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FolderRisk: Caution

CBS C:\Windows\Logs\CBS

Component-Based Servicing (CBS) logs: update and feature installation, sfc /scannow results in CBS.log.

Updated on By AltF4 Formation

What it’s for

CBS.log records everything Component-Based Servicing (CBS) does. CBS is the Windows servicing stack that installs, updates and repairs components, features and updates. The file lives in %windir%\Logs\CBS and also records System File Checker runs (sfc /scannow). For the same kind of problem, DISM.log (in Logs\DISM) traces the DISM layer.

What it contains

  • CBS.log: a detailed and very verbose log of servicing operations. Each line starts with the date, the time and a level (Info, Warning, Error).
  • System File Checker entries, identifiable by the [SR] tag. They cover every sfc run, so check the dates to find the latest one.
  • CbsPersist_* archives, created when the current log is archived.

Risks and best practices

  • CBS.log is the first source for diagnosing a failing update or repair, so keep it until the incident has been analyzed.
  • To read the result of sfc, extract the [SR] lines to a file instead of opening a large log in an editor.
  • A folder that grows abnormally points to repeated update installation attempts. Fix the cause, not the log.
  • If space runs short, delete the old archives and keep the most recent log.

Useful commands

Fenêtre de terminal
:: Extract System File Checker entries (elevated command prompt)
findstr /c:"[SR]" %windir%\Logs\CBS\CBS.log > "%userprofile%\Desktop\sfcdetails.txt"
Fenêtre de terminal
# Folder content, newest first (read-only)
Get-ChildItem "$env:windir\Logs\CBS" -Force | Sort-Object LastWriteTime -Descending | Select-Object Name, Length, LastWriteTime


# Latest errors in the log
Select-String -Path "$env:windir\Logs\CBS\CBS.log" -Pattern ', Error ' | Select-Object -Last 20

Folder contents

Files 1

Logs 1

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