doc/cephfs: add documentation for `mds last-seen`

Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>

diff --git a/doc/cephfs/administration.rst b/doc/cephfs/administration.rst
index 8744a41ddf046388dd6075fb904afefe11e88345..5760e67f73e64853347d9145f3b4e110d08c596c 100644 (file)
--- a/doc/cephfs/administration.rst
+++ b/doc/cephfs/administration.rst
@@ -280,6 +280,17 @@ Mark the file system rank as repaired. Unlike the name suggests, this command
 does not change a MDS; it manipulates the file system rank which has been
 marked damaged.
 
+::
+
+    ceph mds last-seen <name>
+
+Learn the when the MDS named ``name`` was last in the FSMap. The JSON output
+includes the epoch the MDS was last seen. Historically information is limited by
+the following ``mon`` configuration:
+
+
+.. confval:: mon_fsmap_prune_threshold
+
 
 Required Client Features
 ------------------------