GLABEL(8) FreeBSD System Manager's Manual GLABEL(8)
NAME
glabel - disk labelization control utility
SYNOPSIS
glabel create [-v] name dev
glabel destroy [-fv] name ...
glabel label [-v] name dev
glabel stop [-fv] name ...
glabel clear [-v] dev ...
glabel dump dev ...
glabel refresh dev ...
glabel list
glabel status
glabel load
glabel unload
DESCRIPTION
The glabel utility is used for GEOM provider labelization. A label can
be set up on a GEOM provider in two ways: "manual" or "automatic". When
using the "manual" method, no metadata are stored on the devices, so a
label has to be configured by hand every time it is needed. The
"automatic" method uses on-disk metadata to store the label and detect it
automatically in the future.
This GEOM class also provides volume label detection for file systems.
Those labels cannot be set with glabel, but must be set with the
appropriate file system utility, e.g. for UFS the file system label is
set with tunefs(8). Currently supported file systems are:
o UFS1 volume names (directory /dev/ufs/).
o UFS2 volume names (directory /dev/ufs/).
o UFS1 file system IDs (directory /dev/ufsid/).
o UFS2 file system IDs (directory /dev/ufsid/).
o MSDOSFS (FAT12, FAT16, FAT32) (directory /dev/msdosfs/).
o CD ISO9660 (directory /dev/iso9660/).
o EXT2FS (directory /dev/ext2fs/).
o NTFS (directory /dev/ntfs/).
o Swap Linux (directory /dev/swaplinux/).
Support for partition metadata is implemented for:
o GPT labels (directory /dev/gpt/).
o GPT UUIDs (directory /dev/gptid/).
Generic disk ID strings are exported as labels in the format
/dev/diskid/GEOM_CLASS-ident e.g. /dev/diskid/DISK-6QG3Z026.
Generic labels created and managed solely by glabel are created in the
/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, glabel reserves the last sector
of the device to store the label information. If the device already
contains a file system, glabel 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 glabel
under the /dev/label/ directory. Then the file system will correctly
account for the space occupied by the generic label, since the glabel
device will be one sector smaller than the device from which it was
created.
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 /dev/label/bigdisk there will be
additional entries for any partitions which the device contains, like
/dev/label/bigdiskp1 and /dev/label/bigdiskp1a.
glabel 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.
The first argument to glabel indicates an action to be performed:
create Create temporary label name for the given provider. This is the
"manual" method. The kernel module geom_label.ko will be loaded
if it is not loaded already.
label Set up a label name for the given provider. This is the
"automatic" method, where metadata is stored in a provider's
last sector. The kernel module geom_label.ko will be loaded if
it is not loaded already.
stop Turn off the given label by its name. This command does not
touch on-disk metadata!
destroy Same as stop.
clear Clear metadata on the given devices.
dump Dump metadata stored on the given devices.
refresh Refresh / rediscover metadata from the given devices.
list See geom(8).
status See geom(8).
load See geom(8).
unload See geom(8).
Additional options:
-f Force the removal of the specified labels.
-v Be more verbose.
SYSCTL VARIABLES
The following sysctl(8) variables can be used to control the behavior of
the LABEL GEOM class. The default value is shown next to each variable.
kern.geom.label.debug: 0
Debug level of the 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.
kern.geom.label.*.enable: 1
Most LABEL providers implement a 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 devfs(4) tree. It is sometimes desirable to disable
certain label types if they conflict with other classes in
complex GEOM topologies.
EXIT STATUS
Exit status is 0 on success, and 1 if the command fails.
EXAMPLES
The following example shows how to set up a label for disk "da2", create
a file system on it, and mount it:
glabel label -v usr /dev/da2
newfs /dev/label/usr
mount /dev/label/usr /usr
[...]
umount /usr
glabel stop usr
glabel unload
The next example shows how to set up a label for a UFS file system:
tunefs -L data /dev/da4s1a
mount /dev/ufs/data /mnt/data
SEE ALSO
geom(4), loader.conf(5), geom(8), mount(8), newfs(8), sysctl(8),
tunefs(8), umount(8)
HISTORY
The glabel utility appeared in FreeBSD 5.3.
AUTHORS
Pawel Jakub Dawidek <pjd@FreeBSD.org>
FreeBSD 15.1-STABLE-HBSD April 19, 2024 GLABEL(8)