udflabel(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | UDF LABEL AND UUID | EXIT STATUS | LIMITATIONS | AUTHOR | AVAILABILITY | SEE ALSO | COLOPHON

UDFLABEL(8)              System Manager's Manual             UDFLABEL(8)

NAME         top

       udflabel — show or change UDF filesystem label

SYNOPSIS         top

       udflabel [encoding-options] [block-options] [identifier-options]
       device [new-label]

DESCRIPTION         top

       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.

OPTIONS         top

   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 LABEL AND UUID         top

       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.

EXIT STATUS         top

       udflabel returns 0 if successful, non-zero if there are problems
       like block device does not contain UDF filesystem or updating
       failed.

LIMITATIONS         top

       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.

AUTHOR         top

       Pali Rohár <pali.rohar@gmail.com>

AVAILABILITY         top

       udflabel is part of the udftools package since version 2.0 and is
       available from https://github.com/pali/udftools/.

SEE ALSO         top

       mkudffs(8), pktsetup(8), cdrwtool(1), udfinfo(1), wrudf(1)

COLOPHON         top

       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 2021-08-27.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2021-08-14.)  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

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