doc: outline steps to take CephFS fs down

Fixes: https://tracker.ceph.com/issues/23427
Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>
(cherry picked from commit 9aa13bf0b0bf20b4fcf4949af60ebfff1e8fea0a)

diff --git a/doc/cephfs/administration.rst b/doc/cephfs/administration.rst
index e9d9195557d19cae0865985f2d09304855676c07..71a0e4075d10fb00c5db9255aa8cc22c8d1d6593 100644 (file)
--- a/doc/cephfs/administration.rst
+++ b/doc/cephfs/administration.rst
@@ -74,6 +74,22 @@ appear to be eg. exabytes in size, causing load on the MDS as it tries
 to enumerate the objects during operations like stats or deletes.
 
 
+Taking the cluster down
+-----------------------
+
+Taking a CephFS cluster down is done by reducing the number of ranks to 1,
+setting the cluster_down flag, and then failing the last rank. For example:
+
+::
+    ceph fs set <fs_name> max_mds 1
+    ceph mds deactivate <fs_name>:1 # rank 2 of 2
+    ceph status # wait for rank 1 to finish stopping
+    ceph fs set <fs_name> cluster_down true
+    ceph mds fail <fs_name>:0
+
+Setting the ``cluster_down`` flag prevents standbys from taking over the failed
+rank.
+
 Daemons
 -------