This is the section usually known as "frequently asked questions with answers". If you have a problem with your partner, kids or dog, just send it in, as long as it is related to writing CD-Rs or is otherwise entertaining.
Test it. Use the option -dummy to do an empty run of cdrecord. Do everything you would do otherwise and watch if the burning process survives.
If you feed cdrecord directly from mkisofs, then disk intensive processes
such as updating the locate database lower the maximum flow rate
and may corrupt the CD. You better check such processes are not started
via cron, at or anacron while you burn
CD-Rs.
Fragmentation of files is usually so low that its impact isn't noticed. However, you can easily construct pathological cases of fragmentation, which lower the throughput of your hard disks under 100 kbyte/second. So don't do that. :-) Yes, files on a hard disk get fragmented over the years. The faster, the fuller the filesystem is. Always leave 10% or 20% free space, and you should run fine with respect to writing CD-Rs.
If you're uncertain then look at the messages printed while booting. The percentage of fragmentation is reported while checking the filesystems. You can check for this value with the very dangerous command
shell> e2fsck -n /dev/sda5 # '-n' is important!
[stuff deleted -- ignore any errors]
/dev/sda5: 73/12288 files (12.3% non-contiguous)
In this example the fragmentation seems to be very high -- but there are only 73 very small files on the filesystem. So the value is not alarming.
There is an experimental utility called e2defrag to defragment extended-2 filesystems. The current version does not work reliable enough to use it even for private environments. If you really want to defragment your filesystem, make a backup copy (better: two copies), practise restoring the data, then create a new filesystem (that will destroy the old) and restore the data. This sketch is currently the safest technique.
Yes. The only filesystem that isn't reliable and fast enough for writing CD-ROMs from is the network filesystem (NFS). I used UMSDOS myself to share the disk-space between Linux and DOS/Win on a PC (486/66) dedicated for writing CD-ROMs.
Yes. You can put any filesystem you like on the CD. But other operating systems than Linux won't be able to deal with this CD. Here goes the recipe:
dd if=/dev/zero of="empty_file" bs=1024k count=650
shell> /sbin/mke2fs -b 2048 empty_file
empty_file is not a block special device.
Proceed anyway? (y,n) y
mount -t ext2 -o loop=/dev/loop1 empty_file /mnt
cdrecord on empty_file (which is no
longer empty) as if it were an ISO-9660-image.If you want to make an entry in /etc/fstab for such
a CD, then disable the checking of the device file on system
startup. For example:
/dev/cdrom /cdrom ext2 defaults,ro 0 0
The first 0 means "don't include in dumps", the second (=important) one means "don't check for errors on startup" (fsck will fail to check the CD for errors).
There are several software packages available. The newest one is "cdpranoia" and can be downloaded from
http://www.xiph.org/paranoia/
Or you want to try the combination of "cdda2wav" and "sox", available from sunsite and its mirrors:
ftp://sunsite.unc.edu/pub/Linux/apps/sound/cdrom/cdda2wav0.71.src.tar.gzftp://sunsite.unc.edu/pub/Linux/apps/sound/convert/sox-11gamma-cb3.tar.gz
cdda2wav enables you to get a specific interval (or a whole track)
from your audio CD and converts it into a .wav-file. sox converts
the WAV files back into the (audio CD) cdda-format so it can be written to
the CD-R using cdrecord. You don't necessarily need sox if
you use a recent version of cdrecord, because it has built-in
support for .au and .wav files.
The file drivers/scsi/scsi.c contains the information
/*
* Usage: echo "scsi add-single-device 0 1 2 3" >/proc/scsi/scsi
* with "0 1 2 3" replaced by your "Host Channel Id Lun".
* Consider this feature BETA.
* CAUTION: This is not for hotplugging your peripherals. As
* SCSI was not designed for this you could damage your
* hardware !
* However perhaps it is legal to switch on an
* already connected device. It is perhaps not
* guaranteed this device doesn't corrupt an ongoing data transfer.
*/
Please note that this should only be used if your add SCSI devices to the end of the chain. Inserting new SCSI devices into an existing chain disturbs the naming of devices (directory /dev) and may destroy the complete content of your hard disk.
Yes. But you should be aware of the fact that any errors while reading the original (due to dust or scratches) will result in a defective copy. Please note that both methods will fail on audio CDs! You have to use cdrdao or cdda2wav on audio CDs.
First case: you have a CD-writer and a separate CD-ROM drive. By issuing the command
cdrecord -v dev=0,6,0 speed=2 -isosize /dev/scd0
you read the data stream from the CD-ROM drive attached as
/dev/scd0 and write it directly to the CD-writer.
Second case: you don't have a separate CD-ROM drive. In this case you have to use the CD-writer to read out the CD-ROM first:
dd if=/dev/scd0 of=cdimage
This command reads the content of the CD-ROM from the device /dev/scd0 and
writes it into the file "cdimage". The contents of this file are equivalent
to what mkisofs produces, so you can proceede as described earlier
in this document (which is to take the file cdimage as input for cdrecord).
If you want to see a progress-meter and other fancy stuff, then you can also
use Jörg Schillings sdd.
In case you run into errors, then install a recent version of cdrecord, which ships a tool called "readcd" (found under misc/). It gives you the same result as dd, but reads sectors on the CD-ROM several times in case of errors.
Yes. Newer Kernels (2.0.36 and the upcoming 2.2) have built-in support for the joliet format. Remember you have to use both options in your /etc/fstab: the keywords iso9660 and joliet (later is really an extension). For more details, see http://www-plateau.cs.berkeley.edu/people/chaffee/joliet.html.
Just as you do with regular CD-ROM drives. No tricks at all. Note that you have to use the scd devices (SCSI CD-ROM) to mount CD-ROMs for reading, even if you have an ATAPI CD-ROM (remember you configured your ATAPI devices to act like SCSI). Example entry for /etc/fstab:
/dev/scd0 /cdrom iso9660 ro,user,noauto 0 0
Use bzip2 instead of any other compressor like gzip or
pkzip. It will save you up to 30% of disk-space for larger
(>100kb) files. You can download it from
http://www.muraroa.demon.co.uk/
Instead of writing a true audio CD, you can optionally convert your WAV audio files into MP3 audio files and store them on a ISO-9660 filesystem as regular files. Usually MPEG III give you a compression of 1:10. Of course, most CD-players are not able to read files... this is the drawback. On the other hand, why not running the music for your next party from hard disk? 18 Gbyte are enough for 3000-4000 titles. :-)
A software MPEG III-encoder is available from
http://www.stud.ifi.uio.no/~larsi/other/8hz-mp3-cheng.tar.gz
A MPEG III-player is available from
http://homepages.uni-tuebingen.de/student/michael.hipp/mpg123/
For recorded speech, you may want to try to reduce its size using
shorten or "GSM lossy speech compression":
ftp://svr-ftp.eng.cam.ac.uk/pub/comp.speech/http://kbs.cs.tu-berlin.de/~jutta/toast.html
You must have an 1.44 MB bootable floppy-disk. Create an exact image of this floppy-disk by issuing the command
dd if=/dev/fd0 of=boot.img bs=18k
Place this floppy image into the directory holding the collection of your files (or into a subdirectory of it, just as you like). Tell mkisofs about this file with the option '-b' and also use '-c'. For details read the file README.eltorito in the mkisofs-distribution.
An interesting application for a custom bootable CD is as a virus safe DOS- or Windows-system. It saves you the money for the hard disks (if you have a network and use samba to put the user-data on a fileserver). However, this is purely theoretical as nobody reported an actual recipe to me.
Some details about the bootable RedHat CD-ROM is available from http://members.bellatlantic.net/~smithrod/rhjol-technical.html.
There is an overlay filesystem available for Linux, which is mounted over the CD-ROM and intercepts all writing operations. New and modified files are stored elsewhere, but for the user it looks like the CD-ROM is modified. For more information, see http://home.att.net/~artnaseef/ovlfs/ovlfs.html.
If that is not enough for your needs: wait for the UDF-filesystem to be supported by Linux or help developing it (see http://trylinux.com/projects/udf/.
Yes. However, it has been only tested with two writers yet. You need either a recent version of the Linux kernel (2.2.10 as of writing) or a a kernel patch for more buffers in the SCSI generic driver ( ftp://ftp.fokus.gmd.de/pub/unix/cdrecord/alpha; works up to 2.2.5).
The german computer magazine "c't" had a list of tips regarding the blank CD-Rs in their november 1996 issue:
Only chapter 2 is Linux-specific. You can apply chapter 3 and 4 even if you run another family of operating systems than Linux. Please see the files README.NetBSD, README.aix, README.hpux, README.next, README.solaris, README.sunos, README.vms or README.xxxBSD from the cdrecord-distribution.
You have two options. Either you use the built-in configuration file for cdrecord, or you use a shell wrapper like the one shown below. This shell script reads a configuration file, which lists the options and parameters for cdrecord line by line. The names are exactly the same as on the commandline, but without the leading dash. Comments are allowed. Example:
# be verbose
v
# set the speed of the writer
speed=2
# the device-coordinates in the form BUS,ID,LUN
dev=0,6,0
The configuration files for the wrapper belong into /etc/cdrecord and must be referenced on the commandline. Example: if you want to refer to the configuration /etc/cdrecord/mywriter.cfg, then you can issue the command "cdrecord.sh mywriter.cfg -audio track1...". Everthing after mywrite.cfg is passed to cdrecord.
#! /bin/bash
CFGDIR="/etc/cdrecord"
CFG="$1"
shift
ARGS_LEFT="$@"
if [ ! -f "$CFGDIR/$CFG" ]
then
echo "Configuration file $CFGDIR/$CFG not found. Exiting."
exit 1
fi
while read LINE
do
case $LINE in
\#*|"") continue;;
esac
old_IFS="$IFS"
IFS="$IFS="
set -- $LINE
IFS="$old_IFS"
O_NAME="$1"
O_VALUE=""
while shift
do
case $1 in
"") continue;;
esac
O_VALUE="$1"
done
if [ -z "$O_VALUE" ]
then
O_CDRECORD="$O_CDRECORD -$O_NAME "
continue
fi
O_CDRECORD="$O_CDRECORD $O_NAME=$O_VALUE "
done < "$CFGDIR/$CFG"
set -x #DEBUG
exec cdrecord $O_CDRECORD $ARGS_LEFT
echo "Execution of cdrecord failed."
Somewhere behind the first 32 k on the CD, a block with information about the CD is located. You can extract the information with the following shell script:
#! /bin/bash
RD=/dev/cdrom
for i in 32768,7 32776,32 32808,32 32958,128 33086,128 33214,128 \
33342,128 33470,32 33581,16 33598,16 33615,16 33632,16
do
old_IFS="$IFS"
IFS=","
set -- $i
IFS="$old_IFS"
OFFSET=$1
LENGTH=$2
echo "*`dd if=$RD bs=1 skip=$OFFSET count=$LENGTH 2> /dev/null`#"
done
When overwriting CD-RW media, specify the parameter blank=fast to cdrecord. That's all. See the man page of cdrecord for details about this parameter.
First of all, the image for a multi-session CD must be formatted using the ISO-9660 filesystem using RockRidge-extensions. And you must use the option -multi for cdrecord as long as you want to add further sessions. So at least for the first session, you must use -multi.
The images for the second and subsequent sessions are a little bit more complicated to generate. Mkisofs must know where the free space on the CD-R begins. That information can be gathered by using the option -msinfo on cdrecord (see example below).
shell> NEXT_TRACK=`cdrecord -msinfo dev=0,6,0`
shell> echo $NEXT_TRACK
shell> mkisofs -R -o cd_image2 -C $NEXT_TRACK -M /dev/scd5
private_collection/ \
For more information, please read the file README.multi, which is distributed with cdrecord.