PS C:\> help Write-EventLog
When using this cmdlet you must specify the log name, a source, an event id and a message. In this regard it is very similar to EVENTCREATE.EXE. But you can’t use a non-standard source or something ad hoc. You must use a pre-defined or existing source. An easy way to discover the source names is to use Windows Management Instrumentation (WMI).
PS C:\> $log=Get-WmiObject win32_nteventlogfile -filter "filename='system'" PS C:\> $log.Sources System ACPI adp94xx adpahci adpu320 ...
If one of these sources seems appropriate, then you can log your own entry like this.
PS C:\> write-eventlog System -source Server -eventid 12345 -message "I am a custom event log message"
The default entry type is Information. I created my own eventID which has its drawbacks.
PS C:\> get-eventlog system -newest 1 | format-list EventID,EntryType,Source,Message EventID : 12345 EntryType : Information Source : Server Message : The description for Event ID '12345' in Source 'Server' cannot be found. The local computer may not have the necessary registry information or message DLL files to display the message, or you may not have permission to access them. The following inform ation is part of the event:'I am a custom event log message'
I suppose if you wanted to be able to search for the event ID or the message, you could live with the minor “error” in the message.
PS C:\> get-eventlog system -newest 1 -message "*custom event*" Index Time EntryType Source InstanceID Message ----- ---- --------- ------ ---------- ------- 1512222 Jan 25 10:05 Information Server 12345 The des...
Not perfect, but functional. While it is theoretically possible to register new sources, if you are going to go to that length you might as well create a new event log using the New-Eventlog cmdlet.
Normally this cmdlet is aimed at application developers building a formal event log. But IT Pros can use this as well. I’m going to create a custom log and define a few sources as well.
PS C:\> new-eventlog -LogName PSLogging -Source ADSI,WMI,Test,Other
What did I just create?
PS C:\> $log=Get-WmiObject win32_NTEventlogfile -filter "filename='PSLogging'" PS C:\> $log | fl FileSize : 69632 LogfileName : PSLogging Name : C:\Windows\System32\Winevt\Logs\PSLogging.evtx NumberOfRecords : 0
A brand new log. Let’s check my sources.
PS C:\> $log.sources PSLogging ADSI Other Test WMI
Finally, let’s write something to it.
PS C:\> Write-EventLog PSLogging -Source Test -eventID 1000 -Message "I am the first entry"
You can use any event ID you choose, but you’ll likely want to define them in advance.
PS C:\> get-eventlog PSLogging | format-list
Index : 14
EntryType : Information
InstanceId : 1000
Message : I am the first entry
Category : (1)
CategoryNumber : 1
ReplacementStrings : {I am the first entry}
Source : Test
TimeGenerated : 1/25/2012 10:45:47 AM
TimeWritten : 1/25/2012 10:45:47 AM
UserName :
Windows doesn’t care now about the event ID. If I need to add another source, all I need to do is rerun the New-Eventlog cmdlet:
PS C:\> New-EventLog PSLogging -source Scripting
Now I have a new source.
PS C:\> Get-WmiObject win32_NTEventlogfile -filter "filename='PSLogging'" | Select -expand Sources PSLogging ADSI Other Scripting Test WMI
Conclusion
The New-Eventlog cmdlet has a –computername parameter so it would be very easy to define a new eventlog on all servers or desktops where you wanted your own custom logging. Have you implemented custom logging? If so, I’d love to hear about it.