Illustration for How to Fix “An Error Occurred While Preparing the Installation” in macOS Recovery

How to Fix “An Error Occurred While Preparing the Installation” in macOS Recovery

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Illustration for How to Fix “An Error Occurred While Preparing the Installation” in macOS Recovery

Seeing “An Error Occurred While Preparing the Installation” in macOS Recovery usually means the Mac cannot validate or prepare the installer. Common causes include an incorrect date and time, an unreliable internet connection, startup-disk errors, insufficient storage, or an incomplete installer process.

Start by checking the Mac’s date and time in Terminal, then retry the installation. If that does not work, verify the internet connection, repair the startup disk with Disk Utility, and try Recovery again. Back up important files before erasing a disk or reinstalling macOS.

Quick Answer

To fix the error:

  1. Restart the Mac and enter macOS Recovery again.
  2. Connect to a reliable Wi-Fi or Ethernet network.
  3. Open Utilities > Terminal and check the date with date.
  4. Set the correct date and time if necessary.
  5. Open Disk Utility, run First Aid on the internal startup disk, and retry.
  6. If the error continues, free storage, use a different network, or create a bootable macOS installer from another Mac.

Do not erase the disk unless you have a current backup and understand that erasing removes its contents.

Why macOS Shows This Error

During Recovery, macOS must prepare installation files, verify them, and write them to the startup disk. The process can fail when:

  • The Mac’s clock is wrong, causing installer certificate validation to fail.
  • Wi-Fi is weak, blocked, or disconnected.
  • The Recovery environment cannot communicate with Apple’s installation servers.
  • The startup disk has directory or file-system errors.
  • The disk does not have enough free space.
  • Recovery data or installation files are damaged.
  • The Mac restarted during an earlier installation attempt.
  • A hardware problem affects the internal storage or logic board.

The same message can appear for different reasons, so work through the least destructive solutions first.

Before You Start

If macOS still starts normally, back up your files before using Recovery. If it does not start, copy important files to an external disk from another available system when possible.

Have the following ready:

  • Your Mac’s administrator password
  • A reliable internet connection
  • The password for the Wi-Fi network
  • Enough free space on the internal disk
  • An Apple Account password, if Activation Lock or Find My requires it
  • A current backup before erasing or replacing macOS

A reinstall normally attempts to preserve personal files, but any installation or disk operation can fail. Do not interrupt the Mac once installation has begun unless it is clearly frozen for an extended period.

1. Restart macOS Recovery

A temporary Recovery or network connection problem may disappear after a fresh start.

  1. Choose Apple menu > Restart if those options are available.
  2. If the Mac is unresponsive, press and hold the power button until it turns off. Wait a few seconds, then turn it on again.
  3. Start macOS Recovery:
    – On a Mac with Apple silicon, press and hold the power button until Loading startup options appears. Select Options, then choose Continue.
    – On an Intel-based Mac, turn it on and immediately hold Command-R until you see the Apple logo or a spinning globe.
  4. Connect to Wi-Fi if Recovery asks you to select a network.
  5. Choose Reinstall macOS and try again.

If Recovery does not load correctly, see How to Fix macOS Recovery Not Loading.

2. Check the Internet Connection

Recovery downloads installation components, so a connection that works for ordinary browsing may still be unreliable enough to interrupt installation.

Try these steps:

  1. Move closer to the Wi-Fi router.
  2. Disconnect other devices that are using significant bandwidth.
  3. If available, connect the Mac to the router with Ethernet.
  4. Avoid captive-portal networks, such as hotel, school, or café Wi-Fi, because Recovery may not be able to complete the required sign-in page.
  5. Restart the router if other devices are also losing their connection.
  6. Return to the Recovery main window and try Reinstall macOS again.

If possible, test a different network, such as a phone’s personal hotspot. A hotspot may use cellular data, so check your data plan first.

3. Correct the Date and Time in Terminal

An incorrect system date is one of the most useful things to check when macOS cannot prepare an installer. If the date is far in the past or future, installer verification may fail.

Check the current date

  1. In macOS Recovery, choose Utilities > Terminal from the menu bar.
  2. Type the following command and press Return:
date
  1. Compare the result with the current date and time.

If the displayed date is correct, type exit, press Return, close Terminal, and retry the installation. If it is wrong, set it manually.

Set the date manually

The date command uses this format:

MMDDhhmmYYYY

That means:

  • MM is the two-digit month
  • DD is the two-digit day
  • hh is the hour in 24-hour format
  • mm is the minute
  • YYYY is the four-digit year

For example, 2:30 p.m. on July 9, 2025 would be:

date 070914302025

Replace the example with the actual local date and time:

date MMDDhhmmYYYY

The command changes only the temporary system time used by the Recovery environment. It does not erase files. Verify the result:

date

Then type:

exit

Close Terminal and try Reinstall macOS again.

Use network time when available

Some Recovery environments support setting the clock from Apple’s time server:

sntp -sS time.apple.com

If the command reports an error, set the date manually instead. The Mac must have a working network connection for network time to succeed.

4. Repair the Startup Disk with Disk Utility

A file-system problem can prevent the installer from preparing the startup disk. Disk Utility’s First Aid checks the disk structure and repairs certain errors.

  1. Close Terminal if it is open.
  2. In the Recovery window, choose Disk Utility, then click Continue.
  3. Choose View > Show All Devices.
  4. In the sidebar, start with the volumes under the internal physical disk.
  5. Select the macOS data volume, often named Macintosh HD – Data, and click First Aid.
  6. Follow the prompts and wait for the operation to finish.
  7. Run First Aid on the macOS system volume, often named Macintosh HD.
  8. Run First Aid on the container and then the physical internal disk, if those items appear.
  9. Choose Disk Utility > Quit Disk Utility and try the installation again.

First Aid does not normally delete personal files, but it can report that a disk cannot be repaired. If Disk Utility reports hardware or serious disk errors, stop repeated installation attempts and make a backup if possible.

For more detailed disk-repair guidance, see How to Repair a Mac Startup Disk in macOS Recovery.

5. Check Available Storage

The installer needs working space in addition to the size of the macOS installation files. If the startup disk is nearly full, preparation can fail.

If you can start macOS:

  1. Choose Apple menu > System Settings.
  2. Click General, then Storage.
  3. Remove or move large files, old installers, and unused apps.
  4. Empty the Trash if you need to reclaim that space.
  5. Restart into Recovery and try again.

If macOS will not start, avoid deleting random folders from Terminal. System and user data may be stored in separate volumes, and removing the wrong files can make recovery more difficult. Instead, use a backup, an external startup system, or another Mac to copy files before making changes.

6. Try Internet Recovery Again

On an Intel-based Mac, local Recovery may be damaged or unable to provide a usable installer. Internet Recovery downloads the required Recovery environment.

  1. Shut down the Mac.
  2. Turn it on and immediately hold Option-Command-R.
  3. Release the keys when a spinning globe appears.
  4. Connect to Wi-Fi if prompted.
  5. When the Recovery utilities appear, choose Reinstall macOS.

You can also try Option-Command-R if Command-R repeatedly produces the preparation error. The available macOS version depends on the Mac and Apple’s recovery services.

On a Mac with Apple silicon, shutting down and holding the power button loads the startup options screen. Select Options to enter Recovery.

7. Try a Different Recovery Path

If the error continues, the Recovery environment may not be providing a clean installation path.

Possible alternatives include:

  • Entering Recovery again after correcting the date and repairing the disk
  • Trying a different internet connection
  • Using another administrator account if the Mac can start normally
  • Installing from a bootable macOS installer created on another compatible Mac
  • Having Apple or an authorized service provider test the Mac

A bootable installer requires another Mac, a suitable external drive, and the correct macOS installer. Creating one erases the external drive, so do not use a drive containing files you need.

8. Erase the Startup Disk Only as a Last Resort

Erasing the startup disk can remove a persistent file-system problem, but it deletes macOS, apps, settings, and personal data from that disk. Do this only after confirming that important files are backed up or no longer recoverable.

  1. Start macOS Recovery.
  2. Open Disk Utility and choose View > Show All Devices.
  3. Select the internal physical disk or its main volume, depending on the instructions for your Mac.
  4. Click Erase.
  5. Use APFS for modern macOS installations when offered. Follow Disk Utility’s recommended format if it specifies one.
  6. Give the volume a name, such as Macintosh HD.
  7. Confirm the erase operation.
  8. Quit Disk Utility and choose Reinstall macOS.

If Disk Utility cannot erase or partition the internal disk, the problem may involve the disk, its connection, or the Mac’s hardware. Repeatedly forcing the operation is unlikely to help.

Troubleshooting

The date command says the command is not found

Make sure you are in Utilities > Terminal while in macOS Recovery. The date command is included in standard macOS environments. Type it exactly in lowercase and press Return.

The date resets after restarting

That can happen because Recovery is a separate temporary environment. Correct the date again after restarting Recovery, then immediately retry the installation.

First Aid reports that the volume cannot be repaired

Copy important files before erasing anything. If you have a current backup, erase the disk and reinstall macOS. If you do not have a backup, consider professional data recovery before erasing the disk.

The installation starts but returns to Recovery

Disconnect unnecessary external devices, except for the keyboard, mouse, network adapter, or backup drive required for the process. Then retry. If the Mac repeatedly returns to Recovery, inspect the startup disk and check whether it appears normally in Disk Utility.

The Mac asks for an administrator password

Recovery may require the password for a local administrator account. If the Mac is protected by Activation Lock, you may also need the Apple Account associated with the Mac.

The Mac shows “Could not unmount disk”

A volume may be in use by Recovery or another process. Do not force an erase if you still need the files. Follow the steps in How to Fix “Could Not Unmount Disk” Errors on a Mac before trying again.

Nothing fixes the error

At that point, the likely causes include damaged Recovery data, a failing internal disk, a network restriction, or another hardware problem. Try Internet Recovery or a bootable installer. If Disk Utility cannot consistently see or repair the internal disk, arrange service rather than continuing to erase it.

Frequently Asked Questions

Will reinstalling macOS delete my files?

Choosing Reinstall macOS without first erasing the disk is generally intended to replace system files while preserving user data. However, installation failures, existing disk damage, and mistaken Disk Utility actions can cause data loss. Back up first whenever possible.

Does changing the date in Terminal damage the Mac?

No. The date command changes the system clock in the current Recovery environment. Use it carefully, verify the result, and correct the time again if necessary after restarting Recovery.

Can I fix this without an internet connection?

Usually not. Recovery generally needs to download or verify installation components. A bootable installer can provide another installation method, but it must be created in advance on another Mac.

Should I erase the disk immediately?

No. First check the internet connection, correct the date, run First Aid, and retry Recovery. Erasing is appropriate only when you have a backup or accept that all data on the disk will be removed.

What if the internal disk does not appear in Disk Utility?

Choose View > Show All Devices. If the internal disk still does not appear, shut down and try Recovery again. A disk that remains missing may have a hardware or connection problem and should be evaluated by Apple or a qualified repair provider.

Final Thoughts

The most effective first checks are the Mac’s date and time, internet connection, and startup-disk health. Correct the clock in Terminal, run First Aid in Disk Utility, and retry Recovery before considering an erase. If the error persists, use Internet Recovery or a bootable installer, and protect your data before taking any destructive step.