Reinstalling macOS: Complete System Recovery Guide

Introduction / Why This Is Needed

Reinstalling macOS is an effective way to resolve many system issues: unstable operation, frequent crashes, boot errors, or corrupted system files. This guide covers the complete process of creating a bootable installer media and performing a clean reinstall of the operating system on a Macintosh. After completion, you will have a fresh, functional macOS installation. The process will preserve your personal files if you choose the appropriate option, but be sure to back up your data in advance.

Requirements / Preparation

Before starting, complete the following steps:

1. Backup. Create a full copy of all important data to an external drive or cloud storage using Time Machine or manually.
2. Stable internet connection. Required to download the installer image (~12-15 GB) and possibly to download the installer in Recovery Mode.
3. Bootable media (recommended). Prepare a USB flash drive or external SSD with at least 16 GB of capacity (32 GB is better), formatted as Mac OS Extended (Journaled) or APFS. This ensures independence from the internet and speeds up the process.
4. Power. Connect your Mac to power using the adapter to avoid interruption during installation.
5. Apple ID. Ensure you remember your login and password. It may be required for authorization in the Installer.
6. Identify your Mac's architecture. This is important for downloading the correct image:
   • Apple Silicon (M1/M2/M3 and others): Hold the power button to enter Recovery Mode.
   • Intel (up to 2020): Hold Command + R at startup.

Step-by-Step Guide

Step 1: Download the macOS Installer Image

The most reliable method is to download the installer image through the App Store on another working Mac or via Terminal. If you don't have another Mac, you can perform this step already in Recovery Mode (see Step 3), but it will be slower.

Method A: Through the App Store (if available)

1. Open the App Store.
2. Find the required macOS version (e.g., "macOS Sonoma"). If it appears in the "Updates" section or via search, click "Download".
3. The downloaded file Install macOS [Name].app will appear in the Applications folder.

Method B: Through Terminal (universal) Open Terminal and run the command to download the full installer image of the latest compatible version:

softwareupdate --fetch-full-installer

To download a specific version (e.g., Ventura), specify it:

softwareupdate --fetch-full-installer --full-installer-version 13.6.8

After the download completes, the installer app will be in /Applications/.

Step 2: Create a Bootable USB Drive (Optional but Recommended)

If you downloaded the image on another Mac, write it to a flash drive. This will create a bootable installer disk.

1. Connect the formatted flash drive (named MyVolume in the example).
2. Open Terminal.
3. Run the command (replace MyVolume with your drive's name):

sudo /Applications/Install\ macOS\ [Version].app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume

For example, for Sonoma:

sudo /Applications/Install\ macOS\ Sonoma.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume

4. Enter your administrator password when prompted.
5. The process will take 10-20 minutes. Once complete, the flash drive will be ready.

💡 Tip: If the createinstallmedia command is unavailable, ensure you downloaded the full installer image, not the mini-installer.

Step 3: Boot into Recovery Mode

This is the key step to launch the Installer.

• For Mac with Apple Silicon (M1/M2/M3):
  1. Shut down your Mac.
  2. Press and hold the power button until the startup options window appears.
  3. Select the options icon (⚙️) and click "Continue".
• For Mac with Intel processor:
  1. Shut down your Mac.
  2. Turn it on and immediately hold the keys Command (⌘) + R.
  3. Release when you see the Apple logo or the macOS Utilities window.

You will enter the macOS Utilities window.

Step 4: Reinstall macOS

1. In the macOS Utilities window, select "Reinstall macOS" (or "Reinstall Version Name").
2. Click "Continue".
3. Agree to the license agreement.
4. On the disk selection screen:
   • If you want to preserve user data (files, settings), select the main system volume, typically "Macintosh HD".
   • If you want to completely erase the disk (e.g., before selling), first open Disk Utility from the same macOS Utilities menu, format the volume as APFS (named "Macintosh HD"), then return to reinstallation.
5. Select the target volume and click "Install".
6. The installer will begin downloading necessary components (if you are in internet-based Recovery Mode) and start installation. Do not turn off your Mac or close the lid on a laptop.
7. After installation, your Mac will restart. Follow the Setup Assistant instructions to select your country, language, Apple ID, etc.
8. At the "Transfer Information" stage, you can:
   • Restore data from a Time Machine backup.
   • Migrate data from another Mac.
   • Do not transfer information if you want a clean system.

Verify the Result

1. After setup completes, you will see the macOS desktop.
2. Open the Apple menu () → About This Mac. Confirm the correct system version is displayed (e.g., macOS Sonoma 14.x).
3. Test basic functionality: internet access, sound, file system.
4. If you restored from a Time Machine backup, check that your files are present in folders like "Documents", "Downloads", etc.

Potential Issues

Error: "Failed to prepare the installer. An error occurred while creating the bootable installer."

• Cause: The drive is not formatted in APFS/Mac OS Extended, or there is insufficient space.
• Solution: Reformat the flash drive to APFS using Disk Utility, ensure at least 16 GB of free space. Rerun the createinstallmedia command.

Mac boots into Recovery Mode but cannot find the installer image ("No installer found for this Mac")

• Cause: Network connection is unstable or Apple has stopped signing that version of macOS.
• Solution: Use a ready bootable drive created on another Mac. Connect to a reliable Wi-Fi network in Recovery Mode. If the problem persists, try a different macOS version (e.g., a newer one).

Installation stalls at "Less than a minute remaining" or "Preparing Installation"

• Cause: Most often disk issues (bad sectors) or insufficient space on the target partition.
• Solution: In Recovery Mode, open Disk Utility. Run First Aid on the target disk. If errors are not fixed, format the disk as APFS and repeat the installation. Ensure the target disk has at least 20-30 GB of free space.

After reinstall, Mac asks for firmware password

• Cause: A firmware password was enabled on the Mac (for Intel) or full security was enabled (for Apple Silicon).
• Solution: You will need the password set in System Settings → General → Security & Privacy → Firmware Password. Without it, booting macOS is impossible. If the password is lost, contact Apple Support.

System runs slowly after reinstall

• Cause: Drivers for hardware are not installed (especially relevant for older Intel Macs) or data was not restored from Time Machine.
• Solution: Open the App Store and install all available updates. For specific hardware (e.g., printers), visit the manufacturer's website. If you restored from a backup, check if old conflicting settings were transferred. As a last resort, perform a clean install without restoring the backup.