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This is probably trivial to check using cfdisk on a UDF-formatted CD/DVD/Blu-Ray, but I have neither of them at hand.

I have created an UDF formatted partition on a USB hard drive to share data between Linux and Windows computers (FAT doesn't handle 4GB files, NTFS access rights support is not stable under Linux). I have only one problem now - Windows refuses to mount the partition as the file system type id is set to '83' ('Linux'). I have looked quite extensively and can not find what number should I put there?

(follow-up: "With what tool should I format a hard drive as UDF?")

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I don't think that you would get any meaningful results from executing cfdisk on a CD, DVD or Blu-Ray. Partitions are set by a few bytes of the MBR, which happens to exist in harddisks and pen-drives, not in floppies or optical media. – Juliano Jul 2 '09 at 20:30

The answer is partition type 06 (FAT16). Don't ask me why, ask Microsoft.

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5+ years later, this simple answer helped me immensely. Thank you “user48160” whoever and wherever you are now! – JakeGould Mar 12 '15 at 6:26
up vote 6 down vote accepted

It turns out there is no partition table for UDF and there is no partition ID assigned to it. This filesystem has to span the whole disk in oder to be recognized by Windows. Formatting a hard drive as UDF does not touch the existing partition table (be careful - it will contain stale information, and if you mount your drive using it, you will destroy the data!).

As a curiosity - UDF 2.5 and newer creates separate partitions (one or two per disk) for metadata. However, those partitions are also not visible in the standard DOS partition table.

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Just formatted as UDF one of the (MBR) logical partitions on my hard drive and Windows 7 had no problem with it – MarcH Dec 29 '11 at 23:49
@MarcH: so what partition ID does Windows or some tool report the partition as having? (had trouble to formulate the question, sorry if it's ill formed) – ata Mar 27 '12 at 21:08
@Juaco scroll down for the answer. Or have a look at BOOTICE. – MarcH Mar 29 '12 at 8:10
Some partitioning tools let you create partitions without file system. Exactly what you need to assign it a drive letter in Windows and then UDF format it. – DanMan Dec 16 '13 at 11:09

On the CD's and DVD's I deal with, there is no partition table. On your USB hard drive, you've written a partition table to the media. I suspect if you format the entire drive as a UDF disk without the partition table, Windows will have no problem mounting it.

You don't say what size your USB drive is, and you might be reluctant to dedicate the whole drive as UDF, you could try setting the partition type with fdisk as NTFS or one of the other MS 'supported' types.

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I am also booting Linux out of the same drive, so I need one partition to be of a format supported by grub. I just found out that grub2 (experimental) can boot Linux from UDF, so I will try this. – skolima Jul 3 '09 at 8:54

I have got the same problem. My USB hard disk is 320GB. Partition table looks like this:

Disk /dev/sda: 320.0 GB, 320072933376 bytes
255 heads, 63 sectors/track, 38913 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x44fdfe06

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1       27963   224612766    c  W95 FAT32 (LBA)
/dev/sda2           27964       38913    87955875    5  Extended
/dev/sda5           27964       33366    43399566    7  HPFS/NTFS
/dev/sda6           33367       38913    44556246   83  Linux

Partition sda5 is a UDF rev. 1.5 and shoulb be readable by Windows XP and above. Linux reads it properly of course. Windows however is confused. It recognise partition as NTFS and then it assumes it is raw partition.

My experiment with UDF on pendrive showed me that systems tend to mistake UDF with FAT. They interpret UDF as FAT. It must be quite large similarities because i can see directory stucture of random characters. Linux says that disk is corrupted but it don't refuse to use it.

I think UDF (at least rev 1.5) is not well supported on USB drives.

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If the medium used to have FAT, there might be remains causing UDF to be confused with FAT. You should make sure the FAT is wiped/zeroed before formatting with UDF. – Spookbuster Jun 11 at 11:37

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