Permissions alterations lead to non-bootable systems

Several users have reported an issue in which users experimentation with or inavertent modification of permissions on key system resources renders the system unable to boot.

Apple Discussions poster tharrisw writes:

"I was messing around with file permissions and did something very, very stupid. I set the access under 'everyone' of the System Folder to 'no access.' I got the spinning beach ball and no response from any input, so after several minutes I rebooted the machine...On reboot, the machine gets as far as the blue screen with the spinning icon at the bottom, and then it switches back and forth between two shades of blue for eternity."

This type of problem should be relatively easy to fix, and there are several approaches, depending on comfort levels with either the terminal and/or other methods of interacting with the filesystem. At the very worst, users will have to perform an archive and install of the system, but that should only be necessary in a couple of scenarios.

Users should generally be able to locate the improperly modified files. Follow this series of escalating steps:

Fix Permissions Most of the core system resources are listed in the permissions database and, as such, should be fixable by running a permissions fix on the hard drive. Users can do this by booting of the Leopard DVD and running "Disk Utility" from the "Utilities" menu.

Target Disk Mode If users have two Macs available, target disk mode will allow modification of permissions of the affected files through the Finder. To do this, boot the problematic computer into Target Disk mode by holding "T" at bootup. Next, attach it via FireWire to the second computer to mount the hard drive on the second computer. Open it and navigate to the files that were changed, and revert their permissions.

Terminal Users should be able to boot off the Leopard DVD, then open the Terminal application from the "Utilities" menu after choosing their desired language. Using the terminal, users should be able to navigate to and revert the changed files. In the example quoted by the user above, the user needed to change the permissions of the system folder itself to being readable by everyone using the "chmod" command as follows:

• chmod a rwx /System/

However, the specifics of the command may change depending on the initial edits done to the system files. The syntax and specifics of command can be looked up in the manual pages for it by typing "man chmod" in the terminal (the "q" key exits the man page viewer).

In addition to the Leopard DVD, users should be able to access the terminal by booting into single user mode (holding cmd-S at bootup). For these terminal commands, users might need to mount the hard drive before they will run. The command for this is the following to ensure it's writable:

• mount -uw /

The previous methods will work for one or two files, but users might also have propagated permissions to multiple system files by using the "Apply to enclosed items" option for folders. In this case, it is recommended that users perform an Archive and Install reinstallation of OS X on their systems. While users could try to rectify the situation manually, the propagation of permissions through the system files could leave many files inaccessible and it could take a long time to track down each changed file.

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