Submit Hint Search The Forums LinksStatsPollsHeadlinesRSS
14,000 hints and counting!

Avoid a possible Safe Mode boot issue System
OK, the following is quite odd, but very true, as it happened to my machine just yesterday. More than likely, it was just a fluke, but since the issue persisted across reboot attempts, I thought I would share it with the macosxhints readers, just in case anyone else runs into it.

Yesterday, I was trying to install an ATI ROM upgrade for my video card. To do so in 10.4, you have to start up in Safe Mode, which is quite simple -- just hold down Shift at startup. However, when I tried this on my first-gen Dual 2.0GHz G5, I had some very unexpected results.

The first time I tried to boot into Safe Mode, I could hear the hard drives going into their "first aid" check, which is normal. Lots of drive activity, and the spinning gear on the screen. But then, the fans began to ramp up. And ramp up. And up. And up. Soon there was a discrenible breeze in the room as the G5 sucked in every spare molecule of air in the house. If things continued at this rate, my cat was in danger of becoming a hood ornament on the G5's grill.

Then suddenly, everything got very quiet. Too quiet. The G5 had shut itself down. From what I understand, this happens when temperatures get out of range. I suspected some sort of disk issue had caused the machine to get stuck during the first aid portion of the safe boot. In turn, the fans ramped up to try to keep the disks cool. Not being successful, the G5 bailed.

I rebooted into normal mode, which worked fine, and checked the disks. To my surprise, everything was fine with Disk Utility's repair tool. I also repaired permissions (no issues found) just to be sure. Then I booted into Safe Mode again. Same result; the fans ramped way way up, and the machine shut itself off.

I booted normally again, which worked fine again, and was just about to call Apple and open a trouble ticket. Then I noticed I had a CD in the Superdrive (Nascar Racing, in this case). On a lark, I ejected the CD and then again booted into Safe Mode.

This time, the fan's ramped up, but not to max velocity as they had before. A couple minutes later, the fans dropped back to normal speed, and I saw the Safe Mode login screen. Very strange, and as noted, potentially a fluke. I'm not planning on testing it again, though, to find out! In the future, I'll remove any mounted CD prior to trying a Safe Mode boot.
    •    
  • Currently 3.00 / 5
  • 1
  • 2
  • 3
  • 4
  • 5
  (2 votes cast)
 
[19,175 views]  

Avoid a possible Safe Mode boot issue | 15 comments | Create New Account
Click here to return to the 'Avoid a possible Safe Mode boot issue' hint
The following comments are owned by whoever posted them. This site is not responsible for what they say.
Update the Post title w '...by ejecting CD'
Authored by: the_webmaestro on Mar 08, '06 08:26:08AM

It would be good to update the title, so you can get the info without reading the whole story (or at the very least, at a summary at the top).

---
Father of Jeremy Logan



[ Reply to This | # ]
Update the Post title w '...by ejecting CD'
Authored by: robmorton on Mar 08, '06 10:37:39AM

I would agree. I got to the end and thought, ok and... Nice to know I guess.



[ Reply to This | # ]
Update the Post title w '...by ejecting CD'
Authored by: robg on Mar 09, '06 06:52:54AM

I tried, really, but I couldn't come up with a short enough title that included more detail without wrapping the title when viewed on the page.

Sorry;
-rob.



[ Reply to This | # ]
Update the Post title w '...by ejecting CD'
Authored by: the_webmaestro on Mar 09, '06 08:40:44AM

If you can edit your post, you could add it as a summary... It's a nice story... and I don't mind, but it's simple enough just to say "The short version is, 'Macs won't Safe Mode with CD in drive.'"

In any, case don't go thinking that I'll never read your site again if you don't make this change! Have a great day!

Web Maestro Clay

p.s. I hope your gmail acct is working well for you!

---
Father of Jeremy Logan



[ Reply to This | # ]
CD problems
Authored by: bakalite on Mar 08, '06 10:12:17AM

There is a long history of problems with leaving CD's in the drive across a reboot. I don't remember too many issues under os x, but under 9 (and earlier) there were quite a few "problem CD's". If you left these in the drive, the mac just wouldn't boot.

In general, I think it's a good idea not to leave a CD in the drive. It can be hard to get it out if you can't boot (on some models), and if the CD prevents you from booting in the first place...



[ Reply to This | # ]
CD problems
Authored by: ij00mini on Mar 08, '06 10:28:10AM

On my old iMac G3, Apple told me to always leave a CD in the drive, otherwise problems would arise. I remember the CD tray vibrating and whatnot.



[ Reply to This | # ]
CD problems
Authored by: ghay on Mar 08, '06 12:37:10PM

Hold down the mouse button during a reboot - it will spit out the disk.

failing that hold down command-option-o-f and at the prompt type "eject cd" press return, remove disk and type "mac-boot" and press return.

that should cover most macs.



[ Reply to This | # ]
Avoid a possible Safe Mode boot issue
Authored by: sheurich on Mar 08, '06 02:35:08PM

Actually, the mounted CD had nothing to do with your machine shutting down. Surprisingly, the behavior you saw is completely normal. When the system is booted into safe mode, a file system check is forced (even on journaled filesystems) and IF the check finds any inconsistencies (i.e., makes repairs) the system shuts itself down.

From /etc/rc :
32 if [ "${SafeBoot}" = "-x" ]; then
33 fsck -fy || halt
34 else
35 fsck -p || fsck -fy || halt
36 fi

While I am not certain why Apple chose to halt the system, rather than rebooting, after the fsck, this is obviously the intended action. This can be especially disconcerting when booting into safe mode (via an nvram boot-args='-x') on remotely administered Xserve systems.

One could simply change the halt command to a reboot in rc, but without consulting Apple engineers on this issue, this may not be a safe thing to do.



[ Reply to This | # ]
Avoid a possible Safe Mode boot issue
Authored by: Zeitkind on Mar 08, '06 04:58:26PM

Hmm.. I don't see much difference between reboot and halt. I remember halt to be more ungracefully to running tasks, like a reboot -q. Perhaps they want to avoid things happening before a normal reboot. Halt and reboot -q flushes the filesystem caches and force a quite ungracefully shutdown, reboot tends to wait for processes to stop and may write more stuff to the disk which might be unwanted. Both commands send SIGTERM (and subsequently a SIGKILL) to all tasks and do quite the same. Indeed a bit strange and good to know if you do remote controls to OS X machines running for a long time without a fsck.



[ Reply to This | # ]
halt vs. reboot
Authored by: sheurich on Mar 08, '06 08:01:08PM

The difference between halt and reboot, which is a substantial difference, is that halt powers off the machine, while reboot restarts the machine. Halt is not equivalent to 'reboot -q' and in fact both halt and reboot respect the '-q' flag.



[ Reply to This | # ]
halt vs. reboot
Authored by: Zeitkind on Mar 09, '06 12:04:18AM

Of course halt powers off the machine - but what is the difference between restart from scratch and a power cycle - regarding fsck? Apple decided to power off if root fs is modified - but why? Rebooting does the same as halt except erasing the RAM and other non static memory. If you flash a firmware, OK, no question, but if you fsck? The drives are called quite late in the boot process of OF and they also do a bus-reset while rebooting. So why the halt command instead of reboot?



[ Reply to This | # ]
Avoid a possible Safe Mode boot issue
Authored by: kalisphoenix on Mar 08, '06 08:56:09PM

Well, it's going to ruin your frigging day if it's a remote box and you halted instead of rebooting.



[ Reply to This | # ]
Avoid a possible Safe Mode boot issue
Authored by: Norm Nager on Mar 10, '06 12:49:35PM

If you can still edit the title or use it in another venue here's a proposed heading that gets at the issue as well as the prevention without adding to the length:

"CD in drive on Safe boot may rev fans"--proposed revision

"Avoid a possible Safe Mode boot issue"--existing title

Respectfully, Norm



[ Reply to This | # ]
Fans rev up w/ DVD even without Safe boot
Authored by: Norm Nager on Mar 10, '06 01:11:48PM

On a Dual G5 2.0 running OS 10.4.5, I had 2 experiences in which the fans revved up with the common factor of my having left a DVD in drive.

The first time, I had put the G5 to sleep and left the room, only to hear the jet takeoff noise a couple rooms away an hour or so later when it woke. I came in and did the SMU procedure. The DVD-in-drive as possible causal factor never occurred to me.

The second time it happened, I did a re-start while a DVD was in the drive. Zoommmmmmm! After running the SMU procedure, I checked out what I could with several hardware and system diagnostics tools. When the diagnostics could find no problem, I had a vague notion that MAYBE the DVD in the drive could have been implicated. Or maybe the DVD-in-drive was a coincidental, non-causal factor. I have been in the habit since then of removing a DVD before sleeping or re-starting the G5 and have not experienced a reoccurrence.

Thanks to your sharing of your experience and your hint, Rob, I'm now convinced that removing media from the optical drive is not such a bad idea!

Respectfully, Norm



[ Reply to This | # ]
Avoid a possible Safe Mode boot issue
Authored by: gotnospice on Oct 10, '06 11:28:12AM

Okay, my problem is similar but not the same. We have a G5 tower that was just sitting with nothing in the optical drive, and all the sudden turned on it's jets, everything in the room got sucked into the G5. We shut it down and then tried to reboot. It turns on, the fans speed up the Grey Apple comes up and the busy clog starts, then a few seconds later it just shuts off. It will boot in Safe Mode but thats it. First Aid and Permissions ran with no problems, won't start off an External HD with OS on it. Any ideas? When I start up in Verboose mode, the last command I see before the shut off is:
AppleSlewClock didn't supply default, something like that, it's hard to read because it shuts off. Battery issue?



[ Reply to This | # ]