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Simple bash script to create a Bootable ISO from macOS Catalina Install Image from Mac App Store
#!/usr/bin/env bash
#===========================================================================
# Works only with the official image available in the Mac App Store.
# Make sure you download the official installer before running this script.
#===========================================================================
hdiutil create -o /tmp/Catalina.cdr -size 9000m -layout SPUD -fs HFS+J
hdiutil attach /tmp/Catalina.cdr.dmg -noverify -mountpoint /Volumes/install_build
sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/install_build --nointeraction
hdiutil detach "/Volumes/Install macOS Catalina"
hdiutil convert /tmp/Catalina.cdr.dmg -format UDTO -o /tmp/Catalina.iso
mv /tmp/Catalina.iso.cdr ~/Desktop/Catalina.iso
rm /tmp/Catalina.cdr.dmg
@julianxhokaxhiu
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I'm honestly surprised to see how everyone of us is using a different value. Could it be Apple is shipping the ISO image differently based on the HW where you download it? I do my tests inside of a VM.

What about you?

@kaelef
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kaelef commented Sep 16, 2020

I don't know that people are trying small increments. Certainly a very large value will get things to work immediately without having to make multiple attempts. (My test was also in a VM.)

@sebastianherman
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@julianxhokaxhiu I downloaded it on a late 2013 rMBP with 16GB RAM - no idea why this would impact the size.

@kaelef can't speak for others but generally i want an image as small as possible when storing it for later usage

@julianxhokaxhiu
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can't speak for others but generally i want an image as small as possible when storing it for later usage

I do aim for the same. This is why I lowered the size back down again when I saw that 9000m was fitting. But maybe today is no more because of security patches and such. So 9200m sound plausible to me.

@Underdoge
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Tested it with the Big Sur installer from Apple, making the obvious naming and sizing adjustments (12700m worked for me) and it also works fine, thank you.

@julianxhokaxhiu
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julianxhokaxhiu commented Nov 17, 2020

I've created the relative script for Big Sur and you can find it if you're interested: https://gist.github.com/julianxhokaxhiu/286017b9872474d2c9b9fa090f6802bf

Glad you made it up yourself :) Cheers

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