==================
 Create a Cluster
==================

The first step in using Ceph with ``ceph-deploy`` is to create a new Ceph
cluster. A new Ceph cluster has:

- A Ceph configuration file, and
- A monitor keyring.

The Ceph configuration file consists of at least:

- Its own filesystem ID (``fsid``)
- The initial monitor(s) hostname(s), and
- The initial monitor(s) and IP address(es).

For additional details, see the `Monitor Configuration Reference`_.

The ``ceph-deploy`` tool also creates a monitor keyring and populates it with a
``[mon.]`` key.  For additional details, see the `Cephx Guide`_.


Usage
-----

To create a cluster with ``ceph-deploy``, use the ``new`` command and specify
the host(s) that will be initial members of the monitor quorum. ::

	ceph-deploy new {host [host], ...}

For example::

	ceph-deploy new mon1.foo.com
	ceph-deploy new mon{1,2,3}

The ``ceph-deploy`` utility will use DNS to resolve hostnames to IP
addresses.  The monitors will be named using the first component of
the name (e.g., ``mon1`` above).  It will add the specified host names
to the Ceph configuration file. For additional details, execute::

	ceph-deploy new -h


Naming a Cluster
----------------

By default, Ceph clusters have a cluster name of ``ceph``. You can specify
a cluster name if you want to run multiple clusters on the same hardware. For
example, if you want to optimize a cluster for use with block devices, and
another for use with the gateway, you can run two different clusters on the same
hardware if they have a different ``fsid`` and cluster name. ::

	ceph-deploy --cluster {cluster-name} new {host [host], ...}

For example::

	ceph-deploy --cluster rbdcluster new ceph-mon1
	ceph-deploy --cluster rbdcluster new ceph-mon{1,2,3}

.. note:: If you run multiple clusters, ensure you adjust the default
   port settings and open ports for your additional cluster(s) so that
   the networks of the two different clusters don't conflict with each other.


.. _Monitor Configuration Reference: ../../configuration/mon-config-ref
.. _Cephx Guide: ../../../dev/mon-bootstrap#secret-keys