Please Note: Since this document was written, Linux computers have replaced Solaris ones as the default in the public labs. All of these Linux machines have CD burners. They should be easier to use than the Solaris ones as they have more support in the GNOME user interface for removable media. Hopefully the background info found here about CD file systems should still be educational. (09/2007)

One Compact Disk Recordable (CD-R) and two Rewritable (CD-RW) drives are available on the Sun Microsystems workstations titanium.pha.jhu.edu, located in Bloomberg room 430 and tungsten.pha.jhu.edu, which is in room 332.

It is hoped that these drives will make it easier to archive scientific data in a (fairly) permanent format that can be viewed on many different kinds of computers. These drives are not to be used to duplicate copyrighted material.

This web page contains some of the information needed to use the drives to create new Compact Disks. There are many different kinds of CD's, and one uses different software packages to create new disks. Therefore, this page contains many pointers to other web pages, where you can learn what you need to know to create the kind of disk that you desire. No technical support is provided by the Computer Center for these drives beyond this document. (There is an examples document with a few sample commands.) Burning CD's is not hard, but you do have to learn a bit first, and then verify that your new CD's work on the drive on your computer.

Our Drives

Basic CD Creation Process

• Buy the blank CD-R or CD-RW media. Be forewarned that the manufacturers of these drives indicate that some kinds of blank media is better than others. You may need to buy more expensive blank disks to be able to record reliably at the highest drive speeds.
• While waiting for the blank disks to arrive in the mail, read a lot. Once you understand the concepts involved with creating file systems on CD's, making new CD's boils down to paying attention to the details of your files and the various command line arguments. Keep notes on what procedures worked for you. This will make creating the next CD even easier.
• Collect and organize the source information (i.e. files). There are two basic approaches here: duplicating an existing CD or creating your own set of files. To duplicate an existing CD, you probably can just use the dd command to read in the entire source CD (bit copy it) and create a single big disk image file. (This file is then written to the blank CD with cdrw or cdrecord. See the Examples document.)
  To create a CD with your own collection of files:
  • Create a directory tree of files with the right names and file permissions and directory depth. (For example, if you are going to read the final CD on a Windows PC, you may need to ensure that the file names will be unique when truncated to an 8.3 naming scheme, that you do not have more than 8 levels of subdirectories, etc. These are limitations of the different types of file systems, which are described below.
  • Then this directory tree is copied to a world-writable section of titanium or tungsten's hard disk.
  • Pre-mastering software like mkisofs is then used to read in your directory tree and generate a new disk image. That is a single large file which contains a file system containing your files.
  • Double-check that the disk image you have created is correctly structured to create a CD in the desired format. In other words, either list the contents of the image with isoinfo . Or mount the image using fbkmount or hmount and browse its contents with ls or hls to ensure that it looks like what you expect to find on the CD. Then unmount the image.
• Put a blank disk in the CD-R(W) drive. Put a note on the drive with your contact information so other people will know that the drive is in use. Leave an empty case for your disk in case someone removes it.
• Create the new CD using cdrw or cdrecord to send your data to the drive.
• Eject the new disk so other people can use the drive.
• Test the resulting CD on the computers on which it will be used to verify that you followed the correct process.
• If you wanted to make multiple copies of the same disk, you use the same source material to create the second and later copies. You should probably test one here and there to make sure that they also work.
• When finished, delete any files you stored on titanium or tungsten so the disk space is available to other people.

• ISO 9660 A simple file system, sometimes called High Sierra or ISO or iso9660. The ISO definition has many limitations, which led many people to create extensions. Some of those limitations: Only regular files and directories are supported. File names are in all capital letters. File names are in the 8.3 format (eight characters followed by a period followed by three characters). Only certain characters can be used in a filename (alphabet, numeric digits, periods and underscores). Only eight levels of subdirectories are allowed. See the manual page for hsfs and mount_hsfs for more exact Solaris information.
• Rock Ridge This extension to ISO 9660 is a way of storing additional information about files in an ISO 9660 file system (such as longer, 32-character file names). ISO 9660 file systems only support regular files and directories. A Rock Ridge file system can support regular files, directories and symbolic links, as well as device nodes, such as block, character and FIFO. So if you are going to use a CD on a UNIX computer, you will want to include Rock Ridge information.
• Joliet This extension has similiar goals to Rock Ridge. However it was written by Microsoft and is, not surprisingly, incompatible with Rock Ridge. If you are going to use a CD on a Windows computer, you will want to include Joliet information.
• HFS The Hierarchical File System has been the basic file system for MacOS (the operating system on Apple Macintoshes) for many years. Newer versions of MacOS (8.1 and later) support an enhanced HFS file system, called HFS+. This is not a problem, as all MacOS versions are backwards compatible and can read "plain" HFS volumes.
• Hybrid A hybrid CD-ROM has multiple file system types on it. Such a CD can be read by multiple operating systems. Creating a hybrid CD is the way to maximize the usability of your information, at the expense of some additional effort when creating the disk. The mkisofs program, for example, can create discs with ISO 9660, Joliet, HFS and Rock Ridge file systems on the same disc, all sharing the same file data.
• Audio Music is stored on CD's in the form of files in the CDDA format. See the cdda2wav information below for details.
• Bootable Keep in mind that creating a bootable CD for any given operating system will require special procedures (to install boot blocks and operating system components).

Detailed corrections to this web page are happily accepted. Most questions sent Computer Center staffers about this drive will not be answered. We do not have any more experience creating CD's than you do. It is a specialized body of knowledge. One has to read the on-line resources and experiment. Sorry if that sounds harsh, but it has already taken a lot of time to to build the software as well as to learn and summarize the information on this page.

If you develop detailed procedures for creating disks of a particular format, please consider writing them down on a web page so we can make links to it, or incorporate the information here.

A mailing list, cdr@pha.jhu.edu, has been created so that CD-R drive users can share their questions and tips with each other. This is an unmoderated Majordomo-managed mailing list. You can add yourself to it by sending an email message to majordomo@pha.jhu.edu with this text in the BODY of the message (not the subject line, which can contain anything):
subscribe cdr your-userid@pha.jhu.edu
(See this page for more information about Majordomo mailing lists.)

Links to CD-R Documentation

• cdrw -- Recent versions of Solaris include this program, which appears to do everything cdrecord does. It is not clear whether both packages will be needed in the future.
• cdrecord -- This package includes several essential programs. cdrecord is the main one for writing the data to the drive.
  • cdrecord is the program which actually writes data to the blank disk.
  • mkisofs (Make ISO File System) is a pre-mastering utility. It takes a snapshot of a given directory tree and creates a disk image which will correspond to an ISO 9660 file system when written to CD (by cdrecord). It can make either straight ISO file system or one with a combination of extenions - Rock Ridge, Joliet and HFS.
  • cdda2wav retrieves audio tracks from CD-ROM drives and makes WAV, AU, or AIFF files (maybe other formats too) out of them (which can be stored on hard disk or passed through a software pipe to cdrecord). Here are some cdda2wav examples. Definitely read the cdda2wav manual page, including the long section of tips at the end. Note that the current version of cdrecord can convert WAV and AU files into CDDA format as it is writing to the CD, so you do not need the older "sox" program you might see mentioned in various on-line documents.
  • isoinfo is a utility to perform directory like listings of ISO 9660 images (with or without Rock Ridge extensions). There are two related utilities, isovfy and isodump, that you may wish to read about. isoinfo appears to be the most useful way to look at a disk image without mounting it.
• fbkmount and fbkumount -- These allow you to mount and unmount disk images containing ISO 9660 (and Rock Ridge) file systems. Once mounted, you can not only list directories (as you can with the isoinfo program) but also view the actual file contents. YOU MUST UNMOUNT THE FILE SYSTEM WHEN YOU ARE DONE WITH IT. See the manual pages for these programs for their arguments.
• hfsutils-3.2.6 -- This package has several programs for manipulating HFS file systems (Macintosh-specific). The main ones you'll use to get started are hmount, humount, hvol and hls.

THE CONTENTS OF THE /EXPORT/DATA1/CDR-SCRATCH DIRECTORIES WILL BE DELETED EVERY MONDAY MORNING AT 3:35 A.M.

Some tips for avoiding problems with this disk space:

• Know how to use the df and du UNIX commands to keep tabs on how much disk space you are using. Specifically, du -sk directory will tell you how much space (in kilobytes) directory consumes. And df -k . tells you how much space is used and available in the file system you are in.
• Put all of your files inside a directory named after your userid, e.g. /data1/titanium/your-userid. You can make subdirectories inside that for the files that relate to making the CD. But you can also create a little text file called README inside that directory containing information about how long your files are going to be there, which a Computer Center staff member can read when trying to decide what to delete to most quickly free up disk space. (They will not physically walk over to the drive and look for paper notes sitting on top of the drive. Those notes are for other users of the drive who will be walking up with a blank CD.)
• Because it is time consuming, you should do most of your file organizing work somewhere else (your home directory, your own workstation, etc) so this shared space is not used until you are ready to make a disk image or burn the CD.