G5 PPC on Leopard passes tests, still won't boot from internal drive


We had some power flickers yesterday afternoon and now my Mac refuses to boot. My G5 PPC running Leopard will not boot from the internal drives. It will boot from the install DVD. I have run the Command-S with the fsck -fy and Command-V. Both appear to run okay. I can hold the option key down and get options for starting up from both the install DVD and the internal drive. I have unplugged all peripherals other than the keyboard, mouse and monitor. I have unplugged the power for a minute or two. I have, after running the Safe mode, got a series of crash reports that continually refresh at the top of the screen. And I was able to run disk utility/repair and was told all was okay. I now have a gray screen with the Apple and a spinning gear.
Any ideas? Should I try a new install that preserves the old system and files?
Thanks in advance -Rick
Power fluctuations, or brief power failures (when the computer may lose power completely) can cause file system corruption, or often will exacerbate already existing issues. If the Mac, with OS X, then won't boot successfully, and especially if it won't boot to safe boot mode (which you are not too clear about), then a reinstall, using the option to Archive & Install, is probably your easiest fix.
The various messages that you mentioned might just be the normal result of booting to Safe Boot mode, which will prevent some services from properly running, such as network/internet apps.

You could also simply restore from your backup - if you have a current backup.
If you DON'T have a backup, then yesterday should be your "wake up call", demonstrating your need for a backup plan.
I do have an extra system hard drive that I can install. Any thoughts if I should watch the gear spin for a while longer or pull the drive and install the backup system drive.
Thank you, sir.
Also, is there a way to turn off extensions like the old systems by holding down the shift key on bootup?
An OS X system boot can sometimes fix itself, if you wait a bit.
How long, you ask?
I think you can assume that the system won't continue on after "watching the spinning gear" for more than 30 minutes.

observation: An "extra system hard drive" is not a backup - unless that's how it is used, as a backup that you regularly maintain.
If it IS an actual backup of your system, its settings, and your apps and files, then there's no real need to mess around trying to get the existing boot drive to work.
I would NOT suggest that you use your backup hard drive as the primary replacement - unless you already have the idea to use a different backup, and you will continue to maintain your backup plan.
If the problem hard drive is an ORIGINAL hard drive, then it's more than 7 years old, and you might consider replacing with new (and not a spare that might be as old as the G5). This time could be a warning sign that the hard drive is approaching failure.
(just my opinion)

Booting with the shift key down (which boots to Safe Boot mode) is effectively the same as booting without extensions in the old OS 9 days. It does NOT disable ALL extensions, or kexts. It DOES prevent certain processes from starting up normally.
Here's an article that explains what happens: http://macs.about.com/od/usingyourmac/qt/Safe-Boot.htm
or, an Apple support article that might be helpful to you: http://support.apple.com/kb/TS2570
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Thanks, DeltaMac. Your insight is appreciated.
The G5 is a refurbished from one year ago from PowerMax. The drives were new at that time. My backup system drive was supposed to be a 2 gig but they sent a 1 gig so after receiving the correct 2 gig drive, I made the 1 gig drive an emergency system drive and pulled it out.
My working files are stored on the drive in bay 2 BUT there are some files I'd like to retrieve from the startup drive. I backup my files to DVD. I'd like to pull the secondary drive and install my backup system drive. That sounds do-able to me. Then I can restart using option key and force a boot to the old system back up.
My backup system drive was supposed to be a 2 gig but they sent a 1 gig so after receiving the correct 2 gig drive, I made the 1 gig drive an emergency system drive and pulled it out.
I backup my files to DVD.

I'm guessing that you meant 2 TB, and not 2 gig. I haven't seen a 1 or 2 gig hard drives from sale for probably more than 10 years.

comment: I still have doubts about the practicality of backing up files to DVDs. It's one choice, to be sure, but with hard drive storage now in several TB, then backup to DVDs gets less and less practical. I had one customer several years ago who realized that backing up to 20 or 30 DVDs simply took too much time, and there were enough failed burns, which took even more time to recover from, that customer decided that a hard drive solution was MUCH better.
(again, just my opinion)
Right, 2 gig! Haha, you can tell I'm old school.
I rebooted with the shift key down to disable extensions. The screen is now blue and every 5 seconds or so the spinning gear appears for maybe a second and then goes away. This keeps repeating. Is this worth my time to wait for?
Probably not worth waiting.
You COULD boot to verbose safe boot mode, which is restarting while holding Shift-Command-V
That is the same Safe Boot, but now displays some of the system resources as they load. That may stop on a particular item, which could be helpful if you want to continue attempting to boot to your existing system (and that may not be important, or even possible without a reinstall)
I tried the shift command V and it stopped for a minute at:
Sophos Anti Virus on - access kext activated.
Now the screen is showing line after line of error reports, all ending with invalid destination port, if that means anything.