|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | UDF LABEL AND UUID | EXIT STATUS | LIMITATIONS | AUTHOR | AVAILABILITY | SEE ALSO | COLOPHON |
|
|
|
UDFLABEL(8) System Manager's Manual UDFLABEL(8)
udflabel — show or change UDF filesystem label
udflabel [encoding-options] [block-options] [identifier-options]
device [new-label]
When udflabel is invoked without identifier-options and without
specifying new-label then it shows current label of UDF filesystem
on device to standard output terminated by new line. Otherwise it
updates UDF filesystem (up to the revision 2.60) on device with
new specified identifiers from identifier-options. Specifying
new-label is synonym for both --lvid and --vid, see section UDF
LABEL AND UUID.
GENERAL OPTIONS
-h,--help
Display the usage and the list of options.
BLOCK OPTIONS
-b,--blocksize= block-size
Specify the size of blocks in bytes. Valid block size for a
UDF filesystem is a power of two in the range from 512 to
32768 and must match a device logical (sector) size. If
omitted, udflabel tries to autodetect block size. First it
tries logical (sector) size and then all valid block sizes.
--startblock= start-block
Specify the block location where the UDF filesystem starts.
It is used for calculating the block location of the Volume
Recognition Sequence (32 kB after the start block) and the
first Anchor Volume Descriptor Pointer (256 blocks after
the start block).
Normally start block is 0, but for Multisession UDF optical
discs it is the block location where the last session of
Multisession UDF disc starts.
If omitted, udflabel for optical disc tries to detect start
block of the last session from disc Table Of Contents.
Otherwise value 0 is used.
For accessing some previous session of Multisession UDF
optical disc, it is required to specify correct block where
that previous session starts. And also to specify where
that session ends via --lastblock option.
For Multisession UDF disc images stored in file there is no
way to detect where the last session starts and therefore
it is necessary to specify the correct start block location
manually from the original optical disc Table Of Contents.
(Option available since udflabel 2.3)
--lastblock= last-block
Specify the block location where the UDF filesystem ends.
It is used for calculating the block location of second and
third Anchor Volume Descriptor Pointer (256 blocks prior
the last block and the last block itself).
Normally last block is number of disk blocks minus one, but
for Multisession UDF optical discs when reading different
session than the last one (specified by --startblock) it is
the block location where the specified session ends.
If omitted, udflabel for optical disc tried to detect the
last recorded block with fallback to the last block of
device or disk file image.
For accessing some previous session of Multisession UDF
optical disc, it is required to specify correct value for
both --startblock and --lastblock options.
(Option available since udflabel 2.3)
--vatblock= vat-block
Specify the block location of the Virtual Allocation Table.
Virtual Allocation Table is present only on UDF disks with
Virtual Partition Map and must be at the last
written/recorded disk block.
If omitted, udflabel for optical disc tries to detect the
last recorded block with fallback to the last block of
block device or disk file image or block specified by
--lastblock. In most cases, this fallback does not have to
work and for disk file images with Virtual Allocation Table
it is necessary to specify the correct location.
Virtual Allocation Table contains Logical Volume Identifier
(UDF Label).
--force
Force updating UDF disks without write support or write
protected UDF disks. Some UDF disks may have set write
protect flag. Some media, like CD-ROM, DVD-ROM or BD-ROM
are read-only. Other media, like CD-RW or DVD-RW, are
write-once. UDF is designed also for such media where
updating Label or Identifiers is not possible. But in some
rare cases, it could make sense to try and overwrite the
existing Label or Identifiers also for UDF filesystem which
has Access Type either Read-Only or Recordable (Write-
Once). This is possible only if underlying media supports
overwriting. E.g. UDF image of CD-ROM stored on hard disk
or Read-Only UDF image burned to DVD-RAM or BD-RE discs.
Option --force ignores UDF Access Type and treats it as
Overwritable. Also it ignores UDF SoftWriteProtect and
HardWriteProtected flags.
-n,--no-write
Not really, do not write to device. Just simulate and
display what would happen with device. Useful for
determining which UDF blocks would be overwritten.
IDENTIFIER OPTIONS
-u,--uuid= uuid
Specify the UDF uuid. Must be exactly 16 hexadecimal
lowercase digits and is used for first 16 characters of
--fullvsid option. Special value random generates new uuid
from local time and a random number. See section UDF LABEL
AND UUID.
--lvid= new-logical-volume-identifier
Specify the new Logical Volume Identifier.
--vid= new-volume-identifier
Specify the new Volume Identifier.
--vsid= new-volume-set-identifier
Specify the new 17.–127. character of Volume Set
Identifier. See section UDF LABEL AND UUID.
--fsid= new-file-set-identifier
Specify the new File Set Identifier.
--fullvsid= new-full-volume-set-identifier
Specify the new Volume Set identifier. Overwrite previous
--uuid and --vsid options. See section UDF LABEL AND UUID.
--owner= new-owner-name
Specify the new Owner name, person who created the medium
or filesystem. It is stored in UDF Logical Volume Info1,
part of UDF Implementation Use Volume Descriptor. (Option
available since udflabel 2.3)
--organization= new-organization-name
Specify the new Organization name responsible for creating
the medium or filesystem. It is stored in UDF Logical
Volume Info2, part of UDF Implementation Use Volume
Descriptor. (Option available since udflabel 2.3)
--contact= new-contact-information
Specify the new Contact information for the medium or
filesystem. It is stored in UDF Logical Volume Info3, part
of UDF Implementation Use Volume Descriptor. (Option
available since udflabel 2.3)
--appid= new-application-identifier
Specify the new Application Identifier which identifies
application that created medium or filesystem. It is stored
in UDF Primary Volume Descriptor. This identifier can be
empty or must start with * and contain only 7bit ASCII
characters. (Option available since udflabel 2.3)
--impid= new-developer-identifier
Specify the new Developer Identifier for Implementation
Identifier. It is unique identification of the
implementation which created medium or filesystem. It is
stored in UDF Primary Volume Descriptor. This identifier
must start with * and contain only 7bit ASCII characters.
(Option available since udflabel 2.3)
ENCODING OPTIONS
--locale
Treat identifier string options as strings encoded
according to current locale settings (default). Must be
specified as the first argument.
--u8 Treat identifier string options as strings encoded in 8-bit
OSTA Compressed Unicode format without leading Compression
ID byte, which is equivalent to Latin1 (ISO-8859-1). Must
be specified as first argument.
--u16 Treat identifier string options as strings encoded in
16-bit OSTA Compressed Unicode format without leading
Compression ID byte, which is equivalent to UTF-16BE. Note
that it is not possible to include zero byte in command
line options, therefore any character which has at least
one zero byte cannot be supplied (this applies to all
Latin1 characters). Must be specified as the first
argument.
--utf8 Treat identifier string options as strings encoded in
UTF-8. Must be specified as the first argument.
UDF specification does not say anything about a disk label but it
describes that UDF Logical Volume Identifier is an extremely
important field for media identification in a jukebox as that
field is displayed to the user. And based on this statement it is
a common practice for the majority of UDF implementations to use
UDF Logical Volume Identifier as a UDF disk label.
UDF specification does not have a concept of disk UUID like other
filesystems. But mandates that the first 16 characters of UDF
Volume Set Identifier are unique, a non-fixed and a non-trivial
value. Plus first eight characters are hexadecimal digits. Windows
application format.exe and Mac OS X application newfs_udf are
known to violates this requirement and set only the first 8
characters as unique (others are fixed). Since, there are still a
lot of UDF implementations which use in the first 16 characters
only hexadecimal digits and all compliant UDF implementations have
hexadecimal digits in the first 8 characters, the following
algorithm for generating stable UUID was informally chosen and now
is used by udftools, util-linux, grub2 and other projects:
0. If Volume Set Identifier has less then 8 characters then
stop with empty UUID
1. Take the first 16 bytes from UTF-8 encoded string of
Volume Set Identifier
2. If all bytes are hexadecimal digits then use their
lowercase form as UUID
3. If first 8 bytes are not all hexadecimal digits then
convert those 8 bytes to their hexadecimal representation
(resulting in 16 bytes) and use as UUID
4. Otherwise, compose UUID from two 8 byte parts:
1. part: Use the lowercase form of the first 8 bytes
(which are hexadecimal digits)
2. part: Convert next 4 bytes (9.–12. pos.) to their
hexadecimal representation
Which means that this generated UUID has always 16 hexadecimal
lowercase digits. In most cases, this UUID matches case-
insensitively the first 16 characters of UDF Volume Set Identifier
and for all disks compliant to the UDF specification the first 8
bytes of UUID matches case-insensitively the first 8 characters of
UDF Volume Set Identifier. In that algorithm was chosen UTF-8
encoding because it is the only commonly used Unicode
transformation to bytes with fixed points in all hexadecimal
digits.
udflabel returns 0 if successful, non-zero if there are problems
like block device does not contain UDF filesystem or updating
failed.
udflabel is not able to set new Label, Logical Volume Identifier
and File Set Identifier for disks with Virtual Allocation Table
(used by Write Once media).
udflabel prior to version 2.3 was unable to handle Multisession
UDF discs correctly. It always accessed only the first session
(the oldest one) and not the last session (the most recent).
udflabel prior to version 2.2 was unable to print and process
Unicode strings with code points above U+FFFF correctly. When
option --utf8 was specified then input strings were limited to
3-byte UTF-8 sequences and when option --u16 was specified then
input strings were limited just to UCS-2BE strings (subset of
UTF-16BE).
udflabel prior to version 2.2 ignored UDF SoftWriteProtect and
HardWriteProtected flags and overwritten such disks without any
notice.
udflabel prior to version 2.2 was not able to set a new Label,
Logical Volume Identifier and File Set Identifier for disks with
Metadata Partition (used by UDF revisions higher then 2.01).
udflabel prior to version 2.1 was not able to read Label correctly
if the disk had Virtual Allocation Table stored outside of
Information Control Block.
Pali Rohár <[email protected]>
udflabel is part of the udftools package since version 2.0 and is
available from https://github.com/pali/udftools/.
mkudffs(8), pktsetup(8), cdrwtool(1), udfinfo(1), wrudf(1)
This page is part of the udftools (Linux tools for UDF filesystems
and DVD/CD-R(W) drives) project. Information about the project
can be found at ⟨https://github.com/pali/udftools⟩. If you have a
bug report for this manual page, see
⟨https://github.com/pali/udftools/issues⟩. This page was obtained
from the project's upstream Git repository
⟨https://github.com/pali/udftools.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2021-12-09.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
Commands udftools UDFLABEL(8)
Pages that refer to this page: udfinfo(1), mkudffs(8)
|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|