Reinstall Catalina Without Losing Data

16-08-2021
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From Jun 2020 to Aug 2020, Apple has released several beta versions for macOS 11 Big Sur, both developers and testers can install and run it on a supported Mac. You may be one of them, starting to use this new macOS but unfortunately run into some issues and want to revert to previous Catalina or Mojave version.

No worries, here we will list the easy steps to downgrade macOS Big Sur to Catalina without losing data.

How to Reinstall mac OS Without Losing Personal Data. Reinstalling macOS (sometimes also called a “factory reset”) is usually a rare event, and you shouldn’t have to worry about it too much. But there are specific issues, self-inflicted or not, that are much quicker resolved with a clean installation of the OS. Reinstall a previous version of the Mac OS using the appropriate Mac OS Installer. Use Time Machine to restore from a date when your Mac was using a previous version of the o perating system. With any of the downgrade methods, you’re going to lose all the data currently on your Mac. A very small price to pay to be able to reinstall Mac OS without losing data at any time. How to recover any Mac files quickly You might not think about it right now, but it’s likely that at some points you’re going to lose some of your files.

Recover Data After Mac Downgrade

Reinstall Mac Os Catalina Without Losing Data

  • Recover files lost due to macOS update, downgrade, crash, etc.
  • Recover lost, deleted, formatted data
  • 5 recovery modes: Basic, Advanced, Formatted Drive, Trash, Extenal Devices
  • Recover files from internal and external hard drive (USB, SD Card, Media Player)
  • Support file recovery on 200+ formats: video, audio, photo, docs, etc.
  • Preview files before recovery
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Why We Need to Downgrade Big Sur to Catalina?

Reinstall Catalina Without Losing Data

MacOS 11 Big Sur is absolutely the biggest update these years since it has moved from 10 to 11, you can find a bunch of update as following in Big Sur:

  • New design
  • Intuitively customized Safari browser
  • Updated Messages app (better control of conversation)
  • Redesigned Maps for better and easier navigation
  • Improved transparency for Mac App Store downloads
  • Expanded photo editing features
  • Faster updates to the latest version

……

All the revealed new updates added to macOS11 Big Sur stimulate mac users to upgrade and take the first bite on this macOS version. But later, there occurs problems and some of them want to revert to the previous Catalina version for one or another reasons:

  • The Beta version is not perfect, you want to download the official version later;
  • It takes longer time to get used to the new version and you don’t want to waste time;
  • MacOS 11 Big Sur keeps causing problems;
  • Your hardware is not highly compatible on this new version (compromised audio, video or image quality);
  • Your favorite app doesn’t work on the new version;

Reinstall Catalina Without Losing Files

……

No matter what your reason is to revert to an older version, you can refer to following part to downgrade from Big Sur to Catalina without losing data.

How to Downgrade Big Sur to Catalina without Losing Data?

To downgrade Big Sur to Catalina without losing data, here are 6 steps to follow. Before the downgrade, your data matters the most, so don’t forget to back them up though it takes time to finish a backup.

Step 1. Prepare your Mac for downgrade

Reinstall Catalina Without Losing Data

You should quit running programs and leave enough space (15GB to 20GB) to install Catalina after erasing Big Sur from your Mac hard drive. Also, make sure your mac is connected to the internet for later macOS installer download.

Step 2. Backup files (Important and Required)

It is safe to upgrade or downgrade a macOS version, there is no harm done to your files or data, but data loss after mac update or reversion happens sometimes. If you don’t want to render your data under any potential risks, you are highly recommended to back up files.

There are 2 ways to back up file, either back up your files to an external hard drive with Time Machine or upload your data to cloud-based service for storing, like iCloud, DropBox, OneDrive. But here Time Machine backup is recommended.

  1. Connect an external hard drive for backup to your mac;
  2. Run Time Machine and set it up for backup;
  3. Click on the Time Machine icon in menu bar, choose Back up Now;
  4. Wait for the backup to finish.

How To Reinstall Mojave Without Losing Data

Step 3. Erase macOS 11 Big Sur from your Mac

  1. Click Apple icon and go to Restart;
  2. Hold down Command+R when rebooting to reboot your mac in Recovery Mode;
  3. In the pop-up interface, choose Disk Utility>Continue;
  4. Then select your Startup Disk, click on Erase tab;
  5. Choose APFS or macOS Extended format and confirm to Erase.

Step 4. Install macOS Catalina or Mojave

There are 3 methods to install older macOS version on your mac.

Method 1. Download from Mac App Store and Install

  1. Launch Mac App Store;
  2. Search macOS Catalina or Mojave, click Download;
  3. When the download finishes, follow the on-screen instructions to install macOS Catalina or Mojave;

Method 2. Reinstall macOS Catalina or Mojave from Internet

  1. Click on Apple logo>Restart;
  2. Hold down Command+R when rebooting your mac;
  3. In the pop-op macOS Utilities interface, choose Reinstall macOS>Continue;
  4. Agree to the terms and follow the instructions to download and install.

Method 3. Reinstall macOS Catalina or Mojave from Bootable Drive

  1. Create a bootable drive of macOS Catalina or Mojave
  2. Connect the bootable drive to your mac;
  3. Click on Apple logo>Restart;
  4. Hold down Option when rebooting your mac;
  5. Choose the bootable drive with macOS Catalina or Mojave installer;
  6. Click on Continue, agree to the terms and install a previous macOS version onto your mac.

Step 5. Restore Backup with Time Machine

The only change you want for the downgrade is turning back to a previous macOS version, but you want the files and settings the same as before. In this case, you should restore both your files and settings from a Time Machine backup.

  1. Click on Apple Logo>Restart;
  2. Hold down Command+R during mac rebooting;
  3. Choose Restore from Time Machine Backup from the macOS Utilities interface and click on Continue button.
  4. Choose the Time Machine backup disk>Continue;
  5. Select the latest backup, click Restore>Continue.

Step 6. Check if everything is back now!

Catalina

Now, run your apps on macOS Catalina and check if everything goes well.

If the downgrade still causes problems, restart your mac or reinstall Catalina/Mojave to fix it.

What If Data Lost/Deleted after macOS Big Sur Downgrade?

But what if we still got data lost or deleted after macOS Big Sur downgrade to Catalina or Mojave? You can recover them back with Time Machine backup by following the tutorial in above Step 5. If this still cannot get back your files, you need a professional data recovery program---Cisdem Data Recovery.

Cisdem Data Recovery is a program to recover lost, missing, deleted, formatted files from both internal and external hard drive on mac. It applies to data loss due to system crash, update or downgrade, also supports file systems like APFS, HFS+, FAT16, FAT32, exFAT, NTFS, etc.

Main Features of Cisdem Data Recovery

  • Recover lost, deleted, formatted data;
  • 5 recovery modes enable users to recover files lost under different situation;
  • Recover files from internal and external hard drive (USB, SD Card, Media Player)
  • Support file recovery on 200+ formats: video, audio, photo, docs, etc.;
  • Support various file systems: APFS, NTFS, HFS, FAT, etc.;
  • Preview files before recovery;
  • High recovery rate;

How to Recover Data After macOS Downgrade from Big Sur to Catalina?

  1. Download and install Cisdem Data Recovery to your Mac;
    Free Download
  2. Choose a data recovery mode basing on your need. Basic mode runs a quick scan, while Advanced mode runs a deep scan;
  3. Select the location where you lost the files and click Scan;
  4. Preview the found files; All the founded files will be categorized in different folders, check the file and preview before recovery;
  5. Select the found file and recover them onto your mac. Check the box before found files, stop the scanning process if you want to recover before the end of a scanning process. Click Recover to get all lost files after macOS Big Sur downgrade back to your mac.

Conclusion

No matter you want to downgrade from Big Sur to Catalina or Mojave without losing data, or just want to upgrade from an earlier version to the latest macOS, the backup process is mandatory in case of any data loss. If a data loss happens and you don’t have a backup, you will need a dedicated program like Cisdem Data Recovery to do the job.

I’ll admit it: I’ve gotten a little used to working at smaller companies, where there’s no monitoring of company computers, and it’s the Wild West as far as what you can install on them.

That’s no longer the case for me. I now work at Auth0, a company with a headcount that’s quickly approaching 800, with unicorn status and Series F funding, and it’s in the security industry. Naturally, there’s a full-fledged security team that monitors company-issued computers.

In my excitement to take the new version of macOS — Big Sur — out for a spin, I’d forgotten that the Security team hasn’t yet approved it for use. They very quickly (and I should add, nicely) contacted me and let me know that I needed to reinstall macOS Catalina as soon as possible.

There are other reasons why you might need to go back to Catalina after installing Big Sur:

  • It’s still very new, and very new versions of operating systems always have some set of issues, whose effects can run the gamut from mildly annoying to catastrophic. If you can’t afford to lose time dealing with these issues, you should wait for the updates.
  • There are reports that the current version can “brick” MacBook Pros from the 2013 / 2014 era. This isn’t a problem if you’re keeping your old 2013 / 2014 machine around as a backup, but more serious if you’re still using it as your main computer (and yes, a 2013 / 2014 Mac is still a perfectly good machine, even for development work).
  • If you’re a DJ or music producer, Big Sur currently has compatibility problems with some of the hardware and software. If you want to keep DJing, producing, or mixing on your Mac, stay on Catalina for a little bit.

For the benefit of any who need to downgrade, here’s a step-by-step guide to reinstalling Catalina after you’ve installed Big Sur. You’ll need a USB key and the better part of an afternoon.

Step 1: The preliminaries

1a: Start downloading the Catalina installer from the App store

The first thing you’ll need is the macOS Catalina installer.

It’ll take up around 9 gigabytes of space on your hard drive, and the App Store will put in your Applications folder.

Once it’s completely downloaded from the App Store, the installer will start automatically. When this happens, close the installer. You’ll make use of it later.

The installer will take some time to download. Apple’s servers will be busier than usual, as many users are downloading Big Sur and other upgrades.

1b: Back up your files!

In the process of reinstalling Catalina, you’ll need to completely erase your Mac’s hard drive. If you have any files that you can’t live without, this is the time to back them up.

I didn’t have to worry about this, since:

  • All my work product is either code (which lives on GitHub) or content (which lives on GitHub or Google Docs), and
  • I’ve been at Auth0 less than a month, and between onboarding and offsites, there just hasn’t been that much of a chance for me to accumulate that many files on my hard drive!

1c: Get a nice fast USB key that stores at least 16 GB

The process will involve booting your Mac from a USB key containing the macOS Catalina installer, so you’ll need a key with enough space. An 8 GB USB key won’t be big enough. Because digital storage is all about powers of 2, the next size up will be 16 GB.

Reinstall

I strongly recommend that you use a USB 3 key, especially one with read speeds of 300 megabits/second or better, such as the Samsung Fit Plus. Doing so will greatly speed up the process. Don’t use a USB key that you got as conference swag — it may have the space, but more often than not, they tend to be slow, because they’re cheap.

If the USB key contains files that you want to keep, back them up. You’re going to erase the key in the next step.

Step 2: Make a bootable USB key containing the macOS Catalina installer

2a: Format the USB key

Plug the USB key into your Mac, then launch Disk Utility.

Select the USB key in Disk Utility’s left column, then click the Erase button:

You’ll be presented with this dialog box:

Enter MyVolume into the Name field, and for Format, select Mac OS Extended (Journaled). Click the Erase button. This will format the USB key with the volume name of MyVolume.

2b: Install the macOS Catalina installer onto the USB key

In Step 1a, you downloaded the macOS Catalina installer and closed it after it started automatically. In this step, you’ll transfer it to your freshly-formatted USB key.

Open a terminal window and paste the following command into it:

(The command above assumes that you gave the USB key the volume name MyVolume.)

Once you’ve provided sudo with your password, you’ll be asked if you want to erase the USB key. Entering Y in response will start the process of making the USB key a bootable drive and copying the macOS Catalina installer onto it:

The Erasing disk process will be relatively quick, but the Copying to disk process may take a while. This is where using a nice, fast USB 3 key will pay off.

Be patient and let it get to 100%, and wait for the Install media now available message to appear and the command line prompt to return.

2c: If your Mac is from 2018 or later, set it up to boot from external media

Check the year of your Mac’s manufacture by selecting About This Mac under the Apple menu:

  • If your Mac year is 2017 or earlier, you don’t need to follow the rest of this step. Proceed to Step 3.
  • If your Mac’s year is 2018 or later, you’ll need to change its security settings to allow it to boot from an external drive.

Here’s how you change the security settings:

How Do I Reinstall Macos Without Losing Data

  1. Restart your Mac and hold down the ⌘ and R keys when you see the Apple logo. This puts the computer into recovery mode, which provides many setup options.
  2. In the menu bar, select Utilities, and then select Startup Security Utility from the list that appears.
  3. The Startup Security Utility window will appear:
    1. Under the Secure Boot section, select Medium Security. This will allow you to install Catalina without having to connect to a network.
    2. Under the External Boot section, select Allow booting from external media. This will allow you to install Catalina from a USB key or disk drive.

Step 3: Install macOS Catalina

Restart your Mac, and hold down the Option key while it restarts. Your Mac will present you with a choice of startup disks.

Choose the USB key. Your Mac will boot up and you’ll be presented with the macOS Catalina installer screen:

Go ahead and install Catalina.

Once Catalina is installed, you can proceed reinstalling your other software.

Once that’s complete:

  • If your Mac’s year is 2017 or earlier, you’re done installing Catalina. You can now go about reinstalling your software and restoring your backed up files.
  • If your Mac’s year is 2018 or later, you’ll need to restore its original security settings. The process is described in Step 4, below.

Step 4: If your Mac is from 2018 or later, restore the original security settings

If your Mac is from 2018 or later, follow these steps to restore the original security settings once Catalina has been installed:

  1. Restart your Mac and hold down the ⌘ and R keys when you see the Apple logo. This puts the computer into recovery mode, which provides many setup options.
  2. In the menu bar, select Utilities, and then select Startup Security Utility from the list that appears.
  3. The Startup Security Utility window will appear:
    1. Under the Secure Boot section, select Full Security.
    2. Under the External Boot section, select Disallow booting from external media.