CD-Writing HOWTO

CD-Writing HOWTO
Winfried Tr�mper <[email protected]>
v2.4.1, 16 December 1997

This document deals with the process of writing CDs under Linux.

1. Introduction

My first experience with CD Writers was guided by the "Linux CD Writer
mini-HOWTO" by Matt Cutts <[email protected]>. Thanks Matt!

Although my intention was only to upgrade his document, I rewrote it
from the scratch after I realized how much changed since 1994.

1.1. Disclaimer

I (Winfried Truemper) DISCLAIM ALL WARRANTIES WITH REGARD TO THIS
DOCUMENT, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS FOR A CERTAIN PURPOSE; IN NO EVENT SHALL I BE LIABLE FOR ANY
SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF
CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
CONNECTION WITH THE USE OF THIS DOCUMENT. Short: read and use at your
own risk.

1.2. Suggested readings

The CD-R FAQ <http://www.cd-info.com/CDIC/Technology/CD-R/FAQ.html> is
a general FAQ about compact-disk recordables (CD-R).

The Linux CD-ROM HOWTO explains everything one should know about CD-
ROM drives under Linux. As a supplement, you may want to take a look
at the Linux SCSI HOWTO and the Linux Kernel HOWTO.

1.3. Terminology ... lasers at maximum ... fire!

CD-ROM stands for Compact Disc Read Only Memory, a storage medium
utilizing an optical laser to sense microscopic pits on a silver
shimmering disk. (The silver shimmering comes from an aluminized layer
which is the carrier.) The pits represent the bits of the information
(in some way) and are so petite that some billions of them fit on the
disc. Thus a CD is a mass-storage medium.

The Term CD-R is a short form of CD-ROM recordable and refers to a CD
that doesn't have those "microscopic pits" on it's surface... thus
it's empty.

Instead of the aluminium layer (silver) a CD-R has a special film
(colored) into which "microscopic pits" can be burned in. This is done
by giving the laser which normally only senses the pits a little bit
more power so he burns the pits. This action can only be taken once on
a CD-R.

You can leave out some areas for later writing, though, creating a so
called multi-session CD.

This mini-HOWTO deals with the task of writing a CD-R. Welcome on
board, captain.

1.4. Supported CD-Writers

The detailed list of models which have been reported (not) to work
successfully is available from

<http://www.shop.de/cgi-bin/winni/lsc.pl>

The list will be included in future versions of this mini-HOWTO. Most
SCSI cd-writers are supported and the newest version of cdrecord even
supports ATAPI cd-writers.

If your hardware isn't supported you can still use Linux to create an
image of the later CD but then you have to use DOS-Software to write
the image to the CD-R. You may wish to do so because most DOS-software
cannot deal with long filenames available in Linux.

In this case you can skip all hardware-related sections (those about
generic SCSI devices and cdwrite/cdrecord).

1.5. Supported "features"

Currently the software for burning CDs under Linux does support the
following main features:

Feature cdwrite-2.1 cdrecord-1.7
--------------------------------------------
ATAPI support no yes
Multisession only partial yes

RockRidge yes (mkisofs) yes (mkisofs)
El Torito yes (mkisofs) yes (mkisofs)
HFS yes (mkhybrid) yes (mkhybrid)
Joliet yes (mkhybrid) yes (mkhybrid)

RockRidge is an extension to allow longer filenames and a deeper
directory hierarchy. El Torito can be used to produce bootable CDs.
Please see the accompanied documentation for further details upon this
special features. HFS lets a macintosh read the CD-ROM as if it were
an HFS volume. Joliet brings long filenames (among other things) to
some variants of Windows (95, NT).

Section 2.8 lists the availability of the mentioned software.

1.6. Mailinglists

If you want to join the development team (with the intention to
actively _help_ them), send e-mail to

[email protected]

and put the word subscribe in body of the message.

1.7. Availability

The newest version of this document is always available from

<http://www.shop.de/~winni/linux/cdr/>

2. Prepare your Linux-box for writing CD-ROMs

Before November 1997, the software for Linux didn't support ATAPI cd-
writers. As a result, the current release of the HOWTO concentrates on
dealing with SCSI devices.

The good news is, that dealing with ATAPI devices is much easier and
you can still use this HOWTO if you just forget about the "generic
SCSI devices". To find out how to address ATAPI devices you can issue
the command cdrecord -scanbus.

Future versions of this HOWTO will contain more details of dealing
with ATAPI cd-writers.

2.1. Set up the hardware

Shut down your computer, switch it off and hook CD writer to the SCSI-
bus.

Make sure the SCSI-bus is properly terminated and choose a free SCSI-
ID for the writer. Look at the Linux SCSI-HOWTO if you're not sure. If
you're completly clueless, ask an expert.

Switch the power on again and check the messages that the BIOS of the
SCSI-controller prints immediatly after switching the power on. If it
doesn't recognize you writer, go back to step (b). You should see a
message like

missing picture; has anyone a screenshot of it?

2.2. A note on writing CDs under Linux

In contrast to other rumors, the Linux-kernel does _not_ require a
patch in order to write to CDs. Although the file drivers/scsi/scsi.c
from the kernel-sources contains the lines

case TYPE_WORM:
case TYPE_ROM:
SDpnt->writeable = 0;

this does only mean that that CDs and WORMs are not writeable through
the standard-devices /dev/sda-/dev/sdh - which is ok.

Instead of using these devices the writing of CDs is done through the
so called generic SCSI-devices which permit nearly everything - even
writing to CDs.

2.3. Create the generic devices

The Linux SCSI-HOWTO says about generic SCSI-devices:

The Generic SCSI device driver provides an interface for
sending SCSI commands to all SCSI devices - disks, tapes,
CDROMs, media changer robots, etc.

Speaking of the generic devices as interfaces means that they provide
an alternate way of accessing SCSI-hardware than through the standard
devices.

This alternate way is required because the standard devices are
designed to read data block-wise from a disk, tape or cd-rom. Compared
to this, driving a cd-writer (or a scanner) is more exotic, e.g
commands to position the laser must be transmitted. To have a clean
(and therefore fast) implementation of standard-devices, all such
exotic actions must be done through the generic SCSI devices.

As everthing can be done to SCSI-hardware through the generic devices
they are not fixed to a certain purpose - therefore the name generic.

Goto the /dev-directory and check for generic SCSI devices; ls-command
should show sga-sgh:

bash> cd /dev
bash> ls -l sg*
crw------- 1 root sys 21, 0 Jan 1 1970 sga
crw------- 1 root sys 21, 1 Jan 1 1970 sgb
crw------- 1 root sys 21, 2 Jan 1 1970 sgc
crw------- 1 root sys 21, 3 Jan 1 1970 sgd
crw------- 1 root sys 21, 4 Jan 1 1970 sge
crw------- 1 root sys 21, 5 Jan 1 1970 sgf
crw------- 1 root sys 21, 6 Jan 1 1970 sgg
crw------- 1 root sys 21, 7 Jan 1 1970 sgh

If you don't have those device-files then create them by using the
/dev/MAKEDEV-script:

bash> cd /dev/
bash> ./MAKEDEV sg

Now the device-files should show up.

2.4. Enable usage of the generic SCSI and loopback devices

The Linux-kernel needs a module that lends it the ability to deal with
generic SCSI devices. If your running kernel has this feature, it
should be listed in the pseudo-file /proc/devices:

bash> cat /proc/devices
Character devices:
1 mem
2 pty
3 ttyp
4 ttyp
5 cua
7 vcs
21 sg <----- stands for "SCSI Generic device"

30 socksys

Block devices:
2 fd
7 loop <----- we even can use the loop-devices
8 sd
11 sr <----- stands for "SCSI cd-Rom"

Maybe you have to issue the commands insmod sg, insmod loop or insmod
sr_mod to load the modules into the kernel. Check again after you've
tried this.

If one of them doesn't succeed, you must re-configure your kernel and
re-compile it.

bash> cd /usr/src/linux
bash> make config

[..]
*
* Additional Block Devices
*
Loopback device support (CONFIG_BLK_DEV_LOOP) [M/n/y/?] M

[..]
*
* SCSI support
*
SCSI support (CONFIG_SCSI) [Y/m/n/?] Y
*
* SCSI support type (disk, tape, CD-ROM)
*
SCSI disk support (CONFIG_BLK_DEV_SD) [Y/m/n/?] Y
SCSI tape support (CONFIG_CHR_DEV_ST) [M/n/y/?] M
SCSI CD-ROM support (CONFIG_BLK_DEV_SR) [M/n/y/?] M
SCSI generic support (CONFIG_CHR_DEV_SG) [M/n/y/?] M

[..]
ISO9660 cdrom filesystem (CONFIG_ISO9660_FS) [Y/m/n/?] M

Please note that I omitted the not-so-important questions.

2.5. Build and install the kernel

If you have questions regarding to this the Linux Kernel-HOWTO is the
suggested reading. Furthermore your Linux-distribution should ship
with some documentation about this issue.

Hint: while re-compiling, you can continue with steps 2.7-2.9

2.6. Reboot the computer for the changes to take effect.

Don't panic if the Linux-kernel prints the messages faster than you
can read them, at least the initialization of SCSI-devices can be re-
displayed with the command dmesg:

scsi0 : NCR53c{7,8}xx (rel 17)
scsi : 1 host.
scsi0 : target 0 accepting period 100ns offset 8 10.00MHz
scsi0 : setting target 0 to period 100ns offset 8 10.00MHz

Vendor: FUJITSU Model: M1606S-512 Rev: 6226
Type: Direct-Access ANSI SCSI
Detected scsi disk sda at scsi0, channel 0, id 0, lun 0

Vendor: NEC Model: CD-ROM DRIVE:84 Rev: 1.0a
Type: CD-ROM ANSI SCSI
Detected scsi CD-ROM sr0 at scsi0, channel 0, id 4, lun 0

scsi : detected 1 SCSI disk total.
SCSI device sda: hdwr sector= 512 bytes. Sectors= 2131992

Shown above is only that part of the initialization-messages that
report the detection of physically present SCSI-devices.

2.7. Create loopback devices

Goto the /dev-directory and check for loopback devices. It's not
critical if you don't have those devices, but it's convenient if you
do (see 3.5). If you already have them, the ls-command should show
loop0-loop7:

bash> cd /dev
bash> ls -l loop*
brw-rw---- 1 root disk 7, 0 Sep 23 17:15 loop0
brw-rw---- 1 root disk 7, 1 Sep 23 17:15 loop1
brw-rw---- 1 root disk 7, 2 Sep 23 17:15 loop2
brw-rw---- 1 root disk 7, 3 Sep 23 17:15 loop3
brw-rw---- 1 root disk 7, 4 Sep 23 17:15 loop4
brw-rw---- 1 root disk 7, 5 Sep 23 17:15 loop5
brw-rw---- 1 root disk 7, 6 Sep 23 17:15 loop6
brw-rw---- 1 root disk 7, 7 Sep 23 17:15 loop7

If you don't have those device-files, then create them by using the
/dev/MAKEDEV-script:

bash> cd /dev/
bash> ./MAKEDEV loop

The last command only succeeds if you have the loop-module in your
kernel (see 2.4 for handling of modules). If insmod loop does not
help, you must wait until the new kernel is properly installed (see
2.5).

2.8. Get the user-software for burning CDs

2.8.1. Command line utilities

The following package is required to generate prototypes of CD-Rs:

<ftp://tsx-11.mit.edu/pub/linux/packages/mkisofs/> (mkisofs)

<ftp://ftp.ge.ucl.ac.uk/pub/mkhfs> (mkhybrid)

Depending on the model of your cd-writer (see 1.3), one of the
following software for writing prototypes to CD-Rs is required:

<ftp://ftp.fokus.gmd.de/pub/unix/cdrecord/> (cdrecord)

<ftp://sunsite.unc.edu/pub/Linux/utils/disk-management/>
(cdwrite)

Please use the nearest mirrors of these ftp-Servers or get them from a
CD.

Be absolutly sure you have version 2.0 of cdwrite or newer. No older
version and especially no beta-versions will work properly! Don't
trust the man-page of (old) mkisofs which states you need version 1.5
of cdwrite.

For information about ports of cdwrite to Irix and AIX visit the URL

<http://lidar.ssec.wisc.edu/~forrest/>

If you are using a kernel prior to release 2.0.31, you may want to
patch mkisofs to get along a bug in the Linux filesystem code. The
Debian-Distribution ships a patch for release 1.05 of mkisofs (1.11
should work, too) of mkisofs that adds the option '-K' to it (see
3.4); it's available from

<ftp://ftp.debian.org/pub/debian/bo/source/otherosfs/mkisofs_1.11-1.diff.gz>

This patch is only necassary if you want to mount the CD-image via the
loopback-device (see 3.5.).

2.8.2. A graphical user interface (optional)

X-CD-Roast is full X based CD-Writer-Program, and it is the successor
of the cdwtools-0.93. It's available from

<http://www.fh-
muenchen.de/home/ze/rz/services/projects/xcdroast/e_overview.html>

Currently X-CD-Roast is based on a patched version of cdwrite-2.0 and
thus comes with exactly the same features (see 1.4). Future versions
may be based on the alternate cdrecord software.

3. Emperor nero about burning his own classic-CDs [AD64. He misunder�
stood it completly.] If to smoke you turn I shall not cease to fiddle
while you burn."

Usally the writing of a CD under Linux is done in 2 steps:

� packaging the desired software into one big file using the
mkisofs/mkhybrid-utility

� writing the big file to the CD-R with cdwrite or cdrecord

It is also possible to combine the 2 steps into one via a pipe but
that is discouraged because it's not reliable. See below.

3.1. Determine which generic scsi device the writer is attached to

Please note: the current scheme for naming scsi devices under Linux is
unnecessary complicated and not reliable enough. The fact that I
describe it in greater detail here should not be misinterpreted as a
confirmation of this scheme. People with an ATAPI cd-writer can try
"cdrecord -scanbus" to detect the right device and skip the rest of
this section.

After following all steps of the second chapter your system should be
able to deal with the task of writing CDs. This section can be used as
a proof that everything works as intended.

Issue the command dmesg. It should report the messages of the Linux-
kernel including those printed while booting (limitation: only the
last 200) and contain some information about the CD-Writer connected
to the SCSI-bus.

Simple example:

Vendor: YAMAHA Model: CDR100 Rev: 1.11
Type: WORM ANSI SCSI revision: 02
Detected scsi CD-ROM sr1 at scsi0, channel 0, id 3, lun 0

This machine has 4 SCSI-devices connected to it (you can't see it so I
tell you), with SCSI-id's from 0 to 3. The writer is the 4th
physically present SCSI-device and therefore connected to /dev/sgd
(the fourth generic SCSI-device when counting is started with the
letter a). In this case the command
cdwrite --eject --device /dev/sgd

opens the tray and is a test if everything is set up properly. A more
complicated example:

scsi0 : AdvanSys SCSI 1.5: ISA (240 CDB)
scsi1 : Adaptec 1542
scsi : 2 hosts.

Vendor: HP Model: C4324/C4325 Rev: 1.20
Type: CD-ROM ANSI SCSI revision: 02
Detected scsi CD-ROM sr0 at scsi0, channel 0, id 2, lun 0

Vendor: IBM Model: DPES-31080 Rev: S31Q
Type: Direct-Access ANSI SCSI revision: 02
Detected scsi disk sda at scsi1, channel 0, id 0, lun 0

scsi : detected 1 SCSI cdrom 1 SCSI disk total.
SCSI device sda: hdwr sector= 512 bytes.

In this example two SCSI-controllers host 1 SCSI-device each. What a
waste (they are able to host up to 7 devices each). It's not my setup
so stop asking if I have too much money ... Anyway for the purpose of
being an overlookable example this setup is just excellent. :-)

In the above example the CD-Writer has SCSI-id 2 but it is associated
with the first generic SCSI-device /dev/sga because it's the first
physically present SCSI-device which Linux has detected. Hopefully
this shows clearly that the SCSI-id of a device has nothing to do with
the associated generic device.

Two questions are left: what happens if you catch the wrong device?
If you neither specify the option "--<MANUFACTURER>" nor write any
data to the device, usally a warning message is printed and nothing
bad happens:

bash> cdwrite --eject --device /dev/sgb

Unknown CD-Writer; if this model is compatible with any
supported type, please use the appropriate command line
flag.

Manufacturer: IBM
Model: DPES-31080
Revision: S31Q

In this case the device /dev/sbg is a SCSI harddisk (from IBM).

If you write data to the wrong device, you overwrite the original
content of it and probably irrecoverable damage your system. Be
careful, it already happened to me by accident.

3.2. Collect software

Usally this takes up longer than one expects. Remember that missing
files cannot be added once the CD is written. :-)

Also keep in mind that a certain amount of the free space of a CD is
used for storing the information of the iso9660-filesystem (usally a
few MB).

3.3. Storing data on a CD.

The term iso9660 refers to the format in which data is organised on
the CD. To be more precise: it's the filesystem on the CD.

Of course the appearance of files stored in this format is unified by
the Linux-kernel as for every other filesystem, too. So if you mount
a CD into the directory tree, you cannot distinguish it's files from
other files (The mechanism used to unify the appearance of files is
called virtual filesystem, short VFS.)

The features of the iso9660 filesystem are not so rich compared to
those of the extended-2 filesystem which is normally used under Linux.
On the other hand, the CD is only writable once and some features make
no sense anyway. The limitations of the iso9660-filesystem are:

� only 8 levels of sub-directories allowed (counted from the top-
level directory of the CD) use RockRidge Extensions to enlarge this
number

� maximum length for filenames: 32 characters

� 650 MB capacity

3.4. Create an iso9660 filesystem

Before any storage medium (e.g. floppy disk, harddisk or CD) can be
used, it must get a filesystem (DOS speak: get formatted). This
filesystem is responsible for organising and incorporating the files
that should be stored on the medium.

Well, a writable CD is only writable once so if we would write an
empty filesystem to it, it would get formated - but remain completely
empty forever. :-)

So what we need is a tool that creates the filesystem while copying
the files to the CD. This tool is called mkisofs. A sample usage
looks as follows:

mkisofs -r -o cd_image private_collection/
`---------' `-----------------'
| |
write output to take directory as input

The option '-r' sets the permissions of all files to be public
readable on the CD and enables Rock Ridge extensions. That is what one
usually wants and use of this option is recommended until you know
what you're doing (hint: without '-r' the mount-point gets the
permissions of private_collection!).

If you are running a Linux kernel prior to 2.0.31, you should add the
option '-K' to work around a bug in the filesystem code. You need the
patched version of mkisofs for it. This option is equivalent to the
option '-P' of cdwrite. Please see the manual-page of mkisofs for
details. Users of a more recent version of Linux have to worry about
neither.

mkisofs will try to map all filenames to the 8.3-format used by DOS to
ensure highest possible compatibility. In case of naming conflicts
(different files have the same 8.3-name), numbers are used in the
filenames and information about the chosen filename is printed via
STDERR (usually the screen).

DON'T PANIC:

Under Linux you will never see these 8.3 filenames because
Linux makes use of the Rock Ridge extensions which contain
the original file-information (permissions, filename, etc.).

Now you may wonder why the output of mkisofs is not directly sent to
the writer-device. This has two reasons:

� mkisofs knows nothing about driving CD-writers (see section 2.3.)

� It would not be reliable (see section 4.)

Because the timing of the CD-writer is a critical point, we don't feed
it directly from mkisofs (remember Linux is not a real-time operating
system and tasks can be timed badly). Instead it is recommended to
store the output of mkisofs in a separate file on the harddisk. This
file is then an 1:1-image of the later CD and is actually written to
the CD with the tool cdwrite in a second step.

The 1:1-image gets stored in a huge file so you need the same amount
of free disk space that your collected software already eats up.
That's a drawback.

One could think of creating an extra partition for that and writing
the image to that partition instead to a file. I vote against such a
strategy because if you write to the wrong partition (due to a typo),
you can lose your complete Linux-system. Furthermore, it's a waste of
disk-space because the CD-image is temporary data that can be deleted
after writing the CD.

3.5. Test the CD-image

Linux has the ability to mount files as if they were disk-partitions.
This feature is useful to check the directory layout of the CD-image
is ok. To mount the file cd_image created above on the directory
/cdrom, give the command

mount -t iso9660 -o ro,loop=/dev/loop0 cd_image /cdrom

Now you can inspect the files under /cdrom - they appear exactly as
they were on a real CD. To umount the CD-image, just say umount
/cdrom. Warning: If you did not use the option '-K' for mkisofs then
the last file on /cdrom may not be fully readable.

Note:

some ancient versions of mount are not able to deal with
loopback-devices. If you have such an old version of mount
it is a hint to upgrade your Linux-system.

Several people already suggested to put information about
how to get the newest mount-utilities into this mini-HOWTO.
I always refuse this. If your Linux-Distribution ships with
an ancient mount: report it as a bug. If your Linux-
Distribution is not easily upgradable: report it as a bug.

If I included all the information that is necessary to work
around bugs in bad designed Linux-Distributions, this mini-
HOWTO would be a lot bigger and harder to read.

3.6. Remarks on the blank CD-Recordable discs

The german computer magazine "c't" has a list of tips regarding the
blank CDs in their november 1996 issue:

� "no-name" discs are generally not of highest quality and should
better not be used

� if a recordable CD is defective, this is likely to apply to the
whole batch (if you bought more then one at a time); maybe you are
lucky and can at least use the first 500MB of such CDs ...

� don't touch the CDs at their shimmering side before writing

3.7. Write the CD-image to a CD

Not much more left to do. Before showing you the last command, let me
warn you that CD-writers want to be fed with a constant stream of data
because they have only small data-buffers. So the process of writing
the CD-image to the CD mustn't be interupted or a corrupt CD will be
the result.

To be sure nothing can interupt this process, throw all users of the
system and unplug the ethernet-cable ... Read the Bastard operator
from hell to learn about the right attitude to do so. ;-)

If you are mentally prepared, dress up in a black robe, multiply the
SCSI-id of the CD-writer with it's SCSI-revision and light as many
candles, speak two verses of the ASR-FAQ and finally type

cdwrite --device /dev/sgd cd_image
or
cdrecord -v speed=2 dev=4,0 cd_image

depending on which software you want to use. Of course you have to
replace the example SCSI device with the device your writer is
connected to.

Please note that no writer can re-position it's laser and can't
continue at the original spot on the CD when it gets disturbed.
Therefore any strong vibrations or even a shock will completly destroy
the CD you are writing.

3.8. If something goes wrong ...

4. Frequently asked questions with answers

4.1. How sensitive is the burning process?"

Answer: that depends on your writer. Modern ones should have a data-
buffer of 1MB or such and can live 1-2 seconds without data. See the
manuals or ask your manufacturer if you want to know the details.

Regardless of the size of those data-buffers you must guarantee a
constant throughput of 300kb/s or 600kb/s in the long time run.

Disk intensive processes such as updating the locate-database lower
the maximum flow-rate will surely corrupt the CD; you better check
such processes are not started via cron, at or anacron while you burn
CD-Rs.

On the other hand, people reported that they compiled a kernel while
burning a CD without a glitch. Of course you need a fast machine for
such experiments.

4.2. Has fragmentation a bad impact on the throughput?"

Fragmentation is usally so low that it's impact isn't noticed.

If you're uncertain than look at the messages printed while booting,
the percentage of fragmentation is reported while checking the
filesystems. You can check for this value with the very dangerous
command

bash> e2fsck -n /dev/sda5 # '-n' is important!
[stuff deleted - ignore any errors]
/dev/sda5: 73/12288 files (12.3% non-contiguous)

In this example the fragmentation seems to be very high - but there
are only 73 very small files on this filesystem (used as /tmp) so the
value is _not_ alarming.

4.3. Is it possible to store the CD-image on an UMSDOS-filesystem?"

Yes. The only filesystem that isn't reliable and fast enough for
writing CDs from is the network filesystem (NFS).

I'm using UMSDOS myself to share the disk-space between Linux and
DOS/Win on a PC (486/66) dedicated for writing CDs.

4.4. Isn't there some way to get around the iso9660 limitations?"

Yes. You can put any filesystem you like on the CD. But other
operating systems than Linux won't be able to deal with this CD.

Here goes the recipe:

� Create an empty file of 650MB size.

dd if=/dev/zero of="empty_file" bs=1024k count=650

� Create an extended-2 filesystem on this file

bash> /sbin/mke2fs empty_file
empty_file is not a block special device.
Proceed anyway? (y,n) y

� Mount this empty file through the loopback-devices

mount -t ext2 -o loop=/dev/loop1 empty_file /mnt

� Copy files to /mnt and umount it afterwards.

� Use cdwrite or cdrecord on empty_file (which is no longer empty) as
if it were an iso9660-image.

If you want to make an entry in /etc/fstab for such a CD, disable the
checking of it, e.g.:

/dev/cdrom /cdrom ext2 defaults,ro 0 0

The first 0 means "don't include in dumps", the second (=important)
one means "don't check for errors on startup" (fsck will fail to check
the CD for errors).

4.5. How to read and write audio CDs?"

Please get the packages "cdda2wav" and "sox", available from sunsite
and it's mirrors:

<ftp://sunsite.unc.edu/pub/Linux/apps/sound/cdrom/cdda2wav0.71.src.tar.gz>

<ftp://sunsite.unc.edu/pub/Linux/apps/sound/convert/sox-11gamma-
cb3.tar.gz>

cdda2wav enables you to get a specific interval (or a whole track)
from your audio CD and converts it into a .wav-file. sox converts the
wav-files back into the (audio-CD) cdda-format so it can be written to
the CD-R using cdwrite.

4.6. How to probe for SCSI-devices after boot?"

The file drivers/scsi/scsi.c contains the information

/*
* Usage: echo "scsi add-single-device 0 1 2 3" >/proc/scsi/scsi
* with "0 1 2 3" replaced by your "Host Channel Id Lun".
* Consider this feature BETA.
* CAUTION: This is not for hotplugging your peripherals. As
* SCSI was not designed for this you could damage your
* hardware !
* However perhaps it is legal to switch on an
* already connected device. It is perhaps not
* guaranteed this device doesn't corrupt an ongoing data transfer.
*/

4.7. Is it possible to make a 1:1 copy of a data CD?"

Yes. But you should be aware of the fact that any errors while reading
the original (due to dust or scratches) will result in a defective
copy.

First case: you have a CD-writer and a seperate CD-ROM drive. By
issuing the command

cdwrite -v -D /dev/sgc --pad -b $(isosize /dev/scd0) /dev/scd0
or
cdrecord -v dev=3,0 speed=2 -isosize /dev/scd0

you read the data stream from the CD-ROM drive attached as /dev/scd0
and write it directly through /dev/sgc to the CD-R.

Second case: you don't have a seperate CD-ROM drive. You have to use
the writer to read out the CD-ROM in this case:

dd if=/dev/scd0 of=cdimage bs=1c count=`isosize /dev/scd0`

This command is equivalent to the result of mkisofs, so you should
procede as described in chapter 3. Please note that this method will
fail on audio CDs!

4.8. Can Linux read Joliet CDs?"

Yes. But you need to patch the kernel and recompile it. For further
details see

<http://www-
plateau.cs.berkeley.edu/people/chaffee/joliet.html>

4.9. How do I read/mount CD-ROMs with the CD-writer?"

Just as you do with regular CD-ROM drives. No tricks at all. Note that
you have to use the scd-devices (SCSI CD-ROM) to mount CDs for
reading. Example-entry for /etc/fstab:

/dev/scd0 /cdrom iso9660 ro,user,noauto 0 0

5. Troubleshooting

5.1. It doesn't work: under Linux

Please check first if the writer works under other operating systems.
Concretely:

� Does the controller recognize the writer as a SCSI device?

� Does the driver software recognize the writer?

� Is it possible to make a CD using the accompanied software?

If "it doesn't work" even under other operating systems you have a
hardware conflict or defective hardware.

5.2. It doesn't work: under DOS and friends

Try to use Linux. Installation and configuration of SCSI-drivers for
DOS is the hell. Linux is too complicated? Ha!

5.3. SCSI errors during the burning phase

Most likely those errors are caused by

� missing dis-/reconnect feature on the SCSI bus

� unsufficiently cooled hardware

� defektive hardware (should be detected by 5.1.)

Under various circumstances SCSI devices dis- and reconnect themselves
(electronically) from the SCSI bus. If this feature is not available
(check controller and kernel parameters) some writers run into trouble
during burning or fixating the CD-R.

Especially the NCR 53c7,8xx SCSI driver has the feature disabled by
default, so you might want to check it first:

NCR53c7,8xx SCSI support [N/y/m/?] y
always negotiate synchronous transfers [N/y/?] (NEW) n
allow FAST-SCSI [10MHz] [N/y/?] (NEW) y
allow DISCONNECT [N/y/?] (NEW) y

6. Credits

Andreas Erdmann <[email protected]>
provided the example with the YAMAHA-writer

Art Stone <[email protected]>
had the idea to put non-iso9660 filesystems on a CD

Bartosz Maruszewski <[email protected]>
reported spelling mistakes

Bernhard Gubanka <[email protected]>
noticed the need of a recent version of mount to utilize the
loopback device

Brian H. Toby
polished the wording.

Bruce Perens <[email protected]>
gave information about the cdwrite-mailinglist

Dale Scheetz <[email protected]>
helped improving the section about creating the cdimage.

URL of the mkhybrid tool

Edwin H. Kribbs
reported that '-K' requires a patch for mkisofs

Gerald C Snyder <[email protected]>
tested writing of an ext2 CD-ROM (see 4.4)

Ingo Fischenisch <[email protected]>
provided the example with 2 controllers hosting 2 devices

Janne Himanka <[email protected]>
pointer to kernel patch to read Joliet CDs

Joerg Schilling <[email protected]>
information about cdrecord

Jos van Geffen <[email protected]>
noted the problem in 4.9.

Markus Dickebohm <[email protected]>

Pierre Pfister <[email protected]>
helped to develop the recipe on 1:1 copies.

Rick Cochran <[email protected]>
hint about dis-/reconnect disabled by default in the ncr driver

Stephan Noy <[email protected]>
information and experience about writing audio-CDs

Stephen Harris <[email protected]>
contributed hint about writing audio-CDs

The Sheepy One <[email protected]>
suggested using defective CDs as coasters for drinks

Volker Kuhlmann <[email protected]>
noticed that the "cdwrite"-package does not contain mkisofs

End of the Linux CD-Writing mini-HOWTO