1. Reinstall Macos Catalina From Internet
2. Installing Macos Catalina From Usb
3. How To Reinstall Macos Catalina From Usb

Catalina on (1) 2011 MacBook Air 13″, buttery smoothly. Only 4GB’s but works buttery smoothly. Catalina on (1) 2008 iMac 24″, internet, mail photo’s, and all default apps work fine, but only 4GB ram so it can be a tad slow. 8GB’s might be better. Catalina on (1) Late 2012 iMac 27″, buttery smoothly (officially supported machine). The simplest way to reverse an OS update is to restore from an earlier Time Machine backup - one you made before upgrading to Big Sur (or Catalina if you want to go back further). Installing a new version of the Mac OS is generally a fairly pain-free process; this trend continues with macOS Catalina. Even so, it’s a good idea to review our Rocket Yard guides for a clean install of macOS Catalina as well as an upgrade install of Catalina. In Mojave and earlier, a clean re-install is straightforward if time-consuming. You boot into Recovery Mode, use Disk Utility there to wipe your boot volume, then re-install macOS from the main window. What determines the source and version of macOS to be re-installed are the keys you hold down to enter the mode in the first place. How to Reinstall MacOS Catalina. Click the Apple logo Restart. Click on Restart. As soon as the computer starts to shut down, hold down Command +R. Continue holding these keys past the black screen and music you hear when the. You may be prompted to select a user you know the password for.

If you have installed Big Sur, Catalina, Mojave or earlier versions, you may have to reinstall macOS for following reasons:

• Reinstall When There is New macOS Version Available

Apple keeps working constantly to fix bugs, make performance tweaks, add new features or enhance coding. Therefore, doubtless, there will be new versions of macOS available to upgrade and reinstall.

• Your Mac is Running Slow

As we all know, for no specific reason, system reinstallation can magically solve a slow Mac in most cases.

• Your System Keeps Crashing or Works Improperly

When you continuously see error messages appear on your mac, or your programs randomly crash/freeze for no reason, like FaceTime won't work, Contacts or Calendar shows a delay or mess, blue teeth or WiFi won't connect…Then, you have a good reason to reinstall macOS.

• You are Going to Sell the Mac

In the case that you want to sell your mac, besides erasing all your personal data and traces on the mac, you will need to reinstall macOS as well.

It is not complicate to reinstall macOS Big Sur or Catalina, but if you want to reinstall macOS without losing data, there are 3 steps you must follow.

Recover Files after macOS Reinstall

• Recover data lost due to macOS reinstallation, upgrade, downgrade
• Recover data lost due to accident deletion, formatting, etc.
• Restore data from both internal and external storage device
• Recover videos, audios, images, documents, and other 200+ files
• 5 recovery modes to find files back easily
• High recovery rate
• Support Big Sur, Catalina, Mojave and earlier

Free Download

3 Steps to Reinstall macOS Big Sur or Catalina without Losing Data

We all save tons of data on our Mac, so when we decide to reinstall macOS Big Sur/Catalina, the top concern always goes to “will I lost everything if I reinstall macOS”. In fact, reinstallation of macOS doesn’t necessarily cause lost data, it just create a new copy, your existing files and data saved in programs won't be altered or deleted. But just in case of bad luck, we need to do some work on BACKUP, this is crucial for macOS reinstallation without losing data.

Step 1. Prepare Your Mac for Reinstallation.

• Make enough room for Big Sur or Catalina reinstallation, at least 36GB, so the reinstallation process won't pause or stopped for insufficient space.
• Also, quit all apps or programs under work, so your Mac is fully geared to reinstall.
• Check drive conditions. Open Disk Utility and perform the Frist Aid on your hard drive where to reinstall the macOS to make sure your drive is in good condition for reinstallation.

Step 2. Backup All Your Files for macOS Install (Crucial)

Backup is an indispensable step involved in the macOS reinstallation, here are several options to backup your data.

Option One: Using Time Machine

1. Go to Finder>Application, launch Time Machine and choose “Set Up Time Machine”.
2. Click “Select Backup Disk” to choose an external hard drive to back up the files.
3. Then Check the box before “Back Up Automatically”. Also, you can adjust the backup setting in menu “Options”.

If this is the first time you use Time Machine to backup, wait patiently for Time Machine to complete the backup, it will prompt the notification once finishes.

Option Two: Using Hard Drive

1. Connect your hard drive to Mac.
2. Open Finder to check if your hard drive is present under “Devices”.
3. Create a new folder, copy and paste or directly move the items you want to save from Mac to this folder.
4. Finally, eject your hard drive.

Option Three: Using iCloud Service (Backup Desk and Documents Folders)

1. Go to Finder>System Preference, click on “iCloud” to bring up its main interface.
2. Click the “Options” button for “iCloud”, and check the box before “Desktop and Documents Folders”, then click on “Done”.

Most of our mac users prefer to backup all files but apps. So, to save you from troubles of lost data due to macOS reinstallation, you are recommended to keep records of what apps you have installed, the account and password, also, you can take screenshots of the settings.

Step 3. Reinstall macOS Big Sur or Catalina without Losing Data.

Option #1: Reinstall macOS without Losing Data From Internet Recovery

1. Click the Apple icon>Restart.
2. Hold down the key combination: Command+R, you will see the Apple logo.
3. Then choose “Reinstall macOS Big Sur” from utilities window and click “Continue”.
4. Select your hard drive, click “Install” and wait for end of reinstallation.

Option #2 Reinstall macOS without Losing Data From USB

1. Download the macOS Big Sur install from Mac App Store onto your Mac;
2. Then connect the USB flash drive to your Mac;
3. Open Disk Utility program on your Mac, choose the USB flash drive and click Erase to have a clean drive for the reinstallation;
4. Open Terminal, copy and paste sudo /Applications/Install macOS Big Sur.app/Contents/Resources/createinstallmedia;
5. Then add the volume of usb flash drive: --volume /Volumes/MyVolume, replace MyVolume with your usb flash drive name, mine is Untitled;
6. Press Enter, input password and wait for the process to finish;
7. Quit Terminal, restart your Mac, hold Command+R when starting Mac until you see the apple logo;
8. Login into your Mac with password, go to the menu bar>Utilities>Startup Security Utility, enter password again;
9. Choose Medium Security under Secure Boot and allow booting from external media;
10. Restart your Mac, in the same time, hold the Option key;
11. Choose Install macOS Big Sur, click Next and input password, choose Install macOS, continue to finish mac reinstallation from usb.

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What if You Lost Data After macOS Big Sur Reinstallation?

Reinstall Macos Catalina From Internet

However, losing data after reinstallation still happens. It may result from a interrupted installation (power-off/poor internet connection), corrupt setup, insufficient space or improper actions. Then, what to do if you lost data after reinstallation? Here are 2 methods.

Method 1: Use Cisdem Data Recovery to Recover Data

In the case you didn’t do backup before reinstallation, you will need a dedication data recovery program to find the lost data for you.

Here we recommend Cisdem Data Recovery, a powerful mac program allowing users to recover lost/deleted/corrupted/formatted files from a wide range of external or internal storage devices, no matter the file is lost due to human errors, power-off, reinstallation, upgrade, virus attack or disk crash.

Main Features of Cisdem Data Recovery

• Recover files lost due to OS reinstallation, upgrade, downgrade;
• Recover deleted, formatted and lost files;
• Restore files from internal and external hard drive, USB, SD Card, flash drive, etc.;
• Restore videos, audios, images, documents, archives, 200+ types;
• 5 recovery modes: Basic, External Drive, Formatted Drive, Trash, Advanced;
• Preview files before recovery;
• Fast scanning and recovery;

Steps to Recover Lost Data after MacOS Reinstallation

Installing Macos Catalina From Usb

1. Download and install Cisdem Data Recovery on Mac.
   Free Download
2. Choose a Recovery Mode according to your need.
   If you want an efficient recovery, choose “Basic Data Recovery”, if you want to recover files with a higher success rate, try “Advanced Data Recovery”.
3. Select the hard drive where you originally stored the files on mac. Then click “Scan”.
4. Check and preview files found by Cisdem Data Recovery.
5. Select files to recover.
   Check the box before files that you want to recover, then click “Recover” to find back the lost data caused by reinstallation.

Method 2: Use Time Machine to Recover Data with Backup

If you have backed up your files on mac, you can use Time Machine to restore the lost data.

• Step1. Go to Finder>Applications>Time Machine, launch it and choose “Enter Time Machine”.
• Step2. In the popped-up window, use the arrows and timeline to browse the local snapshots and backups.
• Step3. Find the deleted files, then click “Restore” to recover the lost data caused by reinstallation.

Conclusion

The key to reinstall mac OS Big Sur, Catalina or Mojave without losing data is the backup, since no one can guarantee all data will be perfectly maintained after macOS reinstallation. However, if we unfortunately lost files after macOS reinstallation, Time Machine or Cisdem Data Recovery is helpful to recover them back.

So, do you have any other tips to reinstall macOS without losing data? Please share with more of our mac users.

This page illustrates the detailed process of recovering data from a failed Mac computer before you reinstalling the macOS. If you are having the same issue, follow through this page to see how to get data out of the failed Mac computer before macOS reinstallation:

Workable Solutions	Step-by-step Troubleshooting
Phrase 1. Create Bootable USB	Run EaseUS Mac data recovery software on another Mac computer > Create bootable USB...Full steps
Phrase 2. Recover Mac Data	Connect bootable USB to failed Mac > Boot computer from USB > recover data...Full steps

macOS Reinstallation Deletes Everything, What Can I Do

'My macOS Catalina got corrupted, and the login screen doesn't appear. If I reinstall macOS from the recovery menu will my previously installed software and data be deleted? And if so how can I back them up on a hard drive, the data and the software are very important to me.'

Reinstalling macOS of macOS Recovery can help you replace the current problematic OS with a clean version quickly and easily. Technically speaking, simply reinstalling macOS won't erase your disk either delete files. You probably don't need to erase, unless you're selling or giving away your Mac or having an issue that requires you to wipe. Besides, If you suspect there's something wrong with your startup drive, you can use the Disk Utility to scan and repair them from the recovery screen, which might be a quicker and more convenient alternative than erasing and reinstalling your macOS.

How To Reinstall Macos Catalina From Usb

How to Recover Data When Mac Needs to Be Erased and Reinstall macOS

If you're encountering the same issue as said at the beginning of the article, that your computer gets corrupted, and you have to consider a complete restart in Recovery Mode. At this time, you need to use the Disk Utility in macOS Recovery to erase your Mac hard drive first, and go on to reinstall the macOS.

As well all know, erasing the hard disk on Mac will inevitably cause data loss and make the files unrecoverable. How to recover data in the easiest way when Mac failed to start? Don't worry, here comes the EaseUS Mac data recovery software, which enables you to create a bootable USB drive on another Mac that works well, then, restart your Mac from it, and go ahead to recover files. Especially to restore data on system drive under macOS 10.13, it's very safe to recover from bootable media. Useful for any emergency, no secondary data damage!

Now, follow the step-by-step guides below to see how to recover data from Mac that fail to start and need to erase and reinstall OS. The whole tutorials will be divided into two parts: how to create a USB bootable media and how to recover data from bootable media.

How to Create a USB Bootable Media

Step 1. Install and run EaseUS Data Recovery Wizard for Mac on another Mac computer, select 'File' > 'Create Bootable USB'. Then, choose a USB drive to create the bootable disc.

Step 2. The program starts to create a 2GB space and save the boot files. The rest space on the USB can be still used for storage.

Step 3. Once it completes, please follow the guide to boot the corrupted Mac from the bootable disc and start the recovery. We suggest you restore the data to an external hard drive.

How to Recover Data from Mac Hard Disk

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.

After the data recovery, you can use the 'Disk Utility' to erase your Mac disk, and then choose 'Reinstall macOS' to finish the reinstalling.

See More about EaseUS Data Recovery Wizard for Mac

EaseUS Mac data recovery program allows you to recover deleted files from the emptied trash bin, internal/external hard drive, SSD, corrupted or formatted memory card, including memory sticks, SD cards, CF cards, XD & MMC cards. Besides, it also enables you to recover lost Word, Excel, PPT, etc.