FreeBSD 11 and 4+ GB files on optical disc

[Polytropon]

On Thu, 9 Feb 2017 15:04:13 -0800, David Christensen wrote:
> I have a computer:
> 
> dpchrist at freebsd:/usr/home/dpchrist $ freebsd-version
> 11.0-RELEASE-p7
> 
> dpchrist at freebsd:/usr/home/dpchrist $ uname -a
> FreeBSD freebsd 11.0-RELEASE-p1 FreeBSD 11.0-RELEASE-p1 #0 r306420: Thu 
> Sep 29 03:40:55 UTC 2016 
> root at releng2.nyi.freebsd.org:/usr/obj/usr/src/sys/GENERIC  i386
> 
> 
> 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. :-)



> The checksums verify okay on Debian 7.
> 
> 
> But when I put the optical disc into the subject FreeBSD computer and 
> browse to it using Xfce and Thunar, the first thing I notice is that the 
> archive file is listed twice:
> 
> dpchrist at freebsd:/media/HOLGERDANSKE_COM $ ll
> total 8388607
> drwxr-xr-x  1 root  wheel  -           2048 Feb  9 11:05 ./
> drwxr-xr-x  3 root  wheel  uarch          5 Feb  9 14:34 ../
> -rw-r--r--  1 root  wheel  -     4294965248 Feb  9 08:52 201701.tar.cpt
> -rw-r--r--  1 root  wheel  -     4294965248 Feb  9 08:52 201701.tar.cpt
> -rw-r--r--  1 root  wheel  -             49 Feb  9 08:52 201701.tar.cpt.md5
> -rw-r--r--  1 root  wheel  -             81 Feb  9 08:52 
> 201701.tar.cpt.sha256
> 
> 
> When I attempt to verify the checksums, they fail:
> 
> dpchrist at freebsd:/media/HOLGERDANSKE_COM $ cat 201701.tar.cpt.md5
> dd2dfc838c03a1819efceab530a6c7f8 *201701.tar.cpt
> 
> dpchrist at freebsd:/media/HOLGERDANSKE_COM $ md5 -c 
> dd2dfc838c03a1819efceab530a6c7f8 201701.tar.cpt
> MD5 (201701.tar.cpt) = ac49e95889f44adbdaa2f68f4d7bb96e [ Failed ]
> 
> dpchrist at freebsd:/media/HOLGERDANSKE_COM $ cat 201701.tar.cpt.sha256
> 87b0ba7ed7e706f55f571ec73daad0a2ab9820de9db8e0c889ba8541b5b8f40e 
> *201701.tar.cpt
> 
> dpchrist at freebsd:/media/HOLGERDANSKE_COM $ sha256 -c 
> 87b0ba7ed7e706f55f571ec73daad0a2ab9820de9db8e0c889ba8541b5b8f40e 
> 201701.tar.cpt
> SHA256 (201701.tar.cpt) = 
> 10ebce65e89144fe6161b96a43920cf3437a18b34f1e92c7941343fa9a950ad3 [ Failed ]
> 
> 
> 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 to
kB, MB and GB (for example 4294965248/1024/1024/1024 = 3), you
mught or might not be bitten by a file size limitation.

Check what the file system specification says:

	All numbers in ISO 9660 file systems except the single byte
	value used for the GMT offset are unsigned numbers. As the
	length of a file's extent on disk is stored in a 32 bit value,
	it allows for a maximum length of just over 4.2 GB (more
	precisely, one byte less than 4 GiB).

	[...]

	Based on this, it is often assumed that a file on an ISO 9660
	formatted disc cannot be larger than 232-1 in size, as the
	file's size is stored in an unsigned 32 bit value, for which
	232-1 is the maximum.

	It is, however, possible to circumvent this limitation by
	using the multi-extent (fragmentation) feature of ISO 9660
	Level 3 to create ISO 9660 filesystems and single files up
	to 8 TB. With this, files larger than 4 GB can be split up
	into multiple extents (sequential series of sectors), each
	not exceeding the 4 GB limit. For example, the free software
	such as InfraRecorder, ImgBurn and mkisofs as well as Roxio
	Toast are able to create ISO 9660 filesystems that use
	multi-extent files to store files larger than 4 GB on
	appropriate media such as recordable DVDs.

https://en.wikipedia.org/wiki/ISO_9660#The_2.2F4_GiB_file_size_limit

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.



> Any comments or suggestions?

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!" ;-)




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