You might have tried all the possible solution for whatever problem you are facing on your Mac, only then you'll be reading this page. The OS X hardly bothers us with issues, but when it does, it's a real pain to resolve it. As a last resort, we have the only option to erase, install, and reinstall OS X. All this can be done by going to Recovery Mode.
Erasing, installing, and reinstalling OS X isn't as hard as it seems to be. You just need to be alert while dealing with these things. Anyway, we have listed below step-by-step instruction for the same, have a look. And yes, make sure you backup your personal data, as everything will be erased.
How to Install Mac OS X in Recovery Mode
Step #1. As the title of the post says, you'll need to be in the Recovery Mode first. So if you aren't already there, then restart your Mac in Recovery Mode.
Step #2. In the Recovery Mode, click on Disk Utility and then click on Continue.
Step #3. From the left, select the volume which has OS X installed. Then click on Erase tab.
Step #4. Now in the Format menu, select Mac OS Extended (Journaled). Name the volume with whatever you like and then click on Erase.
Step #5. After the process of erasing disk is completed, select Disk Utility → Quit Disk Utility.
Step #6. Now click on Reinstall OS X and click on Continue.
The setup process for reinstalling OS X will begin. When you reach the stage where you have to select the disk, choose the one which you erase in the above process. Besides, you may also be required to authentic with your Apple ID, so make sure you have a working internet connection.
Now all you have to do is to follow the on-screen instructions and wait till the reinstalling process is completed.