AWS Tools for Powershell Get-EC2Instance Filter

Question

Is it possible to filter EC2 Instances by machine hostname? I am trying to find an internal instance but I don't have the IP address or the instanceId. I can't find any examples but I am thinking something this.

$instanceName = "MYMACHINEHOSTNAME"
$filter = New-Object Amazon.EC2.Model.Filter
$filter.Name = "Hostname"
$filter.Value = "$instanceName"
$ec2Instances = (Get-EC2Instance -Region us-west-2 -Filter $filter).Instances

Has anyone done anything like this?

Thanks,

Rhonda

Anthony Neace · Accepted Answer · 2017-07-12 20:43:17Z

Get-EC2Instance doesn't know about OS-level details like that, but you might be able to get what you want from Get-EC2ConsoleOutput. This will output the system log, and I believe that by default, Amazon-owned Windows AMIs RDPCERTIFICATE-SUBJECTNAME will usually match the windows hostname.

Give this a try, I just wrote it to print a collection of InstanceId, Windows Hostname pairs for this case of EC2 Instances based on Amazon-owned Windows AMIs:

# Note: This is designed to work with default Windows AMIs that Amazon supplies.
function Get-EC2InstanceWindowsHostNames
{   
  # Filter to use only windows instances
  $instanceIds = (Get-EC2Instance -Filter @(@{name="platform";value="windows"})).Instances.InstanceId

  $instanceIds | % {    
    $consoleOutput = Get-EC2ConsoleOutput -InstanceId $_

    # Convert from Base 64 string
    $bytes = [System.Convert]::FromBase64String($consoleOutput.Output)
    $string = [System.Text.Encoding]::UTF8.GetString($bytes)

    # If the string contains RDPCERTIFICATE-SUBJECTNAME, we can extract the hostname
    if($string -match 'RDPCERTIFICATE-SUBJECTNAME: .*') {
      $windowsHostName = $matches[0] -replace 'RDPCERTIFICATE-SUBJECTNAME: '

      # Write resulting obj to stdout
      [pscustomobject]@{InstanceID=$($consoleOutput.InstanceId);HostName=$($windowsHostName.Trim())}
    }
  }
}

Example output

InstanceID          HostName
----------          --------
i-abcdefgh          EC2AMAZ-ABCDE
i-12345678          WIN-1ABCD2EFG

Filtering

From there, you can simply match the output of that cmdlet to filter for your hostname:

@(Get-EC2InstanceWindowsHostNames) | ? { $_.HostName -eq 'WIN-1ABCD2EFG' }

Example output

InstanceID HostName
---------- --------
i-12345678 WIN-1ABCD2EFG

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