http://www.dvdrw.com/DVD+RW /+R/ -RW/-R[W]  for Linux
by <appro@fy.chalmers.se>,
January 2006
http://www.ioss.jp/sohodiy/vol02-part01.htmlJapanese Q.	What is this page (not) about? A. 	
Maybe to your disappointment it is not about
	video
(*). The scope of this page is primarily
	computer storage applications of DVD±RW/±R,
	things like backup, archiving, data exchange... The
	downloadable files are an 
optional linux-2.4.patchLinux 2.4 kernel DVD+RW patch  and a
	couple of user-land utilities dubbed as 
tools/?M=Ddvd+rw-tools .
	
	
	
(*)	
Though it doesn't mean that you can't burn
	DVD-Video discs with dvd+rw-tools. [Unlike Video-CD] DVD-Video
	is "molded" in an ordinary data file system and
	therefore no explicit support by the burning program is
	actually required. In other words it is the DVD-Video
	
content preparation which is beyond the scope of this
	page.
	
	
Q.	Kernel patch? This sounds too complicated
	already! Can't I just use [vanilla] cdrecord?
A.	It should be explicitly noted that the user-land
	utilities, dvd+rw-tools,
 do suffice for DVD recording
	without explicit kernel support. So if they 
#tutorialfulfill your requirements , then	
patching the kernel is by all means optional. As
	for cdrecord, DVD recording strategies are somewhat different
	from the one supported by [vanilla] cdrecord, so it simply
	doesn't work (nor does dvdrecord
http://www.freesoftware.fsf.org/dvdrtools/,  despite
	what 
http://www.redhat.com/docs/manuals/linux/RHL-7.3-Manual/release-notes/x86/RedHat
	7.3 Release Notes
 say). On additional note Linux kernel
	version 2.6.10 is equipped with 
http://web.telia.com/~u89404340/packet.htmlpacket
	writing driver
 which supports even DVD rewritable media,
	but I haven't tested it myself, so don't ask:-)
Q.	What is the kernel patch good for then?
A.	DVD+RW (but not DVD+R nor any DVD-dash) is a true random
	write access media and therefore is suitable for housing of an
	arbitrary file system, e.g. 
udf, vfat, ext2, etc. This,
	and this alone, qualifies DVD+RW support for kernel
	implementation. 
However, I have to recommend to
	
deploy it with caution, see #udftutorial 	for further details. Also note that not all OEMs seem to live
	up to the promise of true random write access. As for the
	moment of this writing apparenly only 2nd generation
	Ricoh-based units (see 
http://www.dvdplusrw.org/dvdplusrw.org  for
	generation listings) equipped with later firmware can sustain
	I/O fragmentation (see Technical Ramblings below for further
	details) and perform 
reliably.
Q.	What are the dvd+rw-tools for? A.	As implied/already mentioned - to master the DVD media,
	both +RW/+R and 
-RW/-R[W] . I could simply
	refer to the tutorial below, but figured that couple of words
	about the [original] design ideas behind 
growisofs, the
	principal burning utility,
 wouldn't harm. Even though a
	modified kernel can let you put for example an ext2 file system
	on DVD+RW, it's probably not very practical, because you most
	likely want to access the data on an 
arbitrary computer.
	Or in other words you most likely want ISO9660. The trouble is
	that you might as well want to 
add data now and then.
	And what options do you have in the lack of multiple sessions
	(no, DVD+RW has no notion of multiple sessions)? Complete
	re-mastering which takes more and more time as data set grows?
	Well, yes, 
unless you employ growisofs! Growisofs
	provides the way to both lay down 
and grow an ISO9660
	file system on (as well as to burn an arbitrary pre-mastered
	image to) all supported DVD media.
Q.	But if they support  both + and - recording
	strategies, why are they called dvd+rw-tools?
A.	For historical/nostalgical reasons, as originally they did
	support exclusively DVD+plus. On the other hand now, when the
	vast majority of DVD burners that are being introduced to the
	market today are DVD+capable, the name most likely refers to
	your unit in either case. And you can always consider the plus
	in the name as notion of some unique quality, such as
	"seamless" multi-sessioning, not as reference to some
	particular format:-)
Q.	Do I still need http://cdrecord.berlios.de/old/private/cdrecord.htmlcdrtools ?
A.	Yes. It should be explicitly noted that growisofs is a
	front-end to mkisofs,
 i.e. invokes mkisofs to perform the
	actual ISO9660 file system layout. Secondly, the DVD burners
	available on the market can burn even CD-R[W] media and
	cdrecord is the tool for this job [and this job only].
Q.	Does it work with my DVD burner?
A.	If your unit is http://www.t10.org/drafts.htm#mmc3MMC  compliant,
	then the answer is "
hcn.htmlmost likely  it
	just does." Well, as the probability of your unit being
	non-MMC compliant is virtually zero, the answer in practice is
	unconditionally "
hcn.htmlmost likely ."
	The [core] tools were reported to work with a wide range of
	drives, including 
[but not limited to] HP
	dvd[12345]x0i,
 Ricoh MP512x, Philips
	DVDRW[248]xx,
 SONY DRU-[157]x0, NEC
	ND-[123]xx0,
 TDK indiDVD 4x0N,	
Plextor PX-[57]xx, Benq DW[48]00A,	
OptoRite DD0[24]0x, Lite-On LDW-[48]x1S,	as well as 
-RW/nonplus  units such as
	
Pioneer DVR-x0[4567], LG GxA-40[248]x,	
Toshiba SD-R[56]112, Panasonic UJ-811	and 
LF-D[35]1x...Q.	Is there a GUI front-end available for
	dvd+rw-tools?
A.	http://www.k3b.org/K3b,  version 0.10
	and later, and 
http://ftp.gnome.org/pub/GNOME/sources/nautilus-cd-burner/nautilus-cd-burner, 	version 0.5.1 and later, are both hiding growisofs behind their
	pretty buttons and menus:-) Keep in mind that those are not
	directly related to 
dvd+rw-tools development
	effort and GUI users should turn elsewhere for 
end-user	support. Oh! dvd+rw-tools 5.10.x is a minimum requirement for
	GUI frontends...
Q.	I don't run Linux. What are my options?
A.	Version 5.4 adds support for http://www.mosha.net/05-dvdrw/dvdrw.shtmlOpenBSD /NetBSD.	Version 5.6 adds support for 
Solaris 2.x [ solaris.com.htmlcommercial licensing 	terms for distribution on Solaris are to be settled with 
http://www.inserve.se/Inserve Technology ].
	Version 5.8 features 
http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/creating-dvds.htmlFreeBSD 	port contributed by Matthew Dillon, FreeBSD Development Team
	alumnus. 
Hewlett-Packard Company has donated
	
HP-UX 11 support for
	5.14
(*). IRIX 6.x support appears in
	5.19, while 
tools/win32/Win32  one - in
	6.0.
	
	
	
¡	
Common usage tip! Whenever
	separately available [and unless stated otherwise], do 
use
	character-type device entry with 
dvd+rw-tools,	e.g. OpenBSD/NetBSD users should stick to 
/dev/rcdXc.	
	
	
(*)	
As of 5.14 HP-UX support was classified as
	"initial." Version 5.18 in turn is the one which has
	undergone 
tools/HP/HP quality assurance  testing
	and is delivered on 
http://www.software.hp.com/HP
	software depot
.	
	
Foreword/Disclaimer
Given the absolute lack of initial support from
vendor(s) dvd+rw-tools arose from guesswork. There still is a couple of
fatal failures indicated by vendor-specific error codes (see Technical
Ramblings) and I haven't 
yet figured out the way around them in
kernel. 
User-land utilities on the other hand are
considered matured enough to be deployed in "production
environment."
As of May 2003 I've decided to advise users to
turn to < mailto:cdwrite@other.debian.orgcdwrite@other.debian.org >
on support matters.
 It's an open list, meaning that you don't have
to be 
http://lists.debian.org/cdwrite/subscribed  to post
a problem report. List archives can be found at both 
http://lists.debian.org/cdwrite/subscribe page  and http://www.mail-archive.com/cdwrite@other.debian.org/mail-archive.com .
When submitting report, provide versioning information, exact
command line, 
exact output generated by the program and
complement it with 
dvd+rw-mediainfo output for
resulting recording. Do check couple of last http://lists.debian.org/cdwrite/archived months , as the
issue might have been  discussed 
recently. If you've chosen to
contact me personally and haven't heard back within a week or so, then 
you most likely overlooked something on this page. Please read it more
attentively
keys.txt... Special thanks for hardware donations [in
chronological order]:
http://www.inserve.se/Inserve Technology  
http://www.hp.com/HP  
http://www.linuxfund.org/LinuxFund  
Tutorial
If your burner unit is managed by some
Linux(*) removable media
automounting/autoplaying facility
, such as autofs, supermount,
subfs/submount, magicdev, autorun or similar, take it 
out of its
control! I can't help you with the latter, check your system
documentation (such as google perhaps:-) for specific instructions.
Failure to take your unit out of
Linux(*) automounting/autoplaying facility
control can result in busted recording, a coaster!
 At the
very least you have to make sure your unit is not automounted during
recordings. 
(*) dvd+rw-tools support Solaris volume manager and
IRIX mediad in more gracious manner and it's safe to leave recorder
under 
their control.Remember to consult hcn.htmlHardware Compatibility Notes  for possible
caveats or vendor-specific instructions for your unit. Well, such
reminder belongs at the end of tutorial, but I consider it important
enough to bring it up already here:-)
If you have an IDE unit and run 2.4.x
kernel,
 you most likely want to "route" it through ide-scsi
emulation layer by either:
passing "hdX=ide-scsi"
argument to kernel;
appending following lines to your /etc/modules.conf:
options ide-cd ignore=hdXpre-install sg modprobe ide-scsi
pre-install sr_mod modprobe ide-scsi
pre-install ide-scsi modprobe ide-cd
Keep in mind that once hdXis routed through ide-scsi, you can no longer refer to 
/dev/hdX(*), but to corresponding
/dev/scdN only.
(*) well, except as in hdparm -d [0|1] /dev/hdX. As for DMA settings. Several users of
NEC[-based] units have reported that their systems crash during DVD
recording. The problem appears to be related to DMA settings, at least
switching it off reportedly helps. The problem might be specific to
some IDE chipsets...
If you have an external unit, just get
it working as CD-ROM first. I myself have no personal experience
whatsoever with 
http://www.linux-usb.org/USB  or http://www.linux1394.org/IEEE1394/Firewire  storage devices
of any kind and have to direct you elsewhere for specific instructions.
I however am confident that if you manage to get your drive working
reliably as CD-ROM and CD-R[W]burner, then you won't have any troubles with DVD recording part. USB
connected drives were reported to be working fine since eternity.
Firewire connected drives in turn were reported to fail miserably under
2.4.18. The failure didn't seem to be DVD+RW related as it reportedly
failed burning even CD-R media. Firewire support was substantially
revamped in 2.4.19, and dvd+rw-tools were reported to work with this
and later kernels.
If you're running 2.4.19 or .20, consider
applying 
sg-2.4.19.patchthis drivers/scsi/sg.c patch .
The bug is fixed in .21. I write "consider" and not
"do" for the following reasons:
dvd+rw-tools are not affected by this bug (as they don't use SG_IO
interface), cdrecord [potentially] is;
I however haven't actually experienced the problem with cdrecord
(maybe yet, kernel could have managed to keep buffers neatly aligned
while talking to cdrecord those times I tried), it was VMware that has
failed miserably on me;
As of version 5.6 dvd+rw-tools add support for SG_IO
pass-through or in other words support for Linux 2>=5[.43],
where "generic" SCSI interface can be bypassed by issuing
SG_IO ioctl directly against block device, such as 
/dev/hdX. I wish it worked without need for http://marc.theaimsgroup.com/?t=105410790500005&r=1&w=2interim patches 
ide-cd-2.5.69.patch#1  and ide-cd-2.5.69. patch#2 , (the latter is relative to
2.5.69-75, the 1st problem is addressed in .71, 2nd one - .75-bk3 in
"
http://marc.theaimsgroup.com/?l=linux-kernel&m=105787192005635&w=2last
minute
" prior first 2.6 cut. As for 2.6 in more general sense.
As you can imagine this new interface renders ide-scsi layer
superfluous and "the[ir] official plan™" is to scrap
it. I'm not really fond of the idea, but not for /dev/sg* account. I
mean I [personally] would prefer to keep ide-scsi and use SG_IO
pass-through with 
/dev/scdN, rather than with
/dev/hdX:-)
If you have to make dvd+rw-tools work under Linux
kernel 2.6.8, then upgrade the tool-chain to 5.21.x or later and
manually reward the installed binaries with set-root-uid flag. But the
"supported" recommendation is to just stay away from this
particular kernel version. 
As for 2.6>8, dvd+rw-tools 5.21.x is
requirement.
 Oh! dvd+rw-booktype utility would require set-root-uid
privilege then. Given its semi-official status and the fact that this
utility works only with limited number of units, installation procedure
abstains from installing dvd+rw-booktype set-root-uid, leaving
this security sensitive choice to the end-user.
Download, unpack and compile the tools/?M=Dthe tool-chain . To build the thing do pick the
.tar.gz archive, which contains Makefile as well as .spec file. You
will 
need both C and C++ compilers installed. Separate
source code files found in the 
tools/?M=Ddownload catalog are provided mainly for on-line reference purposes (such as 
tools/growisofs.crevision history :-). 
If your Linux kernel supports multiple ABIs (e.g.
Linux-sparc64 can run even 32-bit Linux-sparc applications, as well as
Linux-x86_64 can execute legacy 32-bit i386 binaries), make sure you
compile for 
native 64-bit ABI (which can normally be done with
'
make TARGET_ARCH=-m64'). The problem here is that 64-bit
kernel has to explicitly convert ioctl structures passed by 32-bit
applications and apparently it does really lousy job when it comes to
CDROM_SEND_PACKET ioctl deployed by dvd+rw-tools.
If you have 1st generation drive (Ricoh
MP5120A and derivatives, see 
http://www.dvdplusrw.org/dvdplusrw.org  for generation
listings), do consider upgrading your firmware (see 
http://ext.ricoh.co.jp/dvd/asia/support/download/mp5120a/Ricoh page for latest version information). Fixed bug descriptions are vague,
but at the very least after upgrade to 1.34 I could no longer reproduce
infrequent "random positioning errors" when 
reading a
file system with a lot of small files. 1.34 adds support for Verbatim
media and 1.37 apparently for Memorex. Version 1.37 also implements a
secret vendor-specific command which 
#booktypereportedly
improves compatibility
 with a number of DVD-ROM drives (more about
this matter in Technical Ramblings). 
Several 2nd generation unit ( http://ext.ricoh.co.jp/dvd/asia/support/download/mp5125a/Ricoh
MP5125A
 and derivatives) users have reported that their systems
lock up the while recording DVD+R, but not DVD+RW. I myself have never
experienced anything similar, but firmware upgrade did help those who
has suffered from this. So that apparently even 2nd generation users
should be considering firmware upgrade. Firmware upgrade is actually
required if you want to burn 4x media in your 2nd generation unit.
Well, it will still burn it at 2.4x, but without firmware upgrade you
should expect deplorable results.
As new media products and brands are being
introduced to the market all the time, it apparently pays off to
periodically check for firmware updates. It's not as
simple as "1st" vs. "2nd generation" units anymore,
so turn to your vendor to be sure. Special note for HP users. HP no
longer posts firmware updates on a web-page. Instead they let some
Windows auto-update gizmo to pick firmware updates among
dvd[1-4]00*.exe files in ftp://ftp.hp.com/pub/information_storage/software/their FTP
directory
, so that readers of this page tend to miss them...
Formatting the DVD+RW media. Virgin
DVD+RW media needs to be initally formatted prior usage. Once again,
only virgin DVD+RW media needs to be formatted. As of version
5.10 growisofs detects blanks and applies initial formatting procedure
automatically. Otherwise same effect can be achieved by passing the
device name, e.g. 
/dev/scd0, as an argument to tools/dvd rw-format.cppdvd+rw-format . To make formatting
process reasonably fast, less than 1 minute, the media gets formatted
only partially, as you can notice by observing a progress indicator
displayed by dvd+rw-format. The final indicator value varies from
firmware to firmware, values as low as 1.6% were observed. But it does
not mean that you can only write that little. The unit keeps formatting
transparently, as you add more data. Oh! Do keep in mind that
DVD capacity of 4.7GB are salesman's GB, i.e. 1000
3 and
not 1024
3.
It was observed that excessive reformats can render
media unusable already after 10-20 reformats. It appears to be a
firmware deficiency, not some common media defect [at least it was
perfectly possible to salvage the media in a unit of different brand],
but I don't recommend [enforced] reformat in either case. Note that
DVD+RW 
re-formatting procedure does not substitute for blanking.If you want to nullify the media, e.g. for privacy reasons, do it
explicitly with '
growisofs -Z /dev/scdN=/dev/zero'. Otherwise just write over
previous recording as it simply wasn't there, no re-formatting is
required.
DVD+R media does not require any formatting
procedure applied and is ready to use out-of-the-box. Apparently, a
reminder that 1st generation units (Ricoh MP5120A and derivatives)
are not capable of burning DVD+R is needed.
Burning with tools/growisofs.cgrowisofs . There is hardly a need for
manual for growisofs. In a nutshell growisofs just passes all command
line arguments to mkisofs and dumps its output directly onto the media.
The first part means that you basically can [well, 
should]
consult 
mkisofs.8.htmlmkisofs manual page  and
accompanying reference documentation (including multi-session related
section[s]) and the second part means that you shouldn't expect an
ISO-image on the standard output (nor make sure you have enough free
temporary storage
:-). Differences from mkisofs command line
are:
you may not use -o option;
you don't have to specify -C option, growisofs will construct one
for you;
there is internal -Z option for initial session recording, this
substitutes for originally suggested 'mkisofs | dd of=/dev/scd0';
Otherwise everything that applies to
[multi-session] mastering with mkisofs applies to growisofs as well. For
example just like with mkisofs you should make a note on which options
you used to master the initial "session" with and stick to
them, e.g.:
growisofs -Z /dev/scd0 
-R -J /some/files
growisofs -M /dev/scd0 
-R -J /more/files
Oh! Do make sure you have at least mkisofs 1.14 on your $PATH (mkisofs 1.14 is part of cdrtools
1.10). If you consider passing 
/same/files as argument, or in
other words consider deploying growisofs for 
incrementalmulti-session backups, then you shall find 
mkisofs-2.01a16-root.diffthis '-old-root' extension  to
mkisofs 
2 mkisofs-2.0-root.diff. 0-2.01 simply indispensable.
The idea and implementation by 
http://home.pages.de/~ohly/#mkisofs-rootPatrick Ohly  is to
"graft" recording sessions as separate directories. Each
backup increment/directory is ment to contain both updated files and
references to previously backed up ones, which facilitates
comparison between increments as well as fine-graded restore.
Number of users asked about opposite to
multi-sessioning: multi-volume support. Being essentially a recording
program growisofs does not support multiple volumes by itself. There're
couple of front-ends I can recommend that arrange for this: 
http://scdbackup.sourceforge.net/main_eng.htmlscdbackup  and
http://www.serice.net/shunt/shunt . But back to
growisofs...
In addition to intuitive -Z interpretation,growisofs [version 3.3 and later] recognizes special form of -Z command
line option which permits burning of arbitrary pre-mastered images. The
"magic" command is:
growisofs -Z /dev/scd0
=image.iso
where image.iso represents an arbitrary
object
 in the file system, such as file, named pipe or device
entry. No, nothing is "growing" here and command name is
counter-intuitive in this particular context. And here is even less
intuitive
:-) If you wish to burn down output generated by an
arbitrary program, you can use:
dumpsomething | growisofs -Z /dev/scd0=
/dev/fd/0Burning DVD±R implies extra limitations:
Needless to say that you have only one shot with -Z
option
:-)Unlike DVD+RW, DVD±R media does have notion of multiple
sessions. 
However! Not all legacy units can "see"
beyond the first one. Few DVD-ROM units are capable of DVD-R
multi-border playback, even fewer support DVD+R multi-sessioning. In
other words  your DVD burner might be the only unit in your vicinity
capable to access data added at different occasions.
Even if your DVD unit does "sense" multiple sessions,
Linux kernel [2.4] sometimes fails to pull that information from the
drive
:-( Till the problem is looked into and resolved you can
work it around by reloading corresponding driver, most likely
'
rmmod sr_mod'.
Linux kernel 2.6 http://marc.theaimsgroup.com/?l=linux-kernel&m=108827602322464&w=2problems
mounting multi-session media
 with last session starting beyond
2.2GB boundary. As fast-acting remedy I can suggest to route your unit
through ide-scsi, the way it was under 2.4. Even though it's declared
unsupported it actually still works in 2.6 (I for one still use it).
If you go for DVD±R multi-sessioning, you have to use
mkisofs from 
ftp://ftp.berlios.de/pub/cdrecord/cdrtools-2.0
or later
 or apply multi.diffthis patch .
And when it comes to DVD+R Double Layer and DVD-RDual Layer recordings,
 growisofs applies yet another limitation,
purely artificial. Taking into consideration Double Layer media prices
growisofs is programmed to 
refuse to perform unappendablerecordings which are less than 1/2 of blank capacity
 and to advice
to use single layer media instead.
DVD-R Dual Layer multi-sessioning is not supported for a reason
discussed on the 
-RW/#nomultisess-RW companion page . Once
again, as of the moment of this writing 
DVD-R Dual Layer
recordings come out unappendable and can not be grown.
And once again, do keep in mind that 4.7GB are
salesman's GB, i.e. 1000
3 and not 10243. If
translated to "real" GB, 
DVD±R[W]capacity is not larger than 4.4GB! It should also be noted that earlier
growisofs versions did not check if there is enough space on media to
accommodate the data set to be burned, meaning that it was your sole
responsibility to make sure "overburn" condition is not
raised. As of version 5.2 growisofs performs the necessary checks
for you and refuses to start recording if "overburn"
condition appears to be unavoidable. This behaviour can be overridden
with 
-overburn command-line option.
If you're satisfied with growisofs, then you
should 
just proceed to #compatthe next chapter and abstain from applying the 
optional 2.4.x kernel patch. If
you haven't stopped reading beyond this line, 
linux-2.4.patchdownload  the patch, apply it, rebuild  the
kernel or modules and re-install (kernel or cdrom.o and sr_mod.o
modules, whichever appropriate), but don't ask 
me http://www.linuxhq.com/patch-howto.htmlhow . As you could
have noticed, patch targets SCSI CD-ROM module. This means that you
have to "route" your IDE unit through ide-scsi to get this one
working. To see it in action, insert formatted DVD+RW media and try to
access it, '
dd if=/dev/scdN count=0'
would do. Then verify that kernel logs "
srN: mmc-3 profile: 1Ah&quot. You should now be
able to '
mkisofs -pad . | dd of=/dev/scdNobs=32k
' or even 'mke2fs -b 2048 /dev/scdN' and observe kernel logging "srN: dirty DVD+RW media.&quot
	
Linux 2.6 DVD+RW kernel support is planned in
line with DVD+MRW kernel support. This [unfortunately] means that
industry has to deliver a DVD+MRW capable unit first. Yes, the last
sentence means that despite all the promises, there are no such units
available on the market yet. As of the 1st of August 2003, Ricoh MP5240A,
Philips DVDRW416K or BenQ DW400A do 
not actually implement
Mt.Rainier/EasyWrite support. It remains to be seen if they will offer
it in form of firmware upgrade. In either case, the [original] project
goal is not only read-write support for DVD+[M]RW capable units
themselves, but even playback of DVD+MRW formatted media in legacy
DVD-ROM units (when defect list will be read and interpreted by OS
software in opposite to Mt.Rainier firmware).
Even though kernel now
permits to build and mount arbitrary file system, there is one thing you
must keep in mind before you just proceed, no matter how
tempting it might appear.
As you might know DVD+RW media can sustain only
around 1000 overwrites. The thing about fully fledged file systems
is that every read [or tight bunch of 'em] is accompanied by
corresponding i-node update or in other words a write! Now, let's say
you lookup the mount point (e.g. ls /mnt/dvd) ten times a day. This
gives you a 100 days lifetime on your mountpoint and therefore media.
Not really much, huh? So do use 
noatime mount option with
DVD+RW media or have it mounted read-only most of the time. However!
Every read-write mount "costs" a super-block update. So that
if you remount the media say 3 times a day, it would last for about a
year [
http://people.mandrakesoft.com/~quintela/supermount/supermount would exhaust the "budget" way sooner]... Defect management
[in firmware, a.k.a. 
http://www.licensing.philips.com/information/mtr/Mt.Rainier ,
or at file system level] would improve the situation, but ideally
file system driver should definitely refrain from modifying the
super-block [marking it dirty] if nothing was actually written since
last mount. Given the development status of 
http://sourceforge.net/projects/linux-udf/Linux UDF  the
chances for seeing the latter implemented [for UDF] are more than just
conceivable. The request is already filed and even possible solution is
being discussed. But why not give UDF a shot already then? By default
UDF write support is unfortunately disabled and you might have to
reconfigure the kernel and rebuild modules. Alternatively [my preferred
option actually] fetch the code at 
http://sourceforge.net/projects/linux-udf/SourceForge  and
build the module separately. Of course you will have to fetch and build
udftools as well. But once it's done just type:
mkudffs --spartable=2 --media-type=cdrw /dev/scd
Nmount -o rw,noatime /dev/scd
N /mnt/cdrom
mkudffs command line options were suggested
by UDF maintainer, Ben Fennema.
Performance optimization. This paragraph
applies only if you've patched the kernel. As some of you might
remember the original recommendation was "do use 
obs=32kfor optimal performance." Well, it was rather naive of me to say
so, as common block device layer 
completely reorganizes the
stream so that '
>/dev/scd0' is as good as '|dd
of=/dev/scd0 obs=32k
'. It should also be noted that dumping to
/dev/scd0 puts quite a pressure on VM subsystem, as the data passes
through block buffer cache. To minimize the pressure and improve
overall system performance bind the cdrom device to a raw device, e.g.
'
raw /dev/raw/raw1 /dev/scd0', growisofs will locate and use
it automatically. obs=32k makes perfect sense with /dev/raw devices,
but dd (as well as most other programs, e.g. tar) won't work as
/dev/raw expects specifically aligned buffer... As 
temporaryworkaround, just to get you going so that you can start figuring things
out, consider 
http://fy.chalmers.se/~appro/LD_*-gallery/index.html?aligned_io#aligned_iothis
"hacklet"
...
Compatibility: caveat lector
This paragraph discusses "DVD-ROM
compatibility," or playability of already recorded media in legacy
units. Blank media compatibility issues, or cases such as failure to
start or fulfill recording because of poor media support by burner
firmware, are beyond the current scope. Turn to your vendor for list of
supported media and/or to the 
mailto:cdwrite@other.debian.orgpublic  to share your
experience.
In order to optimize seek times DVD[-ROM] players
calibrate their mechanics every time the media is loaded by sliding
the optical head some place, picking up the signal and noting the
physical block address underneath the lens. In order for this procedure
to work with re-writable/recordable media, that particular spot has to
be written to [or de-iced in DVD+RW terms]. Some units slide the head to
30mm [radial] to calibrate, some to 35mm. In order to keep such players
"happy," make sure that at least 1GB is written [before you
attempt to mount it in 
DVD-ROM unit].
Other units attempt to seek to lead-out [or vicinity
of it] for calibration purposes. Now the catch is that it's perfectly
possible to produce a DVD+RW disc without lead-out. Most notably media
initially formatted with 
dvd+rw-format [apparently]
doesn't have any lead-out, not to mention that practically whole
surface remains virgin. If you fail to mount/play DVD+RW media, attempt
to
dvd+rw-format -lead-out /dev/scdNwhich relocates the lead-out next to outermost
written sector as well as makes sure there is no virgin surface before
it. Previously written data is 
not affected by this operation.
Then non-finalized DVD+R and Sequential
DVD-R[W] discs don't have lead-out either(*).
If you fail to mount/play DVD+R media and wish to sacrifice the
remaining space for immediate compatibility, just fill the media
up
(**). Alternatively if you master volume in a single take
and don't plan to use it for multi-sessioning
(***), you have
the option to invoke growisofs with 
-dvd-compat option and cut
the real lead-out directly after the first session.
(*) Well, there are lead-outs at the session edges, but
the problem is that "End Physical Sector Number of Data Area"
field in "Control Data Zone" of the lead-in contains address
of the largest media sector, which makes affected DVD[-ROM] players
calibrate at the outermost edge instead of the first session. Actually
I fail to understand why don't they burn the address of last sector of
the first session in the lead-in even on multi-session discs...
(**) But beware the #isofs4gb4GB limit !
If 4GB is already an issue, or if you don't feel like throwing
unrelated data on the media in question, then invoke '
growisofs
-M /dev/scd0=/dev/zero' (supported by 5.6 and later).
Alternative is to re-master the whole volume, naturally with
-dvd-compat option.
(***) E.g. when mastering DVD-Video disc:-) Note that
-dvd-video option [passed to mkisofs] engages
-dvd-compat automatically. Then we have logical format compatibility
issue(s). Probably the very ground for all the controversy around
DVD+RW, rather around DVD+RW media not being playable in a whole range
of players. DVD+RW Alliance was keen to blame on DVD-ROM vendors, even
claiming that they deliberately block playback. But the fact is that
format specifications don't explicitly say that unrecognized format
[designated by "Book Type" field in "Control Data
Zone" of the lead-in] should be treated as 
DVD-ROMand [in my opinion] it was rather naive of them to claim and expect
that the media will be playable in "virtually all players."
This deficiency was recognized by practically all DVD+RW vendors [well,
apparently by "traditional" DVD+RW vendors and not
"latest generation" vendors such as Sony, NEC, TDK...] and a
tools/dvd rw-booktype.cppsecret  vendor-specific command
manipulating this "Book Type" field was implemented. So if
you fail to mount/play DVD+RW media, you 
might have an option to
dvd+rw-booktype -dvd-rom -media /dev/scdNOnce again. Not all vendors support this and you
can't expect this utility to work with all recorders.
It's naturally not possible to manipulate the
"Book Type" field on DVD+R media, that is not after the
lead-in is written [which takes place at the moment the first session
gets closed]. But it might be possible to control how it [lead-in] is
going to be branded by programming the drive 
in advance:
dvd+rw-booktype -dvd-rom -unit+r /dev/scdNMeaning that if you fail to play DVD+R media, you
can attempt to burn another disc with more appropriate unit settings.
For more background information about dvd+rw-booktype, see 
http://www.dvdplusrw.org/Article.asp?aid=42&hl=bitsetting"Compatibility
Bitsettings" article at dvdplusrw.org
.
There [potentially] are other logical
DVD+RW
(*) format incompatibilities, but the "Book
Type" issue discussed above is the only one "officially"
recognized. Well, it's actually understandable as it's the only one
that can be recognized and addressed by a DVD+RW vendor alone.
Recognition of other incompatibilities would require cooperation from
DVD[-ROM] player vendors and that's something they
apparently are not willing to show referring to the fact that DVD+RW
format is not approved [and apparently never will be] by 
http://www.dvdforum.org/DVD Forum (**).
(*) Finalized DVD+R media branded with
DVD-ROM "Book Type" is virtually identical to
DVD-ROM. (**) To which I say "so what?" DVD Forum is an
alliance of manufacturers just like DVD+RW Alliance is. It [or any
other party for that matter] has no authority to deny a technology
development initiative.
Finally there is a physical incompatibility issue.
They claim that there are optical pick-ups out there not being capable
to decode the track because of low reflectivity of DVD+RW media
surface. I write "they claim," because in the lack of
cooperation from 
DVD[-ROM] vendors it's not possible to
distinguish physical from logical format incompatibility, which I find
important to tell apart in order to make sure at least logical format
incompatibility issues don't persist over time. It might be as trivial
as following. As you surely know [already], DVD+RW has same
reflectivity as dual-layer 
DVD-ROM. Now the catch is that
the linear pit density in turn is same as of single-layer one. Meaning
that if player makes assumptions about linear pit density based on
reflectivity, then it won't be able to trace the track... But either
way, there is very little you can do about this one, but to try another
player...
Technical Ramblings
As for multi-session ISO9660 [DVD]
recordings!
 Unfortunately, Linux ISOFS implementation has certain
deficiency which limits interoperability of such recordings. In order
to understand it, have a look at sample ISO9660 layout to the right...
Now, the problem is that isofs i-nodes
(*) are 32 bits wide
(on a 32-bit Linux) and represent offsets of corresponding directory
entries (light-greens), byte offsets from the beginning of media. This
means that no directory (green areas) may cross 4GB boundary without
being effectively corrupted
:-( It should be noted that in
reality it's a bit better than it looks on the picture, as mkisofs
collects all the directories in the beginning of any particular session
(there normally are no blues between greens). The 
first session
is therefore never subject to i-node wrap-around, but not the
subsequent ones! Once again, filesthemselves may reside beyond the 
4GBboundary, but not 
the directories, in
particular not in further sessions. Having noted that directory entries
are actually 
specified to start at even offsets, I figured that
it's 
isofs-2.4.patchperfectly possible  to
"stretch" the limit to 8GB. But in order to 
assure the
maximum interoperability, you should 
not let any session
start past 4GB minus space required for directory
structures
, e.g. if the last session is to fill the media up, it
has to be >400MB. As of version 5.3 growisofs refuses to 
appenda new session beyond 4GB-40MB limit
(**), where 40MB is
pretty much arbitrary chosen large value, large for directory catalogs
that is. Yet it doesn't actually 
guarantee that you can't suffer
from i-node wrap-around. Interim 
isofs-2.4.patchfs/isofs
kernel patch
 was addressed to those who have actually ran into the
problem and have to salvage the data. Even though permanent solution
for this problem appears in Linux kernel 2.6.8 (thanks to Paul Serice
effort), growisofs keeps checking for this 4GB limit in order to ensure
broader compatibility of final recordings.
(*) i-node is a number uniquely identifying a single
file in a file system
(**) well, as DVD+R Double Layer support was introduced
in 5.20, 
-use-the-force-luke=4gms option was added to override
this behaviour (naturally recommended for Linux kernel 2.6>=8 users and
kernel developers only;-)
Why media reload is performed after every
recording with growisofs?
 Well, it's performed only if you didn't
patch the kernel:-) But no, I'm not insisting on patching the kernel!
All I'm saying is that in the lack of kernel support, media reload is
performed for the following reason. In order to optimize file access
kernel maintains so called block cache, so that repetitive requests for
same data are met directly from memory and don't result in multiple
physical I/O. Now the catch is that block cache layer remains totally
unaware of growisofs activities, growisofs 
bypasses the block
cache. This means that block cache inevitably becomes out of sync,
which in turn might appear to you as corrupted data. Media reload is
performed to flush/resync the block cache.
What does [kernel] "DVD+RW support"
really mean? Even though DVD+RW has no notion of [multiple]
sessions, to ensure compatibility with DVD-ROM it's essential to issue
"CLOSE TRACK/SESSION (5Bh)" 
http://www.t10.org/scsi-3.htmMMC  command to
terminate/suspend background formatting (if any in progress) whenever
you intend to eject the media or simply stop writing and want better
read performance (e.g. remount file system read-only). This is what the
patch is basically about: noting when/if media was written to and
"finalizing" at unlock door.
Secondly, whenever you employ fully fledged
file system, I/O requests get inevitably fragmented.
"Fragmented" means following. Even though you can address the
data with 2KB granularity, it [data] is physically laid out in 32KB
chunks. This in turn means that for example writing of 2KB block
involves reading of 32KB chunk, replacing corresponding 2KB and writing
down of modified 32KB chunk. "Fragmented requests" are those
that are smaller than 32KB or/and cross the modulus 32KB boundaries. In
order to optimize the process certain caching algorithm is implemented
in unit's firmware. Obviously it can't adequately meet all possible
situations. And so in such unfortunate situations the drive apparently
stops processing I/O requests returning "COMMAND SEQUENCE ERROR
(2Ch)" ASC. This is the second essential of "DVD+RW
support," namely injecting of "SYNCHRONIZE CACHE (35h)"
MMC command in reply to the error condition in question. The command
flushes the cached buffers which makes it possible to resume the data
flow.
Unfortunately the above paragraph doesn't
seem to apply to the 1st generation drives, Ricoh MP5120A and
derivatives
:-( "SYNCHRONIZE CACHE (35h)" doesn't
seem to be sufficient and the unit keeps replying with "COMMAND
SEQUENCE ERROR (2Ch)" going into end-less loop. This makes it
impossible to deploy arbitrary file system. I'm open for
suggestions... Meanwhile the I've chosen to simply suspend I/O till the
media is unmounted. Even 2nd gen unit were reported to exhibit similar
[but not the same] behaviour under apparently extremely rare
circumstances. At least I failed to reproduce the problem... The problem
reportedly disappears with firmware upgrade...
Then some [most?] of post-2nd gen units, from
most vendors, seem to not bother about complying with
DVD+RW specification, "true random write with 2KB
granularity" part in particular. Instead they apparently expect
host to apply procedure pretty much equivalent to 
DVD-RWRestricted Overwrite. To be more specific host seems to be expected to
coalesce 2KB requests and perform aligned writes at native DVD ECC
blocksize, which is 32KB. Formally this should not be required, but
it's the reality of marketplace:-(
This one really beats me. Sometimes the unit
simply stops writing signaling a vendor specific positioning error,
03h/15h/82h to be specific. Especially if the media is newly formatted.
Couple of work theories. One is that block buffer cache reorders
requests so that they are not sequential anymore, "FLUSH
CACHE" might do the trick. Another one is that under
"underrun" condition background formatting kicks off and has
to be explicitly stopped. "Underrun" is in quotes because
the unit is supposed to handle temporary data stream outages
gracefully. If you run into this (you most likely will), try to
complement growisofs command line with [undocumented]
-poor-man option (which has to be first in the command line).
This option eliminates request reorders and minimizes possibility for
"underrun" condition (by releasing the pressure off VM
subsystem).
The original idea was to implement DVD+RW support in
drivers/cdrom/cdrom.c. Unfortunately SCSI layer maintains private
"writeable" flag controlling the ability to issue WRITE
commands. The flag is impossible to reach for from the Unified CD-ROM
driver. But why am I talking about SCSI when there are only IDE units
out there (at least for the time being)? Well, as you most likely want
to occasionally burn even CD-R[W] with cdrecord you want it to go
through ide-scsi emulation layer anyway. So I figured that SCSI CD-ROM
driver is the one to aim for even for DVD+RW.
Unfortunately it was not possible to implement it
completely in sr_mod.o
:-( Minor drivers/cdrom/cdrom.c
modification was required to sense the media before decision about
whether or not to permit write open. That's because DVD+RW drives are
morphing their behaviour after currently mounted media and it's
essential to identify newly inserted media.
Special comment about "what a dirty
hack!!!" To my great surprise it turned out that time-out value you
pass in cdrom_generic_command is simply ignored and time-out is set to
pre-compiled value of 30 seconds. Unfortunately it's way too low for
formatting purposes and I had to do something about it. Alternative to
"the dirty hack" was to add another argument to sr_do_ioctl
and modify all the calls to it... I've chosen to take over those 31
unused bits from the "quiet" argument instead of modifying
all the calls (too boring).
But even if time-out value passed down to kernel
(with 
either CDROM_SEND_PACKET or SG_IO ioctl) is taken into
consideration, it's apparently not interpreted as user-land code
expects it to. As I figured... There is no documentation on
CDROM_SEND_PACKET, but following the common sense most programmers
(including myself:-) expect it to be interpreted in at least
platform-independent manner, such as milliseconds maybe? SG_IO timeout
in turn is 
http://www.torque.net/sg/p/sg_v3_ho.html#AEN215documented to be measured in milliseconds... Neither of this holds true! Kernel
treats these values as "jiffies," which is a
platform-dependent value representing time elapsed between timer
interrupts. But if we attempt to send down "jiffies," it
might turn out wrong too [at least for the moment of this writing]. The
catch is that [IA-32] kernel developers figured it's cool to shorten
"jiffy," but didn't care to provide user-land with actual
value (well, not of actual interest, too much legacy code to deal with)
nor scsi_ioctl-2.5.69.patchscale  timeouts
accordingly in respect to the legacy value of 10ms.
There is another kernel "deficiency" I ran
into while working on the (original version of) dvd+rw-format utility.
The drive provides background formatting progress status, but
unfortunately it's impossible to access it. That's because progress
counter is returned [in reply to "TEST UNIT READY"] as
"NO SENSE/LOGICAL UNIT NOT READY/FORMAT IN PROGRESS" sense
bytes but with "GOOD" status. Apparently any sense data with
"GOOD" status is discarded by the common SCSI layer.
It was pointed out to me that DVD+RW units work with
Acard 
http://www.acard.com/eng/product/scside.htmlSCSI to
IDE bridges
.
What does http://www.cdfreaks.com/article/113plus  in DVD+RW/+R
stand for?
 Originally this paragraph started as following:
The key feature of DVD+RW/+R media is
high [spatial] frequency wobbled [pre-]groove with addressing
information modulated into it. This makes it possible to resume
interrupted [or deliberately suspended] burning process with accuracy
high enough for DVD[-ROM] player not to "notice" anything at
playback time. Recovery from buffer underrun condition in DVD-RW/-R
case in turn is way less accurate procedure, and the problem is that
the provided accuracy is very much what average player can tolerate.
Now given that both provided and tolerated inaccuracies are
proportional to respectively writing and reading velocities there
basically no guarantee that DVD-RW/-R recording that suffered from
buffer underrun will be 
universally playable.Well, it turned out that I was wrong about one
thing. 
 I failed to recognize that DVD-R[W]
groove also provides for 
adequately accurate recovery from
buffer underrun condition/lossless linking. Not as accurate as DVD+RW,
but accurate enough for splices to be playable in virtually any
DVD-ROM/-Video unit. Yet! When it comes to DVD-R[W] recording
specificaton apparently insists that you choose between
buffer underrun protection and
full DVD-ROM/-Video compatibility.
The specification asserts that the latter is
achieved only in Disc-at-once recording mode and only if data-stream
was maintained uninterrupted throughout whole recording. Once again.
Even though most vendors implement lossless linking in DAO
mode
(*), full DVD-ROM/-Video compatibility is
guaranteed only if recording didn't suffer from buffer underruns. The
problem is that "offended" sectors are denoted with certain
linking chunk appearing as degraded 
user data, few bytes, which
are supposed to be "corrected away" by ECC
procedure
(**). DVD+ splices are in turn only few bits large
and are "accounted" to sync patterns, 
not to user data
area
. So that even if suffered from buffer underrun, DVD+ sector is
logically indistiguishable from DVD-ROM. Which is why it's commonly
referred to that DVD+RW/+R combine DVD-ROM/-Video compatibility with
[unconditional] buffer underrun protection.
As already mentioned, DVD+ groove has
"addressing information modulated into it," ADIP (ADress In
Pre-groove). This gives you an advantage of writing DVD+RW in truly
arbitrary order, even to virgin surface and practically instantly
(after ~40 seconds long initial format procedure). In addition, DVD+RW
can be conveniently written to with 2KB granularity
(***).
DVD-RW in turn can only be 
overwritten in arbitrary order.
Meaning that it either has to be completely formatted first (it takes
an hour to format 1x media), or initially written to in a sequential
manner. And it should also be noted that block overwrite is
never an option if DVD-RW media was recorded in [compatible]
Disc-at-once or even Incremental mode, only whole disc blanking is.
Unlike DVD-R[W], DVD+R[W] recordings can be
suspended at any time without any side effects. Consider following
scenario. You have a lot of data coming in [at lower rate], which is to
be recorded into one file. Meanwhile it turns out that you have to
retrieve previously recorded data. This would naturally require
suspention of recording. Most notably in DVD-R [and naturally DVD-RW
Sequential] case it would result in a hole in the file being recorded.
So called linking area, most commonly 32KB gap, has to be introduced.
So that you either have to wait till the file is complete or figure out
how to deal with holey files. Thanks to ADIP, DVD+R recording is
resumed from the very point it was suspended at. In DVD-RW Restricted
Overwrite case no gaps are introduced, but if the media was formatted
only minimally, suspension/resuming procedure has to be applied and it
takes ~40 seconds to perform one. In DVD+RW case, suspension/resuming
is instant regardless media state.
What does all of the above mean in practice? Well, I
was actually hoping that readers would [be able to] figure it out by
themselves. Apparently a couple of "guiding" words are
needed... It means that it's trivial to employ DVD+RW for housing of
live and arbitrary file system, no special modifications to target file
system driver are required... Real-time VBR (Variable Bit Rate) Video
recordings are children's game...
Sometimes DVD+RW/+R recording strategy is referred
to as packet writing. I myself am reluctant to call it so (or
TAO/SAO/DAO) for the following reason. Despite the fact that DVD-R[W]
provides for lossless linking (within a packet/extent only),
packets/extents are still denoted with certain linking information
which distinguishes it (recording mode in question) from e.g.
Disc-at-once. Now the point is that written DVD+RW/+R media, rather its
Data Zone, does not contain 
any linking information and is
logically indistinguishable from one written in DVD-R[W] Disc-at-once
mode (or DVD-ROM for that matter).
It's maintained that signal from DVD+ groove (the
one essential for recording, not reading) is much stronger, which makes
it quite resistant to dust, scratches, etc. 
Now we can also discuss differences between
Double/Dual Layer implementations. DVD+R Double Layer permits for
arbitrary layer break positioning yet maintaining 
contiguous logical
block addressing
. In other words address of the block following the
break is always address of the block preceding one plus 1, even for
arbitrarily positioned break. 
DVD-R Dual Layer on the
other hand implies unconditionally disjoint logical block addressing
[for arbitrarily positioned layer break that is]. This is because block
addresses as recorded by unit are pre-defined by 
DVD-dashgroove structure. In practice it means that file system layout has to
effectively have a hole, which "covers" twice the space between chosen
layer break position and outermost edge of the recordable area. And in
even more practical terms this means that mastering programs have to be
explicitly adapted for 
DVD-R layer break positioning.
Unlike DVD+plus that is.
(*) According to ftp://ftp.avc-pioneer.com/Mtfuji_6/Spec/Mt. Fuji draft buffer underrun protection is not even an option in DVD-R DAO: "If a
buffer under-run occurs, the logical unit 
shall stop
writing immediately and the logical unit 
shall start
writing of Lead-out." Protection is defined in Incremental Sequential
mode and DVD-RW context. By the way, note that this draft also
discusses DVD+RW. You should be aware that they refer to abandoned
version which has very little to do with DVD+RW/+R implementation being
discussed here.
(**) ECC redundancy does permit for more degradation,
more that this linking chunk that is, so that it hadly affects the
playability.
(***) DVD "native" block size is 32KB, and 2KB
granularity is nothing but a trick, but you're excused from playing it,
i.e. reading 32KB, replacing corresponding 2KB and writing 32KB
back.
