Mac Lab Report

How to Make a Bootable Emergency CD

- 2003.01.02

This article is about creating a master CD-ROM that can be used to return a computer to a standard configuration or repair a machine that is not booting.

If you do this very often, you have your own favorite software tools and special techniques. I am not going to get very specific here - just enough to get a determined power user going.

And it goes without saying that these instructions are OS 9 and lower. This is Low End Mac; we're allowed to do that, right? OS X is a whole other ball game, and the techniques are somewhat different. Further, let me warn you that some of these tasks may render a computer unbootable (giving you a flashing question mark), so don't attempt this on a mission-critical machine unless you're prepared to restore a backup and start from a blank hard drive.

What You Need

First, when preparing your master disk, it's best to have a legal copy of the Mac OS installer available. For example, if you are restoring machines that shipped with OS 8, then it's okay to use an OS 8 installer disk repeatedly on the machines. To be legal, don't use an OS for which you don't have a license.

You'll need a disk burner (CD-R/RW drive), at least one blank CD-R (of course), a copy of Disk Copy on the machine you will be using to burn the disks and construct the master, and a copy of ToastHREF=. Disk Copy is available from Apple's download site, and if you are preparing a disk for older Macs or Power Macs, you can use Apple's OS 7.5.5 installer. These software downloads are available from This is a primary advantage of using Apple technology over Wintel - not only is Windows 3, for example, not available as a download, it's no longer supported by Microsoft (unless it's by accident, already compatible). The process is easier if you are creating the master from a machine which can run the OS you are using; a new iMac will refuse to run the installer for OS 8.1, for example.

Preparing the Master

First, use Disk Copy to create a disk image large enough to hold everything you intend to install. Choose the command "Create New Image" from the Image Menu, and pick the appropriate size. It has to be smaller than the capacity of a CD-ROM, of course; but if you're installing, say, OS 8.1 plus a few non-Microsoft apps, you should be able to fit everything within 200-250 MB. All your installers will be targeted to the disk image instead of the default boot drive, so make sure you pay attention to the destination of each install.

Next, install the OS to the disk image. When installing, make sure you select "install OS for any supported system." You may need to click an "options" or "custom install" button to make this happen; it's a little different from OS 7 to 8 to 9. You can make a slimmer install if you pick an install for the same kind of computer you are using to make the master, but in a hodgepodge lab it's best to be generic.

Then install all the software for which you have licenses. Throw in shareware you've registered, freeware, document templates, and so on. I install FoolProof security software complete with logins, user folders, etc. If you have sufficient licenses, AppleWorks is an excellent program to install on the master, because it does all the basics.

Finally, once everything is installed, open the mounted disk and arrange the icons the way you want them to appear. When you burn the CD, the icons will appear the way you left them in the image; so if they're disorganized and messy, the CD will look the same way.

Burn the Disc

Using Toast, burn the image to CD-ROM by selecting "Mac Volumes" and simply dragging the mounted image into the workspace in the Toast window. I found that some older Macs cannot read CD-RW, so CD-R might be required. Also, it took me about three weeks to figure out that in order to make a bootable CD-R, you have to select "Bootable" in the Toast setup window. Go figure.

Use Two Partitions

If you burn the CD-R with the "session" setting instead of the "disk" setting, you can go back and burn on it again, making a new pseudo-partition that mounts separately on the Mac desktop. What I do is make one partition a stripped down OS, with no applications - just utilities such as Disk Copy, Disk Tools, Apple HD Setup, Drive Setup, etc. The second partition contains the image of the drive I want to copy. The advantage is that you can boot off the "boot partition," use the utilities to erase the hard drive of the target computer (even zero it out if you like), and then copy the new System Folder, applications, etc., in one fell swoop.

Useful Tricks

To disable a System Folder, throw away the System file and the Finder. This makes the System Folder unbootable, so don't do it unless you're sure you need to.

If you have a computer with an un-blessed System Folder, drag the Finder and the System suitcase into the disabled System Folder to make it bootable.

To protect a target computer with At Ease or other security software, boot off the CD, try booting with the CD in the drive and hold down the "c" key as you boot the machine. Otherwise you might need to get the password from someone to make it disable the security software enough to allow you to disable the security, disable the System Folder, or run an installer.

Don't Forget the Sharpie

I've got a zillion CD-Rs with no labels. It's a pain in the neck. Buy a box of Sharpies* and label them. Trust me, it'll pay off later.

* We have since learned that Sharpies and other solvent-based permanent markers may put the data on your CD-R or CD-RW at risk. Read Don't Use Sharpies on CD-R for more information and recommended alternatives. dk

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is a longtime Mac user. He was using digital sensors on Apple II computers in the 1980's and has networked computers in his classroom since before the internet existed. In 2006 he was selected at the California Computer Using Educator's teacher of the year. His students have used NASA space probes and regularly participate in piloting new materials for NASA. He is the author of two books and numerous articles and scientific papers. He currently teaches astronomy and physics in California, where he lives with his twin sons, Jony and Ben.< And there's still a Mac G3 in his classroom which finds occasional use.

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