Thursday, July 5, 2012

How Disk Utility Verifies and Repairs Permissions

Disk Utility is an Apple's inbuilt tool that facilitates a variety of disk-related tasks, such as creation of disk images, mounting or unmounting hard disks, enabling journaling, etc. Apart from these functions, Disk Utility can help you verify and repair your Mac OS X disks. It also allows verifying and repairing disk permissions to resolve a range of application errors. Let us delve deeper into the process followed by Disk Utility to check file permissions.

A majority of installations done in Mac OS X are typically done through package files (the files with '.pkg' extension). For every installation done from a package file in Mac OS X 10.5 or earlier, an associated 'Bill of Materials' (.'bom') file is created and stored in the '/Library/Receipts/' folder. These files consume a small amount of disk space. Every '.bom' file includes a list of files that were installed by the package. These files also contain proper permissions for each installed file.

During the 'Repair Disk Permissions' process, Disk Utility examines every '.bom' file in '/Library/Receipts/' and compares the permissions specified in these files with the actual permissions on each file installed by the package. If these permissions do not match, Disk Utility reports the changes. When you use the 'Repair Disk Permissions' feature, Disk Utility rectifies them.

Disk Utility does not check permissions on all files on your hard disk. It verifies permissions for only those files that were installed as a part of an Apple-originated installer package. These files will be listed in a receipt and thus checked. In addition, if there are files whose permissions can be changed without losing their functionality during normal usage, then these files will not be checked. With Mac OS X 10.6 or later, Disk Utility can verify and repair the same version of Mac OS on which it is running.  

If you still face issues with your hard drive, take help of professional Mac file recovery software like Stellar Phoenix Mac Data Recovery. The software use advanced, proprietary algorithms to safely recover all lost, deleted, or formatted data from Mac hard drives and volumes. It supports recovery from HFS, HFS+, and FAT based volumes. With the help of these tools, you can perform 'Raw recovery' of files based on their signatures. The software supports more than 122 different file types. You can also recover any accidentally deleted files, photos, documents, videos, movies, etc. Further, the tool support the latest Mac OS X 10.7 Lion. 

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