YAML Tutorial Lecture Notes

Introduction to YAML

• YAML stands for 'YAML Ain't Markup Language'.
• It is a serialization language, similar to XML and JSON.
• Used for configuration files in DevOps tools like Docker, Kubernetes, Ansible, Prometheus, etc.
• Known for being human-readable and intuitive.

Why YAML?

• YAML is popular due to its readability and intuitive design.
• Unlike XML and JSON, YAML does not use special characters for data structures.
• Data structures in YAML are defined through line separations and spaces (indentation).

YAML Syntax Basics

Key-Value Pairs

• Simple structure of key: value.
• Strings do not need quotes unless they contain special characters.
• Comments start with #.

Data Types

• Supports strings, numbers, and booleans.
• Booleans can be expressed as true/false, yes/no, and on/off.

Objects and Indentation

• Objects are created by grouping key-value pairs.
• Indentation must be consistent within objects.
• Validators can help ensure correct indentation.

Lists

• Lists are denoted by - for each item.
• Can contain objects or simple values.
• Lists of simple values can also use square brackets [ ].

Multi-Line Strings

• Use | to keep line breaks in multi-line strings.
• Use > to fold new lines into spaces for long strings.

Example Use Cases

Kubernetes Configuration

• YAML is used for defining configurations such as pods.
• Contains metadata, specifications, containers, ports, etc.
• Lists and objects are common in Kubernetes YAML files.

Multi-Component Files

• Separate multiple components in a single YAML file using ---.

Use in Helm and Ansible

• Use placeholders with {{ }} for templating.
• Used in tools like Helm for Kubernetes.

Environment Variables

• Access using $ syntax within YAML files.

Tools and Validation

• Online validators can ensure proper YAML formatting.
• YAML can be converted to/from JSON.

Conclusion

• YAML's human-readability makes it a preferable choice for configuration files.
• It is widely used across various DevOps tools and applications.