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I have an external USB hard drive that I'd like to format to UDF for cross-compatibility with Windows and Macs. I tried exFAT, but for whatever reason, because of the block size (56KB) of the format, it's eaten up a huge portion of the disk space (~400GB actual data, ~900GB used disk space).

Is there a utility on Mac OS X to format hard drives to UDF?

I can't find any built-in to my version (OS X 10.8.2), and mkudffs doesn't appear to be in my $PATH, so I'm not sure where to go from here.

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OS X is supposed to fully support NTFS since Snow Leopard (fully updated), and anything newer. If I were you, I would go with that, unless you use Macs with older OS versions. Sounds simpler. –  Ariane Feb 21 '13 at 1:15
    
@Ariane It doesn't support writing to NTFS, only reading. –  Tyilo Feb 24 '13 at 17:43
    
@Tyilo macbreaker.com/2012/02/… Looks like you need a third-party thingie. –  Ariane Feb 24 '13 at 21:58
    
@Ariane I'm aware of those products, however I wanted to point out that OS X doesn't support NTFS-writing out of the box. –  Tyilo Feb 24 '13 at 22:04
    
@Tyilo Yeah, sorry. An article I'd read sort of implied that, but looks like I'd interpreted it wrong. –  Ariane Feb 24 '13 at 22:07
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3 Answers

Using the Terminal, you might be able to format a disk into UDF. I use the following command to format Blu-Ray-Disks:

newfs_udf -v "Untitled UDF" -r 2.60 /dev/diskX

You might want to first find out under what device name your actual disk is found.

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I put it on Github. –  aross Nov 22 '13 at 14:36
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Someone did some research into how to format a flash drive with udf so it can be used on as many operating systems as possible. His findings are at http://sipa.ulyssis.org/2010/02/filesystems-for-portable-disks/ and there's a script to format the disk properly at http://sipa.ulyssis.org/wp-content/uploads/2010/02/udfhd.pl_.txt

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is there an utility for windows to format a drive in udf like the perl script does? –  Gianluca P. Mar 21 at 21:14
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I only know about ways to do it from Windows, but if you want to format from a Mac, I would avoid it. I would not format a drive into Universal Disk Format since it is mainly read only, and you can encounter some errors. I would suggest formatting it in NTFS seeing as Mac OS X is supposed to be able to see that format now.

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OS X normally mounts NTFS volumes readonly. You can replace the builtin NTFS driver with one that handles writing, but I don't know how solid that is... –  Gordon Davisson Feb 21 '13 at 16:16
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