=====================
 Operating a Cluster
=====================

.. index:: systemd; operating a cluster


Running Ceph with systemd
=========================

In all distributions that support systemd (CentOS 7, Fedora, Debian
Jessie 8 and later, and SUSE), systemd files (and NOT legacy SysVinit scripts) 
are used to manage Ceph daemons. Ceph daemons therefore behave like any other daemons 
that can be controlled by the ``systemctl`` command, as in the following examples:

.. prompt:: bash $

   sudo systemctl start ceph.target       # start all daemons
   sudo systemctl status ceph-osd@12      # check status of osd.12

To list all of the Ceph systemd units on a node, run the following command:

.. prompt:: bash $

   sudo systemctl status ceph\*.service ceph\*.target


Starting all daemons
--------------------

To start all of the daemons on a Ceph node (regardless of their type), run the
following command:

.. prompt:: bash $

   sudo systemctl start ceph.target


Stopping all daemons
--------------------

To stop all of the daemons on a Ceph node (regardless of their type), run the
following command:

.. prompt:: bash $

   sudo systemctl stop ceph\*.service ceph\*.target


Starting all daemons by type
----------------------------

To start all of the daemons of a particular type on a Ceph node, run one of the
following commands:

.. prompt:: bash $

   sudo systemctl start ceph-osd.target
   sudo systemctl start ceph-mon.target
   sudo systemctl start ceph-mds.target


Stopping all daemons by type
----------------------------

To stop all of the daemons of a particular type on a Ceph node, run one of the
following commands:

.. prompt:: bash $

   sudo systemctl stop ceph-osd\*.service ceph-osd.target
   sudo systemctl stop ceph-mon\*.service ceph-mon.target
   sudo systemctl stop ceph-mds\*.service ceph-mds.target


Starting a daemon
-----------------

To start a specific daemon instance on a Ceph node, run one of the
following commands:

.. prompt:: bash $

   sudo systemctl start ceph-osd@{id}
   sudo systemctl start ceph-mon@{hostname}
   sudo systemctl start ceph-mds@{hostname}

For example:

.. prompt:: bash $

   sudo systemctl start ceph-osd@1
   sudo systemctl start ceph-mon@ceph-server
   sudo systemctl start ceph-mds@ceph-server


Stopping a daemon
-----------------

To stop a specific daemon instance on a Ceph node, run one of the
following commands:

.. prompt:: bash $

   sudo systemctl stop ceph-osd@{id}
   sudo systemctl stop ceph-mon@{hostname}
   sudo systemctl stop ceph-mds@{hostname}

For example:

.. prompt:: bash $

   sudo systemctl stop ceph-osd@1
   sudo systemctl stop ceph-mon@ceph-server
   sudo systemctl stop ceph-mds@ceph-server


.. index:: sysvinit; operating a cluster

Running Ceph with SysVinit
==========================

Each time you start, restart, or stop Ceph daemons, you must specify at least one option and one command.
Likewise, each time you start, restart, or stop your entire cluster, you must specify at least one option and one command.
In both cases, you can also specify a daemon type or a daemon instance. ::

    {commandline} [options] [commands] [daemons]

The ``ceph`` options include:

+-----------------+----------+-------------------------------------------------+
| Option          | Shortcut | Description                                     |
+=================+==========+=================================================+
| ``--verbose``   |  ``-v``  | Use verbose logging.                            |
+-----------------+----------+-------------------------------------------------+
| ``--valgrind``  | ``N/A``  | (Dev and QA only) Use `Valgrind`_ debugging.    |
+-----------------+----------+-------------------------------------------------+
| ``--allhosts``  |  ``-a``  | Execute on all nodes listed in ``ceph.conf``.   |
|                 |          | Otherwise, it only executes on ``localhost``.   |
+-----------------+----------+-------------------------------------------------+
| ``--restart``   | ``N/A``  | Automatically restart daemon if it core dumps.  |
+-----------------+----------+-------------------------------------------------+
| ``--norestart`` | ``N/A``  | Do not restart a daemon if it core dumps.       |
+-----------------+----------+-------------------------------------------------+
| ``--conf``      |  ``-c``  | Use an alternate configuration file.            |
+-----------------+----------+-------------------------------------------------+

The ``ceph`` commands include:

+------------------+------------------------------------------------------------+
| Command          | Description                                                |
+==================+============================================================+
|    ``start``     | Start the daemon(s).                                       |
+------------------+------------------------------------------------------------+
|    ``stop``      | Stop the daemon(s).                                        |
+------------------+------------------------------------------------------------+
|  ``forcestop``   | Force the daemon(s) to stop. Same as ``kill -9``.          |
+------------------+------------------------------------------------------------+
|   ``killall``    | Kill all daemons of a particular type.                     |
+------------------+------------------------------------------------------------+
|  ``cleanlogs``   | Cleans out the log directory.                              |
+------------------+------------------------------------------------------------+
| ``cleanalllogs`` | Cleans out **everything** in the log directory.            |
+------------------+------------------------------------------------------------+

The ``[daemons]`` option allows the ``ceph`` service to target specific daemon types
in order to perform subsystem operations. Daemon types include:

- ``mon``
- ``osd``
- ``mds``

.. _Valgrind: http://www.valgrind.org/
.. _initctl: http://manpages.ubuntu.com/manpages/raring/en/man8/initctl.8.html