1UDFLABEL(8) System Manager's Manual UDFLABEL(8)
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6 udflabel — show or change UDF filesystem label
7
10 udflabel [encoding-options] [block-options] [identifier-options] device
11 [new-label]
12
15 When udflabel is invoked without identifier-options and without speci‐
16 fying new-label then it shows current label of UDF filesystem on device
17 to standard output terminated by new line. Otherwise it updates UDF
18 filesystem (up to the revision 2.60) on device with new specified iden‐
19 tifiers from identifier-options. Specifying new-label is synonym for
20 both --lvid and --vid, see section UDF LABEL AND UUID.
21
24 GENERAL OPTIONS
25 -h,--help
26 Display the usage and the list of options.
27 BLOCK OPTIONS
30 -b,--blocksize= block-size
31 Specify the size of blocks in bytes. Valid block size for a UDF
32 filesystem is a power of two in the range from 512 to 32768 and
33 must match a device logical (sector) size. If omitted, udflabel
34 tries to autodetect block size. First it tries logical (sector)
35 size and then all valid block sizes.
36 --vatblock= vat-block
39 Specify the block location of the Virtual Allocation Table. Vir‐
40 tual Allocation Table is present only on UDF disks with Virtual
41 Partition Map and must be at the last written/recorded disk
42 block.
43 If omitted, udflabel for optical disc tries to detect the last
45 recorded block with fallback to the last block of block device
46 or disk file image. In most cases, this fallback does not have
47 to work and for disk file images with Virtual Allocation Table
48 it is necessary to specify the correct location.
49 Virtual Allocation Table contains Logical Volume Identifier (UDF
51 Label).
52 --force
55 Force updating UDF disks without write support or write pro‐
56 tected UDF disks. Some UDF disks may have set write protect
57 flag. Some media, like CD-ROM, DVD-ROM or BD-ROM are read-only.
58 Other media, like CD-RW or DVD-RW, are write-once. UDF is
59 designed also for such media where updating Label or Identifiers
60 is not possible. But in some rare cases, it could make sense to
61 try and overwrite the existing Label or Identifiers also for UDF
62 filesystem which has Access Type either Read-Only or Recordable
63 (Write-Once). This is possible only if underlying media supports
64 overwriting. E.g. UDF image of CD-ROM stored on hard disk or
65 Read-Only UDF image burned to DVD-RAM or BD-RE discs. Option
66 --force ignores UDF Access Type and treats it as Overwritable.
67 Also it ignores UDF SoftWriteProtect and HardWriteProtected
68 flags.
69 -n,--no-write
72 Not really, do not write to device. Just simulate and display
73 what would happen with device. Useful for determining which UDF
74 blocks would be overwritten.
75 IDENTIFIER OPTIONS
78 -u,--uuid= uuid
79 Specify the UDF uuid. Must be exactly 16 hexadecimal lowercase
80 digits and is used for first 16 characters of --fullvsid option.
81 Special value random generates new uuid from local time and a
82 random number. See section UDF LABEL AND UUID.
83 --lvid= new-logical-volume-identifier
86 Specify the new Logical Volume Identifier.
87 --vid= new-volume-identifier
90 Specify the new Volume Identifier.
91 --vsid= new-volume-set-identifier
94 Specify the new 17.–127. character of Volume Set Identifier. See
95 section UDF LABEL AND UUID.
96 --fsid= new-file-set-identifier
99 Specify the new File Set Identifier.
100 --fullvsid= new-full-volume-set-identifier
103 Specify the new Volume Set identifier. Overwrite previous --uuid
104 and --vsid options. See section UDF LABEL AND UUID.
105 ENCODING OPTIONS
108 --locale
109 Treat identifier string options as strings encoded according to
110 current locale settings (default). Must be specified as the
111 first argument.
112 --u8 Treat identifier string options as strings encoded in 8-bit OSTA
115 Compressed Unicode format without leading Compression ID byte,
116 which is equivalent to Latin1 (ISO-8859-1). Must be specified as
117 first argument.
118 --u16 Treat identifier string options as strings encoded in 16-bit
121 OSTA Compressed Unicode format without leading Compression ID
122 byte, which is equivalent to UTF-16BE. Note that it is not pos‐
123 sible to include zero byte in command line options, therefore
124 any character which has at least one zero byte cannot be sup‐
125 plied (this applies to all Latin1 characters). Must be specified
126 as the first argument.
127 --utf8 Treat identifier string options as strings encoded in UTF-8.
130 Must be specified as the first argument.
131
134 UDF specification does not say anything about a disk label but it
135 describes that UDF Logical Volume Identifier is an extremely important
136 field for media identification in a jukebox as that field is displayed
137 to the user. And based on this statement it is a common practice for
138 the majority of UDF implementations to use UDF Logical Volume Identi‐
139 fier as a UDF disk label.
140 UDF specification does not have a concept of disk UUID like other
142 filesystems. But mandates that the first 16 characters of UDF Volume
143 Set Identifier are unique, a non-fixed and a non-trivial value. Plus
144 first eight characters are hexadecimal digits. Windows application for‐
145 mat.exe and Mac OS X application newfs_udf are known to violates this
146 requirement and set only the first 8 characters as unique (others are
147 fixed). Since, there are still a lot of UDF implementations which use
148 in the first 16 characters only hexadecimal digits and all compliant
149 UDF implementations have hexadecimal digits in the first 8 characters,
150 the following algorithm for generating stable UUID was informally cho‐
151 sen and now is used by udftools, util-linux, grub2 and other projects:
152 0. If Volume Set Identifier has less then 8 characters then stop
154 with empty UUID
155 1. Take the first 16 bytes from UTF-8 encoded string of Volume
156 Set Identifier
157 2. If all bytes are hexadecimal digits then use their lowercase
158 form as UUID
159 3. If first 8 bytes are not all hexadecimal digits then convert
160 those 8 bytes to their hexadecimal representation (resulting in
161 16 bytes) and use as UUID
162 4. Otherwise, compose UUID from two 8 byte parts:
163 1. part: Use the lowercase form of the first 8 bytes
164 (which are hexadecimal digits)
165 2. part: Convert next 4 bytes (9.–12. pos.) to their
166 hexadecimal representation
167 Which means that this generated UUID has always 16 hexadecimal lower‐
169 case digits. In most cases, this UUID matches case-insensitively the
170 first 16 characters of UDF Volume Set Identifier and for all disks com‐
171 pliant to the UDF specification the first 8 bytes of UUID matches case-
172 insensitively the first 8 characters of UDF Volume Set Identifier. In
173 that algorithm was chosen UTF-8 encoding because it is the only com‐
174 monly used Unicode transformation to bytes with fixed points in all
175 hexadecimal digits.
176
179 udflabel returns 0 if successful, non-zero if there are problems like
180 block device does not contain UDF filesystem or updating failed.
181
184 udflabel is not able to set new Label, Logical Volume Identifier and
185 File Set Identifier for disks with Virtual Allocation Table (used by
186 Write Once media).
187 udflabel prior to version 2.2 was unable to print and process Unicode
189 strings with code points above U+FFFF correctly. When option --utf8 was
190 specified then input strings were limited to 3-byte UTF-8 sequences and
191 when option --u16 was specified then input strings were limited just to
192 UCS-2BE strings (subset of UTF-16BE).
193 udflabel prior to version 2.2 ignored UDF SoftWriteProtect and Hard‐
195 WriteProtected flags and overwritten such disks without any notice.
196 udflabel prior to version 2.2 was not able to set a new Label, Logical
198 Volume Identifier and File Set Identifier for disks with Metadata Par‐
199 tition (used by UDF revisions higher then 2.01).
200 udflabel prior to version 2.1 was not able to read Label correctly if
202 the disk had Virtual Allocation Table stored outside of Information
203 Control Block.
204
207 Pali Rohár <pali.rohar@gmail.com>
208
211 udflabel is part of the udftools package since version 2.0 and is
212 available from https://github.com/pali/udftools/.
213
216 mkudffs(8), pktsetup(8), cdrwtool(1), udfinfo(1), wrudf(1)
217Commands udftools UDFLABEL(8)