The Linux CD-ROM HOWTO
Jeff Tranter, jeff_tranter@pobox.com
v1.10, 5 January 1997
This document describes how to install, configure, and use CD-ROM
drives under Linux. It lists the supported hardware and answers a num�
ber of frequently asked questions. The intent is to bring new users up
to speed quickly and reduce the amount of traffic in the Usenet news
groups and mailing lists.
1. Introduction
This is the Linux CD-ROM HOWTO. It is intended as a quick reference
covering everything you need to know to install and configure CD-ROM
hardware under Linux. Frequently asked questions related to CD-ROM are
answered, and references are given to other sources of information
related to CD-ROM applications and technology.
1.1. Acknowledgments
Much of this information came from the documentation and source files
provided with the Linux kernel, the Internet alt.cdrom newsgroup FAQ,
and input from Linux users.
Thanks to the Linuxdoc-SGML package, this HOWTO is available in
several formats, all generated from a common source file.
1.2. Revision History
Version 1.0
First version made publicly available
Version 1.1
CDU33A is explicitly supported as of 1.1.20 kernel; notes on
Reveal FX; info on reading audio tracks; info on some alpha
drivers; added troubleshooting section; a few other minor
additions
Version 1.2
ISO-9660 file systems must be mounted read-only starting with
1.1.33 kernel; clarified that SB16 SCSI is supported and newer
Aztech drives are not supported; references to photocd and xpcd
programs; note on new SBPCD auto eject feature
Version 1.3
Minor change to the way SBPCD eject feature is disabled starting
with the 1.1.49 kernel; added info on XA discs and how to
identify them
Version 1.4
HOWTO now available in other languages; IBM and Longshine drives
now supported by SBPCD; alpha driver for Aztech drives; CDU-33
driver no longer auto-probes, supports PhotoCD and audio; more
than 2 SCSI drives are supported; new driver for IDE; reminder
to check drive jumpers; can now set SBPCD auto-eject with IOCTL;
list drivers with multisession support; question on flashing
light on CDU-33
Version 1.5
A long overdue update (I've been busy); document placed under
GPL; info on many new kernel drivers; more info on configuration
and troubleshooting; lots of HTML links added; many other minor
changes
Version 1.6
Added link to eject program; question on file permission patch;
link to Creative Labs Web site; reference to ATA/EIDE FAQ and
FTP site; note that many Creative Labs and Mitsumi drives are
now EIDE; mention Supermount; drives listed as supporting
digital data are obsolete, refer to cdda2wav; more info on
writing CDs; multi-disc EIDE drive info; a few typos fixed
Version 1.7
new kernel version; most README files moved to
/usr/src/linux/Documentation; some drivers are no longer
experimental; a few more supported drives; emphasize that most
drives are now IDE/ATAPI; added questions on Plug and Play
support and identifying drive speed; vger mailing lists being
shut down; other miscellaneous minor changes
Version 1.8
question on why CD-ROM stops working after install; aztcd driver
now supports two CyCDROM drives; more pleading not to use SBPCD
driver with IDE drives; some ATAPI multi-disc changer support;
note on (lack of) support for parallel port drives; latest
stable kernel is 2.0; other miscellaneous minor changes
Version 1.9
removed some questions that were very old and now obsolete; new
e-mail address for author; Chinese translation available; fixed
some links to point to latest software packages; more
information on multimedia book; minor spelling and grammatical
changes
Version 1.10
clarify that new Aztech drives are ATAPI; added CDU31A options
for modular driver; mount option for reading hidden files; added
six month "best before" date; new URL to web page for book;
minor spelling and grammatical changes
1.3. New Versions Of This Document
New versions of this document will be periodically posted to the
comp.os.linux.answers newsgroup. They will also be uploaded to various
anonymous ftp sites that archive such information including
<ftp://sunsite.unc.edu/pub/Linux/docs/HOWTO/>.
Hypertext versions of this and other Linux HOWTOs are available on
many World-Wide-Web sites, including
<http://sunsite.unc.edu/mdw/mdw.html>. Most Linux CD-ROM distributions
include the HOWTOs, often under the </usr/doc/> directory, and you
can also buy printed copies from several vendors. Sometimes the HOWTOs
available from CD-ROM vendors, ftp sites, and printed format are out
of date. If the date on this HOWTO is more than six months in the
past, then a newer copy is probably available on the Internet.
A French translation of this document, by Bruno Cornec
(cornec@stna7.stna.dgac.fr) is available at
<ftp://ftp.ibp.fr/pub2/linux/french/docs/HOWTO/>.
A Japanese translation by Itsushi Minoura (minoura@uni.zool.s.u-
tokyo.ac.jp) is available from <http://jf.linux.or.jp/JF/JF.html/>.
A Chinese translation (BIG-5 encoding) by Yung-kang Wu
(yorkwu@in3.csie.ncu.edu.tw) is available from
<http://www.csie.ncu.edu.tw/~yorkwu/linux/howto/cdrom/>.
If you make a translation of this document into another language, let
me know and I'll include a reference to it here.
1.4. Feedback
I rely on you, the reader, to make this HOWTO useful. If you have any
suggestions, corrections, or comments, please send them to me,
jeff_tranter@pobox.com, and I will try to incorporate them in the next
revision.
I am also willing to answer general questions on CD-ROM and Linux, as
best I can. Before doing so, please read all of the information in
this HOWTO, and send me detailed information about the problem.
If you publish this document on a CD-ROM or in hardcopy form, a
complimentary copy would be appreciated; mail me for my postal
address. Also consider making a donation to the Linux Documentation
Project to help support free documentation for Linux. Contact the
Linux HOWTO coordinator, Greg Hankins (gregh@sunsite.unc.edu), for
more information.
1.5. Distribution Policy
Copyright 1995-1997 Jeff Tranter.
This HOWTO is free documentation; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
This document is distributed in the hope that it will be useful, but
without any warranty; without even the implied warranty of
merchantability or fitness for a particular purpose. See the GNU
General Public License for more details.
You can obtain a copy of the GNU General Public License by writing to
the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139,
USA.
2. CD-ROM Technology
"CD-ROM is read-only memory, and audio compact disc system is
available as package-media of digital data for those purpose. For
playing audio CD, please insert Head-phone jack."
--- from a CD-ROM instruction manual
Don't Panic! The world of CD-ROM technology is not as confusing as
your instruction manual.
CD-ROM stands for Compact Disc Read-Only Memory, a mass storage medium
utilizing an optical laser to read microscopic pits on the aluminized
layer of a polycarbonate disc. The same format is used for audio
Compact Discs. Because of its high storage capacity, reliability, and
low cost, CD-ROM has become an increasingly popular storage media.
The storage capacity of a CD-ROM disc is approximately 650 megabytes,
equivalent to over 500 high density 3.5" floppy disks or roughly
250,000 typed pages.
First generation drives (known as single speed), provided a transfer
rate of approximately 150 kilobytes per second; these are now
generally considered obsolete. Hardware manufacturers have introduced
double speed (300 kB/sec), quad speed (600 kB/sec), 6 times (6X), 8
times (8x), and even higher speed drives.
Most CD-ROM drives use either the Small Computer Systems Interface
(SCSI), ATAPI enhanced IDE interface, or a vendor proprietary
interface. They also typically support playing audio CDs via an
external headphone jack or line level output. Some CDs also allow
reading the frames of data from audio CDs in digital form.
CD-ROMs are usually formatted with an ISO-9660 (formerly called High
Sierra) file system. This format restricts filenames to the MS-DOS
style (8+3 characters). The Rock Ridge Extensions use undefined fields
in the ISO-9660 standard to support longer filenames and additional
Unix style information (e.g. file ownership, symbolic links, etc.).
PhotoCD is a standard developed by Kodak for storing photographic
images as digital data on a CD-ROM. With appropriate software, you can
view the images on a computer, manipulate them, or send them to a
printer. Information can be added to a PhotoCD at a later date; this
is known as multi-session capability.
CD recorders (CD-R) have recently become available. They use a
different media and specialized equipment for recording, but the
resulting disc can be read by any CD-ROM drive.
In the future CD-ROM drive vendors are expected to offer new
technologies that will increase storage capacity by an order of
magnitude.
3. Supported Hardware
This section lists the CD-ROM drivers and interfaces that are
currently supported under Linux. The information here is based on the
latest stable Linux kernel, which at time of writing was version
2.0.27. A development kernel (2.1.x versions) is also available but is
not guaranteed to be stable.
This information is only valid for Linux on the Intel platform. Much
of it should be applicable to Linux on other processor architectures,
but I have no first hand experience or information.
3.1. ATAPI CD-ROM Drives
ATAPI (ATA Packet Interface) is a protocol for controlling mass
storage devices. It builds on the ATA (AT Attachment) interface, the
official ANSI standard name for the IDE interface developed for hard
disk drives. ATAPI is commonly used for hard disks, CD-ROM drives,
tape drives, and other devices. Currently the most popular type of
interface, it offers most of the functionality of SCSI, without the
need for an expensive controller or cables.
The Linux kernel has a device driver that should work with any ATAPI
compliant CD-ROM drive. Vendors shipping compatible drives include
Aztech, Mitsumi, NEC, Sony, Creative Labs, and Vertos. If you have
recently purchased a CD-ROM drive, especially if it is quad speed or
faster, it is almost guaranteed to be IDE/ATAPI.
3.2. SCSI CD-ROM Drives
SCSI (Small Computer Systems Interface) is a popular format for CD-ROM
drives. Its chief advantages are a reasonably fast transfer rate,
multi-device capability, and support on a variety of computer
platforms. Some disadvantages of SCSI are the need for a relatively
expensive controller card and cables.
Any SCSI CD-ROM drive with a block size of 512 or 2048 bytes should
work under Linux; this includes the vast majority of CD-ROM drives on
the market.
You will also need a supported SCSI controller card; see the SCSI
HOWTO for more information on interface hardware.
Note that some CD-ROMs include a proprietary controller with a
modified interface that is not fully SCSI compatible (e.g. it may not
support adding other SCSI devices on the bus). These will most likely
not work under Linux.
3.3. Proprietary CD-ROM Drives
Several CD-ROM drives using proprietary interfaces are available; the
interface is often provided on a sound card. Simple interface cards
equivalent to that provided on the sound card are also available.
These drives generally tend to be lower in cost and smaller than SCSI
drives. Their disadvantages are the lack of standardization and
expandability.
Note that proprietary interfaces are sometimes erroneously referred to
as IDE interfaces, because like IDE hard disks, they use a simple
interface based on the PC/AT bus. To add to the confusion, some
vendors, most notably Creative Labs, have shipped many different types
of CD-ROM drives and have offered proprietary, SCSI, and ATAPI
interfaces on their sound cards.
The table below lists the proprietary CD-ROM drives that are known to
be supported under Linux. Drivers for additional devices may be
available in the latest development kernels or as kernel patches. The
latter can most often be found at
<ftp://sunsite.unc.edu/pub/Linux/kernel/patches/cdrom/>. Also check
the README files included with the kernel distribution, usually
installed /usr/src/linux/Documentation/cdrom/, for the latest
information.
Proprietary CD-ROM Drives
Vendor Model Kernel Driver Notes
------ ----- ------------- --------
Panasonic CR-521 sbpcd Note 1
Panasonic CR-522 sbpcd Note 1
Panasonic CR-523 sbpcd Note 1
Panasonic CR-562 sbpcd Note 1
Panasonic CR-563 sbpcd Note 1
Creative Labs CD-200 sbpcd
IBM External ISA sbpcd Note 2
Longshine LCS-7260 sbpcd
Teac CD-55A sbpcd
Sony CDU-31A cdu31a
Sony CDU-33A cdu31a
Sony CDU-535 sonycd535 Note 3
Sony CDU-531 sonycd535
Aztech CDA268-01A aztcd Note 4
Orchid CDS-3110 aztcd
Okano/Wearnes CDD110 aztcd
Conrad TXC aztcd
CyCDROM CR520ie aztcd
CyCDROM CR940ie aztcd
GoldStar R420 gscd Note 5
Philips/LMS CM206 cm206 Note 6
Mitsumi CRMC LU005S mcd/mcdx Note 7, 8
Mitsumi FX001 mcd/mcdx Note 7, 8
Optics Storage Dolphin 8000AT optcd
Lasermate CR328A optcd
Sanyo H94A sjcd
various various isp16 Note 9
Notes:
1. These drives may be sold under the names Creative Labs, Panasonic,
Matsushita, or Kotobuki.
2. This drive is the same as a Panasonic CR-562.
3. May also be sold under the Procomm name.
4. This driver is for the CDA268-01A only. Other models, including the
CDA268-03I and CDA269-031SE are not proprietary and should use the
IDECD (ATAPI) kernel driver.
5. May also be sold as part of a Reveal Multimedia Kit.
6. The Philips CM205 is not supported by this driver, but there is a
separate alpha release driver available from ftp://sunsite.unc.edu
in /pub/Linux/kernel/patches/cdrom/lmscd0.4.tar.gz
7. May also be sold under the Radio Shack name.
8. There are two drivers available. "mcd" is the original one, and
"mcdx" is a newer driver with more features (but possibly less
stable).
9. This driver works with CD-ROM drives that are attached to the
interface on an ISP16, MAD16 or Mozart sound card.
If a drive listed here is not supported by your kernel, you probably
need to upgrade to a newer version.
If your drive is not one of the models listed here, particularly if it
was bought recently and is quad speed or faster, it probably uses the
IDE/ATAPI interface listed in a previous section. The single most
common error among Linux CD-ROM users is to assume that any drive
connected to a SoundBlaster card should use the SBPCD driver. Creative
Labs and most other vendors are no longer selling proprietary
interface drives, they are following the standard ATAPI/IDE interface.
3.4. Parallel Port Drives
Some vendors sell CD-ROM drives that attach to the PC parallel port.
The standard Linux kernel does not support these drives, and I am not
aware of anyone working on drivers.
4. Installation
Installation of a CD-ROM under Linux consists of these steps:
1. Installing the hardware.
2. Configuring and building the Linux kernel.
3. Creating device files and setting boot time parameters
4. Booting the Linux kernel.
5. Mounting the media.
The next sections will cover each of these steps in detail.
4.1. Installing the Hardware
Follow the manufacturer's instructions for installing the hardware or
have your dealer perform the installation. The details will vary
depending on whether the drive is internal or external and on the type
of interface used. There are no special installation requirements for
Linux. You may need to set jumpers on the drive and/or interface card
for correct operation; some of the kernel drivers include README files
that include this information.
As explained in the file ide-cd, ATAPI CD-ROMS should be jumpered as
"single" or "master", and not "slave" when only one IDE device is
attached to an interface (although this restriction is no longer
enforced with recent kernels).
4.2. Configuring and Building the Kernel
When initially installing Linux from CD-ROM you will likely be using a
boot and/or root disk provided as part of a Linux distribution. If
possible, you should choose a boot disk with the kernel driver for
your CD-ROM device type. If you cannot find a boot disk with the
necessary CD-ROM driver, you have several options:
1. Install over a network
2. Boot DOS, and install the Linux files onto your hard disk
3. Boot DOS, and create a set of floppies to install Linux
4. Find someone who can build you a boot disk with the needed CD-ROM
driver
The Linux Installation HOWTO
<http://sunsite.unc.edu/mdw/HOWTO/Installation-HOWTO.html> has more
information on installing Linux. If you purchased Linux on CD-ROM, it
likely also came with some installation instructions (that little
booklet inside the jewel case, and/or files on the CD).
Once Linux has initially been installed, most users will want to
compile their own kernel, usually for one of these reasons:
� to support a CD-ROM drive or other hardware
� to upgrade to a newer kernel release
� to free up memory resources by minimizing the size of the kernel
The Linux Kernel HOWTO <http://sunsite.unc.edu/mdw/HOWTO/Kernel-
HOWTO.html> should be consulted for the details of building a kernel.
I will just mention here some issues that are specific to CD-ROM
drives.
Obviously, you need to compile in support for your CD-ROM drive when
you do a "make config".
If you have an ATAPI CD-ROM drive, you need to answer yes to the
questions:
Enhanced IDE/MFM/RLL disk/cdrom/tape support (CONFIG_BLK_DEV_IDE) [Y/n/?]
Include IDE/ATAPI CDROM support (CONFIG_BLK_DEV_IDECD) [Y/n/?]
For SCSI CD-ROM drives, enable these options:
SCSI support (CONFIG_SCSI) [Y/n/m/?]
SCSI CD-ROM support (CONFIG_BLK_DEV_SR) [Y/n/m/?]
Also enable support for your SCSI host adapter when prompted, e.g.
Adaptec AHA152X support (CONFIG_SCSI_AHA152X) [Y/n/m/?]
For proprietary interface CD-ROM drives, enable the appropriate
driver. You can use the table listed previously to determine the
driver to use for your model.
Virtually all CD-ROMs use the ISO-9660 file system, so you must also
enable:
ISO9660 cdrom filesystem support (CONFIG_ISO9660_FS) [Y/n/m/?]
Although not needed for CD-ROM operation, if you have a sound card
that is supported under Linux you might want to enable and configure
the kernel sound driver at this time as well. The Sound HOWTO
<http://sunsite.unc.edu/mdw/HOWTO/Sound-HOWTO.html> can be a useful
reference here.
You should then follow the usual procedure for building the kernel and
installing it. Don't boot with the new kernel until you create the
device files and set up any boot time parameters as described in the
next section.
The ISO-9660 filesystem and almost all of the CD-ROM drivers can be
built as loadable kernel modules. This scheme allows the kernel
drivers to be loaded and unloaded without rebooting the kernel,
freeing up memory. I recommend you get your CD-ROM installation
running using compiled-in drivers first. How to use modules is
described in the modules documentation and the Kernel HOWTO
<http://sunsite.unc.edu/mdw/HOWTO/Kernel-HOWTO.html>.
If a drive type listed here is not supported by your kernel, you
likely need to upgrade to a newer version.
It is possible that you need to use a driver that is distributed
separately from the kernel source code. This usually involves patching
the kernel. Again, the Kernel HOWTO
<http://sunsite.unc.edu/mdw/HOWTO/Kernel-HOWTO.html> explains how to
do this.
Note that there is a menu-based kernel configuration program invoked
by "make menuconfig" and an X11-based graphical configuration invoked
as "make xconfig". All three configuration methods offer on-line help.
4.3. Creating Device Files and Setting Boot Time Parameters
The kernel uses device files to identify which device driver to use.
If you are running a standard Linux distribution you may have created
the necessary device files during installation. Under Slackware Linux,
for example, there is a menu-based setup tool that includes CD-ROM
setup, and most systems have a /dev/MAKEDEV script. If you don't use
these methods, you can use the more manual procedure listed in this
section. Even if you use either of these methods, it is recommended
that you at least verify the device files against the information in
this section.
You create the device file by running the shell commands indicated for
your drive type. This should be done as user root. Note that some
Linux distributions may use slightly different CD-ROM device names
from those listed here.
It is recommended that you also create a symbolic link to the CD-ROM
device to make it easier to remember. For example, for an IDE CD-ROM
drive that is the second device on the secondary interface, the link
would be created using
# ln -s /dev/hdd /dev/cdrom
If you want to play audio CDs, you will need to set the protection on
the device file (the real file, not the symbolic link to it) to allow
all users to read, e.g.
# chmod 664 /dev/hdd
# ls -l /dev/hdd
brw-rw-r-- 1 root disk 22, 64 Feb 4 1995 /dev/hdd
When booting Linux, the device drivers attempt to determine whether
the appropriate devices are present, typically by probing specific
addresses. Many of the drivers auto-probe at several addresses, but
because of differences in configuration, possible device conflicts,
and hardware limitations, the drivers sometimes need help identifying
the addresses and other parameters. Most drivers support an option on
the kernel command line to pass this information to the device driver.
This can be done interactively, or more commonly, configured into your
boot loader. With LILO, for example, you would add an append command
such as the following to your /etc/lilo.conf file:
append = "sbpcd=0x230,SoundBlaster"
See the LILO documentation for more information.
In the next section I discuss issues specific to individual device
drivers, including device files, boot parameters, and the capabilities
of the different drivers. You probably only need to read the section
relevant to your drive type. The README files are usually found in the
directory /usr/src/linux/Documentation/cdrom.
4.3.1. Sbpcd Driver
Principal author: Eberhard Moenkeberg (emoenke@gwdg.de)
Multi-session support: yes (but not all drives)
Multiple drive support: yes
Loadable module support: yes
Reading audio frames: yes (CR-562, CR-563, CD-200 only)
Auto-probing: yes
Device file: /dev/sbpcd, major 25
Configuration file: sbpcd.h
Kernel config option: Matsushita/Panasonic CDROM support?
README file: sbpcd
This driver accepts a kernel command line of the form:
sbpcd=<io-address>,<interface-type>
where the first parameter is the base address of the device (e.g.
0x230), and <interface-type> is one of "SoundBlaster", "LaserMate", or
"SPEA". See the file sbpcd.h for hints on what interface type to use.
Using sbpcd=0 disables auto-probing, disabling the driver.
The device file can be created using:
# mknod /dev/sbpcd b 25 0
Up to four drives per controller are supported. The next three drives
on the first controller would use minor device numbers 1 through 3.
If you have more than one controller, create devices with major
numbers 26, 27, and 28, up to a maximum of 4 controllers (this is 16
CD-ROM drives in total; hopefully enough for most users :-).
See the file sbpcd for more information on this driver.
If you recently bought a CD-ROM drive, don't assume that if it
connects to a SoundBlaster card it should use this kernel driver. Most
CD-ROM drives being sold by Creative Labs are now EIDE/ATAPI drives.
Please don't bug the author with questions about using this driver
with IDE drives. I quote from the README file:
sbpcd really, really is NOT for ANY IDE/ATAPI drive!
Not even if you have an "original" SoundBlaster card with an IDE interface!
So, you better have a look into README.ide if your port address is 0x1F0,
0x170, 0x1E8, 0x168 or similar.
I get tons of mails from IDE/ATAPI drive users - I really can't continue
any more to answer them all. So, if your drive/interface information sheets
mention "IDE" (primary, secondary, tertiary, quaternary) and the DOS driver
invoking line within your CONFIG.SYS is using an address below 0x230:
DON'T ROB MY LAST NERVE - jumper your interface to address 0x170 and IRQ 15
(that is the "secondary IDE" configuration), set your drive to "master" and
use ide-cd as your driver. If you do not have a second IDE hard disk, use the
LILO commands
hdb=noprobe hdc=cdrom
and get lucky.
To make it fully clear to you: if you mail me about IDE/ATAPI drive problems,
my answer is above, and I simply will discard your mail, hoping to stop the
flood and to find time to lead my 12-years old son towards happy computing.
4.3.2. Sonycdu535 Driver
Principal author: Ken Pizzini (ken@halcyon.com)
Multi-session support: no
Multiple drive support: no
Loadable module support: yes
Reading audio frames: no
Auto-probing: no
Device file: /dev/sonycd535, major 24
Configuration file: sonycd535.h
Kernel config option: Sony CDU535 CDROM support?
README file: sonycd535
This driver accepts a kernel command line of the form:
sonycd535=<io-address>
where <io-address> is the base address of the controller (e.g. 0x320).
Alternatively you can set the address in the file sonycd535.h and
compile it in.
The device file can be created using:
# mknod /dev/sonycd535 b 24 0
Some Linux distributions use /dev/sonycd for this device. Older
versions of the driver used major device number 21; make sure your
device file is correct.
This driver was previously distributed as a patch but is now part of
the standard kernel. See the file sonycd535 for more information on
this driver.
4.3.3. Cdu31a Driver
Principal author: Corey Minyard (minyard@-rch.cirr.com)
Multi-session support: yes
Multiple drive support: no
Loadable module support: yes
Reading audio frames: yes
Auto-probing: no
Device file: /dev/cdu31a, major 15
Configuration file: cdu31a.h
Kernel config option: Sony CDU31A/CDU33A CDROM support?
README file: cdu31a
This driver accepts a kernel command line of the form:
cdu31a=<io-address>,<interrupt>,PAS
The first number is the I/O base address of the card (e.g. 0x340). The
second is the interrupt number to use (0 means to use polled i/o). The
optional third parameter should be "PAS" if the drive is connected to
a Pro-Audio Spectrum 16 sound card, otherwise left blank.
If the driver is loaded as a module, it uses a slightly different
format. When loading the driver using the modprobe or insmod command,
the parameters take the form:
cdu31a_port=<io-address> cdu31a_irq=<interrupt>
The base io-address is required while the interrupt number is
optional.
The device file can be created using:
# mknod /dev/cdu31a b 15 0
See the file cdu31a for more information on this driver.
Also see the Web page put together by Jeffrey Oxenreider
(zureal@infinet.com) that covers a lot of common problems with these
drives. It can be found at
<http://www.infinet.com/~zureal/cdu31a.html>.
4.3.4. Aztcd Driver
Principal author: Werner Zimmermann (zimmerma@rz.fht-esslingen.de)
Multi-session support: yes
Multiple drive support: no
Loadable module support: yes
Reading audio frames: no
Auto-probing: no
Device file: /dev/aztcd0, major 29
Configuration file: aztcd.h
Kernel config option: Aztech/Orchid/Okano/Wearnes (non IDE) CDROM support?
README file: aztcd
This driver accepts a kernel command line of the form:
aztcd=<io-address>
where the parameter is the I/O base address of the card (e.g. 0x340).
The device file can be created using:
# mknod /dev/aztcd0 b 29 0
Note that this driver is for the CDA268-01A only. Other models,
including the CDA268-03I and CDA269-031SE are not proprietary and
should use the IDECD (ATAPI) kernel driver.
See the file aztcd for more information on this driver.
4.3.5. Gscd Driver
Principal author: Oliver Raupach (raupach@nwfs1.rz.fh-hannover.de)
Multi-session support: no
Multiple drive support: no
Loadable module support: yes
Reading audio frames: no
Auto-probing: no
Device file: /dev/gscd0, major 16
Configuration file: gscd.h
Kernel config option: Goldstar R420 CDROM support?
README file: gscd
This driver accepts a kernel command line of the form:
gscd=<io-address>
specifying the I/O base address of the card (e.g. 0x340).
The device file can be created using:
# mknod /dev/gscd0 b 16 0
See the file gscd and the World-Wide Web site <http://linux.rz.fh-
hannover.de/~raupach> for more information on this driver.
4.3.6. Mcd Driver
Principal author: Martin (martin@bdsi.com)
Multi-session support: no
Multiple drive support: no
Loadable module support: yes
Reading audio frames: no
Auto-probing: no
Device file: /dev/mcd, major 23
Configuration file: mcd.h
Kernel config option: Standard Mitsumi CDROM support?
README file: mcd
This is the older driver for Mitsumi drivers that has been available
for some time. You might want to try the newer mcdx driver, which has
some new features but is possibly less stable.
This driver accepts a kernel command line of the form:
mcd=<io-address>,<irq>
specifying the I/O base address of the card (e.g. 0x340) and the IRQ
request number used.
The device file can be created using:
# mknod /dev/mcd b 23 0
See the file mcd for more information on this driver.
4.3.7. Mcdx Driver
Principal author: Heiko Schlittermann
Multi-session support: yes
Multiple drive support: yes
Loadable module support: yes
Reading audio frames: no (not supported by hardware)
Auto-probing: no
Device file: /dev/mcdx0, major 20
Configuration file: mcdx.h
Kernel config option: Experimental Mitsumi support?
README file: mcdx
This is a newer driver for Mitsumi drivers. The older and possibly
more stable mcd driver is still available.
This driver accepts a kernel command line of the form:
mcdx=<io-address>,<irq>
specifying the I/O base address of the card (e.g. 0x340) and the IRQ
request number used.
The device file can be created using:
# mknod /dev/mcdx0 b 20 0
If you recently bought a Mitsumi CD-ROM drive, don't assume that it
should use this kernel driver. Some Mitsumi models are now EIDE/ATAPI
drives and should use the idecd kernel driver.
See the file mcdx for more information on this driver.
4.3.8. Cm206 Driver
Principal author: David A. van Leeuwen (david@tm.tno.)
Multi-session support: yes
Multiple drive support: no
Loadable module support: yes
Reading audio frames: no
Auto-probing: yes
Device file: /dev/cm206cd, major 32
Configuration file: cm206.h
Kernel config option: Philips/LMS CM206 CDROM support?
README file: cm206
The driver accepts a kernel command line of the form:
cm206=<io-address>,<interrupt>
where the first number is the I/O base address of the card (e.g.
0x340). The second is the interrupt channel.
The device file can be created using:
# mknod /dev/cm206cd b 32 0
See the file cm206 for more information on this driver.
4.3.9. Optcd Driver
Principal author: Leo Spiekman (spiekman@dutette.et.tudelft.nl)
Multi-session support: yes
Multiple drive support: no
Loadable module support: yes
Reading audio frames: no
Auto-probing: no
Device file: /dev/optcd0, major 17
Configuration file: optcd.h
Kernel config option: Experimental Optics Storage ... CDROM support?
README file: optcd
The driver accepts a kernel command line of the form
optcd=<io-address>
to specify the I/O base address of the card (e.g. 0x340).
The device file can be created using:
# mknod /dev/optcd0 b 17 0
See the file optcd for more information on this driver.
4.3.10. Sjcd Driver
Principal author: Vadim V. Model (vadim@rbrf.msk.su)
Multi-session support: no
Multiple drive support: no
Loadable module support: yes
Reading audio frames: no
Auto-probing: no
Device file: /dev/sjcd, major 18
Configuration file: sjcd.h
Kernel config option: Experimental Sanyo H94A CDROM support?
README file: sjcd
The driver accepts a kernel command line of the form:
sjcd=<io-address>,<interrupt>,<dma>
indicating the base address, interrupt, and DMA channel to be used
(e.g. sjcd=0x340,10,5).
The device file can be created using:
# mknod /dev/sjcd b 18 0
See the file sjcd for more information on this driver.
4.3.11. SCSI Driver
Principal author: David Giller
Multi-session support: yes (depending on drive)
Multiple drive support: yes
Loadable module support: yes
Reading audio frames: no
Auto-probing: yes
Device file: /dev/scd0, major 11
Configuration file: cdrom.h
Kernel config option: SCSI CDROM support?
README file: none
There are kernel command line option specific to each type of SCSI
controller. See the SCSI HOWTO for more information.
Multiple drives are supported (up to the limit of the maximum number
of devices on the SCSI bus). Create device files with major number 11
and minor numbers starting at zero:
# mknod /dev/scd0 b 11 0
# mknod /dev/scd1 b 11 1
While the kernel driver itself does not support reading digital audio
frames, some SCSI drives have the capability and will work with the
cdda2wav program (which uses the generic SCSI kernel interface).
4.3.12. IDECD Driver
Principal author: Scott Snyder (snyder@fnald0.fnal.gov)
Multi-session support: yes
Multiple drive support: yes
Loadable module support: no
Reading audio frames: yes (on supported drives)
Auto-probing: yes
Device file: /dev/hd{a,b,c,d}, major 22
Configuration file: cdrom.h
Kernel config option: Include support for IDE/ATAPI CDROMs?
README file: ide-cd
This is the driver for ATAPI CD-ROMS. The driver accepts a kernel
command line of the form
hdx=cyls,heads,sects,wpcom,irq
or
hdx=cdrom
where hdx can be any of {hda,hdb,hdc,hdd}, or simply hd, for the
"next" drive in sequence. Only the first three parameters are required
(cyls,heads,sects). For example hdc=1050,32,64 hdd=cdrom.
Getting the IDE driver to recognize your CD-ROM drive can be tricky,
especially if you have more than 2 devices or more than one IDE
controller. Usually all that is required is to pass the right command
line options from LILO. The file </usr/src/linux/Documentation/ide-
cd> explains how to do this. Read it carefully.
Recent Linux kernels have better support for multiple IDE devices. If
you have problems with an older kernel, upgrading may help.
Some IDE controllers have hardware problems which the kernel driver
can work around. You may need to pass additional parameters to the
driver to enable this. See the documentation for details.
4.4. Booting the Linux Kernel
You can now reboot with the new kernel. Watch for a message such as
the following indicating that the CD-ROM has been found by the device
driver (the message will vary depending on the drive type):
hdd: NEC CD-ROM DRIVE:282, ATAPI CDROM drive
If the bootup messages scroll by too quickly to read, you should be
able to retrieve them using dmesg or tail /var/adm/messages.
If the drive is not found, then a problem has occurred, See the
section on troubleshooting.
4.5. Mounting, Unmounting, and Ejecting Devices
To mount a CD-ROM, insert a disc in the drive, and run the mount
command as root (this assumes you created a symbolic link to your
device file as recommended above and that an empty directory
/mnt/cdrom exists):
# mount -t iso9660 -r /dev/cdrom /mnt/cdrom
The CD can now be accessed under the directory /mnt/cdrom.
There are other options to the mount command that you may wish to use;
see the mount(8) man page for details.
You can add an entry to /etc/fstab to automatically mount a CD-ROM
when Linux boots or to specify parameters to use when it is mounted;
see the fstab(5) man page.
Note that to play audio CDs you should not try to mount them.
To unmount a CD-ROM, use the umount command as root:
# umount /mnt/cdrom
The disc can only be unmounted if no processes are currently accessing
the drive (including having their default directory set to the mounted
drive). You can then eject the disc. Most drives have an eject button;
there is also a standalone eject program that allows ejecting CD-ROMs
under software control.
Note that you should not eject a disc while it is mounted (this may or
may not be possible depending on the type of drive). Some CD-ROM
drivers can automatically eject a CD-ROM when it is unmounted and
insert the CD tray when a disc is mounted (you can turn this feature
off when compiling the kernel or by using a software command).
Its possible that after playing an audio CD you may not be able to
mount a CD-ROM. You need to send a CD audio "stop" command (using a CD
player program) before trying the mount. This problem only appears to
occur with the SBPCD driver.
Stephen Tweedie (sct@dcs.ed.ac.uk) has written the Supermount package
which provides transparent mounting of removable media including CD-
ROM. You can find it at
<ftp://sunsite.unc.edu/pub/linux/patches/diskdrives/>.
4.6. Troubleshooting
If you still encounter problems after following the instructions in
the HOWTO, here are some things to check. The checks are listed in
increasing order of complexity. If a check fails, solve the problem
before moving to the next stage.
4.6.1. Step 1: Make sure you are really running the kernel you com�
piled
You can check the date stamp on the kernel to see if you are running
the one that you compiled with CD-ROM support. You can do this with
the uname command:
% uname -a
Linux fizzbin 2.0.18 #1 Fri Sep 6 10:10:54 EDT 1996 i586
or by displaying the file /proc/version:
% cat /proc/version
Linux version 2.0.18 (root@fizzbin) (gcc version 2.7.2) #1 Fri Sep 6 10:10:54 EDT 1996
If the date stamp doesn't seem to match when you compiled the kernel,
then you are running an old kernel. Did you really reboot? If you use
LILO, did you re-install it (typically by running /sbin/lilo)? If
booting from floppy, did you create a new boot floppy and use it when
booting?
4.6.2. Step 2: Make sure the proper kernel drivers are compiled in
You can see what drivers are compiled in by looking at /proc/devices:
% cat /proc/devices
Character devices:
1 mem
2 pty
3 ttyp
4 ttyS
5 cua
7 vcs
Block devices:
3 ide0
22 ide1
First look for your CD-ROM device driver. These are all block devices,
in this case we can see that the idecd driver with major number 22 was
present.
Also make sure that ISO-9660 filesystem support was compiled in, by
looking at /proc/filesystems:
% cat /proc/filesystems
ext2
msdos
nodev proc
iso9660
You can also see what i/o port addresses are being used by a driver
with the file /proc/ioports:
howto % cat /proc/ioports
...
0230-0233 : sbpcd
...
If any of the drivers you thought you compiled in are not displayed,
then something went wrong with the kernel configuration or build.
Start the installation process again, beginning with configuration and
building of the kernel.
4.6.3. Step 3: Did the kernel detect your drive during booting?
Make sure that the CD-ROM device was detected when the kernel booted.
You should have seen a message on bootup. If the messages scrolled off
the screen, you can usually recall them using the dmesg command:
% dmesg
or
% tail /var/adm/messages
If your drive was not found then something is wrong. Make sure it is
powered on and all cables are connected. If your drive has hardware
jumpers for addressing, check that they are set correctly (e.g. drive
0 if you have only one drive). ATAPI CD-ROMS must be jumpered as
"single" or "master", and not "slave" when only one IDE device is
attached to an interface. If the drive works under DOS then you can be
reasonably confident that the hardware is working.
Many kernel drivers using auto-probing, but some do not, and in any
case the probing is not always reliable. Use the kernel command line
option listed for your kernel driver type. You may want to try several
different values if you are not sure of the i/o address or other
parameters. LILO can be (and usually is) configured to allow you to
enter the parameters manually when booting.
Another possibility is that you used the wrong kernel driver for your
CD-ROM driver. Some documentation may refer to proprietary interfaces
as IDE, leading some to mistakenly believe they are ATAPI drives.
Another possibility is that your drive (or interface card) is one of
the "compatible" type that requires initialization by the DOS driver.
Try booting DOS and loading the vendor supplied DOS device driver.
Then soft boot Linux using Control-Alt-Delete.
If your drive is not listed in this document, it is possible that
there are no drivers for it available under Linux. You can check with
some of the references listed at the end of this document for
assistance.
4.6.4. Step 4: Can you read data from the drive?
Try reading from the CD-ROM drive. Typing the following command should
cause the drive activity light (if present) to come on and no errors
should be reported. Use whatever device file is appropriate for your
drive and make sure a CD-ROM is inserted; use Control-C to exit.
# dd if=/dev/cdrom of=/dev/null bs=2048
^C
124+0 records in
124+0 records out
If this works, then the kernel is communicating with the drive and you
can move on to step 5.
If not, then a possible cause is the device file. Make sure than the
device file in the /dev directory has the correct major and minor
numbers as listed previously for your drive type. Check that the
permissions on the device file allow reading and writing.
A remote possibility is a hardware problem. Try testing the drive
under DOS, if possible, to determine if this could be the case.
4.6.5. Step 5: Can you mount the drive?
If you can read from the drive but cannot mount it, first verify that
you compiled in ISO-9660 file system support by reading
/proc/filesystems, as described previously.
Make sure you are mounting the drive with the "-t iso9660" and "-r"
options and that a known good ISO-9660 CD-ROM (not Audio CD) is
inserted in the drive. You normally must mount drives as user root.
Make sure that the mount point exists and is an empty directory.
If you are automatically mounting the CD-ROM on bootup, make sure that
you have correct entries in the /etc/fstab file.
If you are running the syslog daemon, there may be error messages from
the kernel that you are not seeing. Try using the "dmesg" command:
% dmesg
SBPCD: sbpcd_open: no disk in drive
There may also be errors logged to files in /var/adm, depending on how
your system is configured.
4.6.6. Debugging Audio Problems
If the drive works with CD-ROMs, but not for playing audio CDs, here
are some possible solutions.
You need an application program to play audio CDs. Some applications
may be broken or may not be compatible with your drive. Try other
applications and/or try recompiling them yourself. A good place to
look for software is
<ftp://sunsite.unc.edu/pub/linux/apps/sound/cds/>.
A few of the CD-ROM drivers do not support playing Audio CDs. Check
the README file or source code to see if that is the case.
Check if the audio can be played through the headphone jack. If so,
then the problem is likely related to your sound card. Use a mixer
program to set the input device and volume levels. Make sure you have
installed an audio cable from the CD-ROM drive to the sound card. Make
sure that the kernel sound card driver is installed and working (see
the Sound HOWTO).
4.6.7. When All Else Fails
If you still have problems, here are some final suggestions for things
to try:
� carefully re-read this HOWTO document
� read the references listed at the end of this document, especially
the relevant kernel source README files
� post a question to one of the comp.os.linux or other usenet
newsgroups
� send a question to the Linux mailing list
� try using the latest Linux kernel
� contact your computer dealer
� contact the CD-ROM manufacturer
� send mail to the author of the relevant kernel driver
� send mail to me
� fire up emacs and type Esc-x doctor :-)
5. Applications
This section briefly lists some of the key applications related to CD-
ROM that are available under Linux. Check the Linux Software Map for
the latest versions and archive sites.
5.1. Audio CD Players
Several programs are available for playing audio CDs, either through a
headphone jack or an attached sound card.
Workman
a graphical player running under X11 and supporting a CD
database and many other features
WorkBone
an interactive text-mode player
xcdplayer
a simple X11 based player
cdplayer
a very simple command line based player
Xmcd
an X11/Motif based player
xmitsumi
another X11 based player for Mitsumi drives
xplaycd
another X11 based player, bundled with sound mixer and VU meter
programs
cdtool
command line tools for playing audio CDs
Some of these programs are coded to use a specific device file for the
CD-ROM (e.g. /dev/cdrom). You may be able to pass the correct device
name as a parameter, or you can create a symbolic link in the /dev
directory. If sending the CD output to a sound card, you may wish to
use a mixer program to set volume settings or select the CD-ROM input
for recording.
5.2. PhotoCD
PhotoCDs use an ISO-9660 file system containing image files in a
proprietary format. Not all CD-ROM drives support reading PhotoCDs.
The hpcdtoppm program by Hadmut Danisch converts PhotoCD files to the
portable pixmap format. It can be obtained from
<ftp://ftp.gwdg.de/pub/linux/hpcdtoppm> or as part of the PBM
(portable bit map) utilities, available on many archive sites (look
for "pbm" or "netpbm").
The photocd program by Gerd Knorr kraxel@cs.tu-berlin.de can convert
PhotoCD images into Targa or Windows and OS/2 bitmap files.
The same author has written the program xpcd, an X11-based program for
handling PhotoCD images. You can select the images with a mouse,
preview the image in a small window, and load the image with any of
the five possible resolutions. You can also mark a part of the Image
and load only the selected part. Look for these packages at
<ftp://ftp.cs.tu-berlin.de/pub/linux/Local/misc/>.
The ImageMagick image file manipulation program also supports PhotoCD
files. It is available from
<ftp://ftp.x.org/contrib/applications/ImageMagick/>.
5.3. Mkisofs
Eric Youngdale's mkisofs package allows creating an ISO-9660 file
system on a hard disk partition. This can then be used to assist in
creating and testing CD-ROM file systems before mastering discs.
The tools for actually writing data to writable CD-ROM drives tend to
be vendor specific. They also require writing the data with no
interruptions, so a multitasking operating system like Linux is not
particularly well suited.
5.4. ISO-9660 Utilities
These are some utilities for verifying the format of ISO-9660
formatted discs; you may find them useful for testing suspect CDs. The
package can be found at <ftp://ftp.cdrom.com/pub/cdrom/ptf/>. They
were written by Bill Siegmund and Rich Morin.
6. Answers to Frequently Asked Questions
6.1. How can a non-root user mount and unmount discs?
Most mount commands support the user option. If you make an entry such
as the following in /etc/fstab:
/dev/sbpcd /mnt/cdrom iso9660 user,noauto,ro
then an ordinary user will be allowed to mount and unmount the drive
using these commands:
% mount /mnt/cdrom
% umount /mnt/cdrom
The disc will be mounted with some options that help enforce security
(e.g. programs cannot executed, device files are ignored); in some
cases this may be too restrictive.
Another method is to get the usermount package which allows non-root
users to mount and unmount removable devices such as floppies and CD-
ROMs, but restricts access to other devices (such as hard disk
partitions). It is available on major archive sites.
The archive site ftp.cdrom.com has the source file mount.c which
allows mounting an unmounting of CD-ROMs (only) by normal users. It
runs as a setuid executable.
6.2. Why do I get device is busy when unmounting a CD-ROM?
The disc cannot be unmounted if any processes are accessing the drive,
including having their default directory set to the mounted
filesystem. If you cannot identify the processes using the disc, you
can use the fuser command, as shown in the following example.
% umount /cdrom
umount: /dev/hdd: device is busy
% fuser -v /cdrom
USER PID ACCESS COMMAND
/mnt/cdrom tranter 133 ..c.. bash
6.3. How do I export a CD-ROM to other hosts over NFS?
You need to add an entry to the /etc/exports file. Users on other
machines will then be able to mount the device. See the exports(5) man
page for details.
6.4. Can I boot Linux from a CD-ROM?
When initially installing Linux the most common method is to use a
boot floppy. Some distributions allow booting a Linux kernel on CD
directly from DOS.
I've been told that it is possible to boot from ATAPI CD-ROM drives
which have the appropriate ROM BIOS functions, but I have no first
hand experience.
6.5. How can I read digital data from audio CDs?
Heiko Eissfeldt (heiko@colossus.escape.de) and Olaf Kindel have
written a utility that reads audio data and saves it as .wav format
sound files. The package is called cdda2wav.tar.gz and can be found on
sunsite.unc.edu.
Because CD-ROM drives are changing very quickly, it is difficult to
list which models support reading digital data. You best bet is to get
the latest cdda2wav package and read the documentation.
For more information on this subject, see the web site
http://www.tardis.ed.ac.uk/~psyche/pc/cdrom/CDDA.html and the alt.cd-
rom FAQ listed in the references section.
6.6. Why doesn't the find command work properly?
On ISO-9660 formatted discs without the Rock Ridge Extensions, you
need to add the -noleaf option to the find command. See the find(1)
man page for details.
(In my experience virtually all recent Linux CDs use the Rock Ridge
extensions, so this problem should occur very rarely.)
6.7. Does Linux support any recordable CD-ROM drives?
The X-CD-Roast package for Linux is a graphical front-end for using CD
writers. The package can be found at sunsite.unc.edu in
/pub/Linux/utls/disk-management/xcdroast-0.95.tar.gz
Also see the Linux CD-Writer mini-HOWTO document, found at
<ftp://sunsite.unc.edu/pub/Linux/docs/HOWTO/mini/CD-Writer> or
<http://sunsite.unc.edu/mdw/HOWTO/CD-Writer.html>.
6.8. Why do I get mount: Read-only file system when mounting a CD-
ROM?
CD-ROM is a read-only media. With some early kernels you could mount a
CD-ROM for read/write; attempts to write data to the CD would simple
be ignored. As of kernel version 1.1.33 this was corrected so that CD-
ROMs must be mounted read only (e.g. using the -r option to mount).
6.9. Why does the disc tray open when I shut down the system?
As of the 1.1.38 kernel, the sbpcd driver ejects the CD when it is
unmounted. If you shut down the system, a mounted CD will be
unmounted, causing it to eject.
This feature is for convenience when changing discs. If the tray is
open when you mount or read a CD, it will also automatically be
closed.
I found that this caused problems with a few programs (e.g. cdplay and
workbone). As of the 1.1.60 kernel you can control this feature under
software control. A sample program is included in the sbpcd
documentation file (or use the eject program).
6.10. I have a "special" CD that can't be mounted
The "special" CD is likely an XA disc (like all Photo CDs or "one-
offs" created using CD-R drives). Most of the Linux kernel CD-ROM
drivers do not support XA discs, although you may be able to find a
patch to add support on one of the archive sites.
The sbpcd driver does support XA. If you are using this driver you can
determine if the disc is XA using the following procedure: go into the
file sbpcd.c and enable the display of the "Table of Contents"
(DBG_TOC). Build and install the new kernel and boot from it. During
each mount the TOC info will be written (either to the console or to a
log file). If the first displayed value in the TOC header line is
"20", then it is an XA disc. That byte is "00" with normal disks. If
the TOC display shows different tracks, that is also a sign that it is
an XA disc.
(thanks to Eberhard Moenkeberg for the above information)
Other possibilities for unreadable CDs are:
1. The disc doesn't use an ISO-9660 file system (e.g. some use SunOS
or HFS)
2. It is an audio CD
3. The CD is damaged or defective
4. You put it in the drive upside down :-)
6.11. Do multi-platter CD-ROM drives work with Linux?
Several users have reported success with SCSI multi-disc CD-ROM
changers. You probably need to enable the "Probe all LUNs on each
SCSI device" kernel configuration option. At least one user also had
to increase a SCSI timeout value in the kernel driver. The Nakamichi
MBR-7 7 disc changer and Pioneer 12 disc changer have been reported to
work.
EIDE/ATAPI multi-disc changers are also available. The 2.0 kernel has
rudimentary support for some drives using the CDROM_SELECT_DISC ioctl
function. The IDE-CD kernel driver documentation file includes source
code for a program to select changer slots, or you can use a recent
version of the eject program described earlier.
6.12. I get "/cdrom: Permission denied" errors
Some CDs have root directory file permissions that only allow user
root to read them. The March 1995 InfoMagic CD set is one example.
This is a real inconvenience.
The following patch, courtesy of Christoph Lameter
(clameter@waterf.org) patches the kernel to get around this problem.
From: clameter@waterf.org (Christoph Lameter)
Newsgroups: comp.os.linux.setup
Subject: InfoMagic Developers Set: Fix for CD-ROM permissions
Date: 12 Apr 1995 20:32:03 -0700
Organization: The Water Fountain - Mining for streams of Living Water
NNTP-Posting-Host: waterf.org
X-Newsreader: TIN [version 1.2 PL2]
The March 1995 Edition of the InfoMagic Developers CD-ROM Set has
problems because the information stored in the root directory
permissions is causing the following problems with using the CDs
1. Disc1 will always have the owner/group of 5101/51 and has write
access allowed (?)
2. Disc2 and 3 have rwx set for root and no rights at all for any
other group/user. These discs cannot be accessed from any user other
than root! I run a BBS and I need to make them accessible for download
by others.
I have seen several fixes to this problem already floating
around. Trouble is that these fixes usually change the rights for ALL
directories on the CD. This fix here changes ONLY the rights for the
root directory of the CD-ROM. If you want to run parts of Linux
directly off the CD you might run into trouble if all directories are
readable for everyone and if they are all owned by root.
This fix will set the rights for the root directory to r-xr-xr-x and
the owner/group to the values indicated in the uid and gid options to
the mount command.
To apply:
cd /usr/src/linux/fs/isofs
patch <**THIS MESSAGE**
and recompile kernel (you may have to fix up the patch by hand
depending on your kernel version).
This fix should probably be incorporated into the kernel. What business
does data on a CD have to mess around with the permissions/owners of the
mount-point anyways?
--- inode.c.ORIG Wed Apr 12 17:24:36 1995
+++ inode.c Wed Apr 12 17:59:12 1995
@@ -552,7 +552,15 @@
these numbers in the inode structure. */
if (!high_sierra)
- parse_rock_ridge_inode(raw_inode, inode);
+ { parse_rock_ridge_inode(raw_inode, inode);
+ /* check for access to the root directory rights/owner CL */
+ if((inode->i_sb->u.isofs_sb.s_firstdatazone) == inode->i_ino)
+ { /* Change owner/rights to the ones demanded by the mount command */
+ inode->i_uid = inode->i_sb->u.isofs_sb.s_uid;
+ inode->i_gid = inode->i_sb->u.isofs_sb.s_gid;
+ inode->i_mode = S_IRUGO | S_IXUGO | S_IFDIR;
+ }
+ }
#ifdef DEBUG
printk("Inode: %x extent: %x\n",inode->i_ino, inode->u.isofs_i.i_first_extent);
@@ -805,4 +813,3 @@
}
#endif
-
Note that the above patch is somewhat old and probably won't apply
cleanly against recent 2.0 kernels. Also see the related question on
hidden files later in this document.
6.13. How do I interpret IDE CD kernel error messages?
What does it mean when I get a kernel message from the IDE CD-ROM
driver like "hdxx: code: xx key: x asc: xx ascq: x"?
This is an status/error message from the IDE CD-ROM drive. By default
the IDECD driver prints out the raw information instead of wasting
kernel space with error messages. You can change the default to
display the actual error messages by going into
</usr/src/linux/drivers/block/ide-cd.c>, changing the value of
VERBOSE_IDE_CD_ERRORS to 1, and recompiling the kernel.
6.14. How can I tell what speed CD-ROM I have?
Here's one way. This command measures how long is takes to read 1500K
of data from CD:
% time -p dd if=/dev/cdrom of=/dev/null bs=1k count=1500
1500+0 records in
1500+0 records out
real 5.24
user 0.03
sys 5.07
The transfer rate of single speed drives is 150 kilobytes per second,
which should take about 10 seconds. At double speed it would take five
seconds, quad speed would take 2.5, etc...
The "real" time above is probably the best number to look at -- in
this case it indicates a double speed drive. You can increase the
amount of data transferred to get a more accurate value (in case you
were wondering, the data does not get cached). You should probably run
the command a few times and take the average.
6.15. My CD-ROM stopped working after Linux was installed
The usual symptom is that the boot disk used to initially install
Linux recognized your CD-ROM drive, but after Linux was installed on
the hard drive or floppy and rebooted it no longer recognizes the CD-
ROM.
The most common reason for this problem is that with some Linux
distributions the kernel that is installed on your hard drive (or
floppy) is not necessarily the same one that was on your boot disk.
You selected a boot disk that matched your CD-ROM hardware, while the
kernel you installed is a "generic" kernel that is lacking CD-ROM
support. You can verify this by following the troubleshooting
guidelines discussed previously in this document (e.g. start by
checking /proc/devices).
The solution is to recompile the kernel, ensuring that the drivers for
your CD-ROM drive and any others that are needed (e.g. SCSI
controller, ISO-9660 file system) are included. See the Kernel HOWTO
<http://sunsite.unc.edu/mdw/HOWTO/Kernel-HOWTO.html> if you don't know
how to do this.
If you passed any command line options to the boot disk (e.g.
"hdc=cdrom") you need to add these to your boot program configuration
file (typically /etc/lilo.conf).
6.16. There are "hidden" files on a CD which I can't read
Some CDs have files with the "hidden" bit set on them. Normally these
files are not visible. If you mount the CD with the "unhide" option
then the files should be accessible (this doesn't seem to be
documented anywhere).
7. References
I have already mentioned the README files, typically installed in
</usr/src/linux/Documentation/cdrom/>. These can be a gold mine of
useful information.
The following usenet FAQs are posted periodically to news.answers and
archived at Internet FTP sites such as <ftp://rtfm.mit.edu/>:
� alt.cd-rom FAQ
� comp.periphs.scsi FAQ
� Enhanced IDE/Fast-ATA/ATA-2 FAQ
Several other Linux HOWTOs have useful information relevant to CD-ROM:
� SCSI HOWTO <http://sunsite.unc.edu/mdw/HOWTO/SCSI-HOWTO.html>
� Hardware Compatibility HOWTO
<http://sunsite.unc.edu/mdw/HOWTO/Hardware-HOWTO.html>
� Sound HOWTO <http://sunsite.unc.edu/mdw/HOWTO/Sound-HOWTO.html>
� Kernel HOWTO <http://sunsite.unc.edu/mdw/HOWTO/Kernel-HOWTO.html>
� Distribution HOWTO <http://sunsite.unc.edu/mdw/HOWTO/Distribution-
HOWTO.html>
At least a dozen companies sell Linux distributions on CD-ROM; most of
them are listed in the Distribution HOWTO.
The following Usenet news groups cover CD-ROM related topics:
� comp.publish.cdrom.hardware
� comp.publish.cdrom.multimedia
� comp.publish.cdrom.software
� comp.sys.ibm.pc.hardware.cd-rom
� alt.cd-rom
� alt.cd-rom.reviews
The comp.os.linux newsgroups are also good sources of Linux specific
information.
There is a large archive of CD-ROM information and software at
<ftp://ftp.cdrom.com/pub/cdrom/>.
A FAQ document on IDE and ATA devices can be found at
<ftp://rtfm.mit.edu/pub/usenet/news.answers/pc-hardware-faq/enhanced-
IDE/> and at <http://www.seagate.com/techsuppt/faq/faqlist.html>.
Western Digital, the company that started the IDE protocol, has
information available on the IDE protocol available on their FTP site
at <ftp://fission.dt.wdc.com/pub/standards/atapi>.
A Web site dedicated to multimedia can be found at
<http://viswiz.gmd.de/MultimediaInfo/>. Creative Labs has a Web site
at <http://www.creaf.com/>.
The Linux Documentation Project has produced several books on Linux,
including Linux Installation and Getting Started. These are freely
available by anonymous FTP from major Linux archive sites or can be
purchased in hardcopy format.
The Linux Software Map (LSM) is an invaluable reference for locating
Linux software. The LSM can be found on various anonymous FTP sites,
including <ftp://sunsite.unc.edu/pub/Linux/docs/LSM.gz/>.
The Linux mailing list has a number of "channels" dedicated to
different topics. To find out how to join, send a mail message with
the word "help" as the message body to majordomo@vger.rutgers.edu
(Note: at time of writing these mailing lists were severely overloaded
and a replacement was being sought).
Finally, a shameless plug: If you want to learn a lot more about
multimedia under Linux (especially CD-ROM and sound card applications
and programming), check out my book Linux Multimedia Guide, ISBN
1-56592-219-0, published by O'Reilly and Associates. For details, call
800-998-9938 in North America or check the Web page
<http://www.ora.com/catalog/multilinux/noframes.html>.