mirror of
https://github.com/ceph/ceph
synced 2024-12-22 11:31:55 +00:00
d7cdcc0e25
Signed-off-by: Josh Durgin <josh.durgin@inktank.com>
459 lines
13 KiB
Groff
459 lines
13 KiB
Groff
.TH "RBD" "8" "January 02, 2013" "dev" "Ceph"
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.SH NAME
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rbd \- manage rados block device (RBD) images
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.
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.\" Man page generated from reStructuredText.
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.
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.SH SYNOPSIS
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.nf
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\fBrbd\fP [ \-c \fIceph.conf\fP ] [ \-m \fImonaddr\fP ] [ \-p | \-\-pool \fIpool\fP ] [
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\-\-size \fIsize\fP ] [ \-\-order \fIbits\fP ] [ \fIcommand\fP ... ]
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.fi
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.sp
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.SH DESCRIPTION
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.sp
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\fBrbd\fP 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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.SH OPTIONS
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.INDENT 0.0
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.TP
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.B \-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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.UNINDENT
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.INDENT 0.0
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.TP
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.B \-m monaddress[:port]
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Connect to specified monitor (instead of looking through ceph.conf).
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.UNINDENT
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.INDENT 0.0
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.TP
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.B \-p pool, \-\-pool pool
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Interact with the given pool. Required by most commands.
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.UNINDENT
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.SH PARAMETERS
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.INDENT 0.0
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.TP
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.B \-\-image\-format format
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Specifies which object layout to use. The default is 1.
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.INDENT 7.0
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.IP \(bu 2
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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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.IP \(bu 2
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format 2 \- Use the second rbd format, which is supported by
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librbd (but not the kernel rbd module) at this time. 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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.UNINDENT
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.UNINDENT
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.INDENT 0.0
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.TP
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.B \-\-size size\-in\-mb
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Specifies the size (in megabytes) of the new rbd image.
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.UNINDENT
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.INDENT 0.0
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.TP
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.B \-\-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 \fB1 << order\fP. The default is 22 (4 MB).
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.UNINDENT
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.INDENT 0.0
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.TP
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.B \-\-stripe\-unit size\-in\-bytes
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Specifies the stripe unit size in bytes. See striping section (below) for more details.
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.UNINDENT
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.INDENT 0.0
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.TP
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.B \-\-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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.UNINDENT
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.INDENT 0.0
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.TP
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.B \-\-snap snap
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Specifies the snapshot name for the specific operation.
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.UNINDENT
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.INDENT 0.0
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.TP
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.B \-\-id username
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Specifies the username (without the \fBclient.\fP prefix) to use with the map command.
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.UNINDENT
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.INDENT 0.0
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.TP
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.B \-\-keyfile filename
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Specifies a file containing the secret to use with the map command.
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If not specified, \fBclient.admin\fP will be used by default.
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.UNINDENT
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.INDENT 0.0
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.TP
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.B \-\-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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.UNINDENT
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.INDENT 0.0
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.TP
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.B \-\-shared tag
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Option for \fIlock add\fP 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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.UNINDENT
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.INDENT 0.0
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.TP
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.B \-\-format format
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Specifies output formatting (default: plain, json, xml)
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.UNINDENT
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.INDENT 0.0
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.TP
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.B \-\-pretty\-format
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Make json or xml formatted output more human-readable.
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.UNINDENT
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.SH COMMANDS
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.INDENT 0.0
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.TP
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.B \fBls\fP [\-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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.TP
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.B \fBinfo\fP [\fIimage\-name\fP]
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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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.TP
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.B \fBcreate\fP [\fIimage\-name\fP]
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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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.TP
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.B \fBclone\fP [\fIparent\-snapname\fP] [\fIimage\-name\fP]
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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.
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.sp
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The parent snapshot must be protected (see \fIrbd snap protect\fP).
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This requires format 2.
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.TP
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.B \fBflatten\fP [\fIimage\-name\fP]
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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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.sp
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This requires format 2.
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.TP
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.B \fBchildren\fP [\fIimage\-name\fP]
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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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.sp
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This requires format 2.
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.TP
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.B \fBresize\fP [\fIimage\-name\fP]
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Resizes rbd image. The size parameter also needs to be specified.
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.TP
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.B \fBrm\fP [\fIimage\-name\fP]
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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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.TP
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.B \fBexport\fP [\fIimage\-name\fP] [\fIdest\-path\fP]
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Exports image to dest path (use \- for stdout).
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.TP
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.B \fBimport\fP [\fIpath\fP] [\fIdest\-image\fP]
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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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.TP
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.B \fBcp\fP [\fIsrc\-image\fP] [\fIdest\-image\fP]
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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 format as src\-image.
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.TP
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.B \fBmv\fP [\fIsrc\-image\fP] [\fIdest\-image\fP]
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Renames an image. Note: rename across pools is not supported.
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.TP
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.B \fBsnap\fP ls [\fIimage\-name\fP]
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Dumps the list of snapshots inside a specific image.
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.TP
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.B \fBsnap\fP create [\fIimage\-name\fP]
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Creates a new snapshot. Requires the snapshot name parameter specified.
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.TP
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.B \fBsnap\fP rollback [\fIimage\-name\fP]
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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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.TP
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.B \fBsnap\fP rm [\fIimage\-name\fP]
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Removes the specified snapshot.
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.TP
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.B \fBsnap\fP purge [\fIimage\-name\fP]
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Removes all snapshots from an image.
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.TP
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.B \fBsnap\fP protect [\fIimage\-name\fP]
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Protect a snapshot from deletion, so that clones can be made of it
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(see \fIrbd clone\fP). 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. \fIrbd clone\fP will fail on a nonprotected
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snapshot.
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.sp
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This requires format 2.
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.TP
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.B \fBsnap\fP unprotect [\fIimage\-name\fP]
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Unprotect a snapshot from deletion (undo \fIsnap protect\fP). If cloned
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children remain, \fIsnap unprotect\fP fails. (Note that clones may exist
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in different pools than the parent snapshot.)
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.sp
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This requires format 2.
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.TP
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.B \fBmap\fP [\fIimage\-name\fP]
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Maps the specified image to a block device via the rbd kernel module.
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.TP
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.B \fBunmap\fP [\fIdevice\-path\fP]
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Unmaps the block device that was mapped via the rbd kernel module.
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.TP
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.B \fBshowmapped\fP
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Show the rbd images that are mapped via the rbd kernel module.
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.TP
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.B \fBlock\fP list [\fIimage\-name\fP]
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Show locks held on the image. The first column is the locker
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to use with the \fIlock remove\fP command.
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.TP
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.B \fBlock\fP add [\fIimage\-name\fP] [\fIlock\-id\fP]
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Lock an image. The lock\-id is an arbitrary name for the user\(aqs
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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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.TP
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.B \fBlock\fP remove [\fIimage\-name\fP] [\fIlock\-id\fP] [\fIlocker\fP]
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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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.TP
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.B \fBbench\-write\fP [\fIimage\-name\fP] \-\-io\-size [\fIio\-size\-in\-bytes\fP] \-\-io\-threads [\fInum\-ios\-in\-flight\fP] \-\-io\-total [\fItotal\-bytes\-to\-write\fP]
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Generate a series of sequential writes to the image and measure the
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write throughput and latency. Defaults are: \-\-io\-size 4096, \-\-io\-threads 16,
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\-\-io\-total 1GB
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.UNINDENT
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.SH IMAGE NAME
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.sp
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In addition to using the \-\-pool and the \-\-snap options, the image name can include both
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the pool name and the snapshot name. The image name format is as follows:
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.sp
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.nf
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.ft C
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[pool/]image\-name[@snap]
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.ft P
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.fi
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.sp
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Thus an image name that contains a slash character (\(aq/\(aq) requires specifying the pool
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name explicitly.
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.SH STRIPING
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.sp
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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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.sp
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The striping is controlled by three parameters:
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.INDENT 0.0
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.TP
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.B order
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.TP
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.B The size of objects we stripe over is a power of two, specifially 2^[*order*] bytes. The default
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.TP
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.B is 22, or 4 MB.
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.UNINDENT
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.INDENT 0.0
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.TP
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.B stripe_unit
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.TP
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.B Each [*stripe_unit*] contiguous bytes are stored adjacently in the same object, before we move on
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.TP
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.B to the next object.
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.UNINDENT
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.INDENT 0.0
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.TP
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.B stripe_count
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.TP
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.B After we write [*stripe_unit*] bytes to [*stripe_count*] objects, we loop back to the initial object
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.TP
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.B and write another stripe, until the object reaches its maximum size (as specified by [*order*]. At that
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.TP
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.B point, we move on to the next [*stripe_count*] objects.
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.UNINDENT
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.sp
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By default, [\fIstripe_unit\fP] is the same as the object size and [\fIstripe_count\fP] is 1. Specifying a different
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[\fIstripe_unit\fP] 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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.SH EXAMPLES
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.sp
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To create a new rbd image that is 100 GB:
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.sp
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.nf
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.ft C
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rbd \-p mypool create myimage \-\-size 102400
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.ft P
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.fi
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.sp
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or alternatively:
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.sp
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.nf
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.ft C
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rbd create mypool/myimage \-\-size 102400
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.ft P
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.fi
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.sp
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To use a non\-default object size (8 MB):
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.sp
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.nf
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.ft C
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rbd create mypool/myimage \-\-size 102400 \-\-order 23
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.ft P
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.fi
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.sp
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To delete an rbd image (be careful!):
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.sp
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.nf
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.ft C
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rbd rm mypool/myimage
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.ft P
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.fi
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.sp
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To create a new snapshot:
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.sp
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.nf
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.ft C
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rbd snap create mypool/myimage@mysnap
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.ft P
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.fi
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.sp
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To create a copy\-on\-write clone of a protected snapshot:
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.sp
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.nf
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.ft C
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rbd clone mypool/myimage@mysnap otherpool/cloneimage
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.ft P
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.fi
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.sp
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To see which clones of a snapshot exist:
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.sp
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.nf
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.ft C
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rbd children mypool/myimage@mysnap
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.ft P
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.fi
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.sp
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To delete a snapshot:
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.sp
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.nf
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.ft C
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rbd snap rm mypool/myimage@mysnap
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.ft P
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.fi
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.sp
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To map an image via the kernel with cephx enabled:
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.sp
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.nf
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.ft C
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rbd map mypool/myimage \-\-id admin \-\-keyfile secretfile
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.ft P
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.fi
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.sp
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To unmap an image:
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.sp
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.nf
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.ft C
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rbd unmap /dev/rbd0
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.ft P
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.fi
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.sp
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To create an image and a clone from it:
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.sp
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.nf
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.ft C
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rbd import \-\-format 2 image mypool/parent
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rbd snap create \-\-snap snapname mypool/parent
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rbd snap protect mypool/parent@snap
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rbd clone mypool/parent@snap otherpool/child
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.ft P
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.fi
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.sp
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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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.sp
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.nf
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.ft C
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rbd \-p mypool create myimage \-\-size 102400 \-\-stripe\-unit 65536 \-\-stripe\-count 16
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.ft P
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.fi
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.sp
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To change an image from one format to another, export it and then
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import it as the desired format:
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.sp
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.nf
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.ft C
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rbd export mypool/myimage@snap /tmp/img
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rbd import \-\-format 2 /tmp/img mypool/myimage2
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.ft P
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.fi
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.sp
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To lock an image for exclusive use:
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.sp
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.nf
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.ft C
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rbd lock add mypool/myimage mylockid
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.ft P
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.fi
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.sp
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To release a lock:
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.sp
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.nf
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.ft C
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rbd lock remove mypool/myimage mylockid client.2485
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.ft P
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.fi
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.SH AVAILABILITY
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.sp
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\fBrbd\fP is part of the Ceph distributed file system. Please refer to
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the Ceph documentation at \fI\%http://ceph.com/docs\fP for more information.
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.SH SEE ALSO
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.sp
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\fBceph\fP(8),
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\fBrados\fP(8)
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.SH COPYRIGHT
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2010-2012, Inktank Storage, Inc. and contributors. Licensed under Creative Commons BY-SA
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.\" Generated by docutils manpage writer.
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.
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