Provided by: ceph-common_19.2.1-0ubuntu3_amd64 
NAME
rbd - manage rados block device (RBD) images
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
-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.
-m monaddress[:port]
Connect to specified monitor (instead of looking through ceph.conf).
--cluster cluster-name
Use different cluster name as compared to default cluster name ceph.
-p pool-name, --pool pool-name
Interact with the given pool. Required by most commands.
--namespace namespace-name
Use a pre-defined image namespace within a pool
--no-progress
Do not output progress information (goes to standard error by default for some commands).
PARAMETERS
--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.
-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.
--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.
The default value can be changed with the configuration option rbd_default_order, which takes a
power of two (default object size is 2 ^ rbd_default_order).
--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.
--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.
--snap snap
Specifies the snapshot name for the specific operation.
--id username
Specifies the username (without the client. prefix) to use with the map command.
--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.
--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.
--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.
--format format
Specifies output formatting (default: plain, json, xml)
--pretty-format
Make json or xml formatted output more human-readable.
-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.
--read-only
Map the image read-only. Equivalent to -o ro.
--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
--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.
--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.
--limit
Specifies the limit for the number of snapshots permitted.
COMMANDS
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.
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.
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.
config global get config-entity key
Get a global-level configuration override.
config global list [--format plain | json | xml] [--pretty-format] config-entity
List global-level configuration overrides.
config global set config-entity key value
Set a global-level configuration override.
config global remove config-entity key
Remove a global-level configuration override.
config image get image-spec key
Get an image-level configuration override.
config image list [--format plain | json | xml] [--pretty-format] image-spec
List image-level configuration overrides.
config image set image-spec key value
Set an image-level configuration override.
config image remove image-spec key
Remove an image-level configuration override.
config pool get pool-name key
Get a pool-level configuration override.
config pool list [--format plain | json | xml] [--pretty-format] pool-name
List pool-level configuration overrides.
config pool set pool-name key value
Set a pool-level configuration override.
config pool remove pool-name key
Remove a pool-level configuration override.
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. Note: snapshots are not copied, use deep cp
command to include snapshots.
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.
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.
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.
device map [-t | --device-type device-type] [--cookie device-cookie] [--show-cookie] [--snap-id snap-id]
[--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 or ubbd on Linux or ggate on FreeBSD).
The --options argument is a comma separated list of device type specific options
(opt1,opt2=val,...).
device unmap [-t | --device-type device-type] [-o | --options device-options] [--snap-id snap-id]
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,...).
device attach [-t | --device-type device-type] --device device-path [--cookie device-cookie]
[--show-cookie] [--snap-id snap-id] [--read-only] [--exclusive] [--force] [-o | --options device-options]
image-spec | snap-spec
Attach the specified image to the specified block device (currently only nbd on Linux). This
operation is unsafe and should not be normally used. In particular, specifying the wrong image or
the wrong block device may lead to data corruption as no validation is performed by nbd kernel
driver.
The --options argument is a comma separated list of device type specific options
(opt1,opt2=val,...).
device detach [-t | --device-type device-type] [-o | --options device-options] [--snap-id snap-id]
image-spec | snap-spec | device-path
Detach the block device that was mapped or attached (currently only nbd on Linux). This operation
is unsafe and should not be normally used.
The --options argument is a comma separated list of device type specific options
(opt1,opt2=val,...).
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.
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.
encryption format image-spec format passphrase-file [--cipher-alg alg]
Formats image to an encrypted format. All data previously written to the image will become
unreadable. Supported formats: luks1, luks2. Supported cipher algorithms: aes-128, aes-256
(default).
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.
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.
feature disable image-spec feature-name...
Disable the specified feature on the specified image. Multiple features can be specified.
feature enable image-spec feature-name...
Enable the specified feature on the specified image. Multiple features can be specified.
flatten [--encryption-format encryption-format --encryption-passphrase-file passphrase-file]...
image-spec
If the 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.
group create group-spec
Create a group.
group image add group-spec image-spec
Add an image to a group.
group image list group-spec
List images in a group.
group image remove group-spec image-spec
Remove an image from a group.
group ls [-p | --pool pool-name]
List rbd groups.
group rename src-group-spec dest-group-spec
Rename a group. Note: rename across pools is not supported.
group rm group-spec
Delete a group.
group snap create group-snap-spec
Make a snapshot of a group.
group snap list group-spec
List snapshots of a group.
group snap rm group-snap-spec
Remove a snapshot from a group.
group snap rename group-snap-spec snap-name
Rename group's snapshot.
group snap rollback group-snap-spec
Rollback group to snapshot.
image-meta get image-spec key
Get metadata value with the key.
image-meta list image-spec
Show metadata held on the image. The first column is the key and the second column is the value.
image-meta remove image-spec key
Remove metadata key with the value.
image-meta set image-spec key value
Set metadata key with the value. They will displayed in image-meta list.
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 import 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.
import-diff src-path image-spec
Import an incremental diff of an image and apply 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.
info image-spec | snap-spec
Will dump information (such as size and object size) about a specific rbd image. If the image is
a clone, information about its parent is also displayed. If a snapshot is specified, whether it
is protected is shown as well.
journal client disconnect journal-spec
Flag image journal client as disconnected.
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.
journal import [--verbose] [--no-error] path-name dest-journal-spec
Import image journal from path (use - for stdin).
journal info journal-spec
Show information about image journal.
journal inspect [--verbose] journal-spec
Inspect and report image journal for structural errors.
journal reset journal-spec
Reset image journal.
journal status journal-spec
Show status of image journal.
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.
lock ls image-spec
Show locks held on the image. The first column is the locker to use with the lock remove 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.
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.
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
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.
migration commit image-spec
Commit image migration. This step is run after successful migration prepare and migration execute
steps and removes the source image data.
migration execute image-spec
Execute image migration. This step is run after a successful migration prepare step and copies
image data to the destination.
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]
[--import-only] [--source-spec json] [--source-spec-path path] 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.
An image can also be migrated from a read-only import source by adding the --import-only optional
and providing a JSON-encoded --source-spec or a path to a JSON-encoded source-spec file using the
--source-spec-path optionals.
mirror image demote image-spec
Demote a primary image to non-primary for RBD mirroring.
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 must be disabled for each image individually.
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 must be enabled for each image individually.
The mirror image mode can either be journal (default) or snapshot. The journal mode requires the
RBD journaling feature.
mirror image promote [--force] image-spec
Promote a non-primary image to primary for RBD mirroring.
mirror image resync image-spec
Force resync to primary image for RBD mirroring.
mirror image status image-spec
Show RBD mirroring status for an image.
mirror pool demote [pool-name]
Demote all primary images within a pool or namespace to non-primary. Every mirror-enabled image
in the pool or namespace will be demoted.
mirror pool disable [pool-name]
Disable RBD mirroring within a pool or namespace. When mirroring is disabled on a pool or
namespace in this way, mirroring will also be disabled on all images (within the pool or
namespace) for which mirroring was enabled, whether by default or explicitly.
mirror pool enable [pool-name] mode
Enable RBD mirroring within a pool or namespace. The mirroring mode can either be pool or image.
If configured in pool mode, all images in the pool or namespace 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.
mirror pool info [pool-name]
Show information about the pool or namespace mirroring configuration. For a pool, it includes
mirroring mode, peer UUID, remote cluster name, and remote client name. For a namespace, it
includes only mirroring mode.
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 to be enabled on the pool.
mirror pool peer remove [pool-name] uuid
Remove a mirroring peer from a pool. The peer uuid is available from mirror pool info 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.
mirror pool promote [--force] [pool-name]
Promote all non-primary images within a pool or namespace to primary. Every mirror-enabled image
in the pool or namespace will be promoted.
mirror pool status [--verbose] [pool-name]
Show status for all mirrored images in the pool or namespace. With --verbose, show additional
output status details for every mirror-enabled image in the pool or namespace.
mirror snapshot schedule add [-p | --pool pool] [--namespace namespace] [--image image] interval
[start-time]
Add mirror snapshot schedule.
mirror snapshot schedule list [-R | --recursive] [--format format] [--pretty-format] [-p | --pool pool]
[--namespace namespace] [--image image]
List mirror snapshot schedule.
mirror snapshot schedule remove [-p | --pool pool] [--namespace namespace] [--image image] interval
[start-time]
Remove mirror snapshot schedule.
mirror snapshot schedule status [-p | --pool pool] [--format format] [--pretty-format] [--namespace
namespace] [--image image]
Show mirror snapshot schedule status.
mv src-image-spec dest-image-spec
Rename an image. Note: rename across pools is not supported.
namespace create pool-name/namespace-name
Create a new image namespace within the pool.
namespace list pool-name
List image namespaces defined within the pool.
namespace remove pool-name/namespace-name
Remove an empty image namespace from the pool.
object-map check image-spec | snap-spec
Verify the object map is correct.
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.
pool init [pool-name] [--force]
Initialize pool for use by RBD. Newly created pools must be initialized prior to use.
resize (-s | --size size-in-M/G/T) [--allow-shrink] [--encryption-format encryption-format
--encryption-passphrase-file passphrase-file]... image-spec
Resize rbd image. The size parameter also needs to be specified. The --allow-shrink option lets
the size be reduced.
rm image-spec
Delete an rbd image (including all data blocks). If the image has snapshots, this fails and
nothing is deleted.
snap create snap-spec
Create a new snapshot. Requires the snapshot name parameter to be specified.
snap limit clear image-spec
Remove any previously set limit on the number of snapshots allowed on an image.
snap limit set [--limit] limit image-spec
Set a limit for the number of snapshots allowed on an image.
snap ls image-spec
Dump the list of snapshots of a specific image.
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.
snap purge image-spec
Remove all unprotected snapshots from an image.
snap rename src-snap-spec dest-snap-spec
Rename a snapshot. Note: rename across pools and images is not supported.
snap rm [--force] snap-spec
Remove the specified snapshot.
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.
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.
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.
status image-spec
Show the status of the image, including which clients have it open.
trash ls [pool-name]
List all entries from trash.
trash mv [--expires-at <expires-at>] 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. Use --expires-at to set the expiration time of an image after which
it's allowed to be removed.
trash purge [pool-name]
Remove all expired images from trash.
trash restore image-id
Restore an image from trash.
trash rm [--force] image-id
Delete an image from trash. If the image deferment time has not expired it can be removed using
--force. An image that is actively in-use by clones or has snapshots cannot be removed.
trash purge schedule add [-p | --pool pool] [--namespace namespace] interval [start-time]
Add trash purge schedule.
trash purge schedule list [-R | --recursive] [--format format] [--pretty-format] [-p | --pool pool]
[--namespace namespace]
List trash purge schedule.
trash purge schedule remove [-p | --pool pool] [--namespace namespace] interval [start-time]
Remove trash purge schedule.
trash purge schedule status [-p | --pool pool] [--format format] [--pretty-format] [--namespace
namespace]
Show trash purge schedule status.
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:
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.
stripe-unit
Each [stripe-unit] contiguous bytes are stored adjacently in the same object, before we move on to
the next object.
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 msgr1 on-the-wire protocol (default). For msgr2.1 protocol this
option is ignored: full checksumming is always on in 'crc' mode and always off in 'secure' mode.
• nocrc - Disable CRC32C checksumming for msgr1 on-the-wire protocol. Note that only payload
checksumming is disabled, header checksumming is always on. For msgr2.1 protocol this option is
ignored.
• cephx_require_signatures - Require msgr1 message signing feature (since 3.19, default). This option is
deprecated and will be removed in the future as the feature has been supported since the Bobtail
release.
• nocephx_require_signatures - Don't require msgr1 message signing feature (since 3.19). This option is
deprecated and will be removed in the future.
• 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 for msgr1 on-the-wire protocol (since 4.4, default). For
msgr2.1 protocol this option is ignored: message signing is built into 'secure' mode and not offered in
'crc' mode.
• nocephx_sign_messages - Disable message signing for msgr1 on-the-wire protocol (since 4.4). For
msgr2.1 protocol this option is ignored.
• 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). Overridden by --read-only.
• 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). Equivalent to --exclusive.
• 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 (currently set to 4K for all types of drives,
previously used to be set to 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).
• ms_mode=legacy - Use msgr1 on-the-wire protocol (since 5.11, default).
• ms_mode=crc - Use msgr2.1 on-the-wire protocol, select 'crc' mode, also referred to as plain mode
(since 5.11). If the daemon denies 'crc' mode, fail the connection.
• ms_mode=secure - Use msgr2.1 on-the-wire protocol, select 'secure' mode (since 5.11). 'secure' mode
provides full in-transit encryption ensuring both confidentiality and authenticity. If the daemon
denies 'secure' mode, fail the connection.
• ms_mode=prefer-crc - Use msgr2.1 on-the-wire protocol, select 'crc' mode (since 5.11). If the daemon
denies 'crc' mode in favor of 'secure' mode, agree to 'secure' mode.
• ms_mode=prefer-secure - Use msgr2.1 on-the-wire protocol, select 'secure' mode (since 5.11). If the
daemon denies 'secure' mode in favor of 'crc' mode, agree to 'crc' mode.
• rxbounce - Use a bounce buffer when receiving data (since 5.17). The default behaviour is to read
directly into the destination buffer. A bounce buffer is needed if the destination buffer isn't
guaranteed to be stable (i.e. remain unchanged while it is being read to). In particular this is the
case for Windows where a system-wide "dummy" (throwaway) page may be mapped into the destination buffer
in order to generate a single large I/O. Otherwise, "libceph: ... bad crc/signature" or "libceph: ...
integrity error, bad crc" errors and associated performance degradation are expected.
• udev - Wait for udev device manager to finish executing all matching "add" rules and release the device
before exiting (default). This option is not passed to the kernel.
• noudev - Don't wait for udev device manager. When enabled, the device may not be fully usable
immediately on exit.
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.
• udev - Wait for udev device manager to finish executing all matching "remove" rules and clean up after
the device before exiting (default). This option is not passed to the kernel.
• noudev - Don't wait for udev device manager.
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 https://docs.ceph.com for more information.
SEE ALSO
ceph(8), rados(8)
COPYRIGHT
2010-2014, Inktank Storage, Inc. and contributors. Licensed under Creative Commons Attribution Share
Alike 3.0 (CC-BY-SA-3.0)
dev May 22, 2025 RBD(8)