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124 lines
4.1 KiB
ReStructuredText
124 lines
4.1 KiB
ReStructuredText
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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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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 two RBD images called "bar1" and "bar2", both
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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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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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If the images had XFS filesystems 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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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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http://ceph.com/docs 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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