diff --git a/lib/geom/label/glabel.8 b/lib/geom/label/glabel.8
index 5283a604e45b..a23f425bc5e1 100644
--- a/lib/geom/label/glabel.8
+++ b/lib/geom/label/glabel.8
@@ -1,278 +1,298 @@
 .\" Copyright (c) 2004-2005 Pawel Jakub Dawidek <pjd@FreeBSD.org>
 .\" All rights reserved.
 .\"
 .\" Redistribution and use in source and binary forms, with or without
 .\" modification, are permitted provided that the following conditions
 .\" are met:
 .\" 1. Redistributions of source code must retain the above copyright
 .\"    notice, this list of conditions and the following disclaimer.
 .\" 2. Redistributions in binary form must reproduce the above copyright
 .\"    notice, this list of conditions and the following disclaimer in the
 .\"    documentation and/or other materials provided with the distribution.
 .\"
 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd March 12, 2017
+.Dd September 27, 2023
 .Dt GLABEL 8
 .Os
 .Sh NAME
 .Nm glabel
 .Nd "disk labelization control utility"
 .Sh SYNOPSIS
 .Nm
 .Cm create
 .Op Fl v
 .Ar name
 .Ar dev
 .Nm
 .Cm destroy
 .Op Fl fv
 .Ar name ...
 .Nm
 .Cm label
 .Op Fl v
 .Ar name
 .Ar dev
 .Nm
 .Cm stop
 .Op Fl fv
 .Ar name ...
 .Nm
 .Cm clear
 .Op Fl v
 .Ar dev ...
 .Nm
 .Cm dump
 .Ar dev ...
 .Nm
 .Cm refresh
 .Ar dev ...
 .Nm
 .Cm list
 .Nm
 .Cm status
 .Nm
 .Cm load
 .Nm
 .Cm unload
 .Sh DESCRIPTION
 The
 .Nm
 utility is used for GEOM provider labelization.
 A label can be set up on a GEOM provider in two ways:
 .Dq manual
 or
 .Dq automatic .
 When using the
 .Dq manual
 method, no metadata are stored on the devices, so a label has to be configured
 by hand every time it is needed.
 The
 .Dq automatic
 method uses on-disk metadata to store the label and detect it automatically in
 the future.
 .Pp
 This GEOM class also provides volume label detection for file systems.
 Those labels cannot be set with
 .Nm ,
 but must be set with the appropriate file system utility, e.g.\& for UFS
 the file system label is set with
 .Xr tunefs 8 .
 Currently supported file systems are:
 .Pp
 .Bl -bullet -offset indent -compact
 .It
 UFS1 volume names (directory
 .Pa /dev/ufs/ ) .
 .It
 UFS2 volume names (directory
 .Pa /dev/ufs/ ) .
 .It
 UFS1 file system IDs (directory
 .Pa /dev/ufsid/ ) .
 .It
 UFS2 file system IDs (directory
 .Pa /dev/ufsid/ ) .
 .It
 MSDOSFS (FAT12, FAT16, FAT32) (directory
 .Pa /dev/msdosfs/ ) .
 .It
 CD ISO9660 (directory
 .Pa /dev/iso9660/ ) .
 .It
 EXT2FS (directory
 .Pa /dev/ext2fs/ ) .
 .It
 REISERFS (directory
 .Pa /dev/reiserfs/ ) .
 .It
 NTFS (directory
 .Pa /dev/ntfs/ ) .
 .El
 .Pp
 Support for partition metadata is implemented for:
 .Pp
 .Bl -bullet -offset indent -compact
 .It
 GPT labels (directory
 .Pa /dev/gpt/ ) .
 .It
 GPT UUIDs (directory
 .Pa /dev/gptid/ ) .
 .El
 .Pp
 Generic disk ID strings are exported as labels in the format
 .Pa /dev/diskid/GEOM_CLASS-ident
 e.g.
 .Pa /dev/diskid/DISK-6QG3Z026  .
 .Pp
 Generic labels created and managed solely by
 .Xr glabel 8
 are created in the
 .Pa /dev/label/
 directory.
+Note that generic, automatic labels occupy some space on the device
+and thus should not be added to a device already containing a file system.
+In particular,
+.Nm
+reserves the last sector of the device to store the label information.
+If the device already contains a file system,
+.Nm
+will overwrite the last sector, possibly damaging the file system, and the
+file system may later overwrite the label sector.
+Instead, create a label before initializing the file system, and initialize
+that file system on the device created by
+.Nm
+under the
+.Pa /dev/label/
+directory.
+Then the file system will correctly account for the space occupied by the
+generic label,
+since the
+.Nm
+device will be one sector smaller than the device from which it was created.
 .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
 .Pa /dev/label/bigdisk
 there will be additional entries for any partitions which the device
 contains, like
 .Pa /dev/label/bigdiskp1
 and
 .Pa /dev/label/bigdiskp1a .
 .Pp
 The first argument to
 .Nm
 indicates an action to be performed:
 .Bl -tag -width ".Cm destroy"
 .It Cm create
 Create temporary label
 .Ar name
 for the given provider.
 This is the
 .Dq manual
 method.
 The kernel module
 .Pa geom_label.ko
 will be loaded if it is not loaded already.
 .It Cm label
 Set up a label
 .Ar name
 for the given provider.
 This is the
 .Dq automatic
 method, where metadata is stored in a provider's last sector.
 The kernel module
 .Pa geom_label.ko
 will be loaded if it is not loaded already.
 .It Cm stop
 Turn off the given label by its
 .Ar name .
 This command does not touch on-disk metadata!
 .It Cm destroy
 Same as
 .Cm stop .
 .It Cm clear
 Clear metadata on the given devices.
 .It Cm dump
 Dump metadata stored on the given devices.
 .It Cm refresh
 Refresh / rediscover metadata from the given devices.
 .It Cm list
 See
 .Xr geom 8 .
 .It Cm status
 See
 .Xr geom 8 .
 .It Cm load
 See
 .Xr geom 8 .
 .It Cm unload
 See
 .Xr geom 8 .
 .El
 .Pp
 Additional options:
 .Bl -tag -width indent
 .It Fl f
 Force the removal of the specified labels.
 .It Fl v
 Be more verbose.
 .El
 .Sh SYSCTL VARIABLES
 The following
 .Xr sysctl 8
 variables can be used to control the behavior of the
 .Nm LABEL
 GEOM class.
 The default value is shown next to each variable.
 .Bl -tag -width indent
 .It Va kern.geom.label.debug : No 0
 Debug level of the
 .Nm LABEL
 GEOM class.
 This can be set to a number between 0 and 2 inclusive.
 If set to 0 minimal debug information is printed, and if set to 2 the
 maximum amount of debug information is printed.
 .El
 .Bl -tag -width indent
 .It Va kern.geom.label.*.enable : No 1
 Most
 .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
 and creating label nodes in the
 .Xr devfs 5
 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.
 .Sh EXAMPLES
 The following example shows how to set up a label for disk
 .Dq Li da2 ,
 create a file system on it, and mount it:
 .Bd -literal -offset indent
 glabel label -v usr /dev/da2
 newfs /dev/label/usr
 mount /dev/label/usr /usr
 [...]
 umount /usr
 glabel stop usr
 glabel unload
 .Ed
 .Pp
 The next example shows how to set up a label for a UFS file system:
 .Bd -literal -offset indent
 tunefs -L data /dev/da4s1a
 mount /dev/ufs/data /mnt/data
 .Ed
 .Sh SEE ALSO
 .Xr geom 4 ,
 .Xr loader.conf 5 ,
 .Xr geom 8 ,
 .Xr mount 8 ,
 .Xr newfs 8 ,
 .Xr sysctl 8 ,
 .Xr tunefs 8 ,
 .Xr umount 8
 .Sh HISTORY
 The
 .Nm
 utility appeared in
 .Fx 5.3 .
 .Sh AUTHORS
 .An Pawel Jakub Dawidek Aq Mt pjd@FreeBSD.org