The editor was deeply impressed by Big Sur at WWDC 2020, with a reborn UI design, newly added widgets, control center, and various cool translucent special effects. The upgrade process is not troublesome, download a description file, click Software Update and download nearly 10GB Big Sur Beta. After installation, this simulacrum plus a flat design style, a slightly fake battery icon, and the visible stuttering made the author scream, and the idea of returning to Catalina was born. If you have encountered a similar dilemma, you might as well try the following three approaches.
▍Easiest and safest: time machine
If you have performed a complete backup through Time Machine before upgrading to Big Sur, then congratulations, the downgrade experience will be easy and enjoyable. Time Machine will automatically back up all your files, including applications, music, photos, emails, documents and system files. After you restore, everything will be exactly the same as before.
Specific steps are as follows:
The first step is to connect your "Time Machine" backup disk.
The second step is to restart your Mac, and hold down the Command (⌘)-R keys to restore the system boot from macOS. When you see the Apple logo or the spinning globe, you can release the keys. By the way, you can press different key combinations during restart to achieve different reinstallation operations.
Then we will see the window of "macOS Utilities", we choose the first option here, "Restore from Time Machine Backup", and then click Continue.
Here will let you choose the recovery source, select your Time Machine backup disk, and then continue to the next step.
Then we select the backup files separately, select the recovery target disk, and then click Restore, the system will start the restoration action, you can go to have a meal first, if you have more files, the process will be longer , Usually more than half an hour.
When the entire progress bar is finished, your Mac will be restored to its previous state smoothly.
If you didn’t use Time Machine Backup before upgrading Big Sur, or like the author, only use Time Machine backup after upgrading to Big Sur (Time Machine will not be backward compatible), we can only erase the system disk and reinstall Catalina.
▍U disk installation
There are two ways here. The first one is to reinstall the system through the created system recovery USB disk. The author made a system disk when I replaced the SSD with the Mac before, and it just came in handy at this time.
1. Make a system disk
There are many ways to make a system disk, but first we have to download the Catalina system first, because you can’t download it directly from the App Store in Big Sur, so you may find another Mac or download the system and install it first. file. After downloading, put the system installation file into the "application" folder.
It is very convenient to make a boot disk through macOS. We open "Applications"-"Utilities"-"Terminal" in turn, then enter the code and press Enter (without quotation marks)
「sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume」。
Here Catalina.app is the version of the system you downloaded. If you download it is not Catalina, you need to change it to the corresponding system name. "MyVolume" is the name of your USB flash drive. If your USB flash drive is not this name, just change "MyVolume" in the command to the name of your USB flash drive.
Here are the codes of Mojave, High Sierra and EI Capitan for reference.
Mojave：
sudo /Applications/Install\ macOS\ Mojave.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume
High Sierra：
sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume
Captain:
sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app
After entering the code, the system will prompt you to enter the system password, and then press Enter.
Then the terminal will ask you if you want to erase the volume, enter Y to confirm and press Enter. When the terminal prompts to complete, the creation of the entire boot disk is complete.
One more thing to mention here, if you don't have another Mac on hand, you can also use Floppy Drive under Windows to create a bootable U disk by writing a hard disk image.
2. Reinstall the system
After making the backup (don’t use the time machine), let’s restart the system first, hold down the Command key, and start the selection interface. Usually, the first one is your system disk, and the latter is your U disk system. We choose the second one here and ***.
Wait until the interface of macOS Utilities comes out, click Disk Utility.
Enter the disk tool page, we find the system disk, select and click "Erase" at the top, select APFS as the format, and click Erase. (Remember to backup before erasing) It is not recommended to choose a case-sensitive format, which will cause some software, such as Steam, to be unusable.
After the erasing process is completed, we return to the initial macOS "Utilities" interface, select "Reinstall macOS", and then follow the system prompts. The whole process takes about half an hour.
▍Network installation
If you find it too troublesome to make a U disk, there is also an easier way to let Mac download the system through the network and install it independently.
After backing up your personal data, restart your Mac and press one of the following three key combinations as required.
Command (⌘)-R reinstall the latest macOS installed on your Mac. Option-⌘-R upgrade to the latest macOS compatible with your Mac. Shift-Option-⌘-R reinstalls the macOS that came with the Mac or the closest version that is still available.
We do not choose the first one here. If you have already installed Big Sur, it will only reinstall Big Sur Beta once.
After you release the key, the system may prompt you to enter your password. After you enter it, you can see the familiar "macOS Utilities" window.
The next steps are roughly the same as the above installation with U disk. First use Disk Utility to erase the system disk, then return to the main interface and select "Reinstall macOS". Because this method is installed through a network download system, the time required may be much longer than that of a U disk, so special attention is required.
macOS Big Sur (macos11 new system) official version
macOS Catalina (macos10.15) official version
The latest official version of MacOS Mojave (macos10.14 system)