Provided by: ceph-common_12.2.13-0ubuntu0.18.04.11_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.
--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 and kernel
since version 3.11 (except for striping). 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.
--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 filesystem.
--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)
--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
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.
du [-p | --pool pool-name] [image-spec | snap-spec]
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.
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.
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] [--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.
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.
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.
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.
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.
rm image-spec
Delete an rbd image (including all data blocks). If the image has snapshots, this
fails and nothing is deleted.
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.
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.
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.
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
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.
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.
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.
mv src-image-spec dest-image-spec
Rename an image. Note: rename across pools is not supported.
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 get image-spec key
Get metadata value with the key.
image-meta set image-spec key value
Set metadata key with the value. They will displayed in image-meta list.
image-meta remove image-spec key
Remove metadata key with the value.
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.
snap ls image-spec
Dump the list of snapshots inside a specific image.
snap create snap-spec
Create a new snapshot. Requires the snapshot name parameter specified.
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 rm [--force] snap-spec
Remove the specified snapshot.
snap purge image-spec
Remove all snapshots from an 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 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.
snap limit set [--limit] limit image-spec
Set a limit for the number of snapshots allowed on an image.
snap limit clear image-spec
Remove any previously set limit on the number of snapshots allowed on an image.
map [-o | --options krbd-options ] [--read-only] image-spec | snap-spec
Map the specified image to a block device via the rbd kernel module.
unmap [-o | --options krbd-options ] image-spec | snap-spec | device-path
Unmap the block device that was mapped via the rbd kernel module.
showmapped
Show the rbd images that are mapped via the rbd kernel module.
nbd map [--device device-path] [--read-only] image-spec | snap-spec
Map the specified image to a block device via the rbd-nbd tool.
nbd unmap device-path
Unmap the block device that was mapped via the rbd-nbd tool.
nbd list
Show the list of used nbd devices via the rbd-nbd tool.
status image-spec
Show the status of the image, including which clients have it open.
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.
lock list image-spec
Show locks held on the image. The first column is the locker to use with the lock
remove 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.
lock remove image-spec lock-id locker
Release a lock on an image. The lock id and locker are as output by lock ls.
bench --io-type <read | write> [--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] 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.
trash ls [pool-name]
List all entries from trash.
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.
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.
trash restore image-id
Restore an image from trash.
IMAGE AND SNAP SPECS
image-spec is [pool-name]/image-name
snap-spec is [pool-name]/image-name@snap-name
The default for pool-name is "rbd". If an image name contains a slash character ('/'),
pool-name is required.
You may specify each name individually, using --pool, --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] requires that the STRIPINGV2 feature be supported
(added in Ceph v0.53) and format 2 images be used.
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 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 map and rbd unmap sequences (default
is 60 seconds). In particular, since 4.2 this can be used to ensure that rbd 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 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).
rbd 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 map mypool/myimage --id admin --keyfile secretfile
To map an image via the kernel with different cluster name other than default ceph:
rbd map mypool/myimage --cluster cluster-name
To unmap an image:
rbd 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 --delay to set delay-time, default is 0):
rbd trash mv mypool/myimage
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
ceph(8), rados(8)
COPYRIGHT
2010-2023, Inktank Storage, Inc. and contributors. Licensed under Creative Commons
Attribution Share Alike 3.0 (CC-BY-SA-3.0)