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.
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.
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:
- Internet Explorer
- Key Management Service
- 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