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545 lines
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ReStructuredText
545 lines
20 KiB
ReStructuredText
:orphan:
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===============================================
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rbd -- manage rados block device (RBD) images
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===============================================
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.. program:: rbd
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Synopsis
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========
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| **rbd** [ -c *ceph.conf* ] [ -m *monaddr* ] [--cluster *cluster name*]
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[ -p | --pool *pool* ] [--size *size* ] [ --order *bits* ] [ *command* ... ]
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Description
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===========
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**rbd** is a utility for manipulating rados block device (RBD) images,
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used by the Linux rbd driver and the rbd storage driver for Qemu/KVM.
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RBD images are simple block devices that are striped over objects and
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stored in a RADOS object store. The size of the objects the image is
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striped over must be a power of two.
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Options
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=======
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.. option:: -c ceph.conf, --conf ceph.conf
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Use ceph.conf configuration file instead of the default /etc/ceph/ceph.conf to
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determine monitor addresses during startup.
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.. option:: -m monaddress[:port]
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Connect to specified monitor (instead of looking through ceph.conf).
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.. option:: --cluster cluster name
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Use different cluster name as compared to default cluster name *ceph*.
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.. option:: -p pool-name, --pool pool-name
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Interact with the given pool. Required by most commands.
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.. option:: --no-progress
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Do not output progress information (goes to standard error by
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default for some commands).
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Parameters
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==========
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.. option:: --image-format format-id
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Specifies which object layout to use. The default is 1.
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* format 1 - Use the original format for a new rbd image. This format is
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understood by all versions of librbd and the kernel rbd module, but
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does not support newer features like cloning.
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* format 2 - Use the second rbd format, which is supported by
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librbd and kernel since version 3.11 (except for striping). This adds
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support for cloning and is more easily extensible to allow more
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features in the future.
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.. option:: --size size-in-M/G/T
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Specifies the size (in M/G/T) of the new rbd image.
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.. option:: --order bits
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Specifies the object size expressed as a number of bits, such that
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the object size is ``1 << order``. The default is 22 (4 MB).
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.. option:: --stripe-unit size-in-B/K/M
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Specifies the stripe unit size in B/K/M. See striping section (below) for more details.
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.. option:: --stripe-count num
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Specifies the number of objects to stripe over before looping back
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to the first object. See striping section (below) for more details.
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.. option:: --snap snap
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Specifies the snapshot name for the specific operation.
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.. option:: --id username
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Specifies the username (without the ``client.`` prefix) to use with the map command.
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.. option:: --keyring filename
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Specifies a keyring file containing a secret for the specified user
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to use with the map command. If not specified, the default keyring
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locations will be searched.
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.. option:: --keyfile filename
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Specifies a file containing the secret key of ``--id user`` to use with the map command.
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This option is overridden by ``--keyring`` if the latter is also specified.
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.. option:: --shared lock-tag
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Option for `lock add` that allows multiple clients to lock the
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same image if they use the same tag. The tag is an arbitrary
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string. This is useful for situations where an image must
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be open from more than one client at once, like during
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live migration of a virtual machine, or for use underneath
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a clustered filesystem.
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.. option:: --format format
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Specifies output formatting (default: plain, json, xml)
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.. option:: --pretty-format
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Make json or xml formatted output more human-readable.
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.. option:: -o map-options, --options map-options
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Specifies which options to use when mapping an image. map-options is
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a comma-separated string of options (similar to mount(8) mount options).
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See map options section below for more details.
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.. option:: --read-only
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Map the image read-only. Equivalent to -o ro.
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.. option:: --image-feature feature-name
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Specifies which RBD format 2 feature should be enabled when creating
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an image. Multiple features can be enabled by repeating this option
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multiple times. The following features are supported:
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* layering: layering support
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* striping: striping v2 support
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* exclusive-lock: exclusive locking support
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* object-map: object map support (requires exclusive-lock)
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* fast-diff: fast diff calculations (requires object-map)
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* deep-flatten: snapshot flatten support
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* journaling: journaled IO support (requires exclusive-lock)
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.. option:: --image-shared
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Specifies that the image will be used concurrently by multiple clients.
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This will disable features that are dependent upon exclusive ownership
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of the image.
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.. option:: --whole-object
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Specifies that the diff should be limited to the extents of a full object
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instead of showing intra-object deltas. When the object map feature is
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enabled on an image, limiting the diff to the object extents will
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dramatically improve performance since the differences can be computed
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by examining the in-memory object map instead of querying RADOS for each
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object within the image.
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Commands
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========
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.. TODO rst "option" directive seems to require --foo style options, parsing breaks on subcommands.. the args show up as bold too
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:command:`ls` [-l | --long] [*pool-name*]
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Will list all rbd images listed in the rbd_directory object. With
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-l, also show snapshots, and use longer-format output including
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size, parent (if clone), format, etc.
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:command:`du` [-p | --pool *pool-name*] [*image-spec* | *snap-spec*]
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Will calculate the provisioned and actual disk usage of all images and
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associated snapshots within the specified pool. It can also be used against
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individual images and snapshots.
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If the RBD fast-diff feature isn't enabled on images, this operation will
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require querying the OSDs for every potential object within the image.
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:command:`info` *image-spec* | *snap-spec*
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Will dump information (such as size and order) about a specific rbd image.
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If image is a clone, information about its parent is also displayed.
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If a snapshot is specified, whether it is protected is shown as well.
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:command:`create` (-s | --size *size-in-M/G/T*) [--image-format *format-id*] [--order *bits*] [--stripe-unit *size-in-B/K/M* --stripe-count *num*] [--image-feature *feature-name*]... [--image-shared] *image-spec*
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Will create a new rbd image. You must also specify the size via --size. The
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--stripe-unit and --stripe-count arguments are optional, but must be used together.
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:command:`clone` [--order *bits*] [--stripe-unit *size-in-B/K/M* --stripe-count *num*] [--image-feature *feature-name*] [--image-shared] *parent-snap-spec* *child-image-spec*
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Will create a clone (copy-on-write child) of the parent snapshot.
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Object order will be identical to that of the parent image unless
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specified. Size will be the same as the parent snapshot. The --stripe-unit
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and --stripe-count arguments are optional, but must be used together.
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The parent snapshot must be protected (see `rbd snap protect`).
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This requires image format 2.
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:command:`flatten` *image-spec*
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If image is a clone, copy all shared blocks from the parent snapshot and
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make the child independent of the parent, severing the link between
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parent snap and child. The parent snapshot can be unprotected and
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deleted if it has no further dependent clones.
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This requires image format 2.
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:command:`children` *snap-spec*
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List the clones of the image at the given snapshot. This checks
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every pool, and outputs the resulting poolname/imagename.
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This requires image format 2.
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:command:`resize` (-s | --size *size-in-M/G/T*) [--allow-shrink] *image-spec*
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Resizes rbd image. The size parameter also needs to be specified.
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The --allow-shrink option lets the size be reduced.
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:command:`rm` *image-spec*
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Deletes an rbd image (including all data blocks). If the image has
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snapshots, this fails and nothing is deleted.
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:command:`export` (*image-spec* | *snap-spec*) [*dest-path*]
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Exports image to dest path (use - for stdout).
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:command:`import` [--image-format *format-id*] [--order *bits*] [--stripe-unit *size-in-B/K/M* --stripe-count *num*] [--image-feature *feature-name*]... [--image-shared] *src-path* [*image-spec*]
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Creates a new image and imports its data from path (use - for
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stdin). The import operation will try to create sparse rbd images
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if possible. For import from stdin, the sparsification unit is
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the data block size of the destination image (1 << order).
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The --stripe-unit and --stripe-count arguments are optional, but must be
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used together.
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:command:`export-diff` [--from-snap *snap-name*] [--whole-object] (*image-spec* | *snap-spec*) *dest-path*
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Exports an incremental diff for an image to dest path (use - for stdout). If
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an initial snapshot is specified, only changes since that snapshot are included; otherwise,
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any regions of the image that contain data are included. The end snapshot is specified
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using the standard --snap option or @snap syntax (see below). The image diff format includes
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metadata about image size changes, and the start and end snapshots. It efficiently represents
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discarded or 'zero' regions of the image.
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:command:`merge-diff` *first-diff-path* *second-diff-path* *merged-diff-path*
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Merge two continuous incremental diffs of an image into one single diff. The
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first diff's end snapshot must be equal with the second diff's start snapshot.
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The first diff could be - for stdin, and merged diff could be - for stdout, which
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enables multiple diff files to be merged using something like
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'rbd merge-diff first second - | rbd merge-diff - third result'. Note this command
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currently only support the source incremental diff with stripe_count == 1
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:command:`import-diff` *src-path* *image-spec*
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Imports an incremental diff of an image and applies it to the current image. If the diff
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was generated relative to a start snapshot, we verify that snapshot already exists before
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continuing. If there was an end snapshot we verify it does not already exist before
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applying the changes, and create the snapshot when we are done.
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:command:`diff` [--from-snap *snap-name*] [--whole-object] *image-spec* | *snap-spec*
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Dump a list of byte extents in the image that have changed since the specified start
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snapshot, or since the image was created. Each output line includes the starting offset
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(in bytes), the length of the region (in bytes), and either 'zero' or 'data' to indicate
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whether the region is known to be zeros or may contain other data.
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:command:`cp` (*src-image-spec* | *src-snap-spec*) *dest-image-spec*
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Copies the content of a src-image into the newly created dest-image.
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dest-image will have the same size, order, and image format as src-image.
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:command:`mv` *src-image-spec* *dest-image-spec*
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Renames an image. Note: rename across pools is not supported.
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:command:`image-meta list` *image-spec*
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Show metadata held on the image. The first column is the key
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and the second column is the value.
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:command:`image-meta get` *image-spec* *key*
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Get metadata value with the key.
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:command:`image-meta set` *image-spec* *key* *value*
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Set metadata key with the value. They will displayed in `image-meta list`.
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:command:`image-meta remove` *image-spec* *key*
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Remove metadata key with the value.
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:command:`object-map rebuild` *image-spec* | *snap-spec*
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Rebuilds an invalid object map for the specified image. An image snapshot can be
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specified to rebuild an invalid object map for a snapshot.
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:command:`snap ls` *image-spec*
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Dumps the list of snapshots inside a specific image.
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:command:`snap create` *snap-spec*
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Creates a new snapshot. Requires the snapshot name parameter specified.
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:command:`snap rollback` *snap-spec*
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Rollback image content to snapshot. This will iterate through the entire blocks
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array and update the data head content to the snapshotted version.
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:command:`snap rm` *snap-spec*
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Removes the specified snapshot.
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:command:`snap purge` *image-spec*
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Removes all snapshots from an image.
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:command:`snap protect` *snap-spec*
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Protect a snapshot from deletion, so that clones can be made of it
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(see `rbd clone`). Snapshots must be protected before clones are made;
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protection implies that there exist dependent cloned children that
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refer to this snapshot. `rbd clone` will fail on a nonprotected
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snapshot.
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This requires image format 2.
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:command:`snap unprotect` *snap-spec*
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Unprotect a snapshot from deletion (undo `snap protect`). If cloned
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children remain, `snap unprotect` fails. (Note that clones may exist
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in different pools than the parent snapshot.)
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This requires image format 2.
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:command:`map` [-o | --options *map-options* ] [--read-only] *image-spec* | *snap-spec*
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Maps the specified image to a block device via the rbd kernel module.
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:command:`unmap` *image-spec* | *snap-spec* | *device-path*
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Unmaps the block device that was mapped via the rbd kernel module.
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:command:`showmapped`
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Show the rbd images that are mapped via the rbd kernel module.
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:command:`nbd map` [--device *device-path*] [--read-only] *image-spec* | *snap-spec*
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Maps the specified image to a block device via the rbd-nbd tool.
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:command:`nbd unmap` *device-path*
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Unmaps the block device that was mapped via the rbd-nbd tool.
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:command:`nbd list`
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Show the list of used nbd devices via the rbd-nbd tool.
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:command:`status` *image-spec*
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Show the status of the image, including which clients have it open.
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:command:`feature disable` *image-spec* *feature-name*...
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Disables the specified feature on the specified image. Multiple features can
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be specified.
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:command:`feature enable` *image-spec* *feature-name*...
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Enables the specified feature on the specified image. Multiple features can
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be specified.
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:command:`lock list` *image-spec*
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Show locks held on the image. The first column is the locker
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to use with the `lock remove` command.
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:command:`lock add` [--shared *lock-tag*] *image-spec* *lock-id*
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Lock an image. The lock-id is an arbitrary name for the user's
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convenience. By default, this is an exclusive lock, meaning it
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will fail if the image is already locked. The --shared option
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changes this behavior. Note that locking does not affect
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any operation other than adding a lock. It does not
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protect an image from being deleted.
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:command:`lock remove` *image-spec* *lock-id* *locker*
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Release a lock on an image. The lock id and locker are
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as output by lock ls.
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:command:`bench-write` [--io-size *size-in-B/K/M/G/T*] [--io-threads *num-ios-in-flight*] [--io-total *total-size-to-write-in-B/K/M/G/T*] [--io-pattern seq | rand] *image-spec*
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Generate a series of writes to the image and measure the write throughput and
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latency. Defaults are: --io-size 4096, --io-threads 16, --io-total 1G,
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--io-pattern seq.
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Image and snap specs
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====================
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| *image-spec* is [*pool-name*]/*image-name*
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| *snap-spec* is [*pool-name*]/*image-name*\ @\ *snap-name*
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The default for *pool-name* is "rbd". If an image name contains a slash
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character ('/'), *pool-name* is required.
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You may specify each name individually, using --pool, --image and --snap
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options, but this is discouraged in favor of the above spec syntax.
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Striping
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========
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RBD images are striped over many objects, which are then stored by the
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Ceph distributed object store (RADOS). As a result, read and write
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requests for the image are distributed across many nodes in the
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cluster, generally preventing any single node from becoming a
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bottleneck when individual images get large or busy.
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The striping is controlled by three parameters:
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.. option:: order
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The size of objects we stripe over is a power of two, specifically 2^[*order*] bytes. The default
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is 22, or 4 MB.
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.. option:: stripe_unit
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Each [*stripe_unit*] contiguous bytes are stored adjacently in the same object, before we move on
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to the next object.
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.. option:: stripe_count
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After we write [*stripe_unit*] bytes to [*stripe_count*] objects, we loop back to the initial object
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and write another stripe, until the object reaches its maximum size (as specified by [*order*]. At that
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point, we move on to the next [*stripe_count*] objects.
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By default, [*stripe_unit*] is the same as the object size and [*stripe_count*] is 1. Specifying a different
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[*stripe_unit*] requires that the STRIPINGV2 feature be supported (added in Ceph v0.53) and format 2 images be
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used.
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Map options
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===========
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Most of these options are useful mainly for debugging and benchmarking. The
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default values are set in the kernel and may therefore depend on the version of
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the running kernel.
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libceph (per client instance) options:
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* fsid=aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee - FSID that should be assumed by
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the client.
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* ip=a.b.c.d[:p] - IP and, optionally, port the client should use.
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* share - Enable sharing of client instances with other mappings (default).
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* noshare - Disable sharing of client instances with other mappings.
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* crc - Enable CRC32C checksumming for data writes (default).
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* nocrc - Disable CRC32C checksumming for data writes.
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* cephx_require_signatures - Require cephx message signing (since 3.19,
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default).
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* nocephx_require_signatures - Don't require cephx message signing (since
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3.19).
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* tcp_nodelay - Disable Nagle's algorithm on client sockets (since 4.0,
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default).
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* notcp_nodelay - Enable Nagle's algorithm on client sockets (since 4.0).
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* cephx_sign_messages - Enable message signing (since 4.4, default).
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* nocephx_sign_messages - Disable message signing (since 4.4).
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* mount_timeout=x - A timeout on various steps in `rbd map` and `rbd unmap`
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sequences (default is 60 seconds). In particular, since 4.2 this can be used
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to ensure that `rbd unmap` eventually times out when there is no network
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connection to a cluster.
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* osdkeepalive=x - OSD keepalive timeout (default is 5 seconds).
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* osd_idle_ttl=x - OSD idle TTL (default is 60 seconds).
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Mapping (per block device) options:
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* rw - Map the image read-write (default).
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* ro - Map the image read-only. Equivalent to --read-only.
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* queue_depth=x - queue depth (since 4.2, default is 128 requests).
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Examples
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========
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To create a new rbd image that is 100 GB::
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rbd create mypool/myimage --size 102400
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To use a non-default object size (8 MB)::
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rbd create mypool/myimage --size 102400 --order 23
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To delete an rbd image (be careful!)::
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rbd rm mypool/myimage
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To create a new snapshot::
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rbd snap create mypool/myimage@mysnap
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To create a copy-on-write clone of a protected snapshot::
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rbd clone mypool/myimage@mysnap otherpool/cloneimage
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To see which clones of a snapshot exist::
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rbd children mypool/myimage@mysnap
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To delete a snapshot::
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rbd snap rm mypool/myimage@mysnap
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To map an image via the kernel with cephx enabled::
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rbd map mypool/myimage --id admin --keyfile secretfile
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To map an image via the kernel with different cluster name other than default *ceph*.
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|
|
rbd map mypool/myimage --cluster *cluster name*
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To unmap an image::
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|
|
rbd unmap /dev/rbd0
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|
|
To create an image and a clone from it::
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|
|
|
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
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|
|
|
To create an image with a smaller stripe_unit (to better distribute small writes in some workloads)::
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|
|
|
rbd create mypool/myimage --size 102400 --stripe-unit 65536B --stripe-count 16
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|
|
|
To change an image from one image format to another, export it and then
|
|
import it as the desired image format::
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|
|
|
rbd export mypool/myimage@snap /tmp/img
|
|
rbd import --image-format 2 /tmp/img mypool/myimage2
|
|
|
|
To lock an image for exclusive use::
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|
|
|
rbd lock add mypool/myimage mylockid
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|
|
|
To release a lock::
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|
|
|
rbd lock remove mypool/myimage mylockid client.2485
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|
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|
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Availability
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|
============
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|
|
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**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.
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See also
|
|
========
|
|
|
|
:doc:`ceph <ceph>`\(8),
|
|
:doc:`rados <rados>`\(8)
|