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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.
--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. 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.
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 2.2 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 <pali.rohar@gmail.com>
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 2020-08-13. (At that time,
the date of the most recent commit that was found in the repository
was 2020-03-21.) 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 man-pages@man7.org
Commands udftools UDFLABEL(8)
Pages that refer to this page: udfinfo(1) , mkfs.udf(8) , mkudffs(8)