Use SetupDiag to diagnose Windows 10 upgrade problems

SetupDiag is a free diagnostic tool by Microsoft that is designed to find and parse Windows 10 setup log files to determine why an upgrade or update failed to install on a computer system.
The program can be run on the computer that failed to upgrade or on another computer if relevant log files are available (for example, by copying them to the PC).
 

SetupDiag works only on devices running Windows 10. The second requirement is that it depends on the Microsoft .NET Framework 4.6 which needs to be installed on the device it is run on.
With the upcoming Windows 10 version 1803 just around the corner, it may be the right tool to have in your arsenal if you run into upgrading issues.

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 Here are some examples:

• SetupDiag.exe -- the core command. It will run in online mode which means that it tries to find upgrade logs on the target machine in the directories mentioned above.
• SetupDiag.exe /Output:C:\SetupDiag\Results.log /Mode:Offline /LogsPath:D:\Temp\Logs\LogSet1 - the command runs SetupDiag in offline mode. It will scan the directory LogSet1 for matching log files and issues.
• SetupDiag.exe /Output:C:\SetupDiag\Dumpdebug.log /Mode:Offline /LogsPath:D:\Dump -- the command analyzes the setupmem.dmp file found in d:\dump.

How it works

SetupDiag uses a set of rules files to find matches in upgrade logs. Rules have a name and associated unique identifier.The reliance on rules means that SetupDiag can only identify issues that are defined in its set of rules. 

Microsoft lists a total of 26 unique identifiers on the Microsoft Docs website which SetupDiag identifies in its current version.