Version 1.2


This script calculates the percentage of time a computer has been running, it does not just return the amount of time since last reboot.  It does this by iterating through the System event log looking for shutdown and startup events.  It then calculates how long the server was offline during each reboot and adds this time to a variable.  To properly account for unexpected system outages (crashes), the script queries the remote computer for the most recent event with ID 6008.  This event contains information about the unexpected shutdown, including the date and time of the incident.  The timestamp of this event is extracted from the ReplacementStrings property of the event and used to determine how long the computer was offline and this is added to the downtime variable.  To calculate uptime, the script subtracts the downtime from the total possible uptime for the selected period.

This script is based on a script written by Ed Wilson for a "Hey, Scripting Guy!" article.  I had numerous problems with that script and decided to modify it so that it was more reliable.


This script requires PowerShell 2.0, administrative access to the remote computer, and WinRM must be configured on the remote computer.

Script Code


#* Script Name: getServerUptime 
#* Created: 9/15/2011 
#* Author: James Keeler 
#* Email: James.R.Keeler(at) 
#* Params:    [string]$ComputerName - name of the remote computer. If no parameter 
#*                is given, the default is localhost 
#*            [int]$NumOfDays - number of days for which to calculate the  
#*                uptime.  If no parameter is given, the default is 30 days. The 
#*                maximum number of days allowed is 365. 
#*            [switch]$DebugInfo - turns on debugging 
#* Returns:    The percent downtime and uptime for the given server. 
#* Purpose: Calculates the percent uptime for the given server. 
#* Version:        1.1 
#* Date:         9/27/2011 
#* Time:         5:37 PM 
#* Issue:         Not calculating downtime properly for system crashes 
#* Solution:    Iterate through all event logs to find the last event written 
#*                prior to crash. Use this timestamp to determine outage duration. 
#* Version:        1.2 
#* Date:         11/30/2011 
#* Time:         8:27 AM 
#* Issue:         Script performance 
#* Solution:    Use Invoke-Command to remotely call Get-EventLog 
#* Issue:         Script accuracy 
#* Solution:    Changed the script to use the system generated error message 
#*                for unexpected shutdowns to capture the correct timestamp. 
    Calculates the percent uptime for the given server. 
    The getServerUpTime script returns the uptime for a remote or local  
    Without parameters, getServerUptime returns the uptime for the local  
    computer over the past 30 days. 
.PARAMETER ComputerName 
    Calculates the percent uptime for the specified computers. The default is  
    the local computer. 
    Type the NetBIOS name, an IP address, or a fully qualified domain name of  
    a computer. To specify the local computer, type the computer name, a dot  
    (.), or "localhost". 
.PARAMETER NumberOfDays 
    The function will calculate the uptime of the computer for the past N days, 
    where N equals the value of NumberOfDays. 
    Turn on debugging. 
    PS C:\> .\getServerUptime.ps1 
    Retrieving shutdown and startup events from MyLaptop for the past 30 days... 
    WARNING: This could take several minutes! 
    Name            : MyLaptop 
    NumOfDays       : 30 
    NumOfCrashes    : 1 
    NumOfReboots    : 18 
    MinutesDown     : 12,506.03 
    MinutesUp       : 30,693.97 
    PercentDowntime : 28.9492 % 
    PercentUptime   : 71.0508 % 
    PS C:\> .\getServerUptime.ps1 -ComputerName SVR001 -NumberOfDays 365 
    Retrieving shutdown and startup events from SVR001 for the past 365 days... 
    WARNING: This could take several minutes! 
    Name            : SVR001 
    NumOfDays       : 365 
    NumOfCrashes    : 1 
    NumOfReboots    : 13 
    MinutesDown     : 63.15 
    MinutesUp       : 525,536.85 
    PercentDowntime : 0.0120 % 
    PercentUptime   : 99.9880 % 
          [string] $ComputerName = $env:computername, 
          [int] $NumberOfDays = 30, 
    Process { 
        # Ensure the server is reachable 
        if (Test-Connection -ComputerName $ComputerName -Count 1 -TimeToLive 10 -Quiet) { 
            # Ensure that this is a Windows server that we are working with and  
            # that we have the appropriate permissions 
            if (Test-Path -Path "\\$ComputerName\C$")  
                # Did the user pass in an appropriate value for number of days? 
                # If not, we will assume the default, 30 days.  If the value is 
                # more than 365, we use 365 as the maximum. 
                if ($NumberOfDays -le 0)  
                    $NumberOfDays = 30 
                    Write-Host "Defaulting to 30 days..." 
                } # end if 
                elseif ($NumberOfDays -gt 365)  
                    $NumberOfDays = 365 
                    Write-Host "Using maximum value (365 days)..." 
                } # end elseif 
                # If the -debug switch is set, we set the $DebugPreference variable 
                  if($DebugInfo) { $DebugPreference = "Continue" } 
                  # We begin by assuming 100% uptime.  We will calculate effective  
                  # uptime by subtracting downtime from this value 
                [timespan]$uptime = New-TimeSpan -Days $NumberOfDays 
                [timespan]$downtime = 0 
                $currentTime = Get-Date 
                $startUpID = 6005 
                $shutDownID = 6006 
                $minutesInPeriod = $uptime.TotalMinutes 
                $startingDate = (Get-Date).adddays(-$NumberOfDays) 
                # Output some useful debugging info 
                Write-Debug "Uptime:         $uptime" 
                Write-Debug "Downtime:       $downtime" 
                write-debug "Current time:   $currentTime" 
                Write-Debug "Start time:     $startingDate" 
                Write-Debug "Computer:       $ComputerName" 
                # Warn the user that this could take a while 
                Write-Host -NoNewline "Retrieving shutdown and startup events from " 
                Write-Host "$ComputerName for the past $NumberOfDays days..." 
                Write-Warning "This could take several minutes!" 
                # Create a new PSSession to be used throughout the script 
                $mySession = New-PSSession -ComputerName $ComputerName -ErrorAction Stop 
                # Remotely retrieve the events from the system event log that  
                # occurred in the past $NumberOfDays days ago 
                $events = Invoke-Command -Session $mySession -ScriptBlock {` 
                    Get-EventLog ` 
                        -After (Get-Date).AddDays(-$days) ` 
                        -LogName System ` 
                        -Source EventLog ` 
                    | Where-Object {  
                        $_.eventID -eq  $up ` 
                        -OR ` 
                        $_.eventID -eq $down } 
                } -ArgumentList $NumberOfDays,$startUpID,$shutDownID -ErrorAction Stop 
                # Create a new sorted array object 
                $sortedList = New-object system.collections.sortedlist 
                # If there are shutdown or startup events, add them to the  
                # sorted array, otherwise add zeroes to the array as placeholders 
                if ($events.Count -ge 1)  
                    ForEach($event in $events) 
                        $sortedList.Add( $event.timeGenerated, $event.eventID ) 
                    } #end foreach event 
                } # end if 
                { # There were no shutdown events during this time period 
                    $sortedList.Add( 0, 0 ) 
                } # end else 
                # Count the number of system crashes 
                $crashCounter = 0 
                # Count the number of reboots 
                $rebootCounter = 0 
                # Iterate through the sorted events and add up the downtime 
                For($i = 1; $i -lt $sortedList.Count; $i++ ) 
                    if(    ` 
                        ($sortedList.GetByIndex($i-eq $startupID) ` 
                        -AND ` 
                        ($sortedList.GetByIndex($i-ne $sortedList.GetByIndex($i-1)) )  
                    { # There was a shutdown event paired to the startup event,  
                      # thus it was a planned shutdown 
                        # Write each event to the Debug pipeline 
                        Write-Debug "Shutdown `t $($sortedList.Keys[$i-1])" # Shutdown 
                        Write-Debug "Startup  `t $($sortedList.Keys[$i])" # Startup 
                        # Outage duration = startup timestamp - shutdown timestamp 
                        $duration = ($sortedList.Keys[$i- $sortedList.Keys[$i-1]) 
                        $downtime +$duration 
                        Write-Debug "           Outage duration: $duration" 
                        Write-Debug "           Downtime is now: $downtime" 
                        Write-Debug "" 
                        # Bump the reboot counter 
                    } # end if 
                    elseif(    ` 
                        ($sortedList.GetByIndex($i-eq $startupID) ` 
                        -AND ` 
                        ($sortedList.GetByIndex($i-eq $sortedList.GetByIndex($i-1)) ) 
                    {     # This was an unplanned outage (a system crash).  
                        # Basically this means that we have 2 startup events  
                        # with no shutdown event 
                        # Get the date from the event stating that there was an 
                        # unexpected shutdown 
                        $tempevent = Invoke-Command ` 
                            -Session $mySession ` 
                            -ScriptBlock {` 
                                param([datetime]$date, [string]$log) 
                                Get-EventLog ` 
                                    -Before $date.AddSeconds(1) ` 
                                    -Newest 1 ` 
                                    -LogName System ` 
                                    -Source EventLog ` 
                                    -EntryType Error ` 
                                    -ErrorAction "SilentlyContinue" | ` 
                                Where-Object {$_.EventID -eq 6008} 
                            } -ArgumentList $sortedList.Keys[$i],$($eventlog.log) 
                        # The 6008 event has the data we're looking for in the  
                        # ReplacementStrings property but the date portion of the 
                        # data has a special character that we need to remove, 
                        # [char]8206, so we replace it with a space. 
                        $lastEvent = [datetime](` 
                            ($tempevent.ReplacementStrings[1]).Replace([char]8206, " ")` 
                            + " " + $tempevent.ReplacementStrings[0]) 
                        # Write each event to the Debug pipeline 
                        Write-Debug "CRASH    `t $lastEvent" 
                        Write-Debug "Startup  `t $($sortedList.Keys[$i])" # Startup 
                        # Calculate downtime = Startup timestamp - Last event  
                        # written to any log timestamp 
                        $duration = ($sortedList.Keys[$i- $lastEvent) 
                        $downtime +$duration 
                        Write-Debug "           Outage duration: $duration" 
                        Write-Debug "           Downtime is now: $downtime" 
                        Write-Debug "" 
                        # Bump the crash counter 
                    } # end elseif 
                } #end for item 
                # Subtract downtime from calculated uptime to get true uptime 
                $uptime -$downtime 
                # Create a custom object to hold the results 
                $results = "" | Select-Object ` 
                    Name, ` 
                    NumOfDays, ` 
                    NumOfCrashes, ` 
                    NumOfReboots, ` 
                    MinutesDown, ` 
                    MinutesUp, ` 
                    PercentDowntime, ` 
                $results.Name = $ComputerName 
                $results.NumOfDays = $NumberOfDays 
                $results.NumOfCrashes = $crashCounter 
                $results.NumOfReboots = $rebootCounter 
                $results.MinutesDown = "{0:n2}" -$downtime.TotalMinutes 
                $results.MinutesUp = "{0:n2}" -$uptime.TotalMinutes 
                $results.PercentDowntime = "{0:p4}" -f (1 - $uptime.TotalMinutes/$minutesInPeriod) 
                $results.PercentUptime = "{0:p4}" -f ($uptime.TotalMinutes/$minutesInPeriod) 
                Write-Output $results 
                # Kill our session to the remote computer 
                Remove-PSSession -Session $mySession 
              } # end if 
                  # This usually means that you've encountered a server that  
                  # is not running Windows, like a Linux server 
                  Write-Warning -Message "No access to the default share - \\$ComputerName\C`$" 
              } # end else 
          } # end if 
          { # This server is not online 
              Write-Warning -Message "Unable to connect - $ComputerName" 
          } #end else 
    } # end Process 
#* END OF SCRIPT: getServerUptime 


In no event shall the author of this script be liable in contract, tort, strict liability, warranty or otherwise, for any special, incidental or consequential damages, such as, but not limited to, confusion, delay, dizziness, disruption, loss of product, loss of anticipated profits or revenue, loss of limb, loss of virignity, loss of use of the equipment or system, non-operation or increased expense of operation of other equipment or systems, cost of capital, or cost of purchase or replacement equipment systems or power.  The author issues no guarantee or warranty either explicit or implied, and will not make available support of any kind.  You're on your own, so put on your big-boy pants and deal with it...