WinPE Boot Process

For a good read on WinPE, check out the Microsoft Docs

Winlogon

Winlogon.exe is executed on startup. This will read the WinPE Registry at HKLM\System\Setup for the CmdLine value. By default this is winpeshl.exe. When winpeshl.exe executes, it reads values from winpeshl.ini

Winpeshl.ini

Setup.wim
WinPE.wim
WinRE.wim
MDT
ConfigMgr
Setup.wim

<Does not exist>

WinPE.wim

<Does not exist>

WinRE.wim

[LaunchApp]

AppPath=X:\sources\recovery\recenv.exe

MDT

[LaunchApps]

%SYSTEMROOT%\System32\bddrun.exe,/bootstrap

ConfigMgr

[LaunchApps]

%SYSTEMDRIVE%\sms\bin\x64\TsBootShell.exe

ConfigMgr: TSBootShell.ini

[Shell]
OrgName=OSDeploy
EnableDebugShell=true
Run=X:\sms\bin\x64\TsmBootstrap.exe /env:WinPE /configpath:%CONFIGPATH%

Startnet.cmd

Setup.wim
WinPE.wim
WinRE.wim
MDT
ConfigMgr
Setup.wim

wpeinit

WinPE.wim

wpeinit

WinRE.wim

wpeinit

MDT

wpeinit

ConfigMgr

wpeinit