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How YAML is Used in Kubernetes: YAML files are used to define Kubernetes objects such as pods, deployments, services, config maps, secrets, and many others. These objects describe the desired state of your application or infrastructure, and Kubernetes works t...

kubectl The kubectl command is used to interact with and manage a Kubernetes cluster. It allows administrators and developers to deploy applications, inspect resources, manage cluster components, and view logs. Essentially, kubectl acts as the command-line in...

In a K8S cluster, the default networking policy is to assign each pod the same range of IPs, meaning that there's possibility for overlap and conflicts where multiple pods are assigned the same IP address. Because of this, its common practice to make use of a ...

A Service in Kubernetes is a resource that creates a stable, fixed access point (like an IP or DNS name) for other applications or users to reach a group of pods. Even though the individual pod IPs might change as pods are created or destroyed, the Service ens...

Kubectl setup Install kubectl binary Kubeconfig Setup To access a remote cluster, you'll need to use a kubeconfig file. The kubeconfig file is a YAML file that configures access to a Kubernetes cluster. It stores information such as: Clusters: The Kub...

Secrets Secrets are a Kubernetes object that can be referenced in YAML configurations without having to expose secret information. For example, I can create a secret in K8S which contains a password, and then reference that secret in required YAML files wit...

KUBE-SCHEDULER The scheduler continuously monitors the KUBE-API server for changes to cluster configuration, once a change is made the relevant data in the ETCD store is updated, and the changes are passed to the Kubelet on the relevant nodes. The kube-sch...

What is a kernel module? A kernel module is essentially a piece of code that can be loaded into the operating system's kernel on demand. Think of it like an extension for the kernel, providing additional functionality without requiring a complete system res...

Kernel Tunables In Linux, a tunable refers to a specific type of configuration setting within the kernel. These tunables allow you to customize the behavior of the kernel while the system is running, offering more fine-grained control over how your system ope...

What are initramfs and initrd? initrd and initramfs are temporary root filesystems loaded into memory during the early Linux boot process. Their purpose is to provide the kernel with the necessary drivers, modules, and scripts needed to initialize hardware ...

echo Built-in Linux feature to print out arguments as standard output. echo {string} printf Similar to echo, but allows for more control over the formatting of output. printf {string} Option Function \n newlineprintf "hello \n how are yo...

GREP Grep is used to search file contents for a particular string or pattern. grep [option] {search pattern} {filename} Option Function -i Case insensitive  -v Exclude string 'string|string' OR Statement - used to search for multipl...

The ln command is used to create links between files. There are two types of links: HardLinks & Symbolic Links ln [options] {target name} [link name] Options Function -backup Back up existing destination files. -f Remove existing destina...

Methods for redirecting data through the shell, either from/to files or commands. Standard Input - stdinActs as the source for command input. This is usually coming from your mouse or keyboard.Standard Output - stdoutActs as the destination for command output...

On Linux systems, a relatively common practice amongst high-security systems is to use a disk or filesystem-level encryption. LUKS (Linux Unified Key Setup) LUKS is a Linux disk encryption utility. It helps to protect data by encrypting the contents of a d...

iptables iptables is a Linux Firewall utility that's used to configure rules on the kernel netfilter firewall. iptables processes packets based on chains of rules, deciding whether to allow, drop, or manipulate them. iptables does not preserve connection sta...

firewalld at its core is essentially a wrapper for iptables, but it does include some extra features and improved functionality. With iptables, when you reload a rule, connections can drop. This is a big problem on production servers. Firewalld uses in-plac...

Netfilter (nftables) is an iptables replacement commonly found on modern Debian systems by default.

  Fail2Ban Fail2Ban is a an IPS system that can be configured to monitor basically any service with an authentication mechanism. Monitors: Log files for multiple services (SSH, nginx, Apache, etc.) Uses "jails": Config blocks that define patter...