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LogRisk: Caution

setupact.log C:\Windows\Panther\setupact.log

C:\Windows\Panther\setupact.log: the full narrative of Windows Setup, for diagnosing an install or an upgrade. For errors only, see setuperr.log.

Updated on By AltF4 Formation

What it’s for

setupact.log is the complete account of what Windows Setup did: installation, upgrade, deployment, first-boot configuration. It is the log to open when an install or upgrade fails or drags. Its neighbor setuperr.log keeps only the errors, without the context.

What it contains

  • The installation phases and how long each took.
  • The actions performed, the compatibility checks and the settings applied.
  • Detailed error codes, which setuperr.log repeats on their own.
  • The specialize and OOBE passes of a deployment write their own logs in the UnattendGC subfolder.

Risks and best practices

  • Deleting it changes nothing about how Windows runs, but it wipes the trail of the installation. Keep it at least until the deployment is validated.
  • It names machines, accounts and paths, so review it before sending it to a third party.
  • During an upgrade, the early phases write to $WINDOWS.~BT\Sources\Panther. If the log in C:\Windows\Panther looks too short, look there.

Useful commands

Fenêtre de terminal
# Last lines
Get-Content "$env:windir\Panther\setupact.log" -Tail 50


# Error lines, with the context before them
Select-String -Path "$env:windir\Panther\setupact.log" -Pattern "Error|Failed" -Context 3,0 | Select-Object -Last 10


# Errors isolated by Setup
Get-Content "$env:windir\Panther\setuperr.log" -ErrorAction SilentlyContinue
Fenêtre de terminal
:: Automatic analysis of a failed upgrade with SetupDiag (Microsoft tool, to be downloaded)
SetupDiag.exe /Output:C:\SetupDiag\Results.log

Format

Plain text. Each line starts with a timestamp, then the level (Info, Warning, Error), the emitting component and the message.

Rotation and archiving

The file is written during the setup phases and kept as is: there is no rotation. Copy it with setuperr.log before reinstalling.

How to read it

Look for Error or Failed lines first, then scroll back a few dozen lines to find the action that failed. Cross-check with setuperr.log and, for drivers, with setupapi.dev.log.

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