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https://github.com/ceph/ceph
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112 lines
4.4 KiB
ReStructuredText
112 lines
4.4 KiB
ReStructuredText
==============================
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RBD Kernel Object Operations
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==============================
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.. important:: To use kernel object operations, you must have a running Ceph cluster.
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Load the Ceph RBD Module
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------------------------
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To map an RBD image to a kernel object, first load the Ceph RBD module::
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modprobe rbd
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Get a List of RBD Images
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------------------------
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To mount an RBD image, first return a list of the images. ::
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rbd list
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Map a Block Device with ``rbd``
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-------------------------------
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Use ``rbd`` to map an image name to a kernel object. You must specify the
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image name, the pool name, and the client name. If you use ``cephx``
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authentication, you must also specify a secret. ::
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sudo rbd map {image-name} --pool {pool-name} --name {client-name}
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For example::
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sudo rbd map foo --pool rbd myimage --name client.admin
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If you use ``cephx`` authentication, you must also specify a secret. It may come from a keyring, a file containing the secret, or be specified explicitly on the command line. ::
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sudo rbd map foo --pool rbd myimage --name client.foo --keyring /path/to/keyring
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sudo rbd map foo --pool rbd myimage --name client.foo --keyfile /path/to/file
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Map a Block Device with ``add``
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-------------------------------
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To map an RBD image to a kernel object directly, enter the IP address of
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the monitor, the user name, and the RBD image name as follows::
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echo "{mon-ip-address} name={user-name} rbd {image-name}" | sudo tee /sys/bus/rbd/add
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For example::
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echo "10.20.30.40 name=admin rbd foo" | sudo tee /sys/bus/rbd/add
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If you use ``cephx`` authentication, you must also specify a secret. ::
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echo "10.20.30.40 name=admin,secret=/path/to/secret rbd foo" | sudo tee /sys/bus/rbd/add
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A kernel block device resides under the ``/sys/bus/rbd/devices`` directory and
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provides the following functions:
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+------------------+------------------------------------------------------------+
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| Function | Description |
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+==================+============================================================+
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| ``client_id`` | Returns the client ID of the given device ID. |
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+------------------+------------------------------------------------------------+
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| ``create_snap`` | Creates a snap from a snap name and a device ID. |
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+------------------+------------------------------------------------------------+
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| ``current_snap`` | Returns the most recent snap for the given device ID. |
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+------------------+------------------------------------------------------------+
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| ``major`` | |
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+------------------+------------------------------------------------------------+
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| ``name`` | Returns the RBD image name of the device ID. |
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+------------------+------------------------------------------------------------+
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| ``pool`` | Returns the pool source of the device ID. |
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+------------------+------------------------------------------------------------+
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| ``refresh`` | Refreshes the given device with the SDs. |
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+------------------+------------------------------------------------------------+
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| ``size`` | Returns the size of the device. |
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+------------------+------------------------------------------------------------+
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| ``uevent`` | |
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+------------------+------------------------------------------------------------+
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Show Mapped Block Devices
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-------------------------
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To show RBD images mapped to kernel block devices with the ``rbd`` command,
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specify the ``showmapped`` option. ::
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sudo rbd showmapped
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Images are mounted as devices sequentially starting from ``0``. To list all
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devices mapped to kernel objects, execute the following::
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ls /sys/bus/rbd/devices
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Unmapping a Block Device
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------------------------
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To unmap an RBD image with the ``rbd`` command, specify the ``rm`` option
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and the device name (i.e., by convention the same as the RBD image name). ::
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sudo rbd unmap /dev/rbd/{poolname}/{imagename}
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For example::
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sudo rbd unmap /dev/rbd/rbd/foo
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To unmap an RBD image from a kernel object, specify its index and use ``tee``
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to call ``remove`` as follows, but replace ``{device-number}`` with the number
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of the device you want to remove::
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echo {device-number} | sudo tee /sys/bus/rbd/remove
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