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Version: Windows 10 x64 1909 (Spanish) | Build: 18363.959

According to Microsoft, the limit of the CommandLine element is 1024 characters, but in my tests when it exceeds two hundred something characters it starts behaving strangely. Considering the same element is called Path when in the Microsoft-Windows-Deployment component I'm guessing the documentation is wrong and the actual is limit is 259 characters for both elements.

Sources:

https://docs.microsoft.com/en-us/windows-hardware/customize/desktop/unattend/microsoft-windows-shell-setup-firstlogoncommands-synchronouscommand-commandline

https://docs.microsoft.com/en-us/windows-hardware/customize/desktop/unattend/microsoft-windows-deployment-runsynchronous-runsynchronouscommand-path

How to reproduce:

In the oobeSystem pass, add these under FirstLogonCommands:

<SynchronousCommand wcm:action="add">
  <Order>1</Order>
  <Description>Test</Description>
  <CommandLine>reg add HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run /v Test1 /t REG_SZ /d &quot;cmd /k echo aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa&quot; /f</CommandLine>
</SynchronousCommand>
<SynchronousCommand wcm:action="add">
  <Order>2</Order>
  <Description>Test</Description>
  <CommandLine>reg add HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run /v Test2 /t REG_SZ /d &quot;cmd /k echo aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa&quot; /f</CommandLine>
</SynchronousCommand>

Command 1 gets added properly to registry and executed:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    Test1    REG_SZ    cmd /k echo aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

But Command 2 get added to HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce literally:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce
    Unattend0000000002{373CFC84-60AF-44A4-A316-9BECBAB1AD4B}    REG_EXPAND_SZ    reg add HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run /v Test2 /t REG_SZ /d "cmd /k echo aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" /f

C:\Windows\Panther\UnattendedGC\setupact.log doesn't show anything abnormal:

2020-08-17 19:09:39, Info                         [Shell Unattend] LogonCommands: Set command 'reg add HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run /v Test1 /t REG_SZ /d "cmd /k echo aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" /f' 
2020-08-17 19:09:39, Info                         [Shell Unattend] LogonCommands: Set command 'reg add HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run /v Test2 /t REG_SZ /d "cmd /k echo aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" /f'
Bangaio
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  • Hi, can I ask why you dont run a .cmd or a reg import file.reg to bypass that limitation ? – yagmoth555 Aug 18 '20 at 02:47
  • I'm doing it from an USB stick so I have to do something like `reg add HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce /v Setup /t REG_SZ /d "cmd /c for %A in (D E F G H I J K L N M O P Q R S T U V W X Y Z) do if exist %A:\unattend\Script.cmd %A:\unattend\Script.cmd [...]"` which got long. Since it's stated the limit is 1024 characters I thought it wouldn't be a problem. But I shortened it now after much frustration with it. – Bangaio Aug 18 '20 at 03:47

0 Answers0