doc/ceph-volume high-level description of simple activate at index.rst

Signed-off-by: Alfredo Deza <adeza@redhat.com>
(cherry picked from commit dd6f368158db7f102b485179166ebe73d6ea622f)

diff --git a/doc/ceph-volume/simple/index.rst b/doc/ceph-volume/simple/index.rst
index 6f2534a738e363658faa12b1766e30a4aea074e7..315dea99a106152b1b036871191cabf7cbf670a4 100644 (file)
--- a/doc/ceph-volume/simple/index.rst
+++ b/doc/ceph-volume/simple/index.rst
@@ -17,3 +17,16 @@ Implements the functionality needed to manage OSDs from the ``simple`` subcomman
 By *taking over* management, it disables all ``ceph-disk`` systemd units used
 to trigger devices at startup, relying on basic (customizable) JSON
 configuration and systemd for starting up OSDs.
+
+This process involves two steps:
+
+#. :ref:`Scan <ceph-volume-simple-scan>` the running OSD or the data device
+#. :ref:`Activate <ceph-volume-simple-activate>` the scanned OSD
+
+The scanning will infer everything that ``ceph-volume`` needs to start the OSD,
+so that when activation is needed, the OSD can start normally without getting
+interference from ``ceph-disk``.
+
+As part of the activation process the systemd units for ``ceph-disk`` in charge
+of reacting to ``udev`` events, are linked to ``/dev/null`` so that they are
+fully inactive.