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


mkudffs — create a UDF filesystem


mkudffs [ options ] device [ blocks-count ]


mkudffs is used to create a UDF filesystem on a device (usually a disk). device is the special file corresponding to the device (e.g. /dev/hdX) or file image. blocks-count is the number of blocks on the device. If omitted, mkudffs automagically figures the filesystem size. The order of options matters. Encoding option must be first and options to override default settings implied by the media type or UDF revision should be after the option they are overriding.


Display the usage and list of options.

-l,--label= label
Specify the UDF label. UDF label is synonym for specifying both --lvid and --vid options. If omitted, mkudffs label is LinuxUDF. (Option available since mkudffs 1.1)

-u,--uuid= uuid
Specify the UDF uuid. It must be exactly 16 hexadecimal lowercase digits and is used for first 16 characters of --fullvsid option. If omitted, mkudffs uuid is generated from local time and a random number. (Option available since mkudffs 1.1)

-b,--blocksize= block-size
Specify the size of blocks in bytes. Valid block size for a UDF filesystem is power of two in range from 512 to 32768 and must match a device logical (sector) size. If omitted, mkudffs block size is set to device logical block (sector) size. If logical block (sector) size is unknown (e.g. when creating disk image) then for --media-type=hd is used block size 512 and for other media types 2048.

-m,--media-type= media-type
Specify the media type. Must be specified before --udfrev. Valid media types are:
hd (default)
HD (Hard Disk)
WORM (Write Once Read Many)
MO (Magneto Optical)
CD-ROM (CD Read-Only Memory)
CD-R (CD Recordable)
CD-RW (CD Read-Write)
DVD-ROM (DVD Read-Only Memory)
DVD-R (DVD Recordable)
DVD-RW (DVD Read-Write)
DVD-RAM (DVD Random Access Memory)
BD-R (Blu-ray Disc Recordable)

(Short option variant -m and values cd, dvdr, bdr are available since mkudffs 2.0)

-r,--udfrev= udf-revision
Specify the UDF revision to use, either in hexadecimal BCD (e.g. 0x0201) or decimal (e.g. 2.01) format. Valid revisions are 1.01, 1.02, 1.50, 2.00, 2.01, 2.50 and 2.60. If omitted, mkudffs UDF revision is 2.01, except for Blu-ray Discs which is 2.50. UDF revisions higher then 2.01 are experimental. Option must be specified after --media-type. (Values in decimal format and UDF revisions higher then 2.01 are supported since mkudffs 2.0, UDF revision 1.01 is supported since mkudffs 2.1)

Not really, do not write to device. Just simulate and display what would happen with device. Useful for determining the calculated location of different UDF blocks. (Option available since mkudffs 2.0)

Create a new image file specified by device with blocks-count and fail if file already exists. If omitted, mkudffs creates a new image file only in case it does not exist yet. (Option available since mkudffs 2.0)

--lvid= logical-volume-identifier
Specify the Logical Volume Identifier. If omitted, mkudffs Logical Volume Identifier is LinuxUDF. Most UDF implementations uses this identifier as a disk label.

--vid= volume-identifier
Specify the Volume Identifier. If omitted, mkudffs Volume Identifier is LinuxUDF.

--vsid= volume-set-identifier
Specify the 17.–127. character of Volume Set Identifier. If omitted, mkudffs Volume Set Identifier is LinuxUDF.

--fsid= file-set-identifier
Specify the File Set Identifier. If omitted, mkudffs File Set Identifier is LinuxUDF.

--fullvsid= full-volume-set-identifier
Specify the full Volume Set Identifier. Overwrite previous --uuid and --vsid options. (Option available since mkudffs 1.1)

--uid= uid
Specify the uid of the root (/) directory. If omitted, mkudffs uid is 0. Special value -1 means invalid or not specified uid. (Option available since mkudffs 1.1)

--gid= gid
Specify the gid of the root (/) directory. If omitted, mkudffs gid is 0. Special value -1 means invalid or not specified gid. (Option available since mkudffs 1.1)

--mode= mode
Specify permissions in octal mode bits of the root (/) directory. If omitted, mkudffs mode is 0755. (Option available since mkudffs 2.0)

--bootarea= fill
Specify how to fill UDF boot area which is the first 32kB of the disk and is not used by UDF itself. Option mbr make sense only when running mkudffs on whole disk, not on just one partition. Valid options are:
preserve existing UDF boot area, do not touch it (default for media type different from hd)
erase existing UDF boot area, fill it by zeros (default for hd media type on partitions and on removable disks)
put MBR table with one partition which starts at sector 0 (includes MBR itself) and spans whole disk device, needed only for non-removable hard disks used on Microsoft Windows systems (default for hd media type on non-removable hard disk without partitions), see section WHOLE DISK VS PARTITION

(Option available since mkudffs 2.0)

--strategy= strategy
Specify the allocation strategy to use. Valid strategies are 4 and 4096. If omitted, mkudffs strategy is based on the --media-type.

--spartable, --spartable= spartable-number
Enable usage Sparing Table. Optionally specify also the number of sparing tables. Valid numbers are 1–4. When the spartable number is omitted then two tables are written to the disc. If the option is omitted then usage of Sparing Table depends on the media type. (Option prior to mkudffs 2.0 was available only for cdrw media type)

--sparspace= num-of-entires
Specify the number of entries in Sparing Table. If omitted, the default number of entries is 1024, but depends on the media type. (Option available since mkudffs 2.0)

--packetlen= length
Packet length in a number of blocks used for alignment. All continuous UDF structures would be aligned to packets. It specifies also the size of the Sparing Space and packet length in Sparing Table. It should match the device ECC/packet length. If omitted, default value for DVD discs is 16 blocks, for CD/BD discs it is 32 blocks and otherwise 1 block. (Option prior to mkudffs 2.1 was available only for cdrw and dvdrw media types)

Enable usage of Virtual Allocation Table (VAT). If omitted, usage depends on the media type. (Option available since mkudffs 2.0)

Close disc with Virtual Allocation Table. AVDP is written also to the end of the disc. By default, the disc with Virtual Allocation Table is not closed.

--space= space
Specify the Space Set. Unallocated Space Set is used for media which blocks may be allocated immediately. Freed Space Set is used for media which blocks needs to be specially prepared/erased before allocation. In Space Table is stored list of unallocated extents. In Space Bitmap is stored bitmap of unallocated blocks. Not used for VAT.
Freed Bitmap
Freed Table
Unallocated Bitmap (default)
Unallocated Table

--ad= ad
Specify the Allocation Descriptors of the root (/) directory.
Allocation Descriptors in ICB (default)
Short Allocation Descriptors
Long Allocation Descriptors

Don't Use Extended File Entries for the root (/) directory. Affects only UDF 2.00 or higher. Must be specified after --udfrev.

Treat identifier string options as strings encoded according to the current locale settings (default). Must be specified as the first argument. (Option available since mkudffs 2.0)

Treat identifier string options as strings encoded in 8-bit OSTA Compressed Unicode format, equivalent to Latin1 (ISO-8859-1). Must be specified as first argument.

Treat identifier string options as strings encoded in 16-bit OSTA Compressed Unicode format, equivalent to UCS-2BE. 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.

Treat identifier string options as strings encoded in UTF-8. Must be specified as the first argument.



UDF filesystem is natively supported by large amount of operating systems. See following compatibility table:

Operating system Maximum UDF revision for
Name Version read write
Linux 2.3.17 – 2.4.5 2.00 2.00
2.4.6 – 2.6.25 2.01 2.01
2.6.26 (and new) 2.50 2.01
Windows 98/Me 1.02 none
2000 1.50 none
XP 2.01 none
Vista (and new) 2.60 2.50
Mac OS 8.1 – 8.5 1.02 none
8.6 – 9.2 1.50 1.50
Mac OS X 10.0 – 10.3 1.50 1.50
10.4 2.01 2.01
10.5 (and new) 2.60 2.50
FreeBSD 5 (and new) 1.50 none
NetBSD 4.0 2.60 none
5.0 (and new) 2.60 2.60
OpenBSD 3.8 – 3.9 1.02 none
4.0 – 4.6 1.50
4.7 (and new) 2.60
Solaris 7 (and new) 1.50 1.50
AIX 5.2 (and new) 2.01 2.01

Note that Windows 98 and Windows Me can read UDF filesystem only from CD and DVD optical discs, not from hard disks.


In most cases, operating systems are unable to mount UDF filesystem if UDF block size differs from logical sector size of the device. Typically hard disks have sector size 512 bytes and optical media 2048 bytes. Therefore UDF block size must match the logical sector size of the device.

Linux kernel prior to version 2.6.30 used hardcoded UDF block size of 2048 bytes independently of logical sector size, therefore it was not able to automatically mount UDF filesystem if block size differed from 2048. Since 2.6.30 and prior to 4.11 Linux kernel used a logical sector size of the device as UDF block size, plus it tried fallback to 2048. Since 4.11 it uses logical sector size and fallbacks to any valid block size between logical sector size and 4096. Therefore since version 2.6.30 Linux kernel can automatically mount UDF filesystems correctly if UDF block size matches device logical sector size and since version 4.11 can automatically also mount devices which sector size does not match UDF block size. In any case and also for Linux kernel prior to version 2.6.30, different UDF block size (which is not autodetected) can be manually specified via bs=blocksize mount parameter.


UDF filesystem is supposed to be formatted on the whole media and not to the partitioned hard disk. Mac OS X systems enforce this rule and reject to automatically mount UDF filesystem unless it is formatted on the whole unpartitioned hard disk. Possible partition table (e.g. MBR or GPT) on disk with valid UDF filesystem is ignored. On the other hand, Microsoft Windows systems are unable to detect non-removable hard disks without MBR or GPT partition table. Removable disks do not have this restriction. A consequence is that non-removable hard disks formatted to UDF by Windows Vista+ are not recognized by Mac OS X systems and vice-versa. Note that manual mount of UDF partition on partitioned hard disk on Mac OS X system is possible and working (e.g. by running commands: mkdir /Volumes/DriveName && mount_udf /dev/disk1s1 /Volumes/DriveName). But there is no known way to mount an unpartitioned non-removable disk on Windows system.

Thanks to reserved and unused UDF boot area (first 32kB of UDF filesystem) it is possible to deal with this problem, by putting MBR on such non-removable hard disk just for compatibility reasons with Windows. Such MBR table would contain one partition which starts at sector 0 (includes MBR itself) and spans whole disk device. So the whole disk device and also the first partition on disk points to same sectors. Therefore UDF filesystem can be mounted either from whole disk device (needed for Mac OS X systems) or from first partition (needed for Microsoft Windows systems).

Linux kernel ignores MBR table if contains partition which starts at sector 0. Normally Linux kernel can detect and mount UDF filesystem either on a partition or on whole disk device. It does not have any restrictions.

mkudffs option --bootarea=mbr put such MBR table for compatibility with Microsoft Windows systems into disk when formatting.


In most cases Logical Volume Identifier is used as UDF label. But Linux libblkid prior to version 2.26 used Volume Identifier. Therefore mkudffs --label for compatibility reasons set both Logical Volume Identifier and Volume Identifier.

Linux libblkid prior to version 2.30 incorrectly processed non-ASCII identifier strings encoded in 8-bit OSTA Compressed Unicode format. Therefore mkudffs since version 2.0 for compatibility reasons tries to encode a non-ASCII identifier strings in 16-bit OSTA Compressed Unicode format and then fallbacks to 8-bit format.

For more information about UDF Label and UUID see udflabel(8) section UDF LABEL AND UUID.


mkudffs returns 0 if successful, non-zero if there are problems.


mkudffs cannot create UDF 2.50 Metadata partition, therefore it does not support UDF revisions higher than 2.01 for non Write Once media yet. So there is no support for Blu-ray discs which needs UDF 2.50 (except for Blu-ray Disc Recordable which does not require Metadata partition).


mkudffs prior to version 1.1 was unable to process non-ASCII characters from identifier strings in --utf8 mode, --vsid option was completely broken and --blocksize must have been manually specified for hard disks as default value was hardcoded for optical disks. mkudffs prior to version 2.0 generated broken and unreadable cdr disc images.


Ben Fennema
Pali Rohár <>


mkudffs is part of the udftools package and is available from


pktsetup(8), udflabel(8), cdrwtool(1), udfinfo(1), wrudf(1)
udftools System Management Commands