Wish I had read the comments first...The method described here will not work on a 2018 MBA without upgrading to Catalina from Mojave first. Now I have to download and re-install Mojave, upgrade to Catalina, and then I can maybe do a fresh install. Thanks for nothing MacRumors. This "guide" is trash.
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How to Perform a Clean Installation of macOS 10.15 Catalina
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Is this correct? I was about to update my MacBook Pro to Catalina from Mojave 10.14.6, but this sems like I shouldn't try?
The internet recovery method has a lot of issues when restoring to Mojave after a failed update. The internet recovery is generally the last resort for someone.
Given that the topic of the thread is about a clean install of Catalina, internet recovery is totally straightforward and is by far the easiest option for Macs that have the T2 chip.
I didn't find an exact guide to install catalina from usb drive to macbook pro with T2 chip. I disabled the secure boot but not sure if it will work.
It should work but you'll still need to have the computer connected to the internet while doing the installation.
Exactly this. NO MATTER WHAT YOU TRY: You cannot upgrade any earlier MacOS version from outside of a running OS, it will annoy and nag you over and over again with the message that the old OS version needs to be reinstalled, W T F Apple this is NUTS! So now we can't even install the OS version of our choice anymore off of USB drives, thanks to this ingenious T2 chip. Seriously. If they continue this path, this was the last Mac for me, I am so fed up. All this after my MBP18 came back from a repair where it did not do a thing anymore. Reason: Screwed up T2 firmware. W T F.
And yes, the T2 limitation MUST absolutely show up in the original guide!
Thanks for this! Attempting this now on my early 2015 MBP; coming from High Sierra; Mojave was not good for me! Photos Slideshow Themes would not load pics properly, blurry, pixelated, just terrible! (more about this issue here) Hoping this issue has been fixed with Catalina!
This article guides you through the process of performing a clean installation of macOS 10.15 Catalina using the bootable USB drive method, rather than upgrading your Mac using Apple's standard installation package, which retains existing user data and any user-installed apps.
Creating a bootable USB drive provides you with a convenient way to install a fresh copy of macOS Catalina on multiple Macs. Performing a clean install can also remove annoying quirks and strange behaviors that your Mac may have inherited over time, and often helps to reclaim disk space caused by junk files left by third-party apps.
To follow the steps in this article, you'll need an empty 16GB or larger USB thumb drive (USB-C or USB-A, depending on your Mac) and an hour or two of downtime while the installation procedure completes.
Also, be sure to perform a full backup of your Mac beforehand using Time Machine, so that you can restore your original system from the Recovery partition if something goes wrong.
Click here to read more...
Article Link: How to Perform a Clean Installation of macOS 10.15 Catalina
Could you help me pleaaaaase?
I have erased my main partition and did format again all in repair window.
At the next step I click the install button. And now while it connects to internet, gives an error message and nothing will happen next.
I prepared a external hard drive to boot and install macOS Catalina from it, but the notebook couldn't recognize the drive.
Now I have a macbook pro without an OS in which i cannot install any OS anymore.
I have erased my main partition and did format again all in repair window.
At the next step I click the install button. And now while it connects to internet, gives an error message and nothing will happen next.
I prepared a external hard drive to boot and install macOS Catalina from it, but the notebook couldn't recognize the drive.
Now I have a macbook pro without an OS in which i cannot install any OS anymore.
Your install hasn't started yet because the installer doesn't see an installation destination disk. You may need to unlock the disk in Disk Utility, or if it's a new disk, you need to format it first.
How do I do this? I'm installing from an USB following the instructions of this post. The USB was formatted as Mac OS Jornaled and it has Catalina. I hit back and now I see this screen:
Yes, it would have to be unlocked, which you do by clicking on Disk Utility in that menu. If you're just upgrading the existing operating system, the process is a lot simpler by just running the Catalina installer from the disk rather than from the USB drive, and the net result is exactly the same.
Nothing happens when I click unlock. I'm reading I have to manually erase one of the HDs under my main HD ??? This is insane. 🤯 https://apple.stackexchange.com/questions/380139/the-disk-macintosh-hd-cant-be-unlocked
Yes. I can't erase my HD via Disk Utility in normal login. The minus sign is in off even if my admin user is unlocked. The drive is now unencrypted.
Make sure that Disk Utility is set to "Show all devices" in the View menu. Click on the disk itself– it'll be called something like Apple SSD AP1024 or similar. Choose erase.
OMG what an ordeal. Yesterday morning I downloaded via the Apple Store the latest Catalina version (10.15.7 I think, published September 2020). The intention was to get rid of Big Sur, perform a clean install (my data was backed up) via an USB drive. I followed all the instructions and ended up with no operating system. Maybe somebody will read this and avoid all the things that failed. This is the bunch of stuff I learned yesterday and you shouldn't know or go through as the user of the most expensive OS in the world: all versions of previous MacOS operating systems have a security certificates that expire at a certain point. If you try and install via USB Catalina and previous OS, you will probably receive an error message during installation, something like this:
(Image not mine, just to show the error message)
Saint Internet says this is solved by changing the date via Terminal to a date before the certificate expires. I tried 20 combinations of dates, while shutting off wifi so the computer wouldn't detect the actual date. This took me like 6 hours. But before that I had a bizarre issue while wiping the main HD. My Mac wouldn't allow me to hit the - sign, erase or partition. I have no idea how I managed many times until I deleted the drive, then obviously got the folder image that warns you there's no system. I didn't panic as I thought that was required for the clean installation of Catalina, which never happened because of the certificate thing.
Exhausted I tried to download whatever system available via internet recovery, only to keep getting disconnected over and over and finding out via another frustrated user that you have to change your modem's DNS to Google's so that Apple recognizes a valid DNS and downloads the OS. And also you have to delete your computer from iCloud's find my phone. ??? This last thing WASN'T necessary.
To make things worse, my IP company got bought recently by a bigger one. I had no info on how to access the modem's portal. So I had to call my main ISP, which informed I had to call the bigger company. The person from the bigger company had no clue and sent me back to the ISP. Some tech guy remotely changed the servers and right now BIG SUR (LOOOOL) is being downloaded via ethernet.
I'm angry, frustrated and exhausted that something so simple got so wrong. Apple says the certificates are for security. I call it ********. It's not like I downloaded my OS from some shady trrnt site. If you're downloading from their store, that's the only security you need, because clearly this expiry date makes the previous OS garbage. I hate the company forces users to upgrade everything and we have no saying on what we want to use with the mega expensive machines that BELONG to us as buyers.
So in conclusion I'm back with this awful Linux-like operating system that is Big Sur. 🤢
(Image not mine, just to show the error message)
Saint Internet says this is solved by changing the date via Terminal to a date before the certificate expires. I tried 20 combinations of dates, while shutting off wifi so the computer wouldn't detect the actual date. This took me like 6 hours. But before that I had a bizarre issue while wiping the main HD. My Mac wouldn't allow me to hit the - sign, erase or partition. I have no idea how I managed many times until I deleted the drive, then obviously got the folder image that warns you there's no system. I didn't panic as I thought that was required for the clean installation of Catalina, which never happened because of the certificate thing.
Exhausted I tried to download whatever system available via internet recovery, only to keep getting disconnected over and over and finding out via another frustrated user that you have to change your modem's DNS to Google's so that Apple recognizes a valid DNS and downloads the OS. And also you have to delete your computer from iCloud's find my phone. ??? This last thing WASN'T necessary.
To make things worse, my IP company got bought recently by a bigger one. I had no info on how to access the modem's portal. So I had to call my main ISP, which informed I had to call the bigger company. The person from the bigger company had no clue and sent me back to the ISP. Some tech guy remotely changed the servers and right now BIG SUR (LOOOOL) is being downloaded via ethernet.
I'm angry, frustrated and exhausted that something so simple got so wrong. Apple says the certificates are for security. I call it ********. It's not like I downloaded my OS from some shady trrnt site. If you're downloading from their store, that's the only security you need, because clearly this expiry date makes the previous OS garbage. I hate the company forces users to upgrade everything and we have no saying on what we want to use with the mega expensive machines that BELONG to us as buyers.
So in conclusion I'm back with this awful Linux-like operating system that is Big Sur. 🤢
NOPE! On T2 systems you can boot from Apple Install Media even while external boot is disabled. The thing is, you don't even need to do that. Just run the --eraseinstall from the installer app residing right in /Applications, even ON THE DISK YOU ARE ERASE/INSTALLING. This sorcery is brought to you courtesy of APFS.
@chinchillas --- I just signed up on this forum for the first time, specifically to reach out and ask if there was ever a resolution to this. I just spent literally 7-8 DAYS researching, watching, calling, reading, backing up (multiple times), and attempting to learn everything I could about macOS changes, because operating system changes still freak me out and I'm still annoyed that we're effectively forced into them as software becomes reliant on a few operating systems. I purchased a MacBook in early 2021 that shipped with Catalina and lived comfortably on it until, finally, I had to get at least Big Sur in order to update camera software and update Davinci Resolve. In the process....
I'm glad I read through everyone's horror stories because I was about to have the same one most likely if I had not taken such a ridiculous amount of time.
I thought that surely I could "clean install" Big Sur from a bootable installer, coming from Catalina, but from these three pages, I got the impression that's no longer possible??? I called AppleCare and they told me that I couldn't do a clean install of Big Sur until I was on Big Sur. So what's the point at all of the bootable installer??? Is this all because of the T2 chips?
As soon as I did a "dirty install" of Big Sur today (and proceeded to spend 3 hours fixing Adobe Photoshop to get it to stop from crashing; yes it was compatible, but things happened and that was a whole separate debacle), I didn't like the iOS feeling UI and in conjunction with the frustrations I was having otherwise, wished I could go back.
I learned a lot over the past week but suppose that software alone, I'm stuck now. My question is: can we really no longer downgrade our operating systems at all? Is this security certificate expiration date issue above now making it impossible to roll back? At this point I almost want to clean install something (even Big Sur) just to stick it to Apple after a week of my life and productivity went down the rabbit hole of something as simple as an operating system switch.
I watched a whole bunch of this guy's videos....https://www.youtube.com/watch?v=DM1j4TVt7BY
It's not so much that I think I'm GOING to downgrade, but if I really can't, that bothers me quite a lot and I signed up on this forum just to ask if this ever got resolved at all.
Sounds like a great reason to go with the latest versions. I do a clean install twice a year, all my data is backed up in the cloud or offline on external disks. whole process takes only an hour or two. I am currently on Ventura - it is awesome sure the usual whiners are complaining about bugs, but nope, haven't had any (Well Brave Browser Beta won't run, but that is itz0