> ## Content Index > Fetch the complete content index at: https://linuxhandbook.com/llms.txt > Use this file to discover other available public pages before exploring further. # YAML Basics Every DevOps Engineer Must Know - URL: https://linuxhandbook.com/yaml-basics/ - Published: 2020-11-05T14:31:14.000Z - Updated: 2025-05-31T12:34:58.000Z - Description: As a DevOps engineer, you'll be dealing with YAML files a lot. It is always a good idea to understand the basic YAML syntax. - Author: Rakesh Jain - Tags: Tips, DevOps YAML has gained a lot of popularity over the last few years as it became part of crucial DevOps tools, technologies and processes such as Ansible, [Kubernetes](https://kubernetes.io/?ref=linuxhandbook.com), CI/CD pipelines and so on. We have already covered lots of [tutorials on Ansible](https://linuxhandbook.com/tag/ansible/) and [Kubernetes](https://linuxhandbook.com/tag/kubernetes/). I thought of covering YAML essentials so that you must be aware for a smoother working with your DevOps tools configuration. ## What is YAML? [YAML](https://yaml.org/?ref=linuxhandbook.com) stands for *"YAML Ain't Markup Language"* originally was an acronym for 'Yet Another Markup Language'. YAML is a “data serialization” language and basically a human-readable structured data format. It is designed to be read and write friendly. The object serialization feature of YAML presents itself as a practicable alternative to [JSON](https://www.json.org/json-en.html?ref=linuxhandbook.com). YAML is a superset of JSON with the use of indentation-based scoping to denote the structure like Python. Here's a sample YAML example: ``` --- Student-ID: 314159 First-Name: Linus Last-Name: Torvalds Phone-numbers: - 281.555.7777 - 832.676.8888 - 937.996.9999 Addresses: - Street: 123 Main St. - City: Houston - State: Tx --- ``` ## **YAML basic rules you should always remember** If you don't want to see repeated errors while [parsing your YAML file](https://linuxhandbook.com/tools/yaml-validator/), you must always keep the following in your mind while working on YAML: - Tabs are NOT allowed in YAML. You should use space for indention. - Though the amount of space doesn't matter as long as the child node indentation is more than the parent, it is a good practice to keep the same number of spaces. - There must be space between different elements of YAML (explained later). - YAML is case-sensitive. - YAML file should end with extensions like `.yaml` or `.yml`. - YAML allows UTF-8, UTF-16 and UTF-32 encoding. Let's understand the YAML syntax now. ## **Elements of a YAML file: Basic syntax** A YAML file is used to describe data. In a YAML file the content is all about a **collection of key-value pairs** where the value can be anything ranging from a string to a tree. Let us understand it by an example. This is a Kubernetes service manifest file. ``` kind: Service metadata: name: web-app-svc spec: type: NodePort ports: - port: 8080 #service port targetPort: 8080 #Pod Port nodePort: 30012 #Node Port from the range - 30000-32767 selector: app: web-app ``` It's self explainable that it's a set of key value pair elements: `Name: Value`. As you can see from the file above, a YAML file is constructed of a number of different elements. Together, they can be used to describe a wide variety of structures. ### 1\. Spaces or indentation In YAML, you indent with whitespace, not tabs. And there MUST be a space between elements. Correct specification: ``` Kind: Service ``` Incorrect specification: ``` Kind:Service ``` Because there is no space after the colon in the above statement! ### 2\. Comments in YAML [Comments in YAML](https://linuxhandbook.com/yaml-comments/) can be defined by placing a hash in front of an item '`#`'. Comments can be made at the start of a line of anywhere in the line. Here's an example. ``` #Configuring the port ports: - port: 8080 #service port targetPort: 8080 #Pod Port nodePort: 30012 #Node Port from the range - 30000-32767 ``` As you can see, it has one single line comment and three inline comments. [How to Add Comments in YAMLNew to YAML? See how to add single-line, inline comments in YAML. Also learn about commenting out multiple lines quickly.![](https://linuxhandbook.com/content/images/size/w256h256/2021/08/Linux-Handbook-New-Logo.png)Linux HandbookSagar Sharma![](https://linuxhandbook.com/content/images/2023/01/comment-in-yaml.png)](https://linuxhandbook.com/yaml-comments/) ### 3\. Scalar (key-value) Scalars are the strings and numbers that make up the data on the page. In simple terms they are the key value pairs. ``` kind: Service metadata: name: web-app-svc ``` ### 4\. Collections & Lists List and collection elements or members are the lines that begin at the same indentation level, starting with a dash followed by a space. ``` - web-app-prod - prod-deployments - prom-monitored ``` It is a basic list with each item in the list placed in its own line with an opening dash. ### 5\. Nested collections If you want to create a nested sequence with items and sub-items, you can do so by placing a single space before each dash in the sub-items. ``` - - web-app-prod - prod-deployments - prom-monitored - - web-app-test - staging-deployments - not-monitored ``` ### 6\. Dictionaries Dictionaries comprise a `key: value` format with contents indented. ``` ports: - port: 8080 #service port targetPort: 8080 #Pod Port nodePort: 30012 #Node Port from the range - 30000-32767 ``` You can merge and mix-up collections of lists and dictionaries like this: ``` ports: - port: 8080 #service port targetPort: 8080 #Pod Port nodePort: - 30012 - 30013 - 30014 ``` These are very basic concepts of YAML but essential for a DevOps engineer. > You don't need special editor for YAML. Your favorite text editor should already be supporting YAML or use a plugin if required. There are many things you can dig deeper and learn. For that, you may always refer to [YAML's official documentation](https://yaml.org/?ref=linuxhandbook.com). And if you want, we have an [online t0ol to quickly check your YAML files for any syntax errors](https://linuxhandbook.com/tools/yaml-validator/). [Free Online YAML ValidatorA simple online tool to validate your YAML file for possible syntax errors. Paste your YML content or upload a file to validate syntax.![](https://linuxhandbook.com/content/images/icon/Linux-Handbook-New-Logo-74.png)Linux HandbookAbhishek Prakash![](https://linuxhandbook.com/content/images/thumbnail/yaml-validator-1-1.png)](https://linuxhandbook.com/tools/yaml-validator/) Want to be a better sysadmin or DevOps? Do become a Linux Handbook member today.