diff --git a/lib/geom/label/glabel.8 b/lib/geom/label/glabel.8
--- a/lib/geom/label/glabel.8
+++ b/lib/geom/label/glabel.8
@@ -137,7 +137,7 @@
 .Pa /dev/diskid/DISK-6QG3Z026  .
 .Pp
 Generic labels created and managed solely by
-.Xr glabel 8
+.Nm
 are created in the
 .Pa /dev/label/
 directory.
@@ -164,7 +164,8 @@
 .Pp
 Note that for all label types, nested GEOM classes will cause additional
 device nodes to be created, with context-specific data appended to their
-names. E.g. for every node like
+names.
+E.g. for every node like
 .Pa /dev/label/bigdisk
 there will be additional entries for any partitions which the device
 contains, like
@@ -172,6 +173,17 @@
 and
 .Pa /dev/label/bigdiskp1a .
 .Pp
+.Nm
+requires write access to a device to create, modify, and destroy
+"automatic" labels.
+It will fail to persist changes if they are applied while a file
+system on the device is currently mounted.
+To ensure that modifications are stored across a reboot, the file system
+needs to be unmounted first.
+If the device holds the system's root file system, entering into
+single user mode and mounting in read-only mode is required to persist
+the change.
+.Pp
 The first argument to
 .Nm
 indicates an action to be performed:
@@ -252,12 +264,13 @@
 .Nm LABEL
 providers implement a
 .Xr sysctl 8
-flag and a tunable variable named in the above format. This flag
-controls if the label provider will be active, tasting devices
+flag and a tunable variable named in the above format.
+This flag controls if the label provider will be active, tasting devices
 and creating label nodes in the
 .Xr devfs 4
-tree. It is sometimes desirable to disable certain label types if
-they conflict with other classes in complex GEOM topologies.
+tree.
+It is sometimes desirable to disable certain label types if they
+conflict with other classes in complex GEOM topologies.
 .El
 .Sh EXIT STATUS
 Exit status is 0 on success, and 1 if the command fails.