How to re-install macos high Sierra

Sometimes, you just want to backup stuff in your old MacOs High Sierra and start over.

You saved all needed files on the google drive and ready for a new start.

Here is the steps to follow.

1. shut down the laptop
2. when the laptop start, press CMD + R during power up
3. Once get into the restore mode, select Disk utilities and click continue 
   
4. In the next screen select a disk images under "Disk Images" on the left, then click erase at the top.
5. Once seeing "Erase process is complete, click Done to continue", just click Done
6. Continue to do it until all the disk images under "Disk Images" are gone.
7. Now select "Macintosh HD" under Internal on the left, the blue bar should show mostly free space. 
8. We are done erasing old MacOS, it is time to start new.
9. close Disk utilities window, return to restore mode main window.
10. select "Reinstall MacOS"
11. In the next window, you will notice the wifi connection is also grey out. Click the wifi icon and put in the wifi id and password.
12. click continue, the wizard will connect to apple server in the cloud and guide you through exiting process of creating a new macOS, sit back and enjoy. (Don't forget to download the saved files from google drive once finish.)