ceph-mgr administrator's guide
==============================

Manual setup
------------

Usually, you would set up a ceph-mgr daemon using a tool such
as ceph-ansible.  These instructions describe how to set up
a ceph-mgr daemon manually.

First, create an authentication key for your daemon::

    ceph auth get-or-create mgr.$name mon 'allow profile mgr' osd 'allow *' mds 'allow *'

Place that key into ``mgr data`` path, which for a cluster "ceph"
and mgr $name "foo" would be ``/var/lib/ceph/mgr/ceph-foo``.

Start the ceph-mgr daemon::

    ceph-mgr -i $name

Check that the mgr has come up by looking at the output
of ``ceph status``, which should now include a mgr status line::

    mgr active: $name

High availability
-----------------

In general, you should set up a ceph-mgr on each of the hosts
running a ceph-mon daemon to achieve the same level of availability. 

By default, whichever ceph-mgr instance comes up first will be made
active by the monitors, and the others will be standbys.  There is
no requirement for quorum among the ceph-mgr daemons.

If the active daemon fails to send a beacon to the monitors for
more than ``mon mgr beacon grace`` (default 30s), then it will be replaced
by a standby.

If you want to pre-empt failover, you can explicitly mark a ceph-mgr
daemon as failed using ``ceph mgr fail <mgr name>``.

Calling module commands
-----------------------

Where a module implements command line hooks, using the Ceph CLI's
``tell`` command to call them like this::

    ceph tell mgr <command | help>

Note that it is not necessary to address a particular mgr instance,
simply ``mgr`` will pick the current active daemon.

Use the ``help`` command to get a list of available commands from all
modules.

Configuration
-------------

OPTION(mgr_module_path, OPT_STR, CEPH_PKGLIBDIR "/mgr") // where to load python modules from

``mgr module path``

:Description: Path to load modules from
:Type: String
:Default: ``"<library dir>/mgr"``

``mgr modules``

:Description: List of python modules to load
:Type: String
:Default: ``"rest"`` (Load the REST API module only)

``mgr data``

:Description: Path to load daemon data (such as keyring)
:Type: String
:Default: ``"/var/lib/ceph/mgr/$cluster-$id"``

``mgr tick period``

:Description: How many seconds between mgr beacons to monitors, and other
              periodic checks.
:Type: Integer
:Default: ``5``

``mon mgr beacon grace``

:Description: How long after last beacon should a mgr be considered failed
:Type: Integer
:Default: ``30``