Start cfn-init in Ubuntu instance with cloudformation (yaml)

Question

I try to start the cfn-init with:

Fn::Base64: !Sub | 
  #!/bin/bash
  sudo apt-get -y install python-setuptools
  mkdir aws-cfn-bootstrap-latest
  curl https://s3.amazonaws.com/cloudformation-examples/aws-cfn-bootstrap-latest.tar.gz | tar xz -C aws-cfn-bootstrap-latest --strip-components 1
  sudo easy_install aws-cfn-bootstrap-latest
  sudo /usr/local/bin/cfn-init --stack !Ref 'AWS::StackName' --resource xxx --region !Ref 'AWS::Region'

The first steps work. I can access the instance and cfn-init is installed. When I execute the cfn-init --stack.. command inside my ec2 instance it works fine when I hardcode the values for stackname and region.

How to make it work in the yaml script? It seems it can not read the values for StackName and region.

Subscription

Answer 1

If you are using !Sub you need to wrap your variables with ${} instead of using !Ref

Try this

Fn::Base64: !Sub | 
  #!/bin/bash
  sudo apt-get -y install python-setuptools
  mkdir aws-cfn-bootstrap-latest
  curl https://s3.amazonaws.com/cloudformation-examples/aws-cfn-bootstrap-latest.tar.gz | tar xz -C aws-cfn-bootstrap-latest --strip-components 1
  sudo easy_install aws-cfn-bootstrap-latest
  sudo /usr/local/bin/cfn-init --stack ${AWS::StackName} --resource xxx --region ${AWS::Region}

If you specify template parameter names or resource logical IDs, such as ${InstanceTypeParameter}, AWS CloudFormation returns the same values as if you used the Ref intrinsic function. If you specify resource attributes, such as ${MyInstance.PublicIp}, AWS CloudFormation returns the same values as if you used the Fn::GetAtt intrinsic function.

For more details check AWS - Fn::Sub

Kitchen

I tried with ubuntu. didn'\t work. any solution? – Selfseeking

Answer 2

This worked for me:

        UserData:
          Fn::Base64: !Sub |
            #!/bin/bash

            sudo apt-get install -y build-essential python3-pip
            sudo pip3 install https://s3.amazonaws.com/cloudformation-examples/aws-cfn-bootstrap-py3-latest.tar.gz

Filmer

Answer 3

Amazon published a few different example scripts to do this on various different operating systems.

Original question about installing helper scripts on Ubuntu: https://repost.aws/knowledge-center/install-cloudformation-scripts

Direct link to Ubuntu templates: https://github.com/awslabs/aws-cloudformation-templates/tree/master/aws/solutions/OperatingSystems

Keyser

Answer 4

Fn::Base64: !Sub | 
  #!/bin/bash
  sudo apt-get -y install python-setuptools
  mkdir aws-cfn-bootstrap-latest
  curl https://s3.amazonaws.com/cloudformation-examples/aws-cfn-bootstrap-latest.tar.gz | tar xz -C aws-cfn-bootstrap-latest --strip-components 1
  sudo easy_install aws-cfn-bootstrap-latest
  sudo /usr/local/bin/cfn-init --stack ${AWS::StackName} --resource xxx --region ${AWS::Region}

IF easy_install didn't work for ubuntu 18.04 then use this following command:

python /usr/lib/python2.7/dist-packages/easy_install.py aws-cfn-bootstrap-latest

Shock

Answer 5

If the easy_install command not found then try this it works for me

"UserData": {
  "Fn::Base64": { "Fn::Join":["", [
    "#!/bin/bash\n",
    "apt-get update\n",
    "apt-get install -y python-setuptools\n",
    "mkdir -p /opt/aws/bin\n",
    "apt-get install -y wget\n",
    "wget https://s3.amazonaws.com/cloudformation-examples/aws-cfn-bootstrap-py3-latest.tar.gz\n",
    "python3 -m easy_install --script-dir /opt/aws/bin aws-cfn-bootstrap-py3-latest.tar.gz\n",
    "/usr/local/bin/cfn-init --stack ", { "Ref":"AWS::StackName" }, " --resource WebServer", " --region ", { "Ref": "AWS::Region" }, "\n",
    "\n",
    "/usr/local/bin/cfn-signal --exit-code $? '", { "Ref" : "WaitHandle" }, "'\n"
  ]]}
}

Strath

Answer 6

The previous solutions will not work for Ubuntu 24.04 LTS which uses python3.12. Instead, the package aws-cfn-bootstrap (containing cfn-init etc.) can be installed using a virtual environment for python (version 11 or lower).

An example solution for the UserData section in the Cloudformation template could be as follows:

# python 3.11 virtualenv installation
add-apt-repository -y ppa:deadsnakes/ppa
apt install -y python3.11 python3-pip

# virtualenv set-up (pip binaries will use PATH=/opt/aws/virtualvenv/bin:...)
python3.11 -m pip install virtualenv
virtualenv /opt/aws/virtualvenv
source /opt/aws/virtualvenv/bin/activate

# install aws-cfn-bootstrap dependencies
pip install https://s3.amazonaws.com/cloudformation-examples/aws-cfn-bootstrap-py3-latest.tar.gz

# testing (no need to specify the path)
cfn-init -v --stack ${AWS::StackId} --resource EC2Instance --configsets full_install --region ${AWS::Region}
cfn-signal -e $? --stack ${AWS::StackId} --resource EC2Instance --region ${AWS::Region}

Trimorphism