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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
@kepi
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kepi commented Apr 23, 2020

Current Catalina requires more space. I had to change -size 8000m to -size 10000m.

@julianxhokaxhiu
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Thanks for the report, it worked on my side though, but I tested with the very first release. Updated the script :)

@LogicalChaos
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I tried it with 10.15.4, had to increase it again, I used --size 12000m and it worked. Thanks for the gist.

@julianxhokaxhiu
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Updated again, thanks for the feedback :) Glad it was useful. Cheers!

@panicsteve
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First attempt with 10.15.5 failed:

% sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia  --volume /Volumes/install_build --nointeraction
Password:
Erasing disk: 0%... 10%...
Error erasing disk error number (22, 0)
An error occurred erasing the disk.

I increased the -size arbitrarily to 16000m and it worked. Not sure if that was the actual problem, just passing along the anecdote. :)

@julianxhokaxhiu
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@panicsteve thanks! I did use this very same script recently to make an ISO and it worked just fine. Could be the issue is somewhere else. But thanks for letting us know!

@netinhoteixeira
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Needed run as root:

$ chown +x create-iso.sh
$ sudo ./create-iso.sh

@julianxhokaxhiu
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Updated the script again to 9000m ( ~9GB ) as it's enough to accomodate 10.15.6

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ghost commented Aug 14, 2020

9000m didn't work for me. I made it 12000m and it worked.

@kaelef
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kaelef commented Aug 18, 2020

FYI: I just tried and got the error message when using 9000m for the size. 9200m worked, though.

@sebastianherman
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sebastianherman commented Sep 16, 2020

I had to use 20000m for it to work

@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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