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Rebuilding permissions can stop system hangs.

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Here's something you don't get to say everyday; I've just had a great experience ringing a tech support phone line.


It sounds even weirder when you say it out loud like that, but it's true! In the service sector that likes to say "outsourced to India", Apple - thank God - still prefer, in the UK at least, to put their customers through to someone who speaks the same language as their customers and who knows their subject inside out. That shouldn't read as a racist insult, it's simply the case that 9 times out of 10, even someone who speaks perfectly good regional English, in parts of the world where it's common place to speak a second or third language, is usually doing so with a strong accent which makes telephone communication difficult.


Anyway - back to the tip.


I'd been having a weird, intermittent system hang problem - which I couldn't recreate and therefore trace & resolve myself; it seemed to strike out of the blue no matter what applications I was running. There where no serious side effects, just the inconvenience of having to wait sometimes 30 or 40 seconds for it to snap out of itself and regain consciousness. Made all the more curious by a lack of any discernibly out-of-place output in the console log.


The Apple tech guy was stumped at first, but then he walked me through something I'd never thought to try before, despite being immediately reminded by the tech support guy as he began to explain what we where about to try, that I had heard it mentioned before on various Mac support forums, including this one, as a good way to trace various issues. Not only did doing it seem to make my system much snappier, but I'm fairly sure it's fixed some other minor stability issues too and, so far so good, my major concern - the intermittent hanging issue, has yet to return.


The fix.

I'd always known that certain issues can be resolved by launching Disk Utilities.app and repairing disk permissions. What I didn't know was that doing this by booting from the OS X installer DVD runs a deeper level scan of the hard drive than by doing it from a normal session.


This painless procedure, which can take around 5 - 10 minutes to do has certainly helped fix some system issues which had been building up so gradually on my machine I'd barely noticed them.


Although this tip, I'm sure, is common knowledge to some, it certainly goes to show that even long time users like myself, can always learn new tricks for basic system maintenance and, more importantly, be reminded that it's not always necessary to ring Apple with every little problem if you do some basic things yourself first, to genuinely establish is a problem is minor or symptomatic of perhaps a more major problem.


Step by step:


• Open the main hard drive icon (Macintosh HD) and open the folder "Users" and then the folder "Library"

• Highlight the folder "Caches" and drop it in the trash.

• Empty the trash. Some files from the Caches folder will still be open by the system, but will be unlocked after restarting, so click "Continue", if prompted.

• Insert your original OS X install disk.

• Reboot the machine with the 'C' key held down on the keyboard, until you're presented with the "Choose language" screen from the system installer.

• From the menu at the top of the screen, choose: Applications > Disk Utilities.

• Highlight the top level of your hard drive, which will have either the name of the disk manufacturer or some other text indicating the type of main hard disk you have in your machine, i.e., mine read something like "Western Digital" and then followed by the model / serial number.

• Choose "Verify Disk Permissions" from the top left row of 4 buttons in the side panel on the right.

• If the output text is all green and there are no errors, next highlight the "Macintosh HD" partition and choose "Repair Disk Permissions"

• If you do get any errors, click Verify, then Repair again until the output window text is green, with no error output messages.

• Assuming there are no more errors in the output window, restart your machine.

• Once back into OS X, empty the trash to clear out any files trashed in step 3 which previously couldn't be removed.


You should now notice a much snappier system. I personally felt an increased performance from apps like Quicksilver, EyeTV, Mail.app and Safari immediately and the tool bar applications like TextExpander and SoundSource which I have in my main account's Log-In items list, which had previously taken longer than seemed healthy to launch, now spring into life instantaneously.

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Funny I was told the opposite form my last apple tech call. Here is part of an email she sent me on the subject.


Should I start up from a Mac OS X install disc to repair disk permissions?


When possible, disk permissions should be repaired while started up from a Mac OS X volume (hard disk) that contains updated Mac OS X software, instead of a Mac OS X installation disc. Mac OS X software updates may change permissions on some files to improve security. When this occurs, the version of Disk Utility on the Mac OS X volume is updated to account for the new permissions. Running Disk Utility while started from the Mac OS X volume ensures that the changes made by software updates are preserved.

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Ahh. That's interesting. Any clues anyone?


What ever the reason for conflicting advice, my machine is much snappier now so..

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The Apple Tech's advise makes sense, I wouldn't see it as conflicting.


Obviously if you don't have another bootable drive, your only option is to use the system disk, but as stated it could set permissions wrongly as the version of Disk Utilities on the DVD will be most probably be much older than the system you're updating.


Normally when I repair disk permissions (which isn't often) I boot from my Firewire backup drive, that way I'm running the 10.4.9 version of Disk Utilities.


Overall, I doubt it makes a huge amount of difference which version you use, I've never heard of problems running the install disk version.

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