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Remove mention of FAQ with a broken link. Use ref for intra-docs links and add labels in destination documents. Promptify all CLI example commands. Use standard angle brackets for mandatory arguments in commands. Remove an unused external link definition. Trim spaces at end of lines and convert tabs to spaces. Signed-off-by: Ville Ojamo <git2233+ceph@ojamo.eu>
131 lines
4.5 KiB
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131 lines
4.5 KiB
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.. _rbdmap:
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=========================================
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rbdmap -- map RBD devices at boot time
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=========================================
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.. program:: rbdmap
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Synopsis
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========
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| **rbdmap map**
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| **rbdmap unmap**
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Description
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===========
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**rbdmap** is a shell script that automates ``rbd map`` and ``rbd unmap``
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operations on one or more RBD (RADOS Block Device) images. While the script can be
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run manually by the system administrator at any time, the principal use case is
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automatic mapping/mounting of RBD images at boot time (and unmounting/unmapping
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at shutdown), as triggered by the init system (a systemd unit file,
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``rbdmap.service`` is included with the ceph-common package for this purpose).
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The script takes a single argument, which can be either "map" or "unmap".
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In either case, the script parses a configuration file (defaults to ``/etc/ceph/rbdmap``,
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but can be overridden via an environment variable ``RBDMAPFILE``). Each line
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of the configuration file corresponds to an RBD image which is to be mapped, or
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unmapped.
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The configuration file format is::
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IMAGESPEC RBDOPTS
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where ``IMAGESPEC`` should be specified as ``POOLNAME/IMAGENAME`` (the pool
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name, a forward slash, and the image name), or merely ``IMAGENAME``, in which
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case the ``POOLNAME`` defaults to "rbd". ``RBDOPTS`` is an optional list of
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parameters to be passed to the underlying ``rbd map`` command. These parameters
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and their values should be specified as a comma-separated string::
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PARAM1=VAL1,PARAM2=VAL2,...,PARAMN=VALN
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This will cause the script to issue an ``rbd map`` command like the following::
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rbd map POOLNAME/IMAGENAME --PARAM1 VAL1 --PARAM2 VAL2
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(See the ``rbd`` manpage for a full list of possible options.)
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For parameters and values which contain commas or equality signs, a simple
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apostrophe can be used to prevent replacing them.
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When run as ``rbdmap map``, the script parses the configuration file, and for
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each RBD image specified attempts to first map the image (using the ``rbd map``
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command) and, second, to mount the image.
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When run as ``rbdmap unmap``, images listed in the configuration file will
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be unmounted and unmapped.
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``rbdmap unmap-all`` attempts to unmount and subsequently unmap all currently
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mapped RBD images, regardless of whether or not they are listed in the
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configuration file.
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If successful, the ``rbd map`` operation maps the image to a ``/dev/rbdX``
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device, at which point a udev rule is triggered to create a friendly device
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name symlink, ``/dev/rbd/POOLNAME/IMAGENAME``, pointing to the real mapped
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device.
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In order for mounting/unmounting to succeed, the friendly device name must
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have a corresponding entry in ``/etc/fstab``.
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When writing ``/etc/fstab`` entries for RBD images, it's a good idea to specify
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the "noauto" (or "nofail") mount option. This prevents the init system from
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trying to mount the device too early - before the device in question even
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exists. (Since ``rbdmap.service``
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executes a shell script, it is typically triggered quite late in the boot
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sequence.)
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Examples
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========
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Example ``/etc/ceph/rbdmap`` for three RBD images called "bar1", "bar2" and "bar3",
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which are in pool "foopool"::
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foopool/bar1 id=admin,keyring=/etc/ceph/ceph.client.admin.keyring
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foopool/bar2 id=admin,keyring=/etc/ceph/ceph.client.admin.keyring
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foopool/bar3 id=admin,keyring=/etc/ceph/ceph.client.admin.keyring,options='lock_on_read,queue_depth=1024'
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Each line in the file contains two strings: the image spec and the options to
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be passed to ``rbd map``. These two lines get transformed into the following
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commands::
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rbd map foopool/bar1 --id admin --keyring /etc/ceph/ceph.client.admin.keyring
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rbd map foopool/bar2 --id admin --keyring /etc/ceph/ceph.client.admin.keyring
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rbd map foopool/bar2 --id admin --keyring /etc/ceph/ceph.client.admin.keyring --options lock_on_read,queue_depth=1024
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If the images had XFS file systems on them, the corresponding ``/etc/fstab``
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entries might look like this::
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/dev/rbd/foopool/bar1 /mnt/bar1 xfs noauto 0 0
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/dev/rbd/foopool/bar2 /mnt/bar2 xfs noauto 0 0
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/dev/rbd/foopool/bar3 /mnt/bar3 xfs noauto 0 0
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After creating the images and populating the ``/etc/ceph/rbdmap`` file, making
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the images get automatically mapped and mounted at boot is just a matter of
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enabling that unit::
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systemctl enable rbdmap.service
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Options
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=======
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None
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Availability
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============
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**rbdmap** is part of Ceph, a massively scalable, open-source, distributed
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storage system. Please refer to the Ceph documentation at
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https://docs.ceph.com for more information.
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See also
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========
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:doc:`rbd <rbd>`\(8),
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