Repair Hard Drives and Disk Permissions using Disk Utility

Disk Utility is an important Mac utility which allows you to solve disk related problems.It is  used not only to erase, format, and partition a Mac drive, but also to repair problems that may crop up from time to time. First Aid feature of this tool provides two unique functions. One can help you to repair a hard drive and other for repairing file and folder permissions. 

Repair Disk:- 
Disk Utility repairs hard drive’s directory structure with great excellency. It solves common disk issues, ranging from corrupt directory entries to files left in unknown states, usually from power outages, forced restarts, etc.. After repairing disk you can get rid of even minor problem however, major issues like crashes, damage of Mac disk, cannot be solved.

Repair Disk Permissions:- 

It is designed to restore file or folder permissions to it's origional state. Each item in the file system has read , write and execute permissions. Files Permissions are initially set when an application or group of files are installed but sometimes it gets changed. The installation of application includes a .bom (Bill of Materials) file which lists all the files that were installed, and what their permissions should be set to. Repair Disk Permissions uses the .bom file to verify and repair permission issues.

How Can I Fix an Application That's Not Starting?

There can be a many reasons of this problem, but the most likely cause is a disk permissions error. Disk permissions are flags set with each item in the file system. If these permissions get out of whack, they can prevent an application from running properly or some part of it fails to work. So, in such situations you have to repair disk permissions with Disk Utility. You don’t need to know what the permissions should be; your Mac keeps a database of the default permissions for most applications that you’ve installed.

How do I verify/ repair disk permissions

1. Launch Disk Utility. A window appear , click First Aid tab, you can check in above added image.

2. Select the volume , click the Verify Disk Permissions button which appear underneath the large white text box in the middle of the Disk Utility window (on the left-hand side of the box). Verify Disk Permissions could take a few minutes.

3. It will show you the list of problems, now you can click on Repair Disk Permissions button to repair all these problems.