Note_Tech

All technological notes.

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Kubernetes - YAML File

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• Kubernetes - YAML File
  • Vim
  • YAML
  • Basic Syntax
  • Common Data Structure
    • Scalar - Strings, numbers, boolean, …
    • Mapping - Maps/Dictionaries
    • Sequences - Arrays/Lists
    • Advanced
  • Yaml File in Kubernetes

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Vim

Shortcut	Action
:set nu	Show Line Numbers
V + >	Indent visually selected lines
>>	Indent current line
<<	Outdent current line
5>>	Indent the next 5 lines
=	Auto-align selected lines

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YAML

• YAML / yet another markup language / YAML ain't markup language
  • a human-readable data serialization language that is often used for writing configuration files.

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Basic Syntax

• case sensitive
• extension: .yaml / .yml
• Indentation:
  • whitespace
  • No tabs
• Comments: #
• start marker: 3 hyphens ---
  • signal the beginning of a new YAML document within a single file or stream.

---
# document 1
codename: YAML
name: YAML ain't markup language
release: 2001
---
# document 2
uses:
  - configuration language
  - data persistence
  - internet messaging
  - cross-language data sharing
---
# document 3
company: spacelift
domain:
  - devops
  - devsecops
tutorial:
  - name: yaml
  - type: awesome
  - rank: 1
  - born: 2001
author: omkarbirade
published: true

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Common Data Structure

Scalar - Strings, numbers, boolean, …

• scalar
  • literals Unicode characters.
  • can be strings, numbers, boolean, etc.
• Folding Strings: >
  • interpreted without the new line characters

message: >
  even though
  it looks like
  this is a multiline message,
  it is actually not

# ==
message: "even though it looks like this is a multiline message,it is actually not"

• Block strings: |
  • interpreted with the new lines (\n)

message: |
  this is
  a real multiline
  message

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Mapping - Maps/Dictionaries

• mapping
  • an unordered set of key/value node pairs
  • each of the keys is unique
• example

Fruit: Apple
Vegetable: Carrot
Liquid: Water
Meat: Chicken

Banana:
  Calories: 105
  Fat: 0.4 g
  Carbs: 27 g

Grapes:
  Calories: 62
  Fat: 0.3 g
  Carbs: 16 g

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Sequences - Arrays/Lists

• sequences
  • an ordered series of zero or more nodes.
  • each of the keys is unique
  • a leading hyphen (-).
  • option: enclosed in square brackets []

Fruits:
  - Orange
  - Apple
  - Banna

Vegetables: [Carrot, Cauliflower, Tomato]

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Advanced

Fruits:
  - Banana:
      Calories: 105
      Fat: 0.4 g
      Carbs: 27 g

  - Grapes:
      Calories: 62
      Fat: 0.3 g
      Carbs: 16 g

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Yaml File in Kubernetes

• Contain 4 top level and required fields
  • apiVersion:
    • Version of Kub API
    • value: string
  • kind:
    • Type of object to create
    • Can be pod, service, replicaSet, Deployment
    • value: string
  • metadata:
    • The data about the object
    • value: dictionary
      • be careful with the indentation
  • spec:
    • specification of the object
    • value: dictionary

apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  # user custom label
  labels:
    app: myapp
    type: front-end
spec:
  # a list
  containers:
    - name: nginx-container
      image: nginx

• possible value for apiVersion field

Kind	Version
pod	v1
Service	v1
ReplicaSet	apps/v1
Deployment	apps/v1