Title: Members' Experiences

After nothing but problems with tape drives, I wanted to back up my Linux system to recordable CDs. I had the opportunity to get an Acer 4x4x32 CD re-writer (with 2Mb buffer); I used the IDE version because my system does not have SCSI, and I ensured that it was on a different IDE channel from my main hard disk. The drive came with mounting screws and installing it was not difficult (although I did have to buy a power cable splitter separately); getting it to work with Linux involved reading the CD writing HOWTO (which also contains a list of drives that are known to work), a kernel recompilation, and a quick edit of lilo.conf (it helps to read the manual page of that as well). The Linux "cdrecord" program expects a SCSI device, but the Linux kernel can emulate the SCSI API so that the IDE versions will work (I did find, though, that my old CD-ROM drive only worked as an IDE device and would not work using the SCSI emulator).

The first thing I tried was to write an official Debian CD image to CD-R (not CD-RW) at quad speed. I found that the ide-scsi module would not autoload (it was necessary to run modprobe first); this only applies if you use loadable kernel modules to keep the kernel size down. As a precaution, I exited all applications (including XEmacs, which might autosave and/or garbage collect) and made sure I had enough physical RAM to avoid any danger of thrashing (I upgraded from 32Mb to 96Mb). I was not connected to a network at the time.

The recording ran without a hitch and completed in about 35 minutes, but the resulting CD could not be mounted - there was an error about "root inode not initialised" in the kernel log, although the CD was readable in DOS and Windows. After tracing the problem through the kernel source code (version 2.2.15) I found that it was some kind of bug in the Joliet code (Joliet is a Microsoft extension to the ISO CD standards) and mounting with the option "-o nojoliet" was successful. To prolong the life of the CD writer, I adopted the policy of using my old CD-ROM drive for all reading, even though the writer was a faster reader.

The next thing I tried was to make (and record) an ISO image of my own. This went smoothly once I had read up about the options for mkisofs (I recommend -r and -J for both RockRidge and Joliet extensions). Then I tried writing a CD-RW instead of a CD-R; this was faster - 222Mb in about 6.5 minutes. Finally, I tried re-writing it; I found that you had to "blank" the entire disc before re-writing, a process that took some 20 minutes, and that this had to be done on a separate call of cdrecord; trying to combine these operations did not work, and neither did any of the features that only blank as much of the disc as is actually recorded on. After the blanking operation, it was no longer possible to tell how much of the CD had been written on by visual inspection.

Overall, my experience with CD writing under Linux has been a very positive one, especially in comparison with tape and with the tales of woe that often surround CD writing. Setting up is not instant, but once you have written appropriate shell scripts for your system, there should be little trouble. You also get the ability to write discs that are readable on any CD-ROM drive.

However, note the letter on the subject on the letters pages. I am not sure that rewriting is worth the effort, and recordable CDs are so cheap that it hardly seems worth bothering with rewriting. FG