Radish Logic - Developer Blog

How to Disable Screen Sleep in Raspberry Pi

If you have been using a Raspberry Pi, you might have encountered that the screen sleeps or turns off after some time when you do not use the mouse or keyboard.

The turning off of the display when there is no activity in Raspberry Pi is called Screen Blanking. By default this is enabled.

Screen Blanking or sleeping is good if you want to save power, but distracting (sometimes annoying) if you are doing something in the Raspberry Pi.

To turn this feature off you do not have to install xscreensaver, you only need to disable it in the Raspberry Pi Configuration.

Follow the steps below to disable screen sleeping of your Raspberry Pi.

Steps to disable Screen Blanking or Sleeping with the Raspberry Pi

Click on the Menu button on the upper right (Raspberry Pi Icon) >> Preferences >> Raspberry Pi Configuration.

How to access the C: Drive in Amazon Workspaces

The C: Drive or root volume in AWS Workspaces cannot be seen if you open File Explorer.

This post will show how you can access the C: Drive when it is not shown.

If you want the C: Drive to be shown permanently then reading my post about it here will help.

Below are three ways you can access the C: Drive.

Access C: Drive with Windows File Explorer

To access C: Drive with Windows File Explorer, go to the address bar and enter C:. This will bring you to the C: Drive.

How to show C: Drive in Amazon Workspaces

If you have been using AWS Workspaces then you might have noticed that the C: Drive cannot be seen when you open Windows File Explorer.

File Explorer not showing C: Drive in an Amazon Workspace

The reason why the C: Drive is hidden in Workspaces is because it is the root volume. Users are discouraged from storing files in the root volume because when you need to Rebuild a workspace any changes that you made in the C: Drive will be wiped out. Only the D: Drive or the User Volume will be restored to what its previous snapshot.

There are some use cases when you need to access the C: Drive. It might also be possible that you just want to have the C: Drive visible.

Follow the steps below to make the C: Drive visible in Windows File Explorer in your Amazon Workspaces.

Steps in showing the C: Drive in Amazon Workspaces

Click on Search icon and type regedit. Then click on regedit.

Require Multi-Factor Authentication (MFA) for IAM User in AWS

As a Security Best Practice we should always require IAM Users to have Multi-Factor Authentication (MFA) enabled when accessing the AWS Console.

The problem is how do we require users to configure MFA?

The IAM policy below can be used to require users to enable their MFA. If they do not have MFA, all their permissions will be denied. This will make access to your AWS Account more secure.

IAM Policy that requires IAM Users to have Multi-Factor Authentication (MFA)

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "AllowViewAccountInfo",
            "Effect": "Allow",
            "Action": [
                "iam:ListUsers",
                "iam:ListMFADevices",
                "iam:GetAccountPasswordPolicy",
                "iam:GetAccountSummary"
            ],
            "Resource": "*"
        },
        {
            "Sid": "AllowChangeOwnPasswordsOnFirstLogin",
            "Effect": "Allow",
            "Action": [
                "iam:ChangePassword",
                "iam:GetUser"
            ],
            "Resource": "arn:aws:iam::*:user/${aws:username}"
        },
        {
            "Sid": "AllowChangeOwnPasswordsAfterMFAEnabled",
            "Effect": "Allow",
            "Action": [
                "iam:GetLoginProfile",
                "iam:UpdateLoginProfile"
            ],
            "Resource": "arn:aws:iam::*:user/${aws:username}"
        },
        {
            "Sid": "AllowManageOwnVirtualMFADevice",
            "Effect": "Allow",
            "Action": [
                "iam:CreateVirtualMFADevice",
                "iam:DeleteVirtualMFADevice"
            ],
            "Resource": "arn:aws:iam::*:mfa/${aws:username}"
        },
        {
            "Sid": "AllowManageOwnUserMFA",
            "Effect": "Allow",
            "Action": [
                "iam:DeactivateMFADevice",
                "iam:EnableMFADevice",
                "iam:ListMFADevices",
                "iam:ResyncMFADevice"
            ],
            "Resource": "arn:aws:iam::*:user/${aws:username}"
        },
        {
            "Sid": "DenyAllExceptListedIfNoMFA",
            "Effect": "Deny",
            "NotAction": [
                "iam:ListUsers",
                "iam:ListMFADevices",
                "iam:ChangePassword",
                "iam:GetUser",
                "iam:CreateVirtualMFADevice",
                "iam:DeleteVirtualMFADevice",
                "iam:DeactivateMFADevice",
                "iam:EnableMFADevice",
                "iam:ListMFADevices",
                "iam:ResyncMFADevice"
            ],
            "Resource": "*",
            "Condition": {
                "BoolIfExists": {
                    "aws:MultiFactorAuthPresent": "false"
                }
            }
        }
    ],
    "Id": "RadishLogic.com MFA Required IAM Policy"
}

The name of my IAM Policy is MFA-Required, you may use whatever name you desire to use.

CloudFormation: How to solve Circular Dependency between an Elastic IP and an EC2 Instance

When writing a CloudFormation Template that needs to use the value of an Elastic IP to a file inside an EC2 Instance, you will most likely encounter a Circular dependency between resources error.

I encountered this when configuring OpenSwan IPSec VPN in CloudFormation.

You can try the CloudFormation template below to see the error above.

CloudFormation Template with Circular Dependency Error

Parameters:
  AmazonLinux2AMIID:
    Type: AWS::SSM::Parameter::Value<AWS::EC2::Image::Id>
    Default: /aws/service/ami-amazon-linux-latest/amzn2-ami-hvm-x86_64-gp2

  KeyName:
    Type: AWS::EC2::KeyPair::KeyName

Resources:
  ElasticIP:
    Type: 'AWS::EC2::EIP'
    Properties:
      Domain: vpc
      InstanceId: !Ref EC2Instance
  
  EC2Instance:
    Type: AWS::EC2::Instance
    Properties: 
      ImageId: !Ref AmazonLinux2AMIID
      InstanceType: t2.micro
      KeyName: !Ref KeyName
      UserData: 
        Fn::Base64:
          !Sub |
            #!/bin/bash -ex
            echo "${ElasticIP}" >> /EIPAddress.txt

How to install ChefDK in Amazon Linux 2

The ChefDK is a package that includes everything you need to start using Chef. You will need this if you want to develop using chef.

Since I always use Amazon Web Services (AWS) EC2, I tend to choose Amazon Linux 2 even for projects using Chef.

Below is a step-by-step tutorial on how to install ChefDK in an EC2 instance running Amazon Linux 2.

Installation via shell commands

SSH to your Amazon Linux 2 EC2 Instance and run the command below.

curl https://omnitruck.chef.io/install.sh | sudo bash -s -- -c current -P chefdk

This will install the latest version of ChefDK.

For production systems we should specify the specific version of ChefDK or else this will install the version. To do this we need to add the -v option in the end of the command.

Below is an example where we install ChefDK version 4.7.73.

curl https://omnitruck.chef.io/install.sh | sudo bash -s -- -c current -P chefdk -v 4.7.73

Next is to check if chef was installed properly. Go to the Verification section of this post.

Installation via ChefDK Download Page

Go to https://downloads.chef.io/chefdk.

You may select your desired version for ChefDK. Default is the latest stable version.

Copy the URL for the latest version of Red Hat Enterprise Linux.

How to install Active Directory Administration Tools in Windows Server

If you need Active Directory Users and Computers on your Windows Server, you need to install Active Directory Administration Tools.

The walk through below will also install other AD Administration Tools like DNS configuration and optional if you want to install Group Policy Management.

Tutorial below have been tested in Windows Server 2016, Windows Server 2019 and Amazon Workspaces Windows 10.

I learned the steps below when I was configuring Amazon Workspaces Windows 10 to do Active Directory Administration. I was avoiding to RDP to the AD Domain Controller to lessen the impact when I make adjustments that is why I needed the Active Directory Management Tools inside my Amazon Workspace.

Note: It is best if your Windows Server is already joined to an Active Directory Domain.

Step-by-step Instruction to Install Active Directory Administration Tools

Click on Start Menu and click Server Manager.

On Server Manager click Add roles and features.

EC2 with IAM Role: CloudFormation Sample Template

Creating an EC2 Instance with an IAM Role is easy when you do it via the AWS Console but doing this with CloudFormation is not as direct. You will need an Instance Profile to connect an EC2 with an IAM Role.

TL;DR: See the CloudFormation Template below.

How to get the AWS Account ID in Lambda Python

There are use cases where the need to get the AWS Account ID of the Lambda Function during runtime is required. I thought it was easy as getting the AWS Region but it was not. Luckily there is a way to get it, use the step-by-step instructions below.

To get the AWS Account ID where the Lambda Function is running use the code below.

def lambda_handler(event, context):

    aws_account_id = context.invoked_function_arn.split(":")[4]

    print(aws_account_id)

How does the code work?

The context object that is being passed to the lambda_handler function provides different methods and properties about the lambda function, like invocation and execution environment.