Macbook Pro won't start up after I changed Permissions settings

Next time don't do something to your computer's system software if you don't understand the consequences.

You will need to reinstall OS X to get the computer working:

Reinstall OS X without erasing the drive

Do the following:

1. Repair the Hard Drive and Permissions

Boot from your Snow Leopard Installer disc. After the installer loads select your language and click on the Continue button. When the menu bar appears select Disk Utility from the Utilities menu. After DU loads select your hard drive entry (mfgr.'s ID and drive size) from the the left side list. In the DU status area you will see an entry for the S.M.A.R.T. status of the hard drive. If it does not say "Verified" then the hard drive is failing or failed. (SMART status is not reported on external Firewire or USB drives.) If the drive is "Verified" then select your OS X volume from the list on the left (sub-entry below the drive entry,) click on the First Aid tab, then click on the Repair Disk button. If DU reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported click on the Repair Permissions button. Wait until the operation completes, then quit DU and return to the installer.

If DU reports errors it cannot fix, then you will need Disk Warrior and/or Tech Tool Pro to repair the drive. If you don't have either of them or if neither of them can fix the drive, then you will need to reformat the drive and reinstall OS X.

2. Reinstall Snow Leopard

If the drive is OK then quit DU and return to the installer. Proceed with reinstalling OS X. Note that the Snow Leopard installer will not erase your drive or disturb your files. After installing a fresh copy of OS X the installer will move your Home folder, third-party applications, support items, and network preferences into the newly installed system.

nuyorkster1 wrote:

Next time! Obviously I didn't understand how being the only one to have complete access would change anything. Thanks for the advice, but I don't have any disks since I am traveling...

TIP: Always keep bootable copies of your System & Install DVDs inside your travelling computer bag. Comes in handy when you have to "troubleshoot" away from home.

OK. Well, you're in a bit of a pickle, as they say. There is really nothing you can do if you cannot boot the computer and don't have installer discs. You can go to an Apple retailer or a Best Buy to see if they can reinstall OS X for you.

For future reference: You can purchase an 8 or 16 GB USB flash drive as small as a stick of gum. You can then clone the OS X installer disc to the USB flash drive. Keep it on your pocket keychain so you'll have it with you when you travel. You can also install OS X on a 16 GB flash drive. You will have plenty of space for a few system/disk repair programs as well as backups of the files you need when you're on the road.

Yes, but the computer must be able to startup in Single-user Mode.

Then there may be more that's wrong. While still in single-user mode try this:

/sbin/mount -uw /

diskutil repairPermissions /dev/disk0

I think that will work to repair permissions.

OK. I wasn't sure if it would work. Apparently there are components of OS X that need to be activated in order to repair permissions in single-user mode. A bit beyond my experience.

There is a third-party utility called AppleJack that will do the trick, but I do not know if you can install it from single-user mode. You will need a way to download it. You will find it at MacUpdate or CNET Downloads.

A good article though it doesn't really have a solution for you. You've changed all the permissions for system files. There are just too many of them plus you have to know what permissions to assign.

Wheel is a special group that includes the admin users. It provides additional privileges to special users assigned to the group.

I haven't a real clue as to what you might do. I think your best bet is help at a local Apple store.

Great! Try this for your Home folder:

To fix Home folder permissions

Open the Terminal application in the Utilities folder. At the command line prompt enter or paste the following command line:

sudo chown -R `id -un`:`id -gn` ~

Press RETURN. You will be prompted to enter your admin password which will not be echoed.