Should I choose exFat or NTFS for a "shared" partition in a dual-boot system?

If you're using both Ubuntu and Windows, then yes, you should probably store files you want accessible by both in an NTFS partition. exFAT and FAT32 partitions are other options, but:

• exFAT is patent-encumbered, so support for it is not built in to Ubuntu by default. You can add it without too much trouble, but this is still more trouble than not having to add it at all.

  • Remember, if you have to boot from an Ubuntu live CD for recovery purposes, the live CD won't have exFAT drivers even if your installed system does.
  • You may also want to check your local laws before installing exFAT, to determine whether or not you might incur civil liability due to patent problems. (I'm not trying to discourage you, and I'm not a lawyer. I just want you to be aware of potential issues.)

• FAT32 doesn't support files larger than 4 GiB. These days, you may well have files that large, depending on what you're using your computer for.

• Neither exFAT nor FAT32 support file ownership and permissions. This is usually quite minor when comparing them to NTFS, since while NTFS does support ownership and permissions, it's somewhat complicated to get them properly respected/used when mounting an NTFS volume in a non-Windows operating system like Ubuntu. You can do it, though.

Unless you have a specific reason to do otherwise, your partition for sharing files between Ubuntu and Windows should probably be NTFS. Furthermore, it could even just be the Windows partition, as that is of type NTFS. You cannot install Ubuntu to an NTFS partition, though (except with Wubi, which installs it to a rewriteable disk image that resides inside an NTFS partition).

Since Ubuntu is not as good at repairing damaged NTFS partitions as Windows (though there are Ubuntu utilities for this), you should probably avoid NTFS for machines where Ubuntu is the only operating system. (But for such a machine, you could use use Ubuntu's default partition type, ext4.)

Yes, you should create a separate NTFS partition to share files between Ubuntu and Windows on your computer.

Ubuntu can safely read and write files on the Windows partition itself.
So you do not really need a separate NTFS partition to share files.

I would still recommend a separate partition for important data that is for sharing between different OSes on the same computer.

• If you mean a boot partition, neither; Linux cannot boot off NTFS or exFAT. Additionally exFAT is not recommended for most uses because Ubuntu/Linux cannot currently write to exFAT.

• You don't need a special partition to "share" files; Linux can read and write NTFS (Windows) just fine. On the other hand, consider the following alternatives if you want to create a "shared" partition:

  • FAT32 (vfat): this relatively old-but-simple filesystem has excellent support on Linux (and is native to Windows); it's a good choice for occasional common files like music, small media, documents, etc. It has a 4GB maximum filesize limitation though.
  • ext2/ext3: these native Linux filesystems have good read/write support on Windows via third-party drivers such as ext2fsd. A good choice if you will be using this primarily in Ubuntu/Linux but need read/write support on Windows as well.