Macbook Air Reinstall Os Very Long Download Time

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Whenever there is a new macOS available, the need to reinstall macOS will surge. When you update or reinstall the macOS, the last thing you want is probably losing data on your computer. To reinstall macOS, including the latest Catalina, Mojave, without losing data, you can follow the professional guide to update the OS, which will not cause data loss in most of the case. If you still have worries, back up your Mac in advance or recover the lost files with EaseUS Data Recovery Wizard.

This page covers the full process of how to update and install the latest macOS Big Sur, Catalina, Mojave, etc. on Mac without losing any data. If you need a detailed guide, follow through this page to get the desired macOS installed on your computer now:

Testing conducted by Apple in October 2020 using preproduction MacBook Air systems with Apple M1 chip and 8-core GPU, as well as production 1.2GHz quad-core Intel Core i7-based MacBook Air systems with Intel Iris Plus Graphics, all configured with 16GB RAM and 2TB SSD. Tested with prerelease Shapr3D 3.45.0 using a 288.2MB model. If your Mac is really old - as in so old it's running Mac OS X Snow Leopard or older - it will not have a Recovery partition, the only way to reinstall the OS is to use the discs that shipped with. Several users have reported an issue in which their Mac gets stuck or freezes (becomes unresponsive) during the installation or configuration of an OS X update. Users have stated that software update went smoothly until the Mac was stuck on the “Setting up your Mac” screen at boot for a very long time.

Workable SolutionsStep-by-step Troubleshooting
Phrase 1. Preparations2GB+ memory and 9GB+ storage space left on Mac > 45% + battery > Connect to internet...Full steps
Phrase 2. Change a USB portStart Mac from macOS Recovery > Select 'Reinstall macOS' > 'Continue'...Full steps
Phrase 3. Recover Lost DataAfter macOS installation, run EaseUS Mac data recovery software > Scan and recover lost data...Full steps

Applies To: macOS Big Sur, macOS Catalina, macOS Mojave, macOS High Sierra, macOS Sierra, or earlier Mac operating systems

The need to update or reinstall your macOS always follow the release of a new operating system, the slow performance of your Mac, or a system crash. When it comes to reinstalling macOS, users biggest concern is losing data on their computer.

The good news is that, if you follow the instructions strictly to update your Mac Operating System, the chance to lose data on your Mac is quite slim, since a reinstallation just needs to create a new copy of the OS, your existing files stored on your Mac won't be lost. Thus, as long as you don't choose to erase your startup disk during the reinstallation, you won't lose files. However, you know what 'Slim' means - it's not 100% safe and is still at the risk of losing some data.

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Then how to reinstall macOS without any data loss? To provide a double guarantee to the precious data on your Mac, you can make a copy of the files on your Mac before you perform the reinstallation, or equip your Mac with a data recovery tool that can rescue your data after the reinstallation.

Preparations you Need to Make Before You Reinstall macOS

To reinstall macOS on your computer smoothly. Follow the tips below to prepare your Mac ready for the new macOS update now:

  • Leave at least 2GB memory and 8.8 GB storage space on your Mac
  • Leave at least 45% battery on your Mac
  • Connect Mac to the internet or WiFi
  • Update your Mac Apps to the latest versions
  • Backup all your personal data and even create backups for your present Mac data through Time Machine

Remember to back up your Mac to an external hard drive for preventing system update failure or unexpected troubles from happening. Then follow the detailed guide below to reinstall Mac OS via macOS Recovery mode, which enables you to reinstall macOS, restore your files from Time Machine, repair or erase a disk, and more.

How to Update & Reinstall macOS Without Losing Data

*Print this page or open this page on another device so you can refer to it later.

Step 1. Start up your Mac from macOS Recovery

  • Turn on your Mac and immediately press and hold 'Command + R', 'Option + Command + R', or 'Shift + Option + Command + R'.
  • Release the keys when the Apple logo, a spinning globe, or a pop-up for a firmware password appears.

Step 2. Select 'Reinstall macOS' from the Utilities Window and click 'Continue'.

Step 3. Follow the onscreen instructions to select the hard drive you want to install the OS on and start the installation.

Step 4. Don't put your Mac to sleep mode or close its lid during the installation. It's normal to see your Mac restart several times or the screen is white while you reinstall the Mac OS. Just wait patiently for the process to finish.

If data loss occurred after you reinstalled macOS, you can follow the next part to recover your missing files.

Recover Lost Data After macOS Reinstallation

If you have backed up your Mac before the reinstallation, you can retrieve your data from Time Machine, an external hard drive, or somewhere else, depending on the way you used to make the backup. If you haven't created any backups for your Mac, then you'll need the professional Mac data recovery software tool - EaseUS Data Recovery Wizard, to perform data recovery. With the help of this tool, you can easily recover the data lost due to macOS reinstallation:

Step 1. Select the disk location (it can be an internal HDD/SSD or a removable storage device) where you lost data and files. Click the 'Scan' button.

Step 2. EaseUS Data Recovery Wizard for Mac will immediately scan your selected disk volume and display the scanning results on the left pane.

Step 3. In the scan results, select the file(s) and click the 'Recover Now' button to have them back.

There are lots of data recovery tools available. But EaseUS Data Recovery Wizard, one of the best Mac data recovery tools, is our pick. It fully supports all macOS systems including the newest Big Sur, Catalina, Mojave, High Sierra, Sierra, EI Capitan, Yosemite etc. It allows you to restore all lost data with simple clicks. Office files, music, videos, emails or other archives can all be restored on your own.

macOS installation problem happens all the time. After downloading the macOS installer, you try to install the macOS Catalina/Mojave, macOS Sierra or High Sierra but the installation get stuck. The progress bar has been stuck at 40% or something, showing: 'Installation is in progress. Calculating time remaining...'

If your macOS update also get stuck at 'Installation is in progress. Calculating time remaining...' Here shows you how to confirm if the installation is still going on and how to complete the update successfully.

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1.Check If the Install is Still Going on

Sometimes, it just takes a very long time for you MacBook or iMac to install the macOS Sierra or High Sierra update. So it doesn't necessarily mean that the macOS installation is frozen when the Mac stay at “20 minutes remaining” for two hours. And forcing restarting a Mac during OS installation may cause data loss. Therefore, before taking further action, press Command + L , which will open the log file and shows you if the installation is still going on and the amount of time left.

If you confirm that the installation is frozen, try the following methods to fix.

2. Force Restart Your Mac

Hold down the power button to power off the Mac. Then restart the Mac. After the Mac reboots, try to install the macOS Catalina, Mojave, High Sierra again.

If the installation get stuck when you try to update the Mac from Mac App Store, you may download macOS software from Apple website, which is the Combo updater which includes all the files required to update the macOS.

3. Install macOS in Safe Mode

Another way to install Catalina, Mojave, Sierra or High Sierra successfully is to install the macOS in safe mode. To get your Mac into Safe mode:

As you Mac start up, hold down the Shift key until the Apple logo appears.When you Mac is in Safe mode, go to App Store and get the High Sierra update.

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4. Reset the NVRAM

If the Sierra or High Sierra installation is still won't complete in Safe mode, you can try to reset the NVRAM. NVRAM is a memory section on your Mac that store data like volume settings, screen resolution.

To reset the NVRAM on Mac, restart Mac and hold down Command + Option + P + R.The Mac will restart with options in NVRAM resetting. Now try to update your Mac.

5. Reinstall macOS in Recovery Mode

This will help you to install macOS Sierra or High Sierra and newer versions, without data loss.

  • Restart your mac and hold down the Command + R to boot your Mac into Recovery mode.

  • Click Disk Utility and choose First Aid for your startup drive.

  • Restart the Mac again when this time, press Command + Option + R to get your Mac in Internet Recovery mode.

  • Choose Install a new copy of MAC OS and wait for the installation to complete.

If you have a Time Machine backup, restore your Mac from the backup in Recovery mode. After the restoration, try to install the macOS again.

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6. Clean Install from External Drive

If none of the above methods work for your Mac, you can try to clean install the macOS Sierra or High Sierra from external drive. Here is the complete guide of how to clean install macOS High Sierra on Mac.

7. Recover Mac Files When Catalina/Mojave/High Sierra Installation Is Stuck

After fixing the frozen macOS installation issue, you may found some files missing on your Mac. If so, you can use FonePaw Data Recovery to recover the deleted data from Mac. The program can restore the missing documents, photos and more from hard drive, SD card, USB drive on Mac and Windows PC. Download the Mac version of FonePaw Data Recovery to have a try.

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Step 1. Run the program.

Step 2. Select one or all categories: photos, videos, audio, documents, email or others. Then select the hard drive of your Mac. Click Scan.

Wipe Macbook Clean And Reinstall Mac Os

Step 3. Once the scanning is stopped, you can view the deleted files and choose the needed one to recover to your Mac.

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If the macOS installation on your Mac is still stuck or frozen, describe the problem below.