The SysAdmin's Water Cooler: PowerShell

In order to reduce costs of running test and dev EC2 instances at Amazon I've created a simple script that will run and start or stop an instance based on a schedule. This script is a PowerShell script that relies on the AWS modules to be installed ("Import-Module AWSPowerShell") Refer to the link to Configure PowerShell for AWS (FYI - configure your default profile using AWS access keys as required)

The script is looking for a tag, 'RunningSchedule' and parsing the value that is set within, which is in a format similar to a cron like style using 24 hour clock : H:H:D or H:H:D-D (I didn’t include a minutes field)

First 'H' = Start time Hour

Second 'H' = Stop time Hour

'D' is for day(s) to run, 1 = Monday, 2=Tues, etc. So if you want it to run Mon-Fri, enter 1-5

To disable the schedule completely, use ‘Disabled’ for the value.

Example, to have the server start at 8am, stop at 5pm, and run Mon-Fri use: 8:17:1-5
To have the server run from 10am to 3pm on Wed use: 10:15:3

The script will then either start or stop the server based on the schedule.

It will then send an email with the servers listed that were either started or stopped.

To schedule the script itself, I configured a scheduled task in Windows on a server. Simply run a program "Powershell", path is 'C:\Windows\SysWOW64\WindowsPowerShell\v1.0\powershell.exe'
Include the optional arguments for the path to your script: 'C:\Scripts\AWS-schedule-start-stop-instances.ps1'

Here is the script:

Initialize-awsdefaults

Import-Module AWSPowerShell

#Create arrays
$instanceStart = @()
$instanceStop = @()

$fromEmail = "youremail@domain.com"
$Recipients  = "toemail@domain.com"
$emailserver = "emailserver"

#create filter to limit search on instances only
$filter = New-Object amazon.EC2.Model.Filter
$filter.Name = "resource-type"
$filter.Value = "instance"

#create filter based on tag=RunningSchedule
$filterType = New-Object amazon.EC2.Model.Filter
$filterType.Name = "tag:RunningSchedule"
$filterType.Value = "*"

#join the two filters together
$filter = @($filter,$filterType)

#retrieve the instances based on the filter parameters
$instances = Get-EC2Tag -Filter $filter

#set now date and day of week
$now = Get-Date
$dow = Get-Date -UFormat %u

#cycle through each instance found
foreach($instance in $instances){
    #reset variable to false for each instance through loop
    $startstopInstance = $false
   
    #Get current instance state,  either Running or Stopped
    $state = Get-EC2InstanceStatus -InstanceIds $instance.ResourceId
    $state = $state.InstanceState.Name
   
   #get schedule value
    $schedule = $instance.Value
    $schedule = $schedule.ToLower()
    if ($schedule -eq "disabled"){
    #if disabled then do nothing!
    Write-Host "Disabled schedule"
    }else{
       
       
    #Get Schedule from instance Tag Value, parse the values
    $schedule = $instance.Value -split ':'
    $start = [INT]$schedule[0]
    $stop = [INT]$schedule[1]
    $days = $schedule[2]
       
    #check if multiple days are set to run machine
    if ($days.Length -gt 1){
        $days = $days -split '-'
            #check if current day is between scheduled days, if so set variable to True
            if($dow -ge $days[0] -and $dow -le $days[1]){
            $startstopInstance = $true
            }
    }else{
        #check if current day is equal to scheduled day, if so set variable to True
        if($dow -eq $days){
        $startstopInstance = $true
        }
    }

    if ($startstopInstance -eq $true){
       #check start/stop times, if Start is less than Stop, machine running normal hours, ie; 3am-10pm
      if ($start -lt $stop){
            if ($now.Hour -ge $start -and $now.Hour -le $stop -and $state -ne "running"){
                Start-EC2Instance -InstanceIds $instance.ResourceId
                $instanceStart += $instance.ResourceId
            }elseif(($now.Hour -le $start -or $now.Hour -ge $stop) -and $state -eq "running"){
                Stop-EC2Instance -Instance $instance.ResourceId
                $instanceStop += $instance.ResourceId
            }
       
        #If Start is greater than Stop, therefore machine is running middle of night,ie: 10pm-3am
        }else{
            if ($now.Hour -in $stop..$start -and $state -eq "running"){
                Stop-EC2Instance -Instance $instance.ResourceId
                $instanceStop += $instance.ResourceId
            }elseif($now.Hour -notin $stop..$start -and $state -ne "running"){
                Start-EC2Instance -InstanceIds $instance.ResourceId
                $instanceStart += $instance.ResourceId
            }       
        }
    }
    }
}

#Email list of instances Started and Stopped
#this will list the instances by instance ID that were started or stopped on this run
if ($instanceStart.Count -gt 0 -or $instanceStop.Count -gt 0){

$body = "
The following servers at Amazon have been affected by the automated schedule:
"
if ($instanceStart.Count -gt 0){
$body = $body + "
Servers Started"
 foreach($instance in $instanceStart){
      $filterNameTag = New-Object amazon.EC2.Model.Filter
    $filterNameTag.Name = "tag:Name"
    $filterNameTag.Value = "*"

    $filterNameID = New-Object amazon.EC2.Model.Filter
    $filterNameID.Name = "resource-id"
    $filterNameID.Value = $instance
   

    $filterNameType = New-Object amazon.EC2.Model.Filter
    $filterNameType.Name = "resource-type"
    $filterNameType.Value = "instance"
   
    $filterName = @($filterNameTag,$filterNameID,$filterNameType)
   
    $name = Get-EC2Tag -Filters $filterName

 $body = $body +
"
    " + $name.Value + "(" + $instance +")"
}
}

if ($instanceStop.Count -gt 0){
$body = $body + "

Servers Stopped"
foreach($instance in $instanceStop){
     $filterNameTag = New-Object amazon.EC2.Model.Filter
    $filterNameTag.Name = "tag:Name"
    $filterNameTag.Value = "*"

    $filterNameID = New-Object amazon.EC2.Model.Filter
    $filterNameID.Name = "resource-id"
    $filterNameID.Value = $instance
   
    $filterNameType = New-Object amazon.EC2.Model.Filter
    $filterNameType.Name = "resource-type"
    $filterNameType.Value = "instance"
   
    $filterName = @($filterNameTag,$filterNameID,$filterNameType)
   
    $name = Get-EC2Tag -Filters $filterName

 $body = $body +
"
    " + $name.Value + "(" + $instance +")"

}
}


$subject = "AWS - server start/stop"

send-mailmessage -from $fromEmail -to $Recipients -Subject $subject -body $body  -smtpserver $mailserver

}

It's been a while since I've posted anything here, and I need to get back into the habit of adding to this blog as issues arise.

When trying to remotely run a PowerShell script you may find that you need local administrator access to the remote computer to successfully run the script. If not properly configured, you will receive an access denied message. A simple fix would be to add the user running the script to the local Administrators group, but we don't necessarily want to grant them this level of access.

If you haven't already done so, you must enable PowerShell remoting. This is done by running this command in PowerShell: Enable-PSRemoting on the remote computer. For more info on this command go to this technet link: Enable PSRemoting

Next you need to run this PowerShell command:
Set-PSSessionConfiguration -Name Microsoft.PowerShell -showSecurityDescriptorUI

Confirm that you want to perform this, it will then open a window allowing you to add users/groups with the appropriate permissions. You should now be able to remotely run your PowerShell scripts.

Note: This can impose security risks to your system, so please use this at your own discretion.

For additional information you may reference this page: PowerShell Blog

The SysAdmin's Water Cooler

Friday, September 5, 2014

AWS - Auto schedule EC2 instance to start/stop

Tuesday, March 5, 2013

Access Denied when executing remote powershell