Using the CD writer

This document explains how to use CD writers on our linux computers. The following machines can write CDs.

Machine Main User Writes CDs? Writes DVDs?
grus Diana Worrall yes yes

cetus server yes no

pavo Rhys Morris yes yes

lupus Malcolm Bremer yes yes

monoceros Aaron Robotham yes yes

vela Laura Douglas yes yes

orion All yes yes

eridanus Katy Lancaster yes yes

Machine	Main User	Writes CDs?	Writes DVDs?
grus	Diana Worrall	yes	yes
cetus	server	yes	no
pavo	Rhys Morris	yes	yes
lupus	Malcolm Bremer	yes	yes
monoceros	Aaron Robotham	yes	yes
vela	Laura Douglas	yes	yes
orion	All	yes	yes
eridanus	Katy Lancaster	yes	yes

Writing a DVD is different see our local page here.

Writing a CD is a two-step process. First you create an image of the files to be written to CD. Then you actually write the image to the CD.

Making an image

To make an image suitable for writing to CD do

mkisofs -l -r -o filename.fs directory

where filename.fs is the name of the image to be created and directory is the previously prepared directory which will be written to CD. mkisofs will take a short while to check and build the file system. You will be left with a file called filename.fs containing everything that was in directory in a format suitable for writing to CD. The capacity of a blank CD is 650 Mb (sometimes 700 Mb). Do not exceed this size limit in directory, and be aware that some space may be taken up with file system requirements.

Writing

cdrecord is the command to write to CD. In its simplest form, you can call it with

cdrecord -v filename.fs

where filename.fs is the name of the file prepared with mkisofs. The -v option causes the program to give diagnostic output. Make sure there is a blank medium in the drive! You will have the opportunity to cancel the command (with control-C) before it starts writing. It will take about 20 minutes to write a full CD.

It is important to ensure that

The CD writer is not subject to physical shocks or other movement during the writing process.
The host machine is not heavily loaded or performing any disc-intensive tasks.
Nobody else is using the CD writer when you start.

Advanced use

Rewritable CDs

The CD writer works with rewritable CDs. Before rewriting a CD, you will need to blank it with cdrecord -v blank=fast. Be aware that not all CD-ROM drives will read rewritables.

Multi-session use

Multi-session use substantially expands the usefulness of the CD writer by allowing you to add more than one file system to it. This means you can back up over a period of time rather than waiting for 650-Mb chunks of data to become available.

To make use of this facility, make your first file system with mkisofs as normal, but then write it with the -multi option:

cdrecord -v -multi filename.fs

Now (or later) you can make subsequent file systems to add on to this one. First, use cdrecord to determine the space taken up by your existing files on the CD:

cdrecord -msinfo

This returns two numbers; call them X and Y. Then to make a file system that can be added to the existing one, use some additional arguments to mkisofs:

mkisofs -M 1,1,0 -C X,Y -l -r -o filename2.fs new_directory

(On hercules use -M 1,0,0 instead; on taurus and lupus use -M 0,0,0.) The program will look at the disc and construct a filesystem that can be added to what's already there. Then just write it with

cdrecord -v -multi filename2.fs

You can carry on doing this until disc space runs out. Each `session' is written as a separate track on the CD. Be aware that the top-level directories of the multiple filesystems will be merged; they will appear as one large directory when you mount the CD. Also, note that some old operating systems cannot deal with multi-session CDs, though almost all modern machines can: make sure you test your CD first if possible!

CD copying

Make an image of the files on a CD, then write that image to a blank CD.

Media

Blank CDs and DVDs for group use are available from Rhys or from Stores.

Policy

The CD writers may not be used for reproducing copyright material without permission.

Further information

There is a large number of options to the cdrecord command. Once you have run the startup script, man cdrecord will tell you about some of them. CDrecord has a home page here.

Rhys Morris

Last modified: Mon Jun 26 10:32:53 BST 2006