How to Fix macOS Catalina Installation Issues

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. You should also take basic steps to ensure you can recover from any install issues you may come across.

The most important of these is to back up your Mac before you start the installation process so that you can recover from any installation issues that may arise. 

If you’ve run into an issue and you didn’t first perform a backup, then with any luck, one of our tips will get you back on track. If it does get your Mac going again, remember to back up your Mac before you go any further.

If you need a storage solution to handle your backups, Other World Computing has a large selection of storage options you can choose from.

With backups out of the way, let’s take a look at some of the common and not-so-common macOS Catalina installation issues you may run into:

macOS Catalina Won’t Install

This is the most basic of Catalina installation errors; it simply won’t install. It may be that the installation won’t start, it seems to freeze during the installation, or it never seems to complete.

The two primary causes are; attempting to install on a Mac that Catalina doesn’t support, or trying to install Catalina on a Mac with limited storage space. 

Supported Macs: Most Macs from 2012 or later support macOS Catalina. The lone exception is the 2010-2012 Mac Pro, whose graphics cards don’t meet Catalina requirements. You can find a full list of supported Macs in the Rocket Yard guide:

Storage Space: You’ll need about 6.5 GB of space just to download the macOS Catalina installer. After that, the amount of space needed is dependent on the type of installation you’re performing: a clean install or an upgrade install.

Get Info pane showing amount of disk space used and available.
You can see how much free space is available on the target drive by highlighting the drive and pressing Command-I

A clean install uses up around 20 GB of storage space. In addition, you need to allow for space for your user data, applications, and future updates. As if that weren’t enough, you should keep at least 10 to15 percent of the startup drive free to ensure adequate performance. I normally suggest a good deal more free space than that, but here we’re just talking about a minimum to ensure you can install and use macOS Catalina.

If you’re performing an upgrade install, you need to make sure the startup drive has enough free space for the installer download (6.5 GB), as well as room for the files the installer will copy to the startup drive during installation. It’s difficult to estimate the size of the free space you’ll need since it’s dependent on the version of the Mac OS you’re running before the upgrade. But if you have 25 GB of free space available, you should be able to successfully perform an install of Catalina.

If you’re tight on free space, consider removing unneeded files using one of these methods:

For some of us, even after we clean out unneeded files we’re still short on free space and need to consider upgrading our Mac’s internal drive or adding an external storage system. OWC has you covered if you need to go this route:

Unable to Write Information to Disk

This message (or a variant) will sometimes show up just after you start the installation process, and is most often caused by a corrupt installer file. The simple solution is to delete the macOS Catalina installer and download a new copy.

Disk Utility's First Aid feature used to check the health of a Mac's drive.
Disk Utility’s First Aid should be run to ensure the startup drive and the target drive do not have any issues that could impact installing macOS Catalina.

A new installer will usually take care of the issue, but there’s another problem that could lead to the same message: a damaged target drive for the installation. If you haven’t already done so, you may want to run Disk Utility’s First Aid tool to check and repair the target drive. You should also run First Aid on the startup drive if it isn’t the target for the installation. You can find instructions on using First Aid in:

Could Not Create a Preboot Volume for APFS

The “could not create preboot volume” along with other APFS (Apple File System) errors associated with converting an HFS+ drive to APFS are rarely encountered, an indication of the maturing of the APFS file system.

macOS Catalina requires the use of APFS instead of HFS+. If you’re upgrading from an earlier version of the Mac OS and you were using HFS+, the installer will convert your target drive from HFS+ to APFS. This, in itself, is not an issue. However, in rare occurrences, you may see an error message.

If you encounter this issue, the cure is easy enough: you just need to erase the target drive using Disk Utility. If the target drive was your startup drive, you’ll need to boot into Recovery mode to access Disk Utility. You may also need to restore your Mac’s data using a recent backup before restarting the installation process.

macOS Could Not Be Installed on Your Computer

This may seem like the same issue we started this article with: having a Mac that is supported by Catalina. The difference is that you already verified that your Mac is compatible (see the link to supported Macs above), but you still see the error message.

Date & Time preference pane.
If the Catalina installer is refusing to run, use the Date & Time preference pane to check that the date and time are set correctly.

If that’s the case, open up the Date & Time preference pane and check its settings. Make sure you have both the correct time and the current date properly configured. The best way to ensure that this isn’t a Date & Time issue is to use the option to “Set date and time automatically.” You’ll find this option in the Date & Time tab of the Date & Time preference pane.

Installation Freezes or Failure to Complete

These are actually two issues; the first is the installer freezing during the first phase of the installation process, and the second is when the failure to complete happens after your Mac has rebooted and attempts to load Catalina for the very first time.

In both cases, the first thing to try is to restart your Mac. This fixes the issue for most users experiencing this problem.

Unfortunately, it’s possible that if the installer hangs up at the worst possible spot, your Mac may not be able to restart because of startup drive issues. If this happens to you, you’ll need to use the Mac’s Recovery utility to repair the startup drive using Disk Utility, and/or reinstall the Mac OS or use your backups to recover from.

You can find instructions for using the Recovery utility in the Rocket Yard guide:

Activation Lock Prevents Access to Your Mac

One of the features of newer Macs is the incorporation of T2 Security Chips, which provide a number of useful features, one of which is the ability to erase and deactivate your Mac if it is stolen.

Find My app shown on iOS device.
The Find My app (here shown on an iOS device) can be used to fix an unexpected activation lock on your Mac.

During beta testing, a few people reported that Catalina was failing to complete the installation because it believed the Mac had the activation lock set as if it had been reported stolen. Although I expect this issue to be resolved before macOS Catalina is fully released, if you do come across the issue, here’s how to fix it.

You can correct this issue by using another Mac or iOS device and launching the Find My Mac app, or opening a browser and going to the website. Log in to your iCloud account, if needed, then remove the Mac in question from being associated with your Apple ID.

This should allow you to restart the Mac and complete the Catalina installation.

Unable to Install Catalina on an External Drive

This issue can occur because of the T2 Security Chip found in recent vintage Macs. The T2 chip protects your Mac by default from being booted from an external device. This prevents someone from walking up to your Mac with a USB flash drive, booting your Mac, and accessing your files.

The default settings will also prevent you from installing Catalina on an external drive.

You can find out more about the T2 Security Chip and how to use the Startup Security Utility to configure external boot options in the Rocket Yard guide:

Miscellaneous Fixes for Install Problems

If the install issue you’re having isn’t covered in this guide there are always a few general-purpose tips that may help resolve the problem:

Startup Disk: Occasionally, the startup disk isn’t set or is set incorrectly. In the case of not being set, your Mac may take a very long time to start up as it searches for a device to use to start up from. It may also choose the wrong device to boot from, leaving you wondering what’s going on.

Startup Disk preference pane.
Use the Startup Disk preference pane to ensure your Mac is starting from the correct disk.

This behavior can explain one problem I’ve seen reported: a Mac that seems to complete a clean install but when the Mac finally reboots, it’s back to the original version of the OS, with no changes. In actuality, the clean install was performed, the Mac is just booting from the wrong startup device.

The fix is to open the Startup Disk preference pane and set the startup disk correctly for your Mac.

Reset NVRAM and SMC: The NVRAM and SMC hold information used by your Mac during startup. If either becomes corrupt, it can cause unusual effects on your Mac. Although resetting the NVRAM and SMC are considered a lastditch effort to correct a problem, you should still try it because it does work from time to time.

You can find instructions in the guide:

Did You Have Any Catalina Install Issues?

This is our preliminary list of Catalina installation issues you may come across. But as more people perform the upgrade to Catalina, it won’t be surprising to see a few more issues become common.

With that in mind, did you have any issues installing macOS Catalina, and if so, did you discover a fix for the problem?

Leave a comment below and let us all know.

UPDATE 10.15.19:

If all else fails with your Catalina install and you want to downgrade, check out our article, How to Downgrade from macOS Catalina to Mojave or Earlier.


  • Tom,

    Thanks for the tips. I see that some of the old tricks from previous systems, almost all the way back, might still work on Catalina and Mojave which is on my previous laptop. Just a little more difficult to track things through the system and connect them all. I’ve been workin with Mac products all the way back to the first Apple E and GS computers, which were way more fun to customize and personalize. I’ll give it a try and see if I can find all the associated files. I’m trying to move the Apple programs that didn’t show up in this version of the OS like iMovie, Pages, Keynote, etc. I really don’t like it when Apple decides to eliminate programs that some of us have used and then use the time trying to sell us the news and more TV….like we need another corporation’s ideologically slanted news to clutter our computer experience. I want to enjoy my Mac like I did early Apple products. It is what made Apple great back then and why Steve Jobs was successful. He saw what people needed, but also realized that computers could be fun and made sure Apples were….but that is for a different forum and discussion. Again, thanks for the help.


  • After installing my OWC SSD into the old MacBook Pro (mid 2012 9,2), everything was lovely. So I thought I’d be really up to date and install Catalina.

    It came up with the “macOS could not be installed on your computer” with a cryptic comment about not being able to verify file structure.

    The real problem? When it came down to the “which drive do you want to reboot from?” window, there were no drives listed. The installation had voided the new internal SSD, and I had no other drives (backup 2 TB external) connected.

    Fortunately I put my old Macintosh HD into the external case provided with my SSD install kit, and can run it from there. But, of course, I’m running my OS from a USB 3.0 external drive.

    Is the SSD creating the problem here? Is this a trend with older Macs and OWC drives?

  • I recently bought an excellent condition 2015 Mackbook Pro from you. I had some real problems with Catalina and with the Migration assistant. I have a similar Macbook Pro I bought from you a couple of years ago. It has an issue with the screen/monitor flashing on and off, which is the reason I bought the recent purchase. The old one works with it plugged into a stand-alone monitor, but is erratic when watching the lap screen. Anyway, I tried to use the apple migration assistant utility and it froze during the transfer of apps, programs, and files from the source computer. Then I clicked on cancel, (it said I could continue later) and the new computer gave me a blank/black screen. I tried everything to get it up and running again and finally, the next day, I was able to run it when I held down command and R to put it in restore mode. From there I was able to reinstall Catalina in about 3 hours time. My question: Is there a better way to transfer programs, apps, files and such to the new computer without overwriting the entire operating system, and a way where it doesn’t freeze up and crash? I have about 400GB of stuff I need on the new computer so I can send out the old one for repair. 2nd Question: Do you folks do repairs. I think it is a short or another problem with the screen of the laptop. I love both of the laptops and will enjoy having two functional Macbook Pros at my disposal, along with the tower I bought from your company 2 1/2 years ago. I like the old G5/6 towers and the ability to expand them, but not the fact that I can’t update to the newest OS, but I still use it with several older programs that still function admirably. I’m a senior so I don’t want to necessarily go into a newer Mac Pro that can’t run old versions of OS 10 and programs that I use regularly. Please advise me. Thanks in advance. I am a regular customer and have bought a ton of stuff from you including 3 computers, several hard drives and memory updates.

    • Hi Gerald!

      In response to your second question, I would recommend calling OWC customer service at 1.800.275.4576 – they can best assess the issue by speaking with you directly and then provide potential options.

      As far as the first question, I’ll put the word out there to see if anyone has thoughts on the easiest way to transfer everything without Migration Assistant. Perhaps someone here will have thoughts as well!

    • Migration Assistant is usually the best method to transfer your apps, documents and files to a new Mac, but there are a few other ways.

      Documents and files can just be copied from the old Mac to the New one, just make sure you’re placing them in the same location as the originals.

      The harder item to move over are any third-party apps. In general, I’m more inclined to reinstall a third-party app then try to copy it over. This comes from a long history of very mixed success at copying apps to a new Mac.

      If you want to try the copy method, here is one way that it may work:

      Don’t copy any Apple supplied apps, they should already be installed within Catalina. The exception is old Apple apps that are no longer supplied. You can try copying those, but I would not expect them to work under Catalina.

      Third-party apps can be copied over, make sure you place them in the same directory as the original.

      Now for the hard part, to get third-party apps to work, you will also need to copy over any support files they may use. The problem is while there are a few “normal” locations for these support files to be at, there is no requirement that they be there. Additionally, some locations in the older Mac system may be off-limits for you to copy to in the new Catalina system, so you may need to update the apps anyway to get them to run.

      The following locations may contain support files you need for an app:

      /Library – may contain files or folders specific to a third-party app.
      /Library/Application Support – look for folders with the app’s name.
      /Library/Fonts – if the app launches but the fonts don’t look right, you may be able to find unusual fonts in this folder that the app needs. Don’t copy all the fonts over, just look for ones that are not present in Catalina.
      /Library/PreferencePanes – Look for preference panes for specific apps.
      /LibraryPreferences – Look for specific items related to an app.

      You should also check your home folders Library folder for similar third party files.

      Let us know how it goes and don’t forget that many app developers will have support personal or support forums that may have the answers you need for a specific app.


  • I’m running a 2017 iMac 5K, Core-i7, 64GB, 3TB fusion drive, Radeon Pro 580 8 GB.

    I’d been experiencing macOS Mojave hangs for weeks … the system would go non-distpatchable for 10 minutes – hours, then come back with no log entries (and nothing responding except perhaps that the TCP/IP stack would sometimes [but not always] respond to ICMP echo requests: pings). I’d tried everything including erasing my Mac partition and reinstalling and copying stuff back with Migration Assistant, and still the hangs persisted.

    So when Catalina went golden, as soon as I had some time I wanted to see if Catalina would solve my hang problems.

    I had a 200 GB Boot Camp and a 2.8 TB Mac partition, and was trying to preserve my Boot Camp as Win is a pain to set up again (though now that I’m retired my Win stuff is much less important.)

    I backed up the Mac partition five times: two Carbon Copy Cloner clones and two time machines – one on a USB drive and one on a Synology, and one on Backblaze.

    I did my usual erase the Mac partition, and install Catalina to the Mac partition, and it repeatedly said it couldn’t complete the install. I created a bootable Catalina install flash drive and booted from that.

    By this point, I realized that I’d probably need to sacrifice everything on the fusion drive (and had zero trust in my WinClone backups which had failed me in the past), so I resolved to try and nuke and pave my fusion drive setup.

    I somehow managed to delete the Boot Camp and looked in the GUI at repartitioning the fusion drive and found to my surprise that there was a 2.8 TB APFS partition, with something like 2.8 TB free. I found this curious as my fusion drive is built on a 3 TB rotational drive linked to a 128 GB SSD. I somehow managed to delete the Mac partition and was left with a 5.x TB drive.

    By now I realized the fusion drive was thoroughly hosed, and did a ‘diskutil cs list’ and found to my surprise that there was no longer a core storage volume, thought a ‘diskutil list’ showed that there was a synthesized drive.

    I didn’t want to break open my iMac to reformat the 3TB disk, and couldn’t figure out how to break apart and rebuild my fusion drive. I tried repairing my setup to no avail, until I came open the ‘diskutil resetFusion’ command, which I hadn’t recalling seeing before. This command successfully rebuilt the fusion drive, laying down a fresh APFS file system which I was able to replace with an APFS encrypted file system, and install Catalina. I then migrated everything back from one of my CCC clones.

    The hangs have gone away and have not returned.

    At first I though my situation unique, until I searched the Apple Community forms and found someone in a nearly identical situation. I posted how I dealt with the situation, and he was able to get his system working by doing the same thing through internet recovery and installing from there.

    This leads me to believe that there was some kind of software flaw involving a pre-existing Boot Camp created by Boot Camp Assistant and conversion of a HFS+ drive to APFS, possible only on a 3TB fusion drive. If resetFusion hadn’t existed before, it is Apple’s tacit admission that there was something wrong with a workflow involving stock Apple software – though really this is much more straight-forward than the removal of a drive from a core storage logical volume (via deleting a UUID) and rebuild.

    Anyway, I thought I’d put this out there for anyone else in the same boat, though I’ve yet to rebuild my Boot Camp as I’m enjoying not having those hangs, and may wait until the new Win 10 is stable and I begin to hunger once again for gaming – so many Mac games vanished in the 32 bit extinction.

    Verne Arase
    Former Sr. System Engineer (IBM Mainframes)
    then Sysadmin (Linux, Mac, Windows, Solaris, and some AIX and HPUX, NetBackup, ISC DHCP, BIND DNS, System log aggregator)
    then Sr. Deskstop and Network support (same responsibilities, deprecated title)

  • I tried installing the Catalina update but didn’t have enough space. It asked to quit the installer and select start up disk but none appear in the list. I’m now stuck!

  • Safari will not boot up. reinstalled Catalina twice and still no Safari.

  • My problem has been trying to download Catalina. I have a 75 mbps line. It starts downloading at full speed (6-8 MBps) but after the first gigabyte of the 8.09 GB size, it starts slow down to 100 kbps or less, eventually timing out after 12 hours or more.

  • After installing Catalina on my Mac, all my files that were on my hard drive have ended up on my desktop in a “Security” folder within a folder titled “Relocated Items.” There is a message that says I can save these files if I put them some place other than where they were located originally. Where am I supposed to store them, if not on my hard drive? Anyone know? Any help would be appreciated. I can’t be the only one with this problem.

    • The items in the Relocated Items folder are files that were originally stored within the Mac’s system folders that probably don’t belong there. Especially since the new Catalina system makes use of a read-only system volume.

      You can place the Relocated Items you wish to keep anywhere in the user space, this can be done by placing them anywhere under your user name.



    Yep, I’m yelling :).

    TL;DR: Create a USB Thumb drive installer

    I’ve dealt with the failed attempts at installing Catalina on a Mac Pro 6,1 and my rMBP. In both cases, it was the same issue – Select the drive, click Install, get the spinning beach ball of death.

    I’d heard rumors that the creation of a USB Flash installer fob had been removed from Catalina. This was frustrating – until I tried to create one. Lo and behold! The creation script IS there and it DOES work. So, a 16GB USB-3 thumb drive and 12 minutes of my time later, I had a functioning Catalina USB installer.

    I inserted the flash drive on my Mac Pro, rebooted with Opt held down and there was my Install macOS Catalina volume. using that allowed everything to install as normal and I’m not running an updated Catalina system. The same for my rMBP!

    • That last paragraph was a mess … let’s try again

      I inserted the flash drive on my Mac Pro, rebooted with Opt held down and there was my Install macOS Catalina volume. Using that allowed everything to install as normal and I’m now running an updated Catalina system. The same for my rMBP!

  • I have a Macbook pro retina 2013 Early edition and when I chose the update of Catalina it hangs up on the download so then after a while I come back to the computer and see the preferences window is gone and I have to start the process over. Well with FIBER OPTIC AT&T 1 Gbps internet speed it downloads fast but only up to a certain point then it will stay on that until the preference window disappears again. For example I left the update going while I slept and it’s done the same thing I came in my office and the update was not on the screen so I opened it up and started the process over and it takes me back to where it left off each time but faster , so its stuck on 7.28 GB left to download. This has happened about 5-8 times already. I am thinking of waiting until they get this ironed out. I have my newer laptop going in for BATTERY FAILURE which apple tells me my MBPr was not one of the ones in the RECALL but it sure did fail. And this laptop as alll my MACS are treated as if they are my KIDS. I treat them better than I treat humans. But that’s APPLE for you. I won’t be buying any more laptops from APPLE due to them NOT ALLOWING Customer to UPRADE RAM or Your BATTERY which is very frustrating. I cannot believe apple went this far as to stop us from UPGRADING A BATTERY. THEY ARE GOING to find that LAPTOP sells will be going down. People are going to go for the Mac Pro the latest version that is out NOV or FALL 2019. Thats the last MacBook Pro I will ever buy. Whats next SSD won’t be able to upgrade your self??? I am a MAC GEEK and MAC lover my motto is This “ONCE YOU GO MAC YOU WON’T GO BACK”. True for me since 2007 I have had every MacBook Pro & Mac Book Pro Retina they have made. I upgrade every 3 years to keep my APPLE CARE going. MY POINT I am done with their LAPTOPS. They are making it way to HARD on a CONSUMER who is going to now PAY $4000-$5000 for a NEW MPBr Maxed out by apple to get the most RAM and then I am the owner of the Mac yet apple says YOU CANNOT UPGRADE anymore. Seriously APPLE. BAD MOVE on apples part. I see their LAPTOP SALES DECLINING more people are going to go for the Mac Pro & use iPad iPhone & watch.

    • Hi Daniel,

      The increasing difficulty of user upgrades is frustrating to us all. And though it takes a little bit of skill, it is possible to upgrade the battery yourself on an early 2013 MBP. If you select your model here, it will show you the correct replacement battery. Selecting your model on the Install Videos Page will lead you to an step-by-step instructional video for changing the battery yourself. Perhaps this can be a cost-effective option for you.

      Good luck!

  • I have a question about Hibernatemode 25 and Catalina. The way I see it, it doesn’t work properly under Catalina anymore. Up to and with Mojave you could close the MacBook Pro (mid 2012 no retina) and then the notebook was in deep sleep (Hibernate mode 25) and did nothing until I opened it again. Now under Catalina the notebook apparently only goes into retirement and no longer into deep sleep. But the hibernation mode 25 itself is activated.
    Does anyone know anything about this?
    Many thanks and many greetings