Transform USB labeled install (already Mac OS Extended (Journaled), GUID Partition Map) into a bootable macOS Monterey installer using InstallMacOSX.dmg from USB labeled Ventory.

Prerequisites

• Both USB drives inserted

• Admin access

• install is empty and correctly formatted

• Ventory contains InstallMacOSX.dmg

1. Mount the DMG from Ventory {#mount-the-dmg-from-ventory }

hdiutil attach /Volumes/Ventory/InstallMacOSX.dmg -noverify -mountpoint /Volumes/InstallDMG

Success: Shows /dev/diskX ... /Volumes/InstallDMG

2. Install .pkg to Extract the Full Installer App {#install-.pkg-to-extract-the-full-installer-app }

sudo installer -pkg /Volumes/InstallDMG/InstallMacOSX.pkg -target /

Wait: 2--5 minutes\ Result: /Applications/Install macOS Monterey.app

3. Create Bootable Installer on install {#create-bootable-installer-on-install}

sudo /Applications/Install\ macOS\ Monterey.app/Contents/Resources/createinstallmedia \
--volume /Volumes/install --nointeraction

Duration: 15--30 minutes\ Progress:

Erasing disk...
Copying installer files...
Making disk bootable...

Final message:\ Install media now available at "/Volumes/Install macOS Monterey"

4. Eject Both Drives {#eject-both-drives}

hdiutil detach /Volumes/InstallDMG
hdiutil detach /Volumes/install

Both drives safely unmounted

5. Boot iMac (Mid-2017 27\") from install {#boot-imac-mid-2017-27-from-install }

1. Shut down iMac

2. Insert USB labeled install

3. Power on + hold Option (⌥)

4. Select orange icon: Install macOS Monterey $\rightarrow$ Enter

6. (Optional) Erase Internal Drive via Terminal (After Booting from USB) {#optional-erase-internal-drive-via-terminal-after-booting-from-usb}

diskutil list

Identify internal disk (e.g., disk2, size  500GB--2TB)

# Replace disk2 with your internal disk
diskutil apfs deleteContainer disk2
diskutil apfs createContainer /dev/disk2
diskutil apfs addVolume disk2 APFS "Macintosh HD"

Creates fresh APFS volume: Macintosh HD

7. Install macOS Monterey {#install-macos-monterey}

• Select Install macOS Monterey $\rightarrow$ Continue

• Choose Macintosh HD as destination

• Duration: 30--60 minutes (2--3 restarts)

• Final boot: macOS Monterey setup screen

Done!

Your mid-2017 27\" iMac now runs macOS Monterey.\

• Remove Ventory

• Keep install for future recovery