+Adding MDS
+==========
+
+In the below instructions, ``{id}`` is an arbitrary name, such as the hostname of the machine.
+
+#. Create the mds data directory.::
+
+ mkdir -p /var/lib/ceph/mds/{cluster-name}-{id}
+
+#. Create a keyring.::
+
+ ceph-authtool --create-keyring /var/lib/ceph/mds/{cluster-name}-{id}/keyring --gen-key -n mds.{id}
+
+#. Import the keyring and set caps.::
+
+ ceph auth add mds.{id} osd "allow rwx" mds "allow" mon "allow profile mds" -i /var/lib/ceph/mds/{cluster}-{id}/keyring
+
+#. Add to ceph.conf.::
+
+ [mds.{id}]
+ host = {id}
+
+#. Start the daemon the manual way.::
+
+ ceph-mds --cluster {cluster-name} -i {id} -m {mon-hostname}:{mon-port} [-f]
+
+#. Start the daemon the right way (using ceph.conf entry).::
+
+ service ceph start
+
+#. If starting the daemon fails with this error::
+
+ mds.-1.0 ERROR: failed to authenticate: (22) Invalid argument
+
+ Then make sure you do not have a keyring set in ceph.conf in the global section; move it to the client section; or add a keyring setting specific to this mds daemon. And verify that you see the same key in the mds data directory and ``ceph auth get mds.{id}`` output.
+
+#. Now you are ready to `create a Ceph filesystem`_.
+
Summary
=======
.. _Add/Remove OSDs: ../../rados/operations/add-or-rm-osds
.. _Network Configuration Reference: ../../rados/configuration/network-config-ref
.. _Monitor Config Reference - Data: ../../rados/configuration/mon-config-ref#data
+.. _create a Ceph filesystem: ../../cephfs/createfs