1. Reinstall App Store Mac Catalina Version
2. Reinstall App Store Mac Catalina Download
3. Reinstall App Store Mac Catalina Update

Install macOS Catalina.app does not appear to be a valid OS installer application. This also happens with some older macOS versions, where you get a small.app from the App Store, and that app does the actual download. Whatever the issue was, we need to download the install files with the installer. MacOS Catalina will start to install. When it’s finished, your Mac will restart and it will look like a brand new Mac. Go through the set-up process to set up a user account, add your wifi network, choose a language, and log in to iCloud. Once you’ve set up your Mac, you can eject the installer disk and remove it.

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

Unable to install apps on macOS Catalina; Mac App store blank screen and other issues on macOS Catalina. If you see a bank app store screen or your app store app simply freezes or experiences interim crashing on macOS Catalina, check the following tips out. Additionally, macOS Catalina drives the final nail in the coffin for 32-bit apps. They won’t run at all on Catalina. If you perform a clean install, you won’t have to worry about legacy software hanging around on your Mac. You can simply start fresh. In a nutshell, it comes down to the following argument. 1.Command + R and format App Disk 2.Shift+Option+Command+R. Posted 1 year ago. Copy RayKai answer. Share this post. Copied to Clipboard. Up vote reply of RayKai Down vote reply of RayKai. Try to reset your fusion drive that should Solve your trouble with downgrading to mac mojave.

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

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.

Mac Won't Turn on after Update to macOS Big Sur?

Here are 10 solutions to fix 'Mac won't turn on after update to macOS Big Sur, Catalina or other versions'.

What if You Lost Data After macOS Big Sur Reinstallation?

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

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.

Recently, I reinstalled macOS on my device. Throughout the process, manyattempts failed miserably. But I now have some experience and assorted hints onwhat to try.

DISCLAIMER: All information in this post is provided as-is, and some of it mayvoid your warranty. Neither Chris Warrick nor Apple will be responsible for anydamage to your devices caused as a result of using information in this post.

Contents

The best, safest, least error-prone way to do an install is with a USB stick.Unfortunately, making a USB stick with the macOS installer on it is a nuisance.The expected way to produce macOS install media is to download the installerfrom App Store/Software Update, and run the createinstallmedia command-lineprogram included with that installer app. All is well, as long as macOS works.If it doesn’t, and Recovery can’t install it for you, that can be difficult tosolve.

Apple does not make macOS images publicly available. That’s probably to makeHackintoshing this little bit harder, but this also affects legitimate users.The only thing you can download from Apple is El Capitan. Apple offersInstallMacOSX.dmg on theirwebsite. If you take a look at the instructions, you will see that this isnot a bootable OS X image. This image has a .pkg package. This package isexpected to install /Applications/Install OS X El Capitan.app. Well, we’rein recovery, we can’t install stuff. So, let’s do this the manual way.

Turns out the .pkg format is just an archives all the way down, with allarchives being different formats (at least three).

The first archive is the .pkg file itself. Those files are in XAR format, which was invented by theOpenDarwin community. You can either extract it with pkgutil --expandfoo.pkg foo_files (the last argument is the destination directory, can beanything, will be created by pkgutil) if you have access to that command (it’savailable in Recovery OS), or you can try the xar utility as xar -xffoo.pkg. The structure produced by both tools is a bit different, but we canwork with both.

The second archive-in-archive is the Payload. It’s a gzipped cpio archivethat contains the files installed by this package. If you have BSD tar(default on macOS, easily installable on Linux), you can just do tar -xvf Payload.Otherwise, you can use gunzip -c Payload | cpio -i (or gzcat). Thatwill extract all the files the package has.

Another nested archive is the Scripts archive, although note thatpkgutil will extract it automatically. If it’s not extracted, it’s actually.cpio.gz again, with the same way to extract it.

(PS. If you have 7z around (on Windows/Linux as well), you can just pointit at all the compressed files mentioned in this paragraph.)

Let’s expand the El Capitan package.

We’ve got the installer app, which is what we need to create an install image.Great, let’s try it!

Oh, we’ve got a problem. Turns out there’s one more thing we need to take careof, and it’s the scripts. MacOS packages have scripts, typically shell scripts,that are run at various stages in the install process. We can look at thePackageInfo file, or just look in the Scripts folder, to see thatthere’s an link_package script we need to run. This script creates aContents/SharedSupport directory inside the installer app, andcopies/hardlinks the InstallESD.dmg file (which is the install formerly-DVDimage) to that directory. Let’s try doing this on our own:

And it works! createinstallmedia will now produce valid install media.

If you are in Recovery, you can find an Install app on the filesystem. If youtry to run it, you will get the same error as in the previous paragraph:

This also happens with some older macOS versions, where you get a small.app from the App Store, and that app does the actual download.

Whatever the issue was, we need to download the install files with theinstaller. Open the installer and let it run until the download finishes. Ifthe app asks you to reboot, quit it at this point. If it never asks, you canstill find a way to get files out (after a failed install, they should not beremoved).

The install files can be found in /macOS Install Data on the destinationvolume. For older versions, you will just have InstallESD.dmg, newerversions add more and more files, some of which are hardware-specific (andCatalina has InstallESDDmg.pkg, because Apple loves nesting archives for noreason!). However many files you find, you can just:

1. Copy Install macOS Catalina.app to a read-write volume.

2. Copy the contents of /Volumes/TARGET/macOS Install Data to InstallmacOS Catalina.app/Content/SharedSupport. Make sure you account for hiddenfiles, if any (copy the entire directory). If you did this correctly,InstallESDDmg.pkg (or InstallESD.dmg on older verisons) is in the SharedSupportdirectory (not in a subdirectory).

3. Run createinstallmedia. It should now consider the installer valid. Theavailable options differ slightly depending on the OS version.

If you get this error, it might be because Apple’s signing keys expired, orbecause of other date/time weirdness. Regardless, you can force an install ifyou are sure the installer is not damaged with this command (source):

While messing with all the installer stuff, I found out a fewinteresting/worrying things about the download process.

The first one is that the macOS installer uses plain HTTP without encryption todownload files. That opens you to all the standard issues — an attacker canreplace files you download, and the protocol doesn’t do anything to detecterrors (the installer will verify files, but where do the checksums comefrom?).

The second one is how the download happens. You might have noticed it to be abit slower than usual traffic. The download happens in 10 MB chunks, using theRange HTTP header. The installer asks for 10 MB, gets it, saves, asks foranother chunk. Repeat that over 800 times, and the overhead of the entire HTTPdance becomes noticeable. (I haven’t checked, but I hope the installer at leastuses Keep-Alive. I wouldn’t be particularly surprised if it didn’t, though.)

But this raises another question. The servers clearly support partial downloads.And yet, if your network disconnects during the download, your downloadprogress for that file is reset, and in Catalina, you can go from 8 GB back to500 MB if you’re particularly unlucky. The question is, why? Thisinfrastructure should make it trivial to continue the download, perhapsdiscarding the most recent chunk if you’re concerned about that download of itbeing unsuccessful.

The first time you boot a Mac after a clean install, it starts the SetupAssistant. This app asks for basic OS settings (locale, date/time, useraccounts), and also lets you restore user data from backups.

Sometimes, you might want to access the Terminal or Console from that screen.You can do that with Ctrl + Opt + Cmd + T and Ctrl + Opt + Cmd + C respectively (source).

How could that come in handy? For example, if you want to check if the backupdrive still worked and if the process isn’t stuck (I wrote a test file and alsochecked top).

A few months later, in December, I upgraded to Big Sur and then installed Windows 10alongside it in Boot Camp. I then did some more hacks, which led totwo unbootable OSes.

As part of the upgrade, I had prepared install media and used it to install (soit wouldn’t fail, as it did last time), and made a .dmg of it with DiskUtility. (Also, Apple won’t tell you this, but you need to give Disk UtilityFull Disk Access for disk imaging to work. Otherwise, you get a crypticerror.) I erased the USB drive after installing, but hey, I could get it back.I booted into Internet Recovery and restored my image. Big Sur failed to bootand showed a 🚫 sign. I triedrestoring my Catalina image from the previous reinstall, and that didn’t workdue to a size mismatch. I used a different USB drive than these months ago (Ididn’t have that one with me at the moment), and apparently the one I used hada different size (both are marketed as 16 GB). The images could be mountedfine, and createinstallmedia should have worked, likely producing abootable drive.

Time Machine is Apple’s magical backup solution. Time Machine saves snapshotsof your entire disk. It’s supposed to help restore files that were deleted orchanged in an unwanted way, or help you restore a full macOS install.

Time Machine is great at file recovery, but none of my 3 system restoreattempts were successful. Attempt #1 was a full Time Machine System Restore,from Recovery, back in June. It failed partway through, it couldn’t readeverything from the disk. There might have been underlying hardware issues withthat failure, so I had another attempt.

Attempt #2 was a Migration Assistant restore, as part of the initial setup.This one succeeded, and things worked… except for one fairly important app.This app requires online activation with the vendor, and it wouldn’t reactivateafter the install. Whatever the third-party vendor is doing didn’t like thereinstall. I tried to nuke all the things in ~/Library related to theirsoftware, and ran their nuke-everything uninstaller, but that didn’t work.I reinstalled from scratch and copied over my files, settings and apps from theTime Machine drive.

Attempt #3 involved the System Restore again, this time for the Decemberreinstall. The hardware issues were all fixed in the meantime, so I went for aTime Machine System Restore.

Issue #1: Internet Recovery booted into Catalina. There was an issue on Apple’sside, Big Sur was unavailable in Internet Recovery in December. TMRecovery will not restore a backup created with a newer version of macOS thanyou’re booted into, so I was forced to restore a slightly older Catalinabackup. (I spent most of my time in Windows during that weekend, so other thanthe need to upgrade macOS to Big Sur again, I didn’t really lose any data dueto this.)

Issue #2: It wasted time computing an inaccurate size estimate. Beforerestoring a backup, macOS first checks if it will fit on your drive. When itdoes that, an indeterminate progress bar is shown. macOS won’t tell you theresult of that computation, but you can read the final value from the fullInstaller Log (Cmd + L). On my Mac, the value was 96.2 GB. I was at the Macwhen it was getting close to that value. 94, 95, 96, 96.1, 96.2, 96.3… hold ona second, 96.3 GB? Hopefully that’s just a bunch of extra things that areinstalled from the system image directly, or something like that, right? Ofcourse, since the progress bar is based on the pre-computed size, it becameindeterminate and I couldn’t tell when it would end. 98, 100, 110, 120, 121.2GB is where it ultimately ended. So, not only did it waste 20+ minutescomputing a size, it was off by 25 GB.

Issue #3: The restore didn’t work. The System Restore finished and claimed tohave succeeded, but macOS wouldn’t boot. It showed an Unrecoverable error,SecurityAgent was unable to create requested mechanism. Most people who had asimilar error had it caused by a botched TeamViewer uninstall; I didn’t havethat installed, and it was referring to a different component. So, wipe andfresh reinstall it is.

Reinstall App Store Mac Catalina Version

I copied my stuff from the TM drive, and it was acting weird. Some apps failedto load their settings copied into Library, others started with a “Move to/Applications?” prompt (even though they were in that directory). For somereason, those files had some hidden attribute set on it. I worked around it byputting files in a .zip archive with Keka, and then unzipping them;xattr might also help. (The attribute was likely com.apple.quarantine.)

After I got the Mac to work, I reinstalled Windows and set up rEFInd, and itnow works fine. (I only use rEFInd because I want virtualization in Windows,and that doesn’t work unless you’re warm-rebooting from macOS. I don’t needanything more advanced than the Option key boot menu, but Apple made me use athird-party bootloader.)

We now go back to the original post from June.

Dear Progress Bar Designers: can you please make your progress barsfunctional? The macOS progress bar might look sleek at just 7 px (non-Retina)/6pt = 12 px (Retina) high, but at the same time, you’re looking at individualpixels if you need to know if it works or if it’s stuck. I have had to point mymouse cursor at the end of the filled-in part just to know if it’s working ornot. Or sometimes, put a piece of paper in front of my screen, because there isno mouse cursor when macOS installs on the black screen. How to makethat progress bar easier to use and more informative? Just add numbers on top ofit. For long-running processes, I wouldn’t mind progress bars that said“12.34%”. That specific Setup/Migration Assistant window should be changed (itonly has a remaining time estimate and transfer speed, it should also showmoved data/total size), but wouldn’t more things benefit from a clearindication of the progress? Yes, perhaps it looks less sleek, perhaps itrequires more space for the bar.

Just compare: which is easier to parse? Which is more informative?

I’d honestly be happy enough with option 2, at least it can be read easily andyou can remember the number instead of a vague position.

Reinstall App Store Mac Catalina Download

Reinstall App Store Mac Catalina Update

After all this, I managed to get macOS Catalina installed. After variousfailures in built-in El Capitan recovery and Catalina Internet Recovery, I firstinstalled El Capitan with this hack, then jumped to Mojave because I thoughtthe new Software Update would help (it didn’t, same installer, samefailed-to-extract-package issue), then made a Catalina USB stick, and itfinally clean-installed, but I was worried about the backup disk’s operation,and I used a proxy on my local network to try and speed up Catalina downloadswithout much improvement… but hey, at least it works. Apple should really makeit easier to install their OS and to make boot media even when stuff doesn’twork, even from Windows. The Hackintosh folks can just find someone with aworking Mac and ask them to download from App Store and make install media, orfind less legitimate sources, they probably don’t care as much. But if my ownsystem crashes, I’d probably want to get working install media immediately,myself, and from Apple. Without all this mess.