Mark's Notebook

Recovering from a Computer Crash

After 22 months, my Mac G4 tower finally crashed big time. I was installing the driver for the Logitech Quick Cam Zoom White when it happened, but after examination I'm not at all certain that's what caused the problem. Anyway, the computer would no longer boot. The initial screen (with the large gray apple and the clock movement at the bottom) never goes away, but a random color pattern appeared on the screen above the apple.

Well, no problem. I have installer CDs here; I can boot from them and diagnose the problem. But the computer will no longer boot from the Mac OS X installer CD or the Hardware Test CD. Hmmm ... I've seen this before, on our computer at church. In that case, we had to attach an external drive and install OS X to that drive. In this case, since I have three internal hard disks, maybe I can install OS X to one of the extras. But I have to disconnect the problematic internal drive first. This is not so easy since I have a broken hip and crawling around on the floor is painful.

Anyway, I've installed OS X to another internal drive, I've re-mounted the first drive, and the process of repairing disk permissions is happening now while I type away on Mary's PC. (On a side note, Microsoft Internet Explorer 6.0 for PC really wreaks havoc with my site. The margins are all wrong and there is a horizontal scroll bar that isn't necessary.)

So here are my questions:

• Why won't the Mac boot from the CD even when holding down the "C" key per instructions?
• What does someone do when they encounter this problem but they don't happen to have an extra drive around?

OK, the diagnostics report that there are bad "extents files" or something like that on the disk. In human-speak, this means that thre are some "invisible" files known only to the computer, and they are critical for knowing where my own real files are, and those invisible files are corrupted. The Apple utilities can't fix it, and I don't have any other utilites like Norton.

Well, this gives me an opportunity to do some housecleaning. The process of restoring the disk to working condition looks something like this:

1. Since I can mount the bad disk, I can copy all its files to one of the other disks.
   Note: I did this using a backup program, to make sure I get everything.

2. Wipe the drive clean.

3. Install the OS that came with the computer (Mac OS 10.2).

4. Upgrade to the latest version of the OS (10.2.8), and install all the latest security updates, etc.

5. OK, first major problem. I can't access my own files on the other disks. I can view them, but I can't change them or move them around. This is a Unix and Mac permissions issue. First, I have to change all the owners to me. Then I have to change the "uchg" flag that has kept the files locked even though they belong to me. Changing the owners requires using the Unix "sudo" and "chown" commands. There is some information about the "uchg" problem and how to fix it here.

6. Install the applications that came with the computer, and upgrade all of them to the latest versions.

7. Install my most critical program first: email. Then copy all my old mailboxes back from the backup copy.

8. Install all the other programs I use regularly (it looks like there are about 25 of them).

   Note: I made it a point to install everything using the installers. I did not just copy my programs back from the backup copy. There are two reasons: (1) It makes for a cleaner, smaller install; and (2) it avoids problems should one of those applications have been corrupted by the crash.

   Note: when your application files get corrupted, they can become dangerous. When your document files get corrupted, you might not be able to read them any longer, but they shouldn't mess up your computer.

9. There are still a few random drivers like scanner and Zip drive that I haven't re-installed yet.

10. I still have to copy all my old documents back over from the backup copy.

    Note: This is easiest if all your document files are in well-defined places on your disk. I put most of my files in a "Personal" directory at the root of the disk. For large projects like audio files, I put them in their own directories at the root of the disk. The worst place for your files is the "home" directory your computer makes for you. This is because the computer also puts preference files and other corruptable files there, and when you restore your backup you don't want to retrieve those potentially bad files. If you avoid leaving your files there, you won't get confused when you restore your backup.

It seems I'm back up and running now. The crash occurred at 1:15 pm on Sunday. It's now 4:45 pm on Monday. Deducting eight hours for sleep, it has taken me 19 hours to fix this mess, and I'm still not quite done.

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Last updated Tuesday 13 May 2008