doc/cephadm: rewrite part of adoption.rst

This PR adds a bit of explanatory text to the
section of the cephadm docs that explains how
to convert Ceph deployments that were not deployed
with cephadm to deployments that can be managed by
the cephadm command line tool.

(cherry picked from commit a445653511b07af360bda37175eadf2870e053f7)

diff --git a/doc/cephadm/adoption.rst b/doc/cephadm/adoption.rst
index 5c1d2ad1bca288d0684dd4d4d980969b1e693e9e..82fd04200de5d28a58b437c93258670046ec254d 100644 (file)
--- a/doc/cephadm/adoption.rst
+++ b/doc/cephadm/adoption.rst
@@ -3,14 +3,19 @@
 Converting an existing cluster to cephadm
 =========================================
 
-Cephadm allows you to convert an existing Ceph cluster that
-has been deployed with ceph-deploy, ceph-ansible, DeepSea, or similar tools.
+It is possible to convert some existing clusters so that they can be managed
+with ``cephadm``. This statment applies to some clusters that were deployed
+with ``ceph-deploy``, ``ceph-ansible``, or ``DeepSea``.
+
+This section of the documentation explains how to determine whether your
+clusters can be converted to a state in which they can be managed by
+``cephadm`` and how to perform those conversions.
 
 Limitations
 -----------
 
-* Cephadm only works with BlueStore OSDs.  If there are FileStore OSDs
-  in your cluster you cannot manage them.
+* Cephadm works only with BlueStore OSDs. FileStore OSDs that are in your
+  cluster cannot be managed with ``cephadm``.
 
 Preparation
 -----------