Switch off Virtual Machines on a schedule using an Azure Tag

function Get-SubscriptionsUnderManagementGroup {
    param (
        [Parameter(Mandatory = $true)]
        [string]$ManagementGroupId
    )

    # Array to store subscription IDs
    $subscriptionIds = @()

    # Get the management group hierarchy
    $managementGroup = Get-AzManagementGroup -GroupId $ManagementGroupId -Expand

    if ($managementGroup -and $managementGroup.Children) {       
        # Loop through each child in the management group
        foreach ($child in $managementGroup.Children) {
            if ($child.Type -eq "Microsoft.Management/managementGroups") {
                # Recursively get subscriptions from child management groups
                $childManagementGroupId = $child.Name
                $subscriptionIds += Get-SubscriptionsUnderManagementGroup -ManagementGroupId $childManagementGroupId
            } elseif ($child.Type -match "/subscriptions") {
                # Extract subscription ID
                $subscriptionId = [regex]::Match($child.Name, "([a-f0-9-]{36})").Value
                if ($subscriptionId) {
                    $subscriptionIds += $subscriptionId
                }
            }
        }
    }

    return $subscriptionIds
}

Function: CheckScheduleEntry

This function checks whether the current time is within a specified time range.

function CheckScheduleEntry ([string]$TimeRange) {  
    $rangeStart, $rangeEnd, $parsedDay = $null
    $currentTime = (Get-Date).ToUniversalTime().AddHours(2)
    $midnight = $currentTime.AddDays(1).Date
 
    try {
        if ($TimeRange -like "*->*") {
            $timeRangeComponents = $TimeRange -split "->" | ForEach-Object { $_.Trim() }
            if ($timeRangeComponents.Count -eq 2) {
                $rangeStart = Get-Date $timeRangeComponents[0]
                $rangeEnd = Get-Date $timeRangeComponents[1]
 
                if ($rangeStart -gt $rangeEnd) {
                    if ($currentTime -ge $rangeStart -and $currentTime -lt $midnight) {
                        $rangeEnd = $rangeEnd.AddDays(1)
                    }
                    else {
                        $rangeStart = $rangeStart.AddDays(-1)
                    }
                }
            }
            else {
                Write-Output "`WARNING: Invalid time range format. Expects valid .Net DateTime-formatted start time and end time separated by '->'" 
            }
        }
        else {
            if ([System.DayOfWeek].GetEnumValues() -contains $TimeRange) {
                if ($TimeRange -eq (Get-Date).DayOfWeek) {
                    $parsedDay = Get-Date "00:00"
                }
            }
            else {
                $parsedDay = Get-Date $TimeRange
            }
 
            if ($parsedDay -ne $null) {
                $rangeStart = $parsedDay
                $rangeEnd = $parsedDay.AddHours(23).AddMinutes(59).AddSeconds(59)
            }
        }
    }
    catch {
        Write-Output "`WARNING: Exception encountered while parsing time range. Details: $($_.Exception.Message). Check the syntax of entry, e.g. ' -> ', or days/dates like 'Sunday' and 'December 25'"   
        return $false
    }
 
    if ($currentTime -ge $rangeStart -and $currentTime -le $rangeEnd) {
        return $true
    }
    else {
        return $false
    }
}

Function: AssertVirtualMachinePowerState

This feature ensures that VMs are in the desired power state (running or stopped) on a scheduled basis.

function AssertVirtualMachinePowerState {
    param (
        [Object]$VirtualMachine,
        [string]$DesiredState,
        [bool]$Simulate
    )
 
    $resourceManagerVM = Get-AzVM -ResourceGroupName $VirtualMachine.ResourceGroupName -Name $VirtualMachine.Name -Status
    $currentStatus = $resourceManagerVM.Statuses | Where-Object { $_.Code -like "PowerState*" }
    $currentStatus = $currentStatus.Code -replace "PowerState/", ""
 
    if ($DesiredState -eq "Started" -and $currentStatus -notmatch "running") {
        if ($Simulate) {
            Write-Output "[$($VirtualMachine.Name)]: SIMULATION -- Would have started VM. (No action taken)"
        }
        else {
            Write-Output "[$($VirtualMachine.Name)]: Starting VM"
            $resourceManagerVM | Start-AzVM
        }
    }
    elseif ($DesiredState -eq "StoppedDeallocated" -and $currentStatus -ne "deallocated") {
        if ($Simulate) {
            Write-Output "[$($VirtualMachine.Name)]: SIMULATION -- Would have stopped VM. (No action taken)"
        }
        else {
            Write-Output "[$($VirtualMachine.Name)]: Stopping VM"
            $resourceManagerVM | Stop-AzVM -Force
        }
    }
    else {
        Write-Output "[$($VirtualMachine.Name)]: Current power state [$currentStatus] is correct."
    }
}

The script iterates through all VMs in a given subscription, checks tags, and applies power states according to a schedule. Here's an overview of what the script does:

try {
    # Main script logic
}
catch {
    $errorMessage = $_.Exception.Message
    throw "Unexpected exception: $errorMessage"
}
finally {
    Write-Output "Script finished (Duration: $(("{0:hh\:mm\:ss}" -f ((Get-Date).ToUniversalTime() - $currentTime))))"
}

5. Usage examples

To run the script, use the following command:

.\StartStopVMsBasedOnTag.ps1 -TagName "AutoShutdownSchedule" -ManagementGroupId "MngEnv" -Simulate $true

We run the examples in local PowerShell, but PowerShell can run anywhere, including within your Automation account.

5.1 We tag the virtual machines accordingly.

5.2 After you log in to Azure, examine the PowerShell code and run the commands.

5.3 We used the "-Simulate $true" flag to show what would have happened. If you want to run this in production, you can first simulate and then, when you are satisfied with the test, switch "-Simulate $false" to stop the simulation.

6. Conclusion

Automating VM shutdown schedules using Azure tags can help you optimize resource usage and reduce costs. Following this guide will help you implement a similar solution in your Azure environment. If you have any questions or feedback, please leave a comment below. A copy of this code can be found in my GitHub Repo --> RallTheory/StartStopVMs/StartStopVMsBasedOnTag.ps1 at main · WernerRall147/RallTheory (github.com)

disclaimer

The sample script is not supported by any Microsoft standard support program or service. The sample script or Power BI dashboard is provided AS IS without warranty of any kind. Microsoft further disclaims all implied warranties, including but not limited to the implied warranties of merchantability or fitness for a particular purpose. The entire risk arising out of the use or performance of the sample script and documentation remains with you. In no event shall Microsoft, the authors, or anyone else involved in the creation, production, or delivery of the script or Power BI dashboard be liable for any damages whatsoever (including but not limited to damages for loss of business profits, business interruption, loss of business information, or other pecuniary loss) arising out of the use of or inability to use the sample script or documentation, even if Microsoft has been advised of the possibility of such damages. This blog post was created with the assistance of Generation AI.