How to format CloudFormation Task Definition command

Question

Hi I currently have a Task Definition resource as such:

  WebServerTaskDefinition:
    Type: AWS::ECS::TaskDefinition
    Properties:
      Family: !Ref TaskDefinitionName
      NetworkMode: awsvpc
      RequiresCompatibilities: 
        - FARGATE
      Cpu: !Ref TaskDefinitionCPU
      Memory: !Ref TaskDefinitionMemory
      ExecutionRoleArn: !Ref TaskDefinitionExecutionRole
      ContainerDefinitions: 
        - Name: !Ref ContainerName
          Image: !Ref ContainerImage
          Essential: true
          Cpu: 256
          EntryPoint: sh,-c
          Command: 
          PortMappings:
            - ContainerPort: !Ref ContainerPort

I would like to define ContainerDefinitions Command as

/bin/sh -c "echo '<html> <head> <title>Amazon ECS Sample App</title> <style>body {margin-top: 40px; background-color: #333;} </style> </head><body> <div style=color:white;text-align:center> <h1>Amazon ECS Sample App</h1> <h2>Congratulations!</h2> <p>Your application is now running on a container in Amazon ECS.</p> </div></body></html>' >  /usr/local/apache2/htdocs/index.html && httpd-foreground"

Any suggestions how to put it into yaml? I am getting Template Format Error if I put place the command directly in the template

Arun Kamalanathan · Accepted Answer · 2020-07-28 01:13:33Z

3

The command should be a string according to cloudformation. In YAML sytax, Quotes are required when the string contains special or reserved characters.

Strings containing any of the following characters must be quoted. Although you can use double quotes, for these characters it is more convenient to use single quotes, which avoids having to escape any backslash : :, {, }, [, ], ,, &, *, #, ?, |, -, <, >, =, !, %, @, `

you can read more about when to use the quotes in strings in the YAML documentation

So In your case, you can escape the quotes like this.

WebServerTaskDefinition:
  Type: AWS::ECS::TaskDefinition
  Properties:
    Family: !Ref TaskDefinitionName
    NetworkMode: awsvpc
    RequiresCompatibilities:
      - FARGATE
    Cpu: !Ref TaskDefinitionCPU
    Memory: !Ref TaskDefinitionMemory
    ExecutionRoleArn: !Ref TaskDefinitionExecutionRole
    ContainerDefinitions:
      - Name: !Ref ContainerName
        Command:
          - "/bin/sh -c \"echo '<html> <head> <title>Amazon ECS Sample App</title> <style>body {margin-top: 40px; background-color: #333;} </style> </head><body> <div style=color:white;text-align:center> <h1>Amazon ECS Sample App</h1> <h2>Congratulations!</h2> <p>Your application is now running on a container in Amazon ECS.</p> </div></body></html>' >  /usr/local/apache2/htdocs/index.html && httpd-foreground\""

edited Jul 28, 2020 at 1:13

answered Jul 24, 2020 at 10:20

Arun Kamalanathan

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3 Comments

Huiting Over a year ago

Million thanks it works! Does it mean the command must be in double quotes?

Arun Kamalanathan Over a year ago

Thanks. I love a million. its nothing to do with command or cloudformation. its YAML. I have updated my answer. Glad to help you

Chau Giang Over a year ago

@Arun K, your command below Command property look like a list not a string because, it starts with "-"

lexicore · Accepted Answer · 2020-07-26 13:17:56Z

1

See https://yaml-multiline.info/.

In this case the best would be using |-. For example:

example: |-\n
··Several lines of text,\n
··with some "quotes" of various 'types',\n
··and also a blank line:\n
··\n
··plus another line at the end.\n
··\n
··\n

answered Jul 26, 2020 at 13:17

lexicore

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