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How to clean install macOS Catalina 10.15

After months of waiting, they can raise their hands to the sky: macOS Catalina 10.15 They are already among us, with good news that you can check here.

As you may know by now, the easiest way to install the new operating system is by going to System Preferences (or the Mac App Store) and downloading / installing the update. However, for those who want a really ?pure? experience of the new OS, the most interesting option is to make a clean installation In other words, completely reset your computer's HDD / SSD and install everything from scratch, taking advantage of your machine as if it had just come out of the box.

Below we talk a little more about the clean installation process including the precautions you should take and the stone path to accomplish it.

Before Installing

With or without clean installation, it is very important to always make a backup.

OS X Yosemite 10.10 Icon - Time Machine

The testing phase of operating systems is mainly long to avoid serious issues in the upgrade process but, like no perfect software (and you run risks like even power outages in the process), beware.

The simplest way is to use Time Machine itself, a backup system built into macOS. If you already use it, just open System Preferences and check, before installing Catalina, if everything is enabled properly and if the last backup made by him is recent (today, because it runs every hour).

Time Machine, however, saves absolutely everything on your Mac (including the "junk" and traces of previous operating systems you might want to get rid of). My recommendation here, then, is to take an external HDD / SSD, a USB stick, an SD card or even use a cloud service of your trust to manually save all important files that you can not be without.


If you use iCloud, you don't have to worry about emails, contacts, calendars, notes, reminders, passwords in Safari, photos (as long as you use iCloud's Photo Library feature) and documents (both on your Desk and in the Documents folder, as long as you are using the feature that sends it all to iCloud).

What is a clean facility?

A lot of people like to take advantage of these major new operating system releases to do a clean install, that is, erase everything and start over from scratch without any ?junk? / traces of previous installations.

The good thing about a clean installation is that by getting rid of it you can save a few gigabytes. And by pulling your files back into the new system, you can enjoy better organizing everything and even discarding some things that no longer make sense to keep (that's, of course, an individual assessment that only you can do).

The bad part of a clean install is that you will have to install several third party applications on your Mac again and configure them the way you are used to using them.

How to do a clean install?

13-inch MacBook Pro running macOS Catalina

There are two ways to do this: using macOS Recovery or by creating a boot disk.

Using macOS Recovery

Starting with macOS Sierra 10.12.4, Apple has implemented a very nice feature. With it, simply restart the computer with the keys (Option) (Command) R pressed to begin the macOS installation process. The nice part of this is that, using the shortcut mentioned, the installed system will be the latest version of macOS compatible with your Mac so if you have one of the Macs below you can install macOS Catalina 10.15 that way.

Here are the Macs compatible with the new system:

  • MacBook (2015 or later);
  • MacBook Pro (2012 or later);
  • MacBook Air (2012 or later);
  • iMac (2012 or later);
  • iMac Pro (all models);
  • Mac mini (2012 or later);
  • Mac pro (2013 or later).

The downside to installing MacOS Recovery is that your Mac will become unusable during the operating system download period. And since it can take a few good minutes / hours (depending on your connection and Apple servers), the process can be pretty boring make sure you do it on a free day.

Note that to clean install you need to erase the boot disk before installing macOS. And by erasing the boot disk permanently, all data stored on it is erased! Then confirm that all you really need is in your backup. ?

That done, follow the instructions below:

  1. Select "Disk Utility" in the macOS Recovery utility window and click "Continue."
  2. Select the device or volume in the Disk Utility sidebar.
  3. Click the button or the "Delete" tab.
  4. Fill in these fields: Name: Enter a name for the disk, such as "Macintosh HD." Format: Select Expanded Mac OS (Chronological Record) if you have an HDD or APFS computer if you have an SSD computer. Scheme (if available ): Select ?GUID Partition Map?.
  5. Click "Erase" to begin erasing the disc.
  6. When done, exit Disk Utility to return to the utility window. You are ready to install macOS.

Creating a boot disk

Do you know the problem of leaving your Mac unusable while downloading macOS Catalina 10.15? Well, you don't have to worry about that if you choose the second option, which is to create a system boot disk. To do this, you will need to use an external HDD / SSD, USB stick or SD card (if your Mac has a slot for cards or you have an accessory for it) to be your boot disk. Choose a disc that can be completely erased and formatted (with a name with no spaces and no special characters, preferably), as the system itself will clean it.

You can choose one of two ways to create your installation disc using Terminal or an app.

By the terminal

  1. Download macOS Catalina from the Mac App Store.
  2. When it opens the installation window automatically, close it using the shortcut Q.
  3. In the Finder, open the "Applications" folder, right-click "macOS Catalina Installation" and select "Show Package Contents."
  4. Comes Contents Resources and leave this window open.
  5. Open another Finder window (File New Finder Window or by shortcut N).
  6. Comes Utility Applications and open Terminal.
  7. In the window that opens, type sudo followed by space.
  8. Now, in that window you left open, drag the createinstallmedia file to Terminal.
  9. Type –volume followed by space.
  10. With Finder selected, v in the menu Go Go to Folder.
  11. Type / Volumes and click "Go."
  12. Connect the external HDD / SSD, USB stick or SD card to your Mac and it should appear on the desktop.
  13. Drag its volume (cone) to the Terminal window.
  14. Press Enter to finish sending the command.
  15. If necessary, enter your password.
  16. Type y (from Yes) to allow the external disk to be erased and press Enter.
  17. The installation process will start by deleting the contents of your external HDD / SSD, USB stick or SD card and copying the installer files to it reminding you that this whole process may take a while (about 20 to 30 minutes).
  18. When the process is complete, you can use this external HDD / SSD, USB stick or SD card to boot the macOS Catalina 10.15 installer.

If by chance during this process an alert appears asking about ?SetFile?, you can choose the ?Now No? option (Not Now) as this will not interrupt the creation of the USB installation drive.

Using an app

If you are unfamiliar with Terminal and do not like the way the above process is done, you can choose to do everything using one app. Free DiskMaker X and a hand on the wheel it has instructions for the disc creation process, just follow the step-by-step instructions.

The app has not yet been updated for macOS Catalina (at least as we publish this article), but it is likely to work well since the macOS installation procedure remains basically the same.

Erasing Your Mac and Installing the New System

  1. Restart the computer by holding down the key during the reboot.
  2. Select the external disk created.
  3. Select Disk Utility and click "Continue."
  4. Select the device or volume in the Disk Utility sidebar.
  5. Click the button or the "Delete" tab.
  6. Fill in these fields: Name: Enter a name for the disk, such as ?Macintosh HD?. Format: Select Expanded Mac OS (Timeline) or APFS. Scheme (if available): Select ?GUID Partition Map?.
  7. Click "Erase" to begin erasing the disc.
  8. When done, exit Disk Utility to return to the utility window. You are ready to install macOS.

After the installation is complete, add your files back to your Mac, either by rescuing them from Time Machine or by dragging them from your external drive through Finder.

And who's already running macOS Catalina 10.15? All right? ?