How to do it...

1. Create a new CloudFormation template file and add the first Resource. This is going to be our role that contains references to the managed policies, and also our Inline Policy:

      AWSTemplateFormatVersion: '2010-09-09' 
      Resources: 
        ExampleRole: 
          Type: AWS::IAM::Role 
          Properties: 
            AssumeRolePolicyDocument: 
              Version: "2012-10-17" 
              Statement: 
                - 
                  Effect: Allow 
                  Principal: 
                    Service: 
                      - ec2.amazonaws.com 
                  Action: 
                    - sts:AssumeRole 
            ManagedPolicyArns: 
              - arn:aws:iam::aws:policy/AmazonS3ReadOnlyAccess 
              - arn:aws:iam::aws:policy/AmazonEC2ReadOnlyAccess 
            Path: / 
            Policies: 
              - 
                PolicyName: WriteToCloudWatchLogs 
                PolicyDocument: 
                  Version: "2012-10-17" 
                  Statement: 
                    - 
                      Effect: Allow 
                      Action: 
                        - logs:CreateLogGroup 
                        - logs:CreateLogStream 
                        - logs:PutLogEvents 
                        - logs:DescribeLogStreams 
                      Resource: "*"

2. We now need to create an InstanceProfile resource. A profile encapsulates a single IAM role and, roughly speaking, that's all it's used for. A profile can contain only a single IAM role, so it's not clear why AWS has built this extra layer of abstraction; presumably they have plans to give profiles of other properties aside from roles:

      ExampleInstanceProfile: 
        Type: AWS::IAM::InstanceProfile 
        Properties: 
          Roles: 
            - !Ref ExampleRole 
          Path: /

3. For convenience, we'll add some Outputs that will provide the profile name and ARN to us after the stack is created:

      Outputs: 
        ExampleInstanceProfile: 
          Value: !Ref ExampleInstanceProfile 
        ExampleInstanceProfileArn: 
          Value: !GetAtt ExampleInstanceProfile.Arn

4. You can now create your instance role CloudFormation web console or via the CLI like this:

      aws cloudformation create-stack \
        --stack-name example-instance-profile \
        --template-body file://08-creating-instance-roles.yaml \
        --capabilities CAPABILITY_IAM

This role can now be assigned to your EC2 instances. The Feeding log files in to CloudWatch logs recipe in Chapter 5, Management Tools, shows how you can define a role and assign it to an EC2 instance at launch using CloudFormation.