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Category: Beginner

AWS Security Groups basics explained

In the previous post we talked about bastion host in VPC and how using it we can make our environment more secure. One of the things we had to do is to configure an AWS Security group, which is some Read more…


Using bastion host in AWS environment

One of the ways how you connect and maintain your Linux EC2 instances in AWS VPC is connecting to them using SSH protocol. You can ssh to any EC2 instance which is in a public subnet and corresponding security group Read more…


How to secure your account with AWS AIM password policy

Securing your AWS account according to best practices is extremely important, but unfortunately the AWS IAM password policy feature is ignored in most cases. In this post we will go through the steps needed to be taken to secure your Read more…


Access Internet from AWS EC2 instance in private subnet

When you deploy your web application in AWS VPC subnet, most probably you will follow best practices and separate your app in at least 2 layers – web/application layer and database layer. It is recommended to have a database EC2 Read more…


How to authenticate REST API calls from AWS EC2 instance – AWS CLI example

In the previous post we talked about creating a new IAM role and assigning it to our running EC2 instance. This will allow to authenticate any calls made towards AWS resources from any application running on this EC2. If we Read more…


How to authenticate REST API calls from AWS EC2 instance – Role creation

There are some applications running on your EC2 instance and you need these applications to access some AWS resources. As you know, all requests (REST API calls in this case) should be authenticated. One option is to create a login Read more…


What is a table, row, column, field in SQL database

In the previous post we discussed the basic terms related to relational (SQL) databases – what is a relational (SQL) database, why data should be stored in multiple tables. What issues we face if store data in one SQL table Read more…


Introduction to relational (SQL) databases: Basic concepts

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SQL DataBase (DB) – is a number of tables (objects) which are connected which each other. Using a special software called management system the one can interact with such a system by writing data into database and when needed reading Read more…


do-while loop in Java

In the previous post https://dataguru.guide/index.php/2020/05/07/while-loop-in-java/ we talked about while loop in Java, today we are gonna focus on do-while loop which is slightly different from while loop. The main difference is that the condition of loop execution is checked after Read more…


while loop in Java

In this post I will go through the basic syntax of while loop in Java. More info will follow in the video available on my YouTube channel. So while loop does the same thing basically as for loop, but while Read more…