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If nothing works anymore on the Apple computer, the last upgrade made macOS badly lame or another, larger error occurs, then it can be worthwhile to start the Mac in recovery mode. The so-called "Recovery Mode" is available in different versions - depending on the problem and the system version you want to restore. In the following, I'll show you how to start the correct Mac recovery mode, and how you can call up macOS from another drive for self-repairing the system. But one after anonther…
Basically, this is about key combinations that you press and hold immediately after switching on or restarting the Mac until something happens on the monitor. I explain what the individual combinations trigger in brief here and in a longer version below. Keys that appear are CMD (⌘), SHIFT (⇧), OPTION (⌥), CTRL (⌃) and letters.
The regular recovery mode of the Apple Mac is carried out at system start-up if you turn on the computer immediately Command + R (or cmd + R or ⌘ + R) hold down. With this key combination you ensure that the operating system under which you last worked on the Mac is reinstalled. So if you have just installed macOS 10.14.1 Mojave, then this version will also be installed with the Mac recovery mode, which you call up with Command + R at system start.
Did you downgrade or your Mac is crazy while a more recent version of the macOS operating system is available, then the key combination Option + Command + R (or alt + cmd + R or ⌥ + ⌘ + R) are worthwhile. Make sure that your Mac is restored with the latest macOS version, which of course means that there must be a (fast) internet connection. The operating system with all updates, patches and fixes available to date is loaded and installed from the Apple server. That can take a long time.
If something goes fundamentally wrong with a newer or the current macOS version, the Apple computer does not run properly or too slowly or other errors occur, then it may be worthwhile to reset to the operating system with which the model you are using was delivered has been. You don't need an installation CD-ROM or something for this, but again a key combination for the system start. Presses simultaneously immediately after switching on Shift + Option + Command + R (or Shift + alt + cmd + R or ⇧ + ⌥ + ⌘ + R) to install the macOS version that came with your Mac.
Note: If your Mac is so old that its "original" Mac OS X has become obsolete in the meantime, the oldest version still available will be selected as an alternative.
MacOS recovery information: Support.Apple.com
As mentioned at the beginning, if you have problems with your Mac, you can also start the macOS operating system from another volume. To do this, simply press the Option key (or option, old or ⌥). This leads to the so-called "Startup Manager" being called. In this you can, for example, select an external hard drive on which you have installed macOS and thus start the system. In an emergency, you can fix errors with a "fresh" system without reinstalling or resetting and, for example, repair file permissions.
In case of emergency I bought a small, external SSD hard drive with 128 GB (this model). I plug this in when there are system problems or when the internal hard drive of the Mac goes crazy in order to start a fresh macOS Mojave with the Option key and Startup Manager. From that system, I then call Disk Utility to take action to repair the system. If you want to use this procedure, but get stuck somewhere, then please use it Contact or leave a comment under this post. I am happy to help you solve your Mac problems;)
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Jens has been running the blog since 2012. He appears as Sir Apfelot for his readers and helps them with problems of a technical nature. In his free time he drives electric unicycles, takes photos (preferably with his iPhone, of course), climbs around in the Hessian mountains or hikes with the family. His articles deal with Apple products, news from the world of drones or solutions for current bugs.