• How to use DISM to slipstream updates to install media
• Apparently the latest SSU needs to be slipstreamed and committed first, and then the latest CU slipstreamed afterwards
• https://www.tenforums.com/installation-upgrade/134686-offline-image-update-files-outside-install-wim.html

• Windows 10 image extracted to %UserProfile%\Downloads\W10
• install.wim at %UserProfile%\Downloads\W10\sources\install.wim
• About 30GB of disk space to be safe

• LTSB 2016 and LTSC 2019 seems to have only one Index
• If more than one Index is present, be sure to change commands below and only select the wanted Index

dism.exe /Get-WimInfo /wimFile:"%UserProfile%\Downloads\W10\sources\install.wim"

• With Win10_2004_English_x64, Index 10 is Pro for Workstations

dism.exe /Export-Image /SourceImageFile:"%UserProfile%\Downloads\W10\sources\install.wim" /SourceIndex:"10" /DestinationImageFile:"%UserProfile%\Downloads\install.wim"

dism.exe /Get-WimInfo /wimFile:"%UserProfile%\Downloads\install.wim"

mkdir "%UserProfile%\Downloads\mounted-wim" "%UserProfile%\Downloads\update-packages" "%UserProfile%\Downloads\temp-export"

dism.exe /Mount-WIM /wimFile:"%UserProfile%\Downloads\install.wim" /index:"1" /MountDir:"%UserProfile%\Downloads\mounted-wim"

• Updates should be copied to %UserProfile%\Downloads\update-packages prior to running
• The latest SSU needs to be installed and committed, and the process needs repeated in order to integrate the latest CU

dism.exe /image:"%UserProfile%\Downloads\mounted-wim" /Add-Package /PackagePath:"%UserProfile%\Downloads\update-packages"

dism.exe /image:"%UserProfile%\Downloads\mounted-wim" /Cleanup-Image /StartComponentCleanup /ResetBase

dism.exe /Get-Packages /image:"%UserProfile%\Downloads\mounted-wim"

dism.exe /Unmount-wim /mountdir:"%UserProfile%\Downloads\mounted-wim" /commit

• Need to manually copy the new install.wim to Install media sources folder
• If install.wim is ever above 4GB even after the compress, using Rufus to create a NTFS bootable USB flash drive is required

dism.exe /Export-Image /SourceImageFile:"%UserProfile%\Downloads\install.wim" /SourceIndex:"1" /DestinationImageFile:"%UserProfile%\Downloads\temp-export\install.wim" /Compress:"maximum"