It's not possible to backup an audio CD as an iso image. This format is for data CDs.

You should use cdrdao.

Example:

cdrdao read-cd --read-raw --datafile FILE_NAME.bin --device /dev/cdrom --driver generic-mmc-raw FILE_NAME.toc

Under Ubuntu, you can use Brasero with "CD copy" mode. ps axf shows us the command Brasero is using:

cdrdao read-cd --device /dev/sr0 --read-raw --datafile /home/dooblem/brasero.toc.bin -v 2 /home/dooblem/brasero.toc

Note: there is a Brasero Bug in Ubuntu Lucid with cdrdao.

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