Q: intel imac wont start after changing permission

The settings on the root directory of the original disk were corrupted by those commands.

If those commands were also run recursively (the -R switch was specified on the commands) and the commands updated the whole file system, that'll be a bigger problem.  If there's no backup that can be restored, then this will likely involve writing some scripts to update the settings on the user files, and (probably the easiest approach) reinstalling OS X onto the disk.  (This is a much bigger effort than just fixing the top of the file structure; the settings vary widely across the files in the file system; the ownerships and the access control modifier bit masks.)

You'll need to modify the settings on the root directory of the TDM disk, not on the root directory of the Mac that's working.  That means mounting the disk and updating the settings in the /Volume directory.  (What I posted would only be applicable with the disk local to the original system and not TDM, as / is the root of the whole file system on the current, local Mac.  Other disks are brought online in the /Volumes directory, and you'd want to find and fix the settings there.)

Disk Utility Repair Permissions might help, but you'll want to boot the recovery partition and not Target Disk Mode to get to that; that'll get you access to Disk Utility from the local disk.  Press and hold ⌘R at bootstrap, and use Disk Utility from there.

If that fails, get help.  You're into Unix and file systems pretty deeply here, and the disk is already hosed, and errors with these or other Unix-level commands could well corrupt the other Mac.

If the system is running Snow Leopard you can boot off of the install DVD and run Disk Utility from there.

I cannot boot from the install disk. Anyway, thanks for all the help. I think MrHoffman, you're right, I should seek help, I probably made things worse after so many things I tried.

Why can;t you? If your problem is permissions on the root drive then the system should boot fine off the DVD.

If you are having other problems then you need to start new thread dealing with those problems.

good luck

OK. I fixed the problem, I guess it was a combination of things.

Here is what I did, just in case someone reads this discussion and has a similar problem: This is an old computer, when I bought my new laptop I stopped using it often. I never had a problem before so I thought that may be the PRam battery went dead as it happens with a car that is not used for a long time so:

1) I changed the battery.

Still I couldn't reboot it. Then I kept thinking that my only option was to be able to boot it up from the installer dvd and use the Utility Disk to check and repair the permissions. But I had tried many times to do so with no success except once two days ago. (Then, I didn't know about the permissions repair function so I did not do it) I kept trying to think what I had done before being able to boot from the disk. And I remembered that I had reset the PRAM. So:

2) I reset the PRAM.

3) I started the computer from the DVD. Indeed, this time I was able to do it.

4) I went to the disk utilities and run a permission check. Many problems were stated. I then run the repair permissions function.

5) I also run the check the hardrive (everything was OK)

And that was it! I restarted and this time (it was a slow start up) I passed the spinning wheel, entered my password and I got it. The only thing is that I got few alert pop-ups warning me that some start-up items were disabled.

Thanks to everyone that helped!

Glad you got it worked out. You still might run into a few more glitches especially in your home folder.

The start-up items that were disabled probably have the wrong permissions on them. If you locate them in the Finder you should be able to fix them on a case-by-case basis.

regards

i had same prob as ericgb.  ur solution worked great.  thanx 4 ur help. 

i won't be changing HD permissions again anytime soon.  :-)