FreeBSD 11 and 4+ GB files on optical disc

Polytropon freebsd at
Fri Feb 10 02:17:53 UTC 2017

On Thu, 9 Feb 2017 17:51:34 -0800, David Christensen wrote:
> On 02/09/17 15:55, Polytropon wrote:
> Thanks for the reply.
> > On Thu, 9 Feb 2017 15:04:13 -0800, David Christensen wrote:
> >> I periodically create archive files on Debian 7, encrypt the archive,
> >> create checksum files, burn the archive and checksum files to optical
> >> disc, and then verify the contents of the disc.
> >
> > So I can assume you're using ISO-9660 as the file system for
> > the optical disc - a very important aspect you never mentioned. :-)
> dpchrist at freebsd:/usr/home/dpchrist $ mount | grep /dev/cd0
> /dev/cd0 on /media/HOLGERDANSKE_COM (cd9660, local, nosuid, read-only)

Exactly my assumption. :-)

> >> I suspect that FreeBSD is having problems because the archive file is
> >> larger than 4 GB (?).
> >
> > Well, if you accurately consider the file size conversion ...
> > Check what the file system specification says ...
> > So what you're seeing (file appearing twice) exactly matches
> > the assumption that mkisofs is creating a "split entry" for a
> > source file that the ISO-9660 file system cannot contain due
> > to a size limitation.
> I created the disc on Linux, and have been creating discs just like it 
> for several years.  I guess Linux hides the "split entries"; it "just 
> works".

That is correct, but keep in mind it's an extension to the
specification, so not really "standard" to do so. ISO-9660
has a file size limitation.

> When I browse the disc using Vista 32-bit, Windows Explorer shows the 
> files on the disc correctly.

It seems to support that extension. However, FreeBSD's ISO-9660
implementation seems to be more strict...

> > Don't use ISO-9660. Use tar as a file system (or better, instead
> > of a file system). You can write it to the DVD like this:
> >
> > 	% growisofs -dvd-compat -Z /dev/dvd=2017.01.tar
> >
> > And read (restore) it like this:
> >
> > 	% tar xvf /dev/dvd
> >
> > The advantage: No size limitation imposed by ISO-9660.Additional security: "There are no files on the DVD!" ;-)
> That is not security; that is incompatibility.

Sometimes, incompatibility _is_ security. ;-)

> This is an archive disc.  I have created many such discs over the years. 
>   I need to be able to browse and read them on as many platforms as 
> possible.

That's why tar isn't that bad: Every significant system has
the only two parts needed to access such disk: first the
ability to read raw data from the device, second an implementation
of the tar program. Even though it might sound stupid, this
mechanism works with any media (from floppy, optical discs,
tape, hard disks, USB sticks) and on almost every operating
system (Linux, BSD, Solaris, IRIX, AIX, HP-UX, also on DOS,
and with Linux tools being available on "Windows", even there).

Of course you need to process the file sequencially, but that
is not a big deal because you have created .tar files anyway.
The downside is that you do not really have logical _files_
(no .tar file on the media, but media itself is a .tar "file"),
which might be a problem for archiving tasks.

> How do I browse and read 4+ GB files on optical discs (DVD, BD) 
> correctly on FreeBSD?

By using FreeBSD 11, you're already using the most recent
version of the ISO 9660 VFS driver. I suggest you ask a
specific question on the freebsd-fs@ mailing list. Maybe
there is userland support (maybe through FUSE) for extensions
that allow files bigger than the specification.

Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...

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