How To Hard Reset a Mac OS X Computer & Reinstall The OS.
It is a fact of life that computers slow down. Sometimes this is due to wear and tear, but it can also be something as simple as filling the hard drive with files that are no longer needed. Or accidental deletion of important operating system files.
When that happens, it’s time to think about reinstalling your operating system. This is a huge pain in the neck as it is not a short process, but in the case of macOS it is an easy process. However, you need an internet connection, so don’t think about doing this on the bus or anything else.
I’ve been thinking about doing this for a long time, but procrastination is my friend. But today, for the purposes of this article, I decided to do it.
Step 1 – back up all essential files
This is always the first step before reinstalling the operating system. Therefore, delete any unnecessary files and then back up the rest to cloud storage, USB drive, or removable hard drive.
Don’t forget to back up your iTunes library, iMovie database, and photo database as well. They can be dragged to the portable storage and then dragged back to the computer when the process is complete.
If you’re using Time Machine, this backup process is very simple.
Step 2 – Turn off FileVault
By enabling FileVault, you cannot reformat and reinstall your hard drive. So go to System Preferences Security & Privacy and turn it off. This can take up to 30 minutes, so please be patient. Make coffee or something like that.
Step 3 – Did you encrypt the startup disk?
For security reasons, you should encrypt your boot disk from the beginning. The slight downside to this is that if you forget your encryption password, you can never unlock it again, and you can never reinstall macOS.
Believe me, I speak from a very bitter past experience.
Assuming you know your password, restart your computer and hold down the CMD + R keys at the same time. You will then see the above screen with a lock (which I had to take a photo, since I cannot take screenshots at this stage).
Enter your password and the screen will change to show you this. Again, I had to take the picture with my iPhone, so sorry for the not-so-perfect quality.
If you do not know your password, then you are seriously out of luck, because even Apple cannot unlock it.
Step 4 – Erase Hard Disk Contents
As you can see from the menu above, there is an option called “Disk Utility”. Select this and then select the drive where the operating system is installed. In my case, there is only one disk, but if you are dual boot you will have more than one.
Now click on “Erase” and a small window will appear asking you to enter the desired name of the newly formatted drive as well as the file format type (APFS). I would recommend leaving them as they are.
Erasing takes literally seconds (at least in my experience). When this is done, the “Used” portion of the disk should be tiny (20KB in my case). At this point, everything on your computer is deleted.
Close the Disk Utility window and you will be taken back to the Utilities screen.
Step 5 – Choose your preferred reinstallation option
There are now two options in the Utilities window from which you can choose.
The first is a Time Machine backup. If you’re in the habit of regularly backing up with Time Machine, and once you’ve accidentally deleted a whole bunch of system files, you can simply roll back your computer to a Time Machine backup, say the day before. It would be the equivalent of a Windows PC system restore.
But I don’t use Time Machine (I back up manually). So for me and others like me, the only other option is to choose the Reinstall macOS option. So go ahead and click on it and then click Continue when prompted.
Step 6 – Pretend to Read the User Agreement
You will now be prompted to read the user agreement. Do what everybody else is doing and pretend you are reading and click Agree. Don’t worry, Apple will never know.
Now select the drive to install the operating system. In my case, there is only one disk. Select it and proceed.
The reinstallation process will now begin.
During the process, the computer will restart several times, and this can take up to an hour or more. The nice thing is that from now on he does everything himself, so you can leave and do something else. You don’t get stuck staring at the screen, watching your life slip away.
Step Seven – Copy everything again
After the system is reinstalled, you will have to start the tedious process of restoring it to its previous state. This will include:
- enabling the firewall.
- Enables FileVault.
- re-encryption of the boot disk.
- Reinstalling applications.
- Recovering important files on your computer from backups.
- Add a screen lock PIN.
Basically, you need to go through System Preferences and check each thing one by one. The computer has now returned to factory settings, so any previously made settings and adjustments will no longer be present.
There is an excellent guide called Hardening macOS, which gives you a huge list (40+) of security measures you need to take when you freshly install macOS. I highly recommend that you reach out to him and do as much as possible. Some of this may seem overkill, but you should never be too careful.