Burning CDs on cdf*

Version 0.21

This only covers the CD-writer on cdf2. There is one on cdf1, but it has a somewhat different setup. In the (near ?) future, there should to be a writer on cdf as well.

Starting gcombust:

Enter gcombust & at your prompt. You may prefer to start the program from a directory near where the files you wish to burn to CD reside, to simplify the file selection process.

Setting up gcombust on your account:

When gcombust is first started, it needs to set your preferences. All the listings under "Program paths" should be ok. Under "Devices", choose "Detect scsi drive"; this will find the correct settings for this screen. You don't have to do anything with the rest of the settings. Click OK to dismiss all the screens.

To actually write a CD:

1. With the gcombust window open, choose the "Data Files" tab. Choose "Add directory". This will give a standard selection dialog. To add a file, just select it the normal way. To add a directory, just click on its name once and then click "OK." What you selected will appear in the main window. You can continue to select files or finish selection by clicking "Cancel".
2. Insert a blank CD into the drive :-)
3. Click on the "Burn" tab. In general, you may burn the CD directly from the files, with no intermediate step. If the hard drives appear to be under heavy load or you are accessing files from another computer over NFS, you should create an image file first.
   • To do it directly from files: just make sure "Data Files, no image" is selected.
   • To create an image first: select "ISO-9660 image". Enter a location (on the local machine: under /local) in the text field. Then click "Create image from files." This step is limited by read speed: from a local hard drive it takes 3 minutes or so, over the network it takes up to 15. Once that is done, you are ready to go.
4. Make sure that "Select speed:" is set to 4, "Dummy test run" is NOT selected, and "Eject disk when done" is. Then click "Combust!" Sit back and enjoy the messages. The process (at 4x) takes about 20 minutes to complete a full 650 MB write. When it is done, the CD will pop out of the drive.

If something goes wrong:

The most likely thing to go wrong is a buffer underflow, which shouldn't occur often. If something bad happens, the program will immediately finalize the CD and eject it. Unfortunately it will probably be usable only as a mug coaster.

To label CDs:

Use a felt-tip pen (Sharpies are recommended) and write only on the non-green side of the CD.

To verify CDs:

There is an easy way and a hard way.

The easy way

Take the CD out of the CD-writer and insert it into the CD-ROM drive. On gcombust, select the "Verify" tab. Under "Verify from:" select "Data files", and in the "Verify against (ie the copy):" enter /mnt/cdrom. Then click the "Verify" button. The output box will show any differences that arise (basically there shouldn't be any). Unfortunately, you can't do anything else in gcombust while verifying.

The hard way

Use diff. If you don't know how, read the man pages. Hey, I said it was harder. On the other hand, you can burn and verify simultaneously.

In both cases, you will probably use the kernel automounter to get the CD mounted without root privileges; be forewarned that it won't let you eject the disk for at least a minute after you stop accessing it. You will have to umount it manually if you want it out before then.

To burn CDs specifically for CDF dataset backup:

Aha! The fun stuff. As of right now, please do this only from cdf2. The stuff that has been burned to CD already is listed here. The files being prepared for backup are located under /cdf/data2c/foo/data (/local/data2c/foo/data on cdf2). Each dataset is in its own directory (for example, cmuflt/.)

Find something ready to be burned

The check is that the dataset directory contains nothing but subdirectories titled data*.

Prepare the subdirectory

If it does not already contain a file named index, create one, just containing the text

This disk is <subdirectory name>.

For example, if the subdirectory were electrons_1a/data4, the file would say

This disk is electrons_1a/data4.

Start up gcombust and select that directory

The directory to add is the data* subdirectory. You want to deselect the option "Include dirname" on the right of the "Data Files" screen.

Burn and verify

With this setup it is relatively easy to use diff to verify the disk. The command is simply

diff -r /mnt/cdrom /local/data2c/foo/data/<subdirectory name>

For example, with subdirectory electrons_1a/data4, the command is

diff -r /mnt/cdrom /local/data2c/foo/data/electrons_1a/data4

Label

Label the CD with the subdirectory name.