Linux – DEVOPS DONE RIGHT

All Redis Setup Under 7 Minutes!

Redis is a popular open-source in-memory database that supports multiple data structures like strings, hashes, lists, and sets. But similar to other tools, we can scale standalone Redis to a particular extent, but not beyond that. That’s why we have a cluster mode setup in which we can scale Redis nodes horizontally and then distribute data among those nodes.

Generally, we categorize the Redis setup into three different types:

Standalone
Leader-Follower (Replication)
Leader-Leader(Sharding)

Standalone Setup

In a Standalone setup, the complexity is minimal, but we cannot scale the solution if the data increases. Also, the fail-over and high availability will not be supported inside it.

AWS Gateway LoadBalancer: A Load Balancer that we deserve

Nowadays, LoadBalancing is one of the basic needs for the application systems to perform optimally while considering some important factors like- scalability and high availability. Every cloud is providing LBaaS (LoadBalancing as a Service) as an offering so the consumers don’t have to worry about the setup and management of load-balancers by themselves.

But it’s not like that cloud is offering a single type of load balancer for every use case because for different use-case we require a different type of load balancer. For example- we have different load-balancers for Layer4 and Layer7 level traffic.

Recently AWS had a new family member in their load-balancer family and they named it “Gateway Load Balancer“. So gateway load-balancer is a load-balancing service provided by AWS to send traffic to the different appliances, applications, firewalls, etc. that are not part of the current VPC.

Debugging in Shell Script

What is Shell?

The UNIX shell program interprets user commands which are either directly entered by the user, or which can be read from a file called the shell script or shell program. Shell scripts are interpreted, not compiled. The shell reads commands from the script line per line and searches for those commands on the system.

The below command is used to check known shells in a UNIX system.

root@localhost$ cat /etc/shells 
# List of acceptable shells for chpass(1).
# Ftpd will not allow users to connect who are not using
# one of these shells.

/bin/bash
/bin/csh
/bin/dash
/bin/ksh
/bin/sh
/bin/tcsh
/bin/zsh

To change the shell, just write down the shell name; since a shell is an executable file (program), the current shell activates it and it gets executed. A new prompt is usually shown because each shell has its typical appearance.

Proc File System in Linux

I’d like to share an interesting finding with you today. Perhaps, many of you must be already familiar with it but being a newbie, it really intrigued me.

I have recently enrolled myself in the DevOps Ninja program conducted by my organisation- OpsTree. Everything that I’m learning here is new to me and often amuses me. One day, I was working on an assignment and executed the top command. I left the task as it is and meanwhile started browsing something on the internet. Suddenly a question struck my mind that from where the top command fetches its data ( you can see how I got digressed from my main assignment :p).

That’s Why Iptable Is Not A Good Fit For Domain Name?

Context

Let’s first talk about how it all started with and what we achieved.

It’s all started with a healthy discussion with a team where our team members were discussing many aspects of different fields of technology. So, one of our colleagues mentioned OpenVPN. So, we discussed the different working field, architecture, workflow of OpenVPN, in which role of iptables comes into the picture because for Linux architecture, OpenVPN support iptables as it’s primary firewall utility or can say OpenVPN support iptables as it’s a firewall for filtering workflow.

So in-between discussion, I mentioned that I am using iptables in OpenVPN to block traffic for the domain name and it is working fine. So, my colleague asked me about how you implemented & how is it possible to use iptables for domain and they discussed multiple logical explanations like OSI layer support and many other things. So, we decided to do POC of this discussion and try to write-up some blog or points to make clear that is it possible use iptables for the domain name and if not, what are the area that we can cover with iptables for the domain name and try to cover up flaws of this. Continue reading