通常，大多数macOS 更新(macOS updates)不会导致您的Mac出现任何问题。但是，有时某些更新会破坏功能并使您的系统出现故障。如果您是此类问题的受害者，您可能希望在Mac(Mac)上回滚更新。
不过，回到您最喜欢的旧 macOS 版本并不简单。Mac上根本没有任何选项可以让您将 macOS 降级到旧版本的操作系统。
这并不是说根本没有办法在你的Mac上降级 macOS 。有几种方法可以帮助您回滚更新并恢复到更新机器之前运行的 macOS 版本。
通过恢复 Time Machine 备份降级 macOS(Downgrade macOS By Restoring a Time Machine Backup)
如果您已经是Mac用户很长一段时间了，您可能已经知道什么是 Time Machine备份。它是您Mac(Mac)的完整备份，包含您的所有文件、应用程序甚至系统文件。
Time Machine备份的好处在于它还可以备份您的操作系统。这意味着如果您在更新到最新的 macOS 版本之前创建了 Time Machine 备份，您可以恢复备份并让您的(created a Time Machine backup)Mac降级。
恢复备份会恢复您在进行备份时拥有的所有文件、应用程序和旧版本的 macOS。
- 通过单击顶部的Apple标志并选择(Apple)Shut Down来关闭您的Mac。
- 将Time Machine备份磁盘连接到Mac并确保它已打开。
- 按下Mac上的(Mac)电源(Power)按钮将其打开。然后立即同时按住Command和R按钮。这将重新引导您进入Mac恢复模式。
- macOS实用程序(Utilities)列表将出现在您的屏幕上。单击列表中显示(Click)从 Time Machine 备份(Restore From Time Machine Backup)恢复的第一个以恢复您的备份。
- 系统将要求您选择保存备份的磁盘。从屏幕上的列表中选择您的磁盘，然后单击继续(Continue)以继续恢复备份。
- 在以下屏幕上，您将看到所选磁盘上的可用备份。您还将看到每个备份的 macOS 版本，以便准确了解要将Mac降级到的 macOS 版本。
选择备份并单击继续(Continue)。
- 在以下屏幕上选择您的主Mac驱动器，然后点击(Mac)Restore。它将用备份中的内容替换驱动器上的所有内容。
恢复备份后重新启动您的Mac，您将回到旧版本的 macOS。
通过安装旧版本的 macOS 来降级 macOS(Downgrade macOS By Installing An Older Version Of macOS)
如果您在更新到最新的 macOS 之前没有创建Time Machine备份，则无法使用上述方法。但是，Time Machine并不是在(Time Machine)Mac上降级 macOS 版本的唯一方法。
您可以在Mac上下载并安装旧 macOS 的新版本。这会将您的机器带到您选择的操作系统版本。请记住，尽管这会擦除 Mac 上的所有数据(erase all the data on your Mac)。
使用这种方法分为三个阶段。
下载旧版本的 macOS(Download An Old Version of macOS)
由于您将安装新的 macOS 副本，因此您需要先将整个操作系统下载到您的Mac上。
如果您像往常一样搜索官方Mac App Store以查找新的 macOS 版本，您只会感到失望。这是因为，尽管App Store有旧版本的操作系统可供下载，但它们并不总是显示在搜索结果中。
您最好的选择是使用下面给出的直接下载链接为您的Mac获取您喜欢的 macOS 版本。
下载文件后，暂时不要打开它。使用 Finder将其移动到Applications文件夹。(Applications)
创建可启动的 macOS USB 安装程序(Create a Bootable macOS USB Installer)
您现在将为您选择的 macOS 版本创建一个可引导的USB安装程序。(USB)您将使用此USB在(USB)Mac上重新安装操作系统。
- 将 12GB 或更高容量的USB驱动器插入您的Mac。确保上面没有内容。
- 打开Finder窗口并记下USB驱动器的卷名。
- 单击Dock 中的Launchpad，搜索Terminal，然后在 Mac 上启动应用程序。
- 当终端(Terminal)打开时，输入以下与您的 macOS 版本匹配的命令之一，然后按 Enter(Enter)。确保将MyVolume替换为您在步骤 2 中记下的USB驱动器的名称。
macOS 莫哈韦：(macOS Mojave:)
sudo /Applications/Install\ macOS\ Mojave.app/Contents/Resources/createinstallmedia – volume /Volumes/MyVolume
macOS 高山脉：(macOS High Sierra:)
sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia – volume /Volumes/MyVolume
macOS 塞拉利昂：(macOS Sierra:)
sudo /Applications/Install\ macOS\ Sierra.app/Contents/Resources/createinstallmedia – volume /Volumes/MyVolume – applicationpath /Applications/Install\ macOS\ Sierra.app
macOS 埃尔卡皮坦：(macOS El Capitan:)
sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia – volume /Volumes/MyVolume – applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app
- 出现提示时输入您的密码，它将开始创建您的可启动USB安装程序。
- 您的USB驱动器现在应该已准备就绪，您可以开始降级 macOS。
安装旧版本的 macOS(Install An Old Version Of macOS)
您要做的是从新创建的可引导安装程序引导您的 Mac(boot your Mac from the newly created bootable installer)。然后它会让你在你的Mac上安装你喜欢的 macOS 版本。
- 关闭你的 Mac。
- 打开 Mac 并按住Option键。
- 启动管理器(Startup Manager)将在您的屏幕上打开。选择您的USB驱动器以从中启动您的Mac。
- 按照屏幕上的说明安装 macOS。
- 您的 Mac 现在应该已降级。
How To Downgrade macOS
Nоrmally, most macOS updates do not cause any issues on your Mac. However, there are times when certain updates break features and make your system buggy. If you’ve been a victim of such an issue, you might want to roll back the update on your Mac.
Getting back to your favorite-old macOS version isn’t straightforward, though. There’s simply no option anywhere on the Mac that lets you downgrade macOS to an older version of the operating system.
That’s not to say that there’s no method at all to downgrade macOS on your Mac. There are a couple of ways to help you roll back the update and get back to the version of macOS you were running before updating the machine.
Downgrade macOS By Restoring a Time Machine Backup
If you’ve been a Mac user for quite some time, you probably already know what a Time Machine backup is. It’s a full backup of your Mac containing all of your files, apps, and even the system files.
The great thing about a Time Machine backup is that it backs up your operating system as well. What that means is if you had created a Time Machine backup before updating to the latest macOS version, you can restore the backup and get your Mac downgraded.
Restoring the backup restores all of your files, apps, and the older version of macOS you had when you made the backup.
- Turn off your Mac by clicking on the Apple logo at the top and selecting Shut Down.
- Connect your Time Machine backup disk to your Mac and make sure it’s turned on.
- Press the Power button on your Mac to turn it on. Then immediately press and hold down both Command and R buttons at the same time. This will reboot you into the Mac recovery mode.
- The macOS Utilities list will appear on your screen. Click on the first one in the list that says Restore From Time Machine Backup to restore your backup.
- You’ll be asked to choose the disk where your backup is saved. Select your disk from the list on your screen and click on Continue to proceed with restoring the backup.
- On the following screen, you’ll see the backups available on your chosen disk. You’ll also see the macOS version of each of your backups so you know exactly what version of macOS you’re downgrading your Mac to.
Select the backup and click on Continue.
- Select your main Mac drive on the following screen and hit Restore. It’ll replace all the contents on your drive with the ones from your backup.
Restart your Mac when the backup is restored and you’ll be back to an older version of macOS.
Downgrade macOS By Installing An Older Version Of macOS
If you didn’t create a Time Machine backup before updating to the latest macOS, you can’t use the above method. However, Time Machine isn’t the only way to downgrade the macOS version on your Mac.
You can download and install a fresh version of an old macOS on your Mac. This’ll bring your machine to your chosen version of the operating system. Keep in mind though this will erase all the data on your Mac.
There are three stages to using this method.
Download An Old Version of macOS
Since you’ll be installing a fresh copy of macOS, you’re going to need to first download the entire operating system to your Mac.
If you search the official Mac App Store like you normally do to find new macOS versions, you’re only going to be disappointed. It’s because, although the App Store has older versions of the operating system available for download, those aren’t always displayed in the search results.
Your best option is to use the direct download links given below to get your preferred version of macOS for your Mac.
When the file is downloaded, don’t open it just yet. Move it to the Applications folder using the Finder.
Create a Bootable macOS USB Installer
You’ll now create a bootable USB installer for your chosen macOS version. You’ll use this USB to do a fresh installation of the operating system on your Mac.
- Plug in a 12GB or higher USB drive to your Mac. Ensure it has no content on it.
- Open a Finder window and note down the volume name of your USB drive.
- Click on Launchpad in the Dock, search for Terminal, and launch the app on your Mac.
- When Terminal opens, type in one of the following commands that match your version of macOS and hit Enter. Make sure to replace MyVolume with the name of your USB drive you noted down in step 2.
macOS Mojave:
sudo /Applications/Install\ macOS\ Mojave.app/Contents/Resources/createinstallmedia – volume /Volumes/MyVolume
macOS High Sierra:
sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia – volume /Volumes/MyVolume
macOS Sierra:
sudo /Applications/Install\ macOS\ Sierra.app/Contents/Resources/createinstallmedia – volume /Volumes/MyVolume – applicationpath /Applications/Install\ macOS\ Sierra.app
macOS El Capitan:
sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia – volume /Volumes/MyVolume – applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app
- Enter your password when prompted and it’ll begin to create your bootable USB installer.
- Your USB drive should now be ready and you can start to downgrade your macOS.
Install An Old Version Of macOS
What you’re going to do is boot your Mac from the newly created bootable installer. It’ll then let you install your preferred macOS version on your Mac.
- Shut down your Mac.
- Turn on your Mac and hold down the Option key.
- The Startup Manager will open on your screen. Select your USB drive to boot your Mac from it.
- Follow the on-screen instructions to install macOS.
- Your Mac should now be downgraded.
