11.1. Introduction

Linux offers a host of CD/DVD writing and authoring utilities. The entire field is evolving rapidly, and CD/DVD standards are in a chaotic state. There are several competing, incompatible standards, and more are looming on the horizon as commercial distributors toil to develop a magical disc that will permit playback but not copying. This chapter sidesteps all of this drama and introduces some basic techniques for writing data CDs and DVDs. You'll need the cdrtools and dvd+rw-tools packages.

To create discs the easy way, use K3b. It is a graphical frontend to cdrtools, cdrdao, mkisofs, growisofs, and other command-line editing tools. K3b makes it easy to set up your drives and to give users any necessary root privileges, such as those required by cdrecord and cdrdao. The layout is logical and simple to use; it gets my vote as the best CD/DVD writer on any platform. Of course, the Linux world offers many more choices, such as GCombust, X-CD-Roast, and Gnome Toaster. These are all simple to use, so this chapter will cover the command-line tools. Understanding these will also make the graphical tools more useful, as you'll understand the commands and weird terminology.

A major change in the 2.6 kernel is that you no longer need to use SCSI emulation for CD/DVD drives. Instead of running cdrecord scanbus to find the SCSI bus addresses, simply use the /dev names of the devices:

# cdrecord dev=/dev/hdc <commands>

If you have upgraded from a 2.4 to a 2.6 kernel and you used IDE-SCSI for your CD/DVD drives, be sure that the IDE-SCSI entries are removed from your bootloader, or you'll get strange boot errors.

11.1.1 Glossary of Formats and Standards

Here are the hardware standards:

CD-R

CD-Recordable, or WORM (Write Once, Read Many). CD-Rs are universal and should be readable in any CD-ROM drive.

CD-RW

CD-Rewritable, or WMRM (Write Many, Read Many). A drive must be "multiread" to be able to read CD-R and CD-RW discs. CD-RWs should be readable in all contemporary drives.

CD-ROM

Compact Disc-Read-Only Memory. Commercially produced discs are pressed, not burned with a laser, and cannot be written to.

Mount Rainier ReWrite

The circuitry needed by a drive to support UDF.

DVD-Video

The standard used on commercially produced movie discs, playable on all DVD machines.

DVD-R and DVD+R

WORM format. Playable on all DVD players. DVD-R has two different, incompatible disc types: DVD-R(A) and DVD-R(G). You can't use A discs in G writers, and vice versa.

DVD-RAM

Rewritable, designed for data storage. Theoretically, it can take up to 100,000 rewrites per disc. You can also record and play movies on a PC, but a standalone DVD player probably won't be able to read DVD-RAMs.

DVD-R/RW

Designed for recording movies. This DVD standard is supported by the DVD Forum (http://www.dvdforum.com).

DVD+R/RW

A competing, incompatible standard to DVD-R/RW, supported by the DVD+RW Alliance (http://www.dvdrw.com). Only DVD+R/RW supports UDF.

The newest generation of DVD drives for computers support all formats. Standalone DVD recorders are still fighting standards wars between the DVD+ and DVD- formats.

Here are the CD and DVD filesystem standards:

El Torito

Bootable format specification.

UDF

Universal Disk Format, the industry-standard incremental packet-writing filesystem. This allows dropping files directly on to a disc, just like on a 3.5" diskette. It was expected that Linux would fully support this in the 2.6 kernel, but it's not there yet.

ISO-9660

The old file layout standard, allowing only 8.3 filenames (from the ancient MS-DOS days, where filenames could have only up to 8 letters and had to have 3-letter file extensions).

Rock Ridge

Extensions to ISO-9660, allowing long filenames and Unix-style symlinks. It preserves all file attributes, such as ownership and permissions. Unix file attributes are not displayed when the disc is read on a Windows system.

Joliet

Microsoft extension to the ISO-9660 filesystem that allows Unicode characters to be used in filenames, as well as long filenames. It also creates truncated filenames for MS-DOS compatibility (these weird-looking things: FILENA~1.TXT). It allows filenames of up to 64 characters, including spaces, and is readable by Windows 95 or later and by Macintosh computers running the Joliet Volume Access extension. Macs will not read Joliet filenames that are longer than 31 characters.

Here are the CD standards books:

Yellow Book

Physical format for data CDs

Orange Book

Physical format for recordable CDs, with multisession capability:

Part I: CD-MO (Magneto-Optical)

Part II: CD-R (Write-once; includes "hybrid" spec for PhotoCD)

Part III: CD-RW (Re-writable)

Red Book

CD Audio standard that describes the physical properties of the disc and the digital audio encoding

These books can be purchased from http://www.licensing.philips.com, if you really want to get into the gory details.

These are the write options:

Session

Any single recorded segment on a disc, which can contain data files or a number of music tracks. A disc can contain several sessions.

Track

The program area of a CD is divided into tracks; each track can contain data of only one type. A disc (even a DVD) holds a maximim of 99 tracks—the number is hardcoded.

Multisession

Allows adding files to a single disc over time, rather than having to record all of your files in a single session. For a disc to be readable, the session must be "closed," or fixated. However, this prevents adding more files to the disc. Multisession links the individual sessions and updates the disc's table of contents so that it appears as a single directory.

SAO (session-at-once)

A single, complete session (lead-in, program, and lead-out areas) of a CD-R or CD-RW disc, written in one uninterrupted sequence.

DAO (disc-at-once)

Writes the entire CD in one pass, or session. The entire burn must complete without interruption, and no more sessions may be added. This is the most reliable way to record audio tracks.

TAO (track-at-once)

Allows the writes to be done in multiple passes. There is a maximum of 99 tracks per disc. Sometimes this causes audio CDs to not play correctly on audio disc players, though I've found it to be reliable.

For more information on DVDs, see the DVD FAQ at http://www.dvddemystified.com/dvdfaq.html.

For more information on CDs, see the CD Recordable FAQ at http://www.cdrfaq.org.