As a rule, most OSes only support one or two "native" filesystems. By native, I mean that the writers of the OS also wrote the specification for the data layout on disk. As such, Linux has ext2fs as its filesystem.
If you just run one OS, and you have just one FS, then you have no problem. If, on the other hand, you run more than one OS, then things start getting complicated. Imagine that you want to read a text file that you have in Linux into a Word document. How do you copy a file from one filesystem to another?
Well, one possibility is to use network resources, such as NFS, Samba or even FTP. You boot one OS, say Linux, and copy the file onto the server. You then boot the other OS, say Windows Me, and you copy the file from the server back to the PC, but now it's on the second filesystem. A bit of a lengthy task, and not everyone has easy access to a networked server. On top of that, there are some problems with compatibility of network protocols, since not all OSes support the same protocols.
Another possibility is to use removeable media, such as floppy disks or CD-RW. The problem with this method is that floppies are only any use for small amounts of data (text files, for instance), and other media also suffer from portability problems. CD-RW, DVD-RAM and Zip are far from having universally available drivers and support. So, though I can easily write an UDF formatted CD-RW with Windows, I can only read it with Solaris, and I can neither read nor write to it under OS/2.
The last choice is to directly access the native partition of the other OS. As a rule, this requires that you have drivers for the other OS. The biggest problem is that the drivers tend to be third party, so they aren't as reliable as drivers written by the organization that actually defined the layout of the filesystem. A word of warning, though. If you use third party drivers for read-only access to a filesystem, then you're unlikely to come to any harm; if you try to write to the filesystem, then you risk losing all your data if the drivers make a mess of things. It doesn't take much (superblock, directory structures) to totally destroy a filesystem.
Here is a summary of my experiences of accessing filesystems between OSes. Where I say "No" I mean "not that I know of". There are a few links to third party sites. In some cases, there may be several FS drivers available for a given OS/FS combination (such as NTFS for Windows 9x).
|FS\OS||Windows 9x||WNT/W2K||Mac OS X||OS/2||Linux||FreeBSD||Solaris||DOS||Oberon|
|FAT16||Native||Native||OS RW||Native||OS RW||OS RW?||OS RW||Native||OS RW|
|FAT32||Native1||No/Native||OS RW||3P RW||OS RW||don't know||OS RW||No||don't know|
|NTFS||3P||Native2||OS RO||No||OS RW3||OS RO||3P RO||No||No|
|HPFS||No||Native4||No||Native||3P RO||No||No||3P RW?||No|
|ext2fs||No||3P||3P||3P RW||Native||OS RW||3P RO||No||No|
3P - third party
R - read-only
OS - ships with OS
RW - read/write
? - I'm not sure
1 most versions of OS
2 WNT supports NTFS, W2K both NTFS and NTFS5
3 on Linux 2.2.X, writing is unreliable!
4 NT 3.5 had an HPFS driver which also works with NT 4 (not supported by Microsoft). No support for W2K
5 FreeBSD UFS
6 Solaris UFS
Copyright © Paul John Floyd 2005 - 2006, 2008