Difference between UserData and cfn-helper with CloudFormation AWS

Question

Difference between UserData and cfn-helper with CloudFormation AWS

562 views Asked by giò At 26 December 2024 at 20:15

I am starting to use CloudFormation for orchestration/provisioning and I see there are two ways to install packages:

First way is with a bash script in userdata section, example:

"UserData": {
          "Fn::Base64": {
            "Fn::Join": [
              "\n",
              [
                "#!/bin/bash",
                "apt-get update",
                "apt-get upgrade -y",
                "apt-get install apache2 -y",
                "echo \"<html><body><h1>Welcome</h1>\" > /var/www/index.html",

Another way is to use cfn-init:

"UserData"       : { "Fn::Base64" : { "Fn::Join" : ["", [
             "yum update -y aws-cfn-bootstrap\n",

             "# Install the files and packages from the metadata\n",
             "/opt/aws/bin/cfn-init -v ",
             "         --stack ", { "Ref" : "AWS::StackName" },
             "         --resource WebServerInstance ",
             "         --configsets Install ",
             "         --region ", { "Ref" : "AWS::Region" }, "\n"
        ]]}}

Is there any reasons to use cfn-init and not bash in UserData?

Original Q&A

There are 1 answers

**Souvik Sarkhel** · Answer 1 · 2015-08-26 06:58:58

Actually it makes no difference if you use bash in UserData or cfn-init. But to use cnf-init you need to install the package aws-cfn-bootstrap as you have already done and also need to define

"Resources": {
  "MyInstance": {
    "Type": "AWS::EC2::Instance",
    "Metadata" : {
      "AWS::CloudFormation::Init" : {
        "config" : {
          "packages" : {
            :
          },
          "groups" : {
            :
          },
          "users" : {
            :
          },
          "sources" : {
            :
          },
          "files" : {
            :
          },
          "commands" : {
            :
          },
          "services" : {
            :
          }
        }
      }
    },
    "Properties": {
      :
    }
  }
}

cfn-init is like a clean way to get things done instead of you needing to do yum install in bash of UserData though you will get the same outcome from both the methods.

TechQA.

Difference between UserData and cfn-helper with CloudFormation AWS

There are 1 answers

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