multiCD

Introduction

I wanted to backup my entire Linux system. I wanted to do it by making direct copies of the files (no tar, compression, or archiving) so if I just wanted to look at one of the files on one of the CDs, I could. This also makes it very easy to restore from backups. Backing up my entire Linux system takes more than one CD, so I was running the du command on a bunch of directories to see what would fit on which CD. This was very tedious and time consuming, so I wrote multiCD to do this work for me.

Description

multiCD has a fairly large number of options, and can be configured to run in a variety of ways. I'll talk about some of the more interesting features:

multiCD can run in an interactive or non-interactive mode.

• Interactive mode assumes that you will be burning more than one disc. You tell multiCD which files to backup, and it will prompt you to insert a disc each time it is ready to burn one.
• Non-interactive mode copies the files to an image file, and then burns just a single CD. It assumes you have left a CD in your burner. This is useful if you want to call multiCD from a script or a cron job.

multiCD can be configured to run in a multi-threaded mode. If your machine can handle it, you can burn one CD image while another image is having the next set of files copied to it. This option can be disabled on slower machines. Since non-interactive mode burns only one CD, multi-threading is only used in interactive mode. When running with this feature enabled, it's best to redirect stderr somewhere. I send the output of cdrecord, along with some other status information, to stderr. When cdrecord is running in the background at the same time as the main process, their output will overlap. I usually do something like:
multiCD 2> err
and then in another terminal I do:
tail -f err
so that I can watch the progress of cdrecord.

Selecting which files to backup is simple and powerful. For example, you can tell it to backup / (everything), but have it exclude certain sub directories like /tmp /dev /mnt /usr/tmp /proc, etc. It only backs up regular files, directories, and symlinks. All other files are automatically skipped. Also, if there is a problem reading a file because of permissions or whatever, it is automatically skipped. A warning is printed to STDERR whenever a file is skipped.

Options like the type of file system to create, or the capacity of the CD's to burn can be changed.

multiCD can be configured to run in a mode where it simply creates a series of image files, without burning anything to discs. Some people find this useful if they want to burn the CDs later.

This was developed on Linux, but should run fine on any Unix-like system.

Configuration

The documentation in the global config file in /etc/multiCDrc explains all of the options that are available. multiCD can get configuration information from any of three places:

• The global configuration file: /etc/multiCDrc
• A per-user configuration file called .multiCDrc, located in the user's home directory.
• From the command line.

Requirements

• A Unix-like operating system.
• The cdrecord program.
• Perl 5 or better.

News

• 5/5/01: Version 1.5 released. The only thing I want to add, but haven't yet, is support for ISO9660 file systems. If anyone knows of a way to create an empty ISO9660 file system of a certain size, then please let me know.

  I've decide that having incremental backup capability probably isn't worthwhile for mutliCD. To do such a thing, all of the old files would have to be copied from the CD to the image file, all of the files that aren't in the master file system would have to be deleted from the image, and then new and modified files would have to be copied from the master set to the image. Doing all of that would be slower than just getting a whole new copy of the master set.
  Changes made:

  • Added support for global configuration file.
  • Does a little check to make sure that it doesn't attempt to add a file that's larger than a CD to the backup image.
  • Finally got around to making the GPL status official.
• 4/20/01: Still alive. Sort of. I've been crazy busy at school. I do plan to work on this project a little more, and do some of the things I said I would, but I just haven't had the time. I'm graduating soon, so we'll see what happens...
• 2/7/01: Version 1.02 released. Changes made:
  • Fixed minor bugs, changed some minor features, made some things easier to use.
  • Made the first steps toward having the ability to do incremental backups. Incremental backup ability will be in the next release. See the info about the addfiles option in the sample config file.
• 1/21/01: Version 1.01 released. Changes made:
  • Fixed one major bug: It only worked with Perl version 5.6 or newer. I made multiCD so it is now compatible with any version of Perl 5.
  • Fixed some minor bugs.
  • Changed the way the user specifies the name/location of image files.
  • Added option that allows user to create a series of disc images without burning any of them.
  • Added option so the user can skip being prompted for the first disc.
• 1/15/01: Version 1.0 released.

License

The Author

If you find this program useful, let me know. If you find a bug, let me know, and I will fix it. Also, if you want a certain feature added, send me an email and I will consider it. My name is Dan Born. Feel free to get in touch with me.

• email: djb4@cs.geneseo.edu
  
• web page: http://multicd, rmdashrf.org/~dan/