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lakshi

macrumors 6502
Original poster
Feb 7, 2008
276
2
Hello, i have latest macbook air with catalina osx that i formatted to factory set it and then couldnt reinstall catalina osx on it and was getting error...now i want to create a bootable usb drive with catalina dmg file and install on it...can anyone direct me to a dmg file of catalina?
 

chabig

macrumors G4
Sep 6, 2002
11,320
9,011
To reinstall macOS, follow Apple’s instructions.


If you absolutely think a bootable installer is for you, they have instructions for that too.

 

lakshi

macrumors 6502
Original poster
Feb 7, 2008
276
2
My MacBook air is the early 2020 version and im installing macOS Catalina 10.15 on it...will i be downgrading if i do that or there wont be any problems?
 

hallux

macrumors 68040
Apr 25, 2012
3,437
1,005
If that MBA has a T2 chip on it, won't the OP need to enable the ability to boot from a USB drive, which requires an OS installed with a functioning account in order to authenticate to make that change.
 

lakshi

macrumors 6502
Original poster
Feb 7, 2008
276
2
It was a working macbook air with someone elses ID and Password that i wanted to erase so i factory set it and proceeded to reinstall macos on it but got it download error....can i install on it using bootable usb with catalina 10.15?
 

hallux

macrumors 68040
Apr 25, 2012
3,437
1,005
That Macbook Air DOES have the T2 chip - https://support.apple.com/en-us/HT208862
SecureBoot, part of that T2 chip, by default does NOT allow booting from USB drives (which is required for reinstalling from a USB stick) - https://support.apple.com/en-us/HT208330

In order to even ENTER the screens shown there, the Mac needs to have a functioning OS installed on it with an admin account with a known password. Only once that password is entered will you be able to make the changes needed to allow boot to USB.

What does this mean? With no OS on the drive at this point your only option is to get it reinstalled using Internet Recovery.
 

lakshi

macrumors 6502
Original poster
Feb 7, 2008
276
2
ok will try reinstall macos from macos recovery...
which one to try:


  • If you erased your entire disk instead of just the startup volume on that disk, macOS Recovery might offer only the macOS that came with your Mac, or the closest version still available. You can upgrade to a later version afterward.
or

 

hallux

macrumors 68040
Apr 25, 2012
3,437
1,005
Either one, the first just requires that you then install updates once the OS install is complete.
 

lakshi

macrumors 6502
Original poster
Feb 7, 2008
276
2
I dont have the macbook with me at the moment, will post tommorow and let you know which format i erased the hard disk on
 

lakshi

macrumors 6502
Original poster
Feb 7, 2008
276
2
i earlier formatted my macbook and was unable to install macos now it wont boot. When i turn on the computer i hold command and R and release when i see logo. Now it shows a circle with world in it and i choose wifi network. Then it shows a progress bar. It then says " security settings do not allow this mac to use an external startup disk". Gives 2 options:
Startup disk and
Restart
I then press restart and command and R and release when i see the logo then same loop again...
Someone please help me out....
 

Apple_Robert

Contributor
Sep 21, 2012
34,728
50,588
In the middle of several books.
You need to contact Apple Support. I believe you will have to visit an Apple Store or send it in to have the OS reinstalled. Since you deleted the OS without turning off “Secure Boot” first, you will continue to get the error message, because “Secure Boot” is still turned on.”

When the T2 chip models first came out, many forum members here ran into the same problem and had to get Apple assistance.
 

lakshi

macrumors 6502
Original poster
Feb 7, 2008
276
2
Ok, thanks a lot for the info...on my way to the apple store tomorrow...
 
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