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Algorithm Types

Encryption Algorithms       (AES, DES, RSA...)
Authentication Algorithms   (MD5, SHA-256, SHA-512, HMAC ...)

Security

Encryption Types:
Symmentric      Single key (K) will be used for Encryption and Decryption (AES, DES)

Asymmentric Two keys (KU, KR) will be used for Encryption and Decryption (RSA)

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• curl -s -o /dev/null -w "%{http_code}" https://www.yahoo.com to print only the http status code.
• curl -s -D - -o /dev/null https://www.yahoo.com to print only the response headers.
  • -D - dump headers to stdout indicated by -
  • -o /dev/null send output (HTML) to /dev/null essentially ignoring it
• https://everything.curl.dev/usingcurl/verbose/writeout
• https://codeahoy.com/general/curl-display-request-response-headers

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• Node - a physical or virtual machine that hosts services
  • Nodes also referred to as members.
  • Examples
    • Your computer
    • An AWS EC2 instance
    • A bare metal machine in your private data center
• Service - executing software that provides utility via an interface
  • Typically long-lived process listening on a port(s)
  • Examples
• A web server (nginx, apache, iis)

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• Chef provides a Domain Specific Language (DSL) for specifying Infrastrcture as a Code and the automation necessary to deploy, configure, and manage servers based on that code.
• Allowing the specification of what the final configuration should be and not the steps necessary to make that happen.
• Multiparts: ChefDK (Development Kit), Chef Server and Chef Client.
• Desired State Configuration:
  • Specify a server configuration's end result, not the steps to go there.
  • "Test and Repair" approach allows chef to only make changes necessary to get the server back to the desired state configuration.
  • If server is already in desired state, no changes will occur.
• Two ways of applying configuration (Imperative & Declarative style)
  • Imperative Approach (This applies to an single entity and it's gonna differ based on entities)

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# This is a single line comment.

=begin
	This is a multiline comment.
=end

x = 10

print "#{x}\n"

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python requests

• get request example:

  r = requests.get("url", params={}, auth=(username, password))

• dir(r) to get response object attributes.

• post request example:

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• Pseudo File System

  • Only exists in RAM while the system in running.
  • /proc contains information about the processes running on a system. Processes are are listed by PID.
  • /sys contains information about the systems hardware and kernel modules and no process information is listed here.
  • man proc for more info.

• Linux Kernel Module

  • Linux kernel is the core framework of the operating system.
  • GNU/Linux (GNU-The Open Source Tools Project / Linux-The Actual Kernel).
  • Linux Kernel is Monolithic (it handles all memory and device management).

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Introduction to Playbooks and Common Modules

• Know how to work with commonly used Ansible modules
• Create playbooks to configure systems to a specified state
• Use variables to retrieve the results of running commands
• Use conditionals to control play execution
• Configure error handling
• Selectively run specified tasks in playbook using tags

Know how to work with commonly used Ansible modules

• Core modules to be familiar with

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go modules notes:

• go mod tidy
  • removes unused dependencies
  • adds the required dependencies
• go get github.com/user/module
  • this will add github.com/user/project as dependency under go.mod
• go mod why github.com/user/project
  • this provides information about where the package is used under a project
• go get variations
• go get github.com/julienschmidt/httprouter@latest to get the latest version of a package

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Data Strctures And Algorithm

• Big O Notation is used to describe the performance of an alogrithm.
• It is used to check if the algorithm is going scale well if the input grows really large.
• O(n)

O(1)

• O(1) notation
• It doesn't matter how big the array is. It can be either one or one million items.
• All we are doing below is printing the first item.
• Below method has a single operation and takes constant amount of time to run.