Unregistering and deleting an event log

Today, I’ve decided to write about unregistering and deleting Windows event logs, because searching the web about this subject brings up some very dangerous results with dangerous consequences.

Event Viewer in Windows Vista: In comparison to its predecessor in Windows Server 2003, it has become several times more elaborate to accommodate the vast logging infrastructure introduced in this version of Windows.

Event Viewer in Windows Vista: In comparison to its predecessor in Windows Server 2003, it has become several times more elaborate to accommodate the vast logging infrastructure introduced in this version of Windows.

Problem: A user notices redundant event logs in Event Viewer or PowerShell, i.e. the program with which they were associated are now gone and their contents is irrelevant. These event logs might be occupying valuable disk space, e.g. 128 MB. Deleting them is tempting.

This article requires Windows PowerShell 2.0 or later, which comes with Windows 7 and Windows Server 2008 R2.

Cautious approach

If reclaiming disk space is the goal, then empty the log and forget about it. An empty log that occupies a just few bytes is not a problem on a computer that has 165,606 files.

Unregistering and deleting the log file only makes sense when the sheer number of these logs is causing a slowdown (e.g. when there are 100 redundant logs) or when eliminating all traces of an app from a computer is important (e.g. mandated by a corporate policy).

A word of warning

The following event logs are part of Windows; if you unregister them by accident, the ensuing dire consequences may force you to reinstall Windows. You can empty them if you wish, but never unregister them:

  • Application
  • HardwareEvents
  • Internet Explorer
  • Key Management Service
  • Security
  • System
  • Windows PowerShell

Unregistering and deleting via PowerShell

To see a list of registered event logs in PowerShell, issue a Get-EventLog -List order. Here is an example of the result:

PS C:\Windows\system32> Get-EventLog -list

Max(K) Retain OverflowAction        Entries Log
  ------ ------ --------------        ------- ---
  20,480      0 OverwriteAsNeeded      32,288 Application
     512      1 OverwriteOlder              0 Autodesk REX
     512      7 OverwriteOlder              1 COMODO Internet Security
     512      7 OverwriteOlder            142 GhostBuster
  20,480      0 OverwriteAsNeeded           0 HardwareEvents
     512      7 OverwriteOlder              0 Internet Explorer
  20,480      0 OverwriteAsNeeded           0 Key Management Service
     128      0 OverwriteAsNeeded         671 OAlerts
  20,480      0 OverwriteAsNeeded       6,362 Security
  20,480      0 OverwriteAsNeeded      55,179 System
     512      7 OverwriteOlder          1,211 TuneUp
  15,360      0 OverwriteAsNeeded         387 Windows PowerShell

To delete an event log from the list, use Remove-EventLog -LogName command, as follows:

PS C:\Windows\system32> Remove-EventLog -LogName "Autodesk REX"
PS C:\Windows\system32> Remove-EventLog -LogName GhostBuster

There won’t be any message indicating success, but failure would be reported. Below is an example of what happens if you try to delete a non-existing log or try deleting an existing log without administrative privileges.

PS C:\Windows\system32> Remove-EventLog -LogName System2
Remove-EventLog : The Log name "System2" does not exist in the computer "localhost".
At line:1 char:1
+ Remove-EventLog -LogName System2
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (:) [Remove-EventLog], InvalidOperationException
+ FullyQualifiedErrorId : Microsoft.PowerShell.Commands.RemoveEventLogCommand
 
PS C:\Windows\system32> Remove-EventLog -LogName System
Remove-EventLog : Requested registry access is not allowed.
At line:1 char:1
+ Remove-EventLog Security
+ ~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : SecurityError: (:) [Remove-EventLog], SecurityException
+ FullyQualifiedErrorId : NewEventlogException,Microsoft.PowerShell.Commands.RemoveEventLogCommand
 
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Posted on 13 June 2014, in Windows Administration and tagged , , , , , , . Bookmark the permalink. Leave a comment.

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