YAML Fundamentals

Learning objectives#

• Write maps, lists and nested structures
• Use multi-line strings
• Avoid indentation and type pitfalls
• Validate YAML

Explanation#

YAML uses key: value pairs. Indentation (spaces only, never tabs) shows nesting.

Lists use a dash per item, or inline [a, b].

Multi-line strings: | keeps line breaks (scripts), > folds them into spaces.

Watch types: yes/no and on/off can be read as booleans by some parsers; quote version numbers like "3.10" so they are not treated as numbers.

Code example: One file, all the basics#

1app:
2  name: shop-api
3  replicas: 3
4  version: "1.10"          # quoted: stays a string, not 1.1
5  features:
6    - search
7    - payments
8  env: { ASPNETCORE_ENVIRONMENT: Production, LOG_LEVEL: Information }
9  startup_script: |
10    dotnet ef database update
11    dotnet Shop.Api.dll
12  description: >
13    This long text is folded
14    into a single line.

{ "app": { "name": "shop-api", "replicas": 3, "version": "1.10",
  "features": ["search", "payments"],
  "env": { "ASPNETCORE_ENVIRONMENT": "Production", "LOG_LEVEL": "Information" },
  "startup_script": "dotnet ef database update\ndotnet Shop.Api.dll\n",
  "description": "This long text is folded into a single line.\n" } }

This example is illustrative. Copy or download it and run it in your own environment; the expected output is shown above.

Step-by-step explanation#

1. Two-space indentation nests keys under app.
2. Dashes create a list.
3. Inline braces create a map on one line.
4. | keeps lines; > folds them.

Real-world use case#

Common mistakes#

Best practices#

• Two spaces per level
• Quote ambiguous values
• Validate with yamllint or your editor
• Keep files short; split when large

Remember this#

Practice exercise#

1regions:
2  - centralindia
3  - southindia
4  - westeurope

Mini quiz#

Want more? Practise all DevOps MCQs · DevOps interview questions

Related topics#

My notes#

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