name contains a slash character ('/'), *pool-name* is required.

The *journal-name* is *image-id*.

You may specify each name individually, using --pool, --namespace, --image, and
--snap options, but this is discouraged in favor of the above spec syntax.

Striping
========

RBD images are striped over many objects, which are then stored by the
Ceph distributed object store (RADOS).  As a result, read and write
requests for the image are distributed across many nodes in the
cluster, generally preventing any single node from becoming a
bottleneck when individual images get large or busy.

The striping is controlled by three parameters:

.. option:: object-size

  The size of objects we stripe over is a power of two. It will be rounded up the nearest power of two.
  The default object size is 4 MB, smallest is 4K and maximum is 32M.

.. option:: stripe_unit

  Each [*stripe_unit*] contiguous bytes are stored adjacently in the same object, before we move on
  to the next object.

.. option:: stripe_count

  After we write [*stripe_unit*] bytes to [*stripe_count*] objects, we loop back to the initial object
  and write another stripe, until the object reaches its maximum size.  At that point,
  we move on to the next [*stripe_count*] objects.

By default, [*stripe_unit*] is the same as the object size and [*stripe_count*] is 1.  Specifying a different
[*stripe_unit*] and/or [*stripe_count*] is often referred to as using "fancy" striping and requires format 2.


Kernel rbd (krbd) options
=========================

Most of these options are useful mainly for debugging and benchmarking.  The
default values are set in the kernel and may therefore depend on the version of
the running kernel.

Per client instance `rbd device map` options:

* fsid=aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee - FSID that should be assumed by
  the client.

* ip=a.b.c.d[:p] - IP and, optionally, port the client should use.

* share - Enable sharing of client instances with other mappings (default).

* noshare - Disable sharing of client instances with other mappings.

* crc - Enable CRC32C checksumming for data writes (default).

* nocrc - Disable CRC32C checksumming for data writes.

* cephx_require_signatures - Require cephx message signing (since 3.19,
  default).

* nocephx_require_signatures - Don't require cephx message signing (since
  3.19).

* tcp_nodelay - Disable Nagle's algorithm on client sockets (since 4.0,
  default).

* notcp_nodelay - Enable Nagle's algorithm on client sockets (since 4.0).

* cephx_sign_messages - Enable message signing (since 4.4, default).

* nocephx_sign_messages - Disable message signing (since 4.4).

* mount_timeout=x - A timeout on various steps in `rbd device map` and
  `rbd device unmap` sequences (default is 60 seconds).  In particular,
  since 4.2 this can be used to ensure that `rbd device unmap` eventually
  times out when there is no network connection to a cluster.

* osdkeepalive=x - OSD keepalive timeout (default is 5 seconds).

* osd_idle_ttl=x - OSD idle TTL (default is 60 seconds).

Per mapping (block device) `rbd device map` options:

* rw - Map the image read-write (default).

* ro - Map the image read-only.  Equivalent to --read-only.

* queue_depth=x - queue depth (since 4.2, default is 128 requests).

* lock_on_read - Acquire exclusive lock on reads, in addition to writes and
  discards (since 4.9).

* exclusive - Disable automatic exclusive lock transitions (since 4.12).

* lock_timeout=x - A timeout on waiting for the acquisition of exclusive lock
  (since 4.17, default is 0 seconds, meaning no timeout).

* notrim - Turn off discard and write zeroes offload support to avoid
  deprovisioning a fully provisioned image (since 4.17). When enabled, discard
  requests will fail with -EOPNOTSUPP, write zeroes requests will fall back to
  manually zeroing.

* abort_on_full - Fail write requests with -ENOSPC when the cluster is full or
  the data pool reaches its quota (since 5.0).  The default behaviour is to
  block until the full condition is cleared.

* alloc_size - Minimum allocation unit of the underlying OSD object store
  backend (since 5.1, default is 64K bytes).  This is used to round off and
  drop discards that are too small.  For bluestore, the recommended setting is
  bluestore_min_alloc_size (typically 64K for hard disk drives and 16K for
  solid-state drives).  For filestore with filestore_punch_hole = false, the
  recommended setting is image object size (typically 4M).

* crush_location=x - Specify the location of the client in terms of CRUSH
  hierarchy (since 5.8).  This is a set of key-value pairs separated from
  each other by '|', with keys separated from values by ':'.  Note that '|'
  may need to be quoted or escaped to avoid it being interpreted as a pipe
  by the shell.  The key is the bucket type name (e.g. rack, datacenter or
  region with default bucket types) and the value is the bucket name.  For
  example, to indicate that the client is local to rack "myrack", data center
  "mydc" and region "myregion"::

    crush_location=rack:myrack|datacenter:mydc|region:myregion

  Each key-value pair stands on its own: "myrack" doesn't need to reside in
  "mydc", which in turn doesn't need to reside in "myregion".  The location
  is not a path to the root of the hierarchy but rather a set of nodes that
  are matched independently, owning to the fact that bucket names are unique
  within a CRUSH map.  "Multipath" locations are supported, so it is possible
  to indicate locality for multiple parallel hierarchies::

    crush_location=rack:myrack1|rack:myrack2|datacenter:mydc

* read_from_replica=no - Disable replica reads, always pick the primary OSD
  (since 5.8, default).

* read_from_replica=balance - When issued a read on a replicated pool, pick
  a random OSD for serving it (since 5.8).

  This mode is safe for general use only since Octopus (i.e. after "ceph osd
  require-osd-release octopus").  Otherwise it should be limited to read-only
  workloads such as images mapped read-only everywhere or snapshots.

* read_from_replica=localize - When issued a read on a replicated pool, pick
  the most local OSD for serving it (since 5.8).  The locality metric is
  calculated against the location of the client given with crush_location;
  a match with the lowest-valued bucket type wins.  For example, with default
  bucket types, an OSD in a matching rack is closer than an OSD in a matching
  data center, which in turn is closer than an OSD in a matching region.

  This mode is safe for general use only since Octopus (i.e. after "ceph osd
  require-osd-release octopus").  Otherwise it should be limited to read-only
  workloads such as images mapped read-only everywhere or snapshots.

* compression_hint=none - Don't set compression hints (since 5.8, default).

* compression_hint=compressible - Hint to the underlying OSD object store
  backend that the data is compressible, enabling compression in passive mode
  (since 5.8).

* compression_hint=incompressible - Hint to the underlying OSD object store
  backend that the data is incompressible, disabling compression in aggressive
  mode (since 5.8).

`rbd device unmap` options:

* force - Force the unmapping of a block device that is open (since 4.9).  The
  driver will wait for running requests to complete and then unmap; requests
  sent to the driver after initiating the unmap will be failed.


Examples
========

To create a new rbd image that is 100 GB::

       rbd create mypool/myimage --size 102400

To use a non-default object size (8 MB)::

       rbd create mypool/myimage --size 102400 --object-size 8M

To delete an rbd image (be careful!)::

       rbd rm mypool/myimage

To create a new snapshot::

       rbd snap create mypool/myimage@mysnap

To create a copy-on-write clone of a protected snapshot::

       rbd clone mypool/myimage@mysnap otherpool/cloneimage

To see which clones of a snapshot exist::

       rbd children mypool/myimage@mysnap

To delete a snapshot::

       rbd snap rm mypool/myimage@mysnap

To map an image via the kernel with cephx enabled::

       rbd device map mypool/myimage --id admin --keyfile secretfile

To map an image via the kernel with different cluster name other than default *ceph*::

       rbd device map mypool/myimage --cluster cluster-name

To unmap an image::

       rbd device unmap /dev/rbd0

To create an image and a clone from it::

       rbd import --image-format 2 image mypool/parent
       rbd snap create mypool/parent@snap
       rbd snap protect mypool/parent@snap
       rbd clone mypool/parent@snap otherpool/child

To create an image with a smaller stripe_unit (to better distribute small writes in some workloads)::

       rbd create mypool/myimage --size 102400 --stripe-unit 65536B --stripe-count 16

To change an image from one image format to another, export it and then
import it as the desired image format::

       rbd export mypool/myimage@snap /tmp/img
       rbd import --image-format 2 /tmp/img mypool/myimage2

To lock an image for exclusive use::

       rbd lock add mypool/myimage mylockid

To release a lock::

       rbd lock remove mypool/myimage mylockid client.2485

To list images from trash::

       rbd trash ls mypool

To defer delete an image (use *--expires-at* to set expiration time, default is now)::

       rbd trash mv mypool/myimage --expires-at "tomorrow"

To delete an image from trash (be careful!)::

       rbd trash rm mypool/myimage-id

To force delete an image from trash (be careful!)::

       rbd trash rm mypool/myimage-id  --force

To restore an image from trash::

       rbd trash restore mypool/myimage-id

To restore an image from trash and rename it::

       rbd trash restore mypool/myimage-id --image mynewimage


Availability
============

**rbd** is part of Ceph, a massively scalable, open-source, distributed storage system. Please refer to
the Ceph documentation at http://ceph.com/docs for more information.


See also
========

:doc:`ceph <ceph>`\(8),
:doc:`rados <rados>`\(8)