linux/Documentation/filesystems/udf.rst
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   1.. SPDX-License-Identifier: GPL-2.0
   2
   3===============
   4UDF file system
   5===============
   6
   7If you encounter problems with reading UDF discs using this driver,
   8please report them according to MAINTAINERS file.
   9
  10Write support requires a block driver which supports writing.  Currently
  11dvd+rw drives and media support true random sector writes, and so a udf
  12filesystem on such devices can be directly mounted read/write.  CD-RW
  13media however, does not support this.  Instead the media can be formatted
  14for packet mode using the utility cdrwtool, then the pktcdvd driver can
  15be bound to the underlying cd device to provide the required buffering
  16and read-modify-write cycles to allow the filesystem random sector writes
  17while providing the hardware with only full packet writes.  While not
  18required for dvd+rw media, use of the pktcdvd driver often enhances
  19performance due to very poor read-modify-write support supplied internally
  20by drive firmware.
  21
  22-------------------------------------------------------------------------------
  23
  24The following mount options are supported:
  25
  26        ===========     ======================================
  27        gid=            Set the default group.
  28        umask=          Set the default umask.
  29        mode=           Set the default file permissions.
  30        dmode=          Set the default directory permissions.
  31        uid=            Set the default user.
  32        bs=             Set the block size.
  33        unhide          Show otherwise hidden files.
  34        undelete        Show deleted files in lists.
  35        adinicb         Embed data in the inode (default)
  36        noadinicb       Don't embed data in the inode
  37        shortad         Use short ad's
  38        longad          Use long ad's (default)
  39        nostrict        Unset strict conformance
  40        iocharset=      Set the NLS character set
  41        ===========     ======================================
  42
  43The uid= and gid= options need a bit more explaining.  They will accept a
  44decimal numeric value and all inodes on that mount will then appear as
  45belonging to that uid and gid.  Mount options also accept the string "forget".
  46The forget option causes all IDs to be written to disk as -1 which is a way
  47of UDF standard to indicate that IDs are not supported for these files .
  48
  49For typical desktop use of removable media, you should set the ID to that of
  50the interactively logged on user, and also specify the forget option.  This way
  51the interactive user will always see the files on the disk as belonging to him.
  52
  53The remaining are for debugging and disaster recovery:
  54
  55        =====           ================================
  56        novrs           Skip volume sequence recognition
  57        =====           ================================
  58
  59The following expect a offset from 0.
  60
  61        ==========      =================================================
  62        session=        Set the CDROM session (default= last session)
  63        anchor=         Override standard anchor location. (default= 256)
  64        lastblock=      Set the last block of the filesystem/
  65        ==========      =================================================
  66
  67-------------------------------------------------------------------------------
  68
  69
  70For the latest version and toolset see:
  71        https://github.com/pali/udftools
  72
  73Documentation on UDF and ECMA 167 is available FREE from:
  74        - http://www.osta.org/
  75        - https://www.ecma-international.org/
  76