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The Linux CD-ROM HOWTO Jeff Tranter, tranter@pobox.com v1.13, 23 January 1998 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. ______________________________________________________________________ Table of Contents 1. Introduction 1.1 Acknowledgments 1.2 Revision History 1.3 New Versions Of This Document 1.4 Feedback 1.5 Distribution Policy 2. CD-ROM Technology 3. Supported Hardware 3.1 ATAPI CD-ROM Drives 3.2 SCSI CD-ROM Drives 3.3 Proprietary CD-ROM Drives 3.4 Parallel Port Drives 3.5 Alternate Drivers 4. Installation 4.1 Installing the Hardware 4.2 Configuring and Building the Kernel 4.3 Creating Device Files and Setting Boot Time Parameters 4.3.1 Sbpcd Driver 4.3.2 Sonycdu535 Driver 4.3.3 Cdu31a Driver 4.3.4 Aztcd Driver 4.3.5 Gscd Driver 4.3.6 Mcd Driver 4.3.7 Mcdx Driver 4.3.8 Cm206 Driver 4.3.9 Optcd Driver 4.3.10 Sjcd Driver 4.3.11 Bpcd Driver 4.3.12 SCSI Driver 4.3.13 IDECD Driver 4.4 Booting the Linux Kernel 4.5 Mounting, Unmounting, and Ejecting Devices 4.6 Troubleshooting 4.6.1 Step 1: Make sure you are really running the kernel you compiled 4.6.2 Step 2: Make sure the proper kernel drivers are compiled in 4.6.3 Step 3: Did the kernel detect your drive during booting? 4.6.4 Step 4: Can you read data from the drive? 4.6.5 Step 5: Can you mount the drive? 4.6.6 Debugging Audio Problems 4.6.7 When All Else Fails 5. Applications 5.1 Audio CD Players 5.2 PhotoCD 5.3 Mkisofs 5.4 ISO-9660 Utilities 6. Answers to Frequently Asked Questions 6.1 How can a non-root user mount and unmount discs? 6.2 Why do I get device is busy when unmounting a CD-ROM? 6.3 How do I export a CD-ROM to other hosts over NFS? 6.4 Can I boot Linux from a CD-ROM? 6.5 How can I read digital data from audio CDs? 6.6 Why doesn't the find command work properly? 6.7 Does Linux support any recordable CD-ROM drives? 6.8 Why do I get mount: Read-only file system when mounting a CD-ROM? 6.9 Why does the disc tray open when I shut down the system? 6.10 I have a "special" CD that can't be mounted 6.11 Do multi-platter CD-ROM drives work with Linux? 6.12 I get "/cdrom: Permission denied" errors 6.13 How do I interpret IDE CD kernel error messages? 6.14 How can I tell what speed CD-ROM I have? 6.15 My CD-ROM stopped working after Linux was installed 6.16 There are "hidden" files on a CD which I can't read 6.17 Where is the CD-ROM API documented? 6.18 Why don't I see long filenames on this Windows CD-ROM? 6.19 Is Microsoft's Joliet filesystem supported? 7. References ______________________________________________________________________ 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 SGML Tools 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 Version 1.11 added reference for parallel port drives; added info on bpcd driver; new URL for Chinese version; alternate CR-56x driver; info on bootable CDs; answered question on CD-ROM API; Linux Multimedia Guide is now available in French and Japanese Version 1.12 added link to Polish translation; CD Writing is no longer a mini-HOWTO; added two questions related to Joliet filesystem Version 1.13 added index entries; placed under LDP license rather than GPL; SuperProbe replaced by reference to kernel based automounter 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/LDP/HOWTO/>. 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@ms4.hinet.net) is available from <http://linux.ntcic.edu.tw/~yorkwu/linux/howto/cdrom/>. A Polish translation by Bartosz Maruszewski (b.maruszewski@zsmeie.torun.pl) is available from <http://www.jtz.org.pl/Html/CDROM-HOWTO.pl.html>. Most translations of this and other Linux HOWTOs can also be found at <http://sunsite.unc.edu/pub/Linux/docs/HOWTO/translations/> and <ftp://sunsite.unc.edu/pub/Linux/docs/HOWTO/translations/>. 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, 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 under Linux, as best I can. Before doing so, please read all of the information in this HOWTO, and then send me detailed information about the problem. Please do not ask me about using CD-ROM drives under operating systems other than Linux. 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, Tim Bynum (linux-howto@sunsite.unc.edu), for more information. 1.5. Distribution Policy Copyright (c) 1995-1998 by Jeff Tranter. This document may be distributed under the terms set forth in the LDP license at <http://sunsite.unc.edu/LDP/COPYRIGHT.html>. 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. Hardware manufacturers then introduced double speed (300 kB/sec), quad speed (600 kB/sec), and higher. As I write this, 24 times (24X) drives are readily available and affordable. 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) are also available and are becoming increasingly affordable. 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 2.0.33. 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 in /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 MicroSolutions Backpack bpcd 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 via a parallel port. The only drive of this type that is currently supported in the Linux kernel is the MicroSolutions Backpack. Linux kernel drivers for several more of these drives are available separately as kernel patches or loadable modules. For the latest information check <http://www.torque.net/linux-pp.html>. 3.5. Alternate Drivers There is an alternate kernel driver available for Panasonic/Matsushita CR-56x drives written by Zoltan Vorosbaranyi. It can be found at <ftp://ftp.tarki.hu/pub/linux/pcd/pcd-0.29.tar.gz>. 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/LDP/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: o to support a CD-ROM drive or other hardware o to upgrade to a newer kernel release o to free up memory resources by minimizing the size of the kernel The Linux Kernel HOWTO <http://sunsite.unc.edu/LDP/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/LDP/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/LDP/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/LDP/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. 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. Bpcd Driver Principal author: Grant R. Guenther (grant@torque.net) Multi-session support: unknown Multiple drive support: no Loadable module support: yes Reading audio frames: no Auto-probing: yes Device file: /dev/bpcd, major 41 Configuration file: bpcd.h Kernel config option: MicroSolutions backpack CDROM support? README file: bpcd The driver accepts a kernel command line of the form: bpcd=<io-address> indicating the base address to be used (e.g. bpcd=0x3bc). The device file can be created using: # mknod /dev/bpcd b 41 0 This driver is included with the 2.1 kernel source distribution. See the file bpcd for more information on this driver. 4.3.12. 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). 4.3.13. 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. Recent 2.0 and 2.1 kernels support a kernel-based automounter which provides transparent mounting of removable media including CD-ROM. You can find the tools needed to use it at <ftp.kernel.org:/pub/linux/daemons/autofs/>. 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/cdrom/>. 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: o carefully re-read this HOWTO document o read the references listed at the end of this document, especially the relevant kernel source README files o post a question to one of the comp.os.linux or other usenet newsgroups o send a question to the Linux mailing list o try using the latest Linux kernel o contact your computer dealer o contact the CD-ROM manufacturer o send mail to the maintainer of the relevant kernel driver (look in the file /usr/src/linux/MAINTAINERS) o send mail to me o 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/unixfreeware/archive/>. 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 On some systems you may need to be root when running the fuser command in order to see the processes of other users. 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. Michael Fulbright (msf@redhat.com) reports that with the right CD-ROM, ROM BIOS, and ATAPI CD-ROM drive it is possible to boot directly from CD. The latest version of mkisofs also supports creating such disks. He has added some patches to support the El Torito standard for bootable CDs. 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/cdda/ 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/utils/disk-management/xcdroast-0.95.tar.gz Also see the Linux CD-Writing HOWTO document, found at <ftp://sunsite.unc.edu/pub/Linux/docs/HOWTO/CD-Writing.html> or <http://sunsite.unc.edu/LDP/HOWTO/CD-Writing.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/LDP/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). 6.17. Where is the CD-ROM API documented? If you want to write your own application, such as an audio CD player program, you will need to understand the application programming interface (API) provided by Linux. Originally the CD-ROM kernel drivers used their own ioctl() functions to support features specific to each drive. Header files such as /usr/include/linux/sbpcd.h describe these. Because many of the drivers were based on other drivers, the interfaces, while not identical, have a lot in common. More recently there has been an initiative headed by David van Leeuwen (david@tm.tno.nl) to standardize the API for CD-ROM drives, putting common code in one place and ensuring that all drivers exhibit the same behaviour. This is documented in the file /usr/src/linux/Documentation/cdrom/cdrom-standard.tex. Several kernel drivers support this. I expect that by the next major kernel release (3.0?) all CD-ROM drivers will conform to this API. My book, Linux Multimedia Guide, goes into quite a bit of detail on how to program CD-ROM drives, especially for audio functions. See the end of the References section. 6.18. Why don't I see long filenames on this Windows CD-ROM? If you have a CD-ROM which has long filenames under Windows but not under Linux, it may be formatted using Microsoft's proprietary Joliet filesystem. See the next question for a solution. 6.19. Is Microsoft's Joliet filesystem supported? Microsoft has created an extension to the ISO CD-ROM format called Joliet. At the time of writing, support for Joliet was in progress and patches were available from <http://www- plateau.cs.berkeley.edu/people/chaffee/joliet.html> or <ftp://www- plateau.cs.berkeley.edu/pub/multimedia/linux/joliet/>. 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/>: o alt.cd-rom FAQ o comp.periphs.scsi FAQ o Enhanced IDE/Fast-ATA/ATA-2 FAQ Several other Linux HOWTOs have useful information relevant to CD-ROM: o SCSI HOWTO <http://sunsite.unc.edu/LDP/HOWTO/SCSI-HOWTO.html> o Hardware Compatibility HOWTO <http://sunsite.unc.edu/LDP/HOWTO/Hardware-HOWTO.html> o Sound HOWTO <http://sunsite.unc.edu/LDP/HOWTO/Sound-HOWTO.html> o Kernel HOWTO <http://sunsite.unc.edu/LDP/HOWTO/Kernel-HOWTO.html> o Distribution HOWTO <http://sunsite.unc.edu/LDP/HOWTO/Distribution- HOWTO.html> o CD Writing HOWTO <http://sunsite.unc.edu/LDP/HOWTO/CD-Writing.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: o comp.publish.cdrom.hardware o comp.publish.cdrom.multimedia o comp.publish.cdrom.software o comp.sys.ibm.pc.hardware.cd-rom o alt.cd-rom o 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/>. 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. As well as the original English version, French and Japanese translations are now in print. For details, call 800-998-9938 in North America or check the Web page <http://www.ora.com/catalog/multilinux/noframes.html> or my home page <http://www.pobox.com/~tranter/>.