Public/New-PackerBaseAMI.ps1

<#
.Synopsis
    Create a Windows Base AMI using Packer, Encrypted by default
.DESCRIPTION
    Create a Windows Base AMI using Packer, Encrypted by default
.EXAMPLE
   New-PackerBaseAMI -AccountNumber '111111111111' -Alias 'ExampleAlias' -BaseOS 'Windows_Server-2025-English-Full-Base' -IamRole 'ExampleRoleName' -Region 'us-east-1' -InstanceType 't3.medium' -OutputDirectoryPath 'c:\example\directory'
.NOTES
    Author: Robert D. Biddle
    https://github.com/RobBiddle
    https://github.com/RobBiddle/PackerBaseAMI
    PackerBaseAMI Copyright (C) 2017 Robert D. Biddle
    This program comes with ABSOLUTELY NO WARRANTY; for details type `"help New-PackerBaseAMI -full`".
    This is free software, and you are welcome to redistribute it
    under certain conditions; for details type `"help New-PackerBaseAMI -full`".
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    GNU General Public License for more details.
    You should have received a copy of the GNU General Public License
    along with this program. If not, see <http://www.gnu.org/licenses/>.
    The GNU General Public License does not permit incorporating your program
    into proprietary programs. If your program is a subroutine library, you
    may consider it more useful to permit linking proprietary applications with
    the library. If this is what you want to do, use the GNU Lesser General
    Public License instead of this License. But first, please read
    <http://www.gnu.org/philosophy/why-not-lgpl.html>.
#>

function New-PackerBaseAMI {
    [CmdletBinding()]
    [Alias()]
    [OutputType([String])]
    Param
    (
        # AWS Account Number, without dashes
        [Parameter(Mandatory = $true,
            ValueFromPipelineByPropertyName = $true,
            Position = 0)]
        [String]
        $AccountNumber,

        # Friendly Name for Account
        [Parameter(Mandatory = $false,
            ValueFromPipelineByPropertyName = $true)]        
        [String]
        $Alias = $AccountNumber,

        # Base Operating System
        [Parameter(Mandatory = $true, 
            ValueFromPipelineByPropertyName = $false)]
        [String]
        $BaseOS = 'Windows_Server-2025-English-Full-Base',

        # Do Not Encrypt the new AMI
        [Parameter(Mandatory = $false, 
            ValueFromPipelineByPropertyName = $false)]
        [Switch]
        $DoNotEncrypt,

        # IAM Role to use
        [Parameter(Mandatory = $true, 
            ValueFromPipelineByPropertyName = $false)]
        [String]
        $IamRole,

        # AWS Region
        [Parameter(Mandatory = $true,
            ValueFromPipelineByPropertyName = $true)]
        [String]
        $Region,
        
        # Output Path for Log Files, if not specified then output is to users' home Directory
        [Parameter(Mandatory = $false,
            ValueFromPipelineByPropertyName = $false)]
        [ValidateScript( {
                if ((Test-Path $_)) {
                    Write-Output "Outputing log files to: $_"
                }else {
                    Throw "$_ is not a valid directory"
                }
            })]
        [String]
        $OutputDirectoryPath = '~',

        # Name of stored AWS Profile to use
        [Parameter(Mandatory = $false,
            ValueFromPipelineByPropertyName = $false)]
        [String]
        $AwsProfileName = $AwsProfileName,

        # EC2 Instance Type to use for building the AMI
        [Parameter(Mandatory = $false,
            ValueFromPipelineByPropertyName = $false)]
        [String]
        $InstanceType = 't3.medium',

        [Parameter(Mandatory = $false,
            ValueFromPipelineByPropertyName = $false)]
            [switch]
            $debugMode
    )

    Begin {
        $null = Confirm-PackerIsInstalled
        $null = Confirm-AwsModulesAreInstalled
        $RunDateTime = Get-ShortDate -FilenameCompatibleFormat
    }
    Process {
        # Get Temporary AWS Credentials via IAM Switch Role process
        $GetTemporaryCredentials_Params = @{
            AccountNumber = $AccountNumber
            Alias         = $Alias
            Region        = $Region
            IamRole       = $IamRole
        }
        if ($AwsProfileName) {
            $GetTemporaryCredentials_Params += @{
                AwsProfileName = $AwsProfileName
            }
        }
        $AwsTemporaryCredentials = Get-AwsTemporaryCredential @GetTemporaryCredentials_Params
        # Store Temporary AWS Credentials in environment variables for Packer to access
        $Env:AWS_ACCESS_KEY_ID = $AwsTemporaryCredentials.Credentials.AccessKeyId
        $Env:AWS_SECRET_ACCESS_KEY = $AwsTemporaryCredentials.Credentials.SecretAccessKey
        $Env:AWS_SESSION_TOKEN = $AwsTemporaryCredentials.Credentials.SessionToken
        $Env:AWS_DEFAULT_REGION = $Region
        # Hashtable of credentials for parameter splatting
        $AwsCredentialParams = @{
            AccessKey    = $AwsTemporaryCredentials.Credentials.AccessKeyId
            SecretKey    = $AwsTemporaryCredentials.Credentials.SecretAccessKey
            SessionToken = $AwsTemporaryCredentials.Credentials.SessionToken
        }
        # Validate BaseOS Parameter input
        if (Get-Command Get-EC2ImageByName -ErrorAction SilentlyContinue | Out-Null) {
            $OldImageNameValues = @(Get-EC2ImageByName @AwsCredentialParams -Region $Region)
        } else {
            $OldImageNameValues = @()
        }
        
        $NewImageNameValues = @((Get-SSMLatestEC2Image @AwsCredentialParams -Region $Region -Path ami-windows-latest | Sort-Object Name).Name)
        $ValidBaseOSStrings = $OldImageNameValues
        $ValidBaseOSStrings += $NewImageNameValues 
        $ValidBaseOSStrings = $ValidBaseOSStrings -imatch 'Windows' | Sort-Object
        if ($BaseOS -notin $ValidBaseOSStrings) {
            Write-Warning "Valid Values for BaseOS are: `n$($ValidBaseOSStrings | Foreach-Object {"`n$_"})"
            Break
        }

        # Query for AMI
        if ($BaseOS -in $OldImageNameValues) {
            # Support for old images
            $AmiToPack = Get-EC2ImageByName @AwsCredentialParams -Region $Region -Name $BaseOS -ErrorAction SilentlyContinue -WarningAction SilentlyContinue
        } elseif ($BaseOS -in $NewImageNameValues) {
            $AmiToPack = Get-Ec2Image @AwsCredentialParams -Region $Region (Get-SSMLatestEC2Image @AwsCredentialParams -Region $Region -Path ami-windows-latest -ImageName $BaseOS)
        }

        if (-NOT $AmiToPack) {
            Write-Error "No Matching AMI Found"
            Break
        }

        $NewAMIName = "$($AccountNumber)_$($AmiToPack.Name)"
        $vpcId = (Get-EC2Vpc @AwsCredentialParams -Region $Region | Select-Object -First 1).VpcId
        $supportedAZs = (Get-EC2InstanceTypeOffering @AwsCredentialParams -Region $Region -LocationType availability-zone -Filter @{Name='instance-type'; Values=@($InstanceType)}).Location
        $subnetId = (Get-EC2Subnet @AwsCredentialParams -Region $Region | Where-Object { $_.VpcId -eq $vpcId -and $_.AvailabilityZone -in $supportedAZs } | Select-Object -First 1).SubnetId
        if (-not $subnetId) {
            Write-Error "No subnet found in an availability zone that supports instance type '$InstanceType' in region '$Region'."
            Break
        }
        if ($DoNotEncrypt) {
            $encrypt_boot = "false"
        }
        else {
            $encrypt_boot = "true"
        }

        # Build the Packer Template
        if ($BaseOS -match '2025') {
            # Windows Server 2025 removed wmic.exe which EC2Launch v2 depends on.
            # This causes EC2Launch v2 to fail at the preReady stage and skip UserData.
            # Use SSM Run Command after Packer launches the instance to install WMIC
            # and trigger sysprep directly, bypassing UserData entirely.
            $PackerBuildId = [guid]::NewGuid().ToString()
            $builders = [PSCustomObject]@{
                type                  = "amazon-ebs"
                communicator          = "none"
                disable_stop_instance = "true"
                encrypt_boot          = $encrypt_boot
                region                = $Region
                Vpc_Id                = $vpcId
                Subnet_Id             = $subnetId
                instance_type         = $InstanceType
                source_ami            = $AmiToPack.ImageId
                ami_name              = $NewAMIName
                run_tags              = [PSCustomObject]@{
                    PackerBuildId = $PackerBuildId
                }
                aws_polling           = [PSCustomObject]@{
                    delay_seconds = 30
                    max_attempts  = 90
                }
            }
            $PackerTemplate = [PSCustomObject]@{
                builders = @($builders)
            }
        } else {
            # Build UserData for the Packer Template
            if ($BaseOS -match '2012') {
                # UserData for EC2Config
                $UserDataFile = "$(Split-Path (Get-Module PackerBaseAMI).Path -Parent)\Private\UserDataEC2Config.xml"
            } elseif ($BaseOS -match '2016|2019') {
                # UserData for EC2Launch
                $UserDataFile = "$(Split-Path (Get-Module PackerBaseAMI).Path -Parent)\Private\UserDataEC2Launch.xml"
            } else {
                # UserData for EC2Launch V2
                $UserDataFile = "$(Split-Path (Get-Module PackerBaseAMI).Path -Parent)\Private\UserDataEC2LaunchV2.xml"
            }
            $builders = [PSCustomObject]@{
                type                  = "amazon-ebs"
                communicator          = "none"
                disable_stop_instance = "true"
                encrypt_boot          = $encrypt_boot
                region                = $Region
                Vpc_Id                = $vpcId
                Subnet_Id             = $subnetId
                instance_type         = $InstanceType
                source_ami            = $AmiToPack.ImageId
                ami_name              = $NewAMIName
                user_data_file        = $UserDataFile
            }
            $PackerTemplate = [PSCustomObject]@{
                builders = @($builders)
            }
        }

        # Export the Packer Template to a JSON file
        $PackerTemplate | ConvertTo-Json -Depth 10 | Out-File $OutputDirectoryPath\temptemplate.json -Encoding default -Force
        $PackerTemplateJsonFilePath = (Get-Item $OutputDirectoryPath\temptemplate.json).FullName

        # Find Packer Executable
        $PackerExecutable = (Get-PackerExecutable).FullName
        # Load amazon-ebs plugin
        $PackerArgs = "plugins install `"github.com/hashicorp/amazon`""
        Write-Output "Installing Packer amazon plugin..."
        $PackerPluginProcess = Start-Process -FilePath $PackerExecutable `
            -ArgumentList $PackerArgs `
            -RedirectStandardOutput "$OutputDirectoryPath\PluginInstall-$RunDateTime-Log.txt" `
            -RedirectStandardError "$OutputDirectoryPath\PluginInstall-$RunDateTime-Errors.txt" `
            -PassThru -WindowStyle Hidden;
        $PackerPluginProcess | Wait-Process

        # Run Packer
        Write-Output "Starting Packer Process using Template: $PackerTemplateJsonFilePath"
        if ($debugMode) {
            Write-Output "Debug Mode Enabled"
            $PackerArgs = "build -debug $PackerTemplateJsonFilePath"
            $PackerProcess = Start-Process -FilePath $PackerExecutable `
            -ArgumentList $PackerArgs;
        } else {
            $PackerArgs = "build $PackerTemplateJsonFilePath"
            $PackerProcess = Start-Process -FilePath $PackerExecutable `
            -ArgumentList $PackerArgs `
            -RedirectStandardOutput "$OutputDirectoryPath\$NewAMIName-$RunDateTime-Log.txt" `
            -RedirectStandardError "$OutputDirectoryPath\$NewAMIName-$RunDateTime-Errors.txt" `
            -PassThru -WindowStyle Hidden;
        }
        
        Write-Output "Packer Process ID: $($PackerProcess.Id)"
        Write-Output "Logfiles will be prefixed with $NewAMIName-$RunDateTime and located in $((Get-Item $OutputDirectoryPath).FullName)"

        if ($BaseOS -match '2025') {
            # Windows Server 2025: EC2Launch v2 fails at preReady because wmic.exe was removed.
            # The installEgpuManager task uses wmic.exe to check for Elastic Graphics support.
            # Installing WMIC is impractical (requires Windows Update or FoD ISO not available on EC2).
            # Instead, we remove the broken task from the EC2Launch v2 config via SSM, then sysprep.
            # This fix persists in the AMI so instances launched from it won't hit the same issue.
            Write-Output "Windows Server 2025 detected. Will patch EC2Launch v2 config and run sysprep via SSM..."

            # Wait for the Packer instance to launch and find it by the build tag
            Write-Output "Waiting for Packer instance to launch..."
            $instanceId = $null
            $ssmTimeout = (Get-Date).AddMinutes(5)
            while (-not $instanceId -and (Get-Date) -lt $ssmTimeout) {
                Start-Sleep -Seconds 10
                $reservation = Get-EC2Instance @AwsCredentialParams -Region $Region -Filter @(
                    @{Name = "tag:PackerBuildId"; Values = @($PackerBuildId)},
                    @{Name = "instance-state-name"; Values = @("running")}
                )
                if ($reservation.Instances) {
                    $instanceId = $reservation.Instances[0].InstanceId
                }
            }

            if (-not $instanceId) {
                Write-Warning "Could not find Packer instance within timeout. Check Packer logs for errors."
                return
            }
            Write-Output "Found Packer instance: $instanceId"

            # Wait for SSM Agent to come online
            Write-Output "Waiting for SSM Agent to register..."
            $ssmReady = $false
            $ssmTimeout = (Get-Date).AddMinutes(5)
            while (-not $ssmReady -and (Get-Date) -lt $ssmTimeout) {
                Start-Sleep -Seconds 15
                try {
                    $ssmInfo = Get-SSMInstanceInformation @AwsCredentialParams -Region $Region `
                        -InstanceInformationFilterList @{Key = "InstanceIds"; ValueSet = @($instanceId)}
                    if ($ssmInfo -and $ssmInfo.PingStatus -eq "Online") {
                        $ssmReady = $true
                    }
                } catch {
                    # SSM not ready yet, retry
                }
            }

            if (-not $ssmReady) {
                Write-Warning "SSM Agent did not come online within timeout. Check instance: $instanceId"
                return
            }
            Write-Output "SSM Agent online. Patching EC2Launch v2 config and running sysprep..."

            # Send SSM Run Command to remove the installEgpuManager task and trigger sysprep
            $ssmCommand = Send-SSMCommand @AwsCredentialParams -Region $Region `
                -InstanceId @($instanceId) `
                -DocumentName "AWS-RunPowerShellScript" `
                -Parameter @{
                    commands = @(
                        "Start-Transcript -Path 'C:\ProgramData\Amazon\EC2Launch\log\PackerBaseAMI-SSM.log' -Force",
                        "Write-Output 'Patching EC2Launch v2 config to remove installEgpuManager task (requires wmic.exe removed in Server 2025)...'",
                        "`$configPath = 'C:\ProgramData\Amazon\EC2Launch\config\agent-config.yml'",
                        "`$config = Get-Content -Path `$configPath -Raw",
                        "Write-Output `"Original config length: `$(`$config.Length) characters`"",
                        "`$config = `$config -replace '(?m)^\s*-\s*task:\s*installEgpuManager.*(\r?\n)', ''",
                        "Set-Content -Path `$configPath -Value `$config -Force",
                        "Write-Output 'installEgpuManager task removed from EC2Launch v2 config.'",
                        "Write-Output 'Running EC2Launch v2 sysprep with shutdown...'",
                        "Stop-Transcript",
                        "& 'C:\Program Files\Amazon\EC2Launch\ec2launch.exe' sysprep --shutdown=true"
                    )
                }

            Write-Output "SSM Command sent (ID: $($ssmCommand.CommandId))."
            Write-Output "Transcript log on instance: C:\ProgramData\Amazon\EC2Launch\log\PackerBaseAMI-SSM.log"
            Write-Output "Packer (PID: $($PackerProcess.Id)) is waiting for shutdown, then will create the AMI."
        }

        Write-Output "This process will take roughly 20 minutes to complete. 10 minutes if you chose not to encrypt."
    }
    End {

    }
}