Creating system backups using DVD-RAM media and Universal Disk Format

Universal Disk Format (UDF) allows you to manipulate files directly on the DVD-RAM media.

The system backup image is an archived file composed of many files that cannot be manipulated. However, the installation packages and any files that are not contained in the backup image, can be directly manipulated on the DVD-RAM. After the DVD is mounted the files can be changed by using an editor or new files can be copied to the DVD using the various copy and restore commands such as the cp, mv, restore commands.

With UDF and DVD-RAM, system space is only needed for the backup image. A high-level description of the UDF backup process is as follows:

Create a backup of a volume group to a file (archive) on a hard disk containing enough space to hold the backup image.
Populate UDF with files needed to boot and install a system.
Copy backup to DVD-RAM media.

The mkcd or the mkdvd command with the -U flag is used to create a UDF file system on the DVD-RAM.

UDF allows for the possibility of changing files directly on the DVD-RAM media, such as a bosinst.data file and image.data or vgname.data file. Without UDF for example, to add a user-defined bosinst.data file to a backup image, you must restore the backup image to a location, add the file, and then back up the files again.

Or, you had to create a supplemental diskette containing the changed bosinst.data file, and use the supplemental diskette in conjunction with the backup. However, some system configurations might not provide diskette drives, making this procedure more difficult.