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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
@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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sebastianherman commented Sep 17, 2020

@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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julianxhokaxhiu commented Sep 17, 2020

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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Underdoge commented Nov 17, 2020

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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