The rbd command enables you to create, list, introspect and remove block device images. You can also use it to clone images, create snapshots, rollback an image to a snapshot, view a snapshot, etc. For details on using the rbd command, see RBD – Manage RADOS Block Device (RBD) Images for details.
Important
To use Ceph Block Device commands, you must have access to a running Ceph cluster.
Before you can add a block device to a node, you must create an image for it in the Ceph Storage Cluster first. To create a block device image, execute the following:
rbd create {image-name} --size {megabytes} --pool {pool-name}
For example, to create a 1GB image named foo that stores information in a pool named swimmingpool, execute the following:
rbd create foo --size 1024
rbd create bar --size 1024 --pool swimmingpool
Note
You must create a pool first before you can specify it as a source. See Storage Pools for details.
To list block devices in the rbd pool, execute the following (i.e., rbd is the default pool name):
rbd ls
To list block devices in a particular pool, execute the following, but replace {poolname} with the name of the pool:
rbd ls {poolname}
For example:
rbd ls swimmingpool
To retrieve information from a particular image, execute the following, but replace {image-name} with the name for the image:
rbd --image {image-name} info
For example:
rbd --image foo info
To retrieve information from an image within a pool, execute the following, but replace {image-name} with the name of the image and replace {pool-name} with the name of the pool:
rbd --image {image-name} -p {pool-name} info
For example:
rbd --image bar -p swimmingpool info
Ceph Block Device images are thin provisioned. They don’t actually use any physical storage until you begin saving data to them. However, they do have a maximum capacity that you set with the --size option. If you want to increase (or decrease) the maximum size of a Ceph Block Device image, execute the following:
rbd resize --image foo --size 2048
To remove a block device, execute the following, but replace {image-name} with the name of the image you want to remove:
rbd rm {image-name}
For example:
rbd rm foo
To remove a block device from a pool, execute the following, but replace {image-name} with the name of the image to remove and replace {pool-name} with the name of the pool:
rbd rm {image-name} -p {pool-name}
For example:
rbd rm bar -p swimmingpool