Linux filesystems accessible from FreeBSD 8-stable?

Erik Trulsson ertr1013 at
Fri Sep 24 20:20:23 UTC 2010

On Fri, Sep 24, 2010 at 08:48:00PM +0100, Frank Shute wrote:
> On Thu, Sep 23, 2010 at 01:59:40PM -0400, Leif Walsh wrote:
> >
> > I can't seem to get a definitive answer on this from the internet,
> > there's a lot of conflicting information.
> > 
> > I have some data drives formatted with ext4, which I'd like to access
> > from freebsd, preferably without totally reformatting because I don't
> > have much temp space for copying.  Read-only would be fine, read-write
> > would be much preferred.
> > 
> > Is this possible?  Am I missing the big "ext4 drivers in
> > freebsd/fuse/something" sign?  Does anyone happen to know if it's
> > possible to migrate an ext4 drive back to ext3, which it seems I can
> > access from bsd if I let it pretend the journal doesn't exist?
> > 
> Wikipedia seems to think you're right in thinking you can migrate (or
> mount only?) an ext4 as ext3:

Well, not quite.  That article says:

  The ext3 file system is partially forward compatible  with ext4, that
  is, an ext4 filesystem can be mounted as an ext3 partition (using
  "ext3" as the filesystem type when mounting). However, if the ext4
  partition uses extents (a major new feature of ext4), then the ability
  to mount the file system as ext3 is lost.

So, if an ext4 filesystem can be mounted as ext3 (and presumably as
ext2 since ext3 filesystems can be mounted as ext2) seems to depend on
how the ext4 filesystem was created/used.

<Insert your favourite quote here.>
Erik Trulsson
ertr1013 at

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