ceph/doc/man/8/rbdmap.rst

:orphan:

=========================================
 rbdmap -- map RBD devices at boot time
=========================================

.. program:: rbdmap

Synopsis
========

| **rbdmap map**
| **rbdmap unmap**


Description
===========

**rbdmap** is a shell script that automates ``rbd map`` and ``rbd unmap``
operations on one or more RBD (RADOS Block Device) images. While the script can be
run manually by the system administrator at any time, the principal use case is
automatic mapping/mounting of RBD images at boot time (and unmounting/unmapping
at shutdown), as triggered by the init system (a systemd unit file,
``rbdmap.service`` is included with the ceph-common package for this purpose).

The script takes a single argument, which can be either "map" or "unmap".
In either case, the script parses a configuration file (defaults to ``/etc/ceph/rbdmap``,
but can be overrided via an  environment variable ``RBDMAPFILE``). Each line
of the configuration file corresponds to an RBD image which is to be mapped, or
unmapped.

The configuration file format is::

    IMAGESPEC RBDOPTS

where ``IMAGESPEC`` should be specified as ``POOLNAME/IMAGENAME`` (the pool
name, a forward slash, and the image name), or merely ``IMAGENAME``, in which
case the ``POOLNAME`` defaults to "rbd". ``RBDOPTS`` is an optional list of
parameters to be passed to the underlying ``rbd map`` command. These parameters
and their values should be specified as a comma-separated string::

    PARAM1=VAL1,PARAM2=VAL2,...,PARAMN=VALN 

This will cause the script to issue an ``rbd map`` command like the following::

    rbd map POOLNAME/IMAGENAME --PARAM1 VAL1 --PARAM2 VAL2 

(See the ``rbd`` manpage for a full list of possible options.)

When run as ``rbdmap map``, the script parses the configuration file, and for
each RBD image specified attempts to first map the image (using the ``rbd map``
command) and, second, to mount the image.

When run as ``rbd unmap``, the script parses the configuration file, and
attempts to first unmount, and then unmap, each image specified.

If successful, the ``rbd map`` operation maps the image to a ``/dev/rbdX``
device, at which point a udev rule is triggered to create a friendly device
name symlink, ``/dev/rbd/POOLNAME/IMAGENAME``, pointing to the real mapped
device.

In order for mounting/unmounting to succeed, the friendly device name must
have a corresponding entry in ``/etc/fstab``.

When writing ``/etc/fstab`` entries for RBD images, it's a good idea to specify
the "noauto" (or "nofail") mount option. This prevents the init system from
trying to mount the device too early - before the device in question even
exists. (Since ``rbdmap.service``
executes a shell script, it is typically triggered quite late in the boot
sequence.)


Examples
========

Example ``/etc/ceph/rbdmap`` for two RBD images called "bar1" and "bar2", both
in pool "foopool"::

    foopool/bar1    id=admin,keyring=/etc/ceph/ceph.client.admin.keyring
    foopool/bar2    id=admin,keyring=/etc/ceph/ceph.client.admin.keyring

Each line in the file contains two strings: the image spec and the options to
be passed to ``rbd map``. These two lines get transformed into the following
commands::

    rbd map foopool/bar1 --id admin --keyring /etc/ceph/ceph.client.admin.keyring
    rbd map foopool/bar2 --id admin --keyring /etc/ceph/ceph.client.admin.keyring

If the images had XFS filesystems on them, the corresponding ``/etc/fstab``
entries might look like this::

    /dev/rbd/foopool/bar1 /mnt/bar1 xfs noauto 0 0
    /dev/rbd/foopool/bar2 /mnt/bar2 xfs noauto 0 0

After creating the images and populating the ``/etc/ceph/rbdmap`` file, making
the images get automatically mapped and mounted at boot is just a matter of
enabling that unit::

    systemctl enable rbdmap.service


Options
=======

None


Availability
============

**rbdmap** is part of Ceph, a massively scalable, open-source, distributed
storage system. Please refer to the Ceph documentation at
http://ceph.com/docs for more information.


See also
========

:doc:`rbd <rbd>`\(8),