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Erick Lumunge

Erick is a passionate programmer with a computer science background who loves to learn about and use code to impact lives positively.

Nairobi •
241 posts •
Linux

ufw in Linux

ufw (Uncomplicated Firewall) is a Linux utility that runs on top of iptables used to manage netfilter and managing the firewall. We look at ufw in Ubuntu and how to manage the firewall.

Erick Lumunge
Linux

vmstat command in Linux

We use the vmstat command for system performance monitoring in Linux. It reports statistics about threads, system calls, CPU activity, memory, disks, and more.

Erick Lumunge
Linux

firewalld in RHEL

firewalld is a Linux utility used to manage firewall rules. In this article we discuss firewall management using firewalld.

Erick Lumunge
Linux

iptables in Linux

We use iptables to create firewall rules. In this article we learn about iptables and how to manage firewall rules in Linux.

Erick Lumunge
Linux

journalctl in Linux

In Linux, systemd provides a centrally managed journal where all kernel and userland processes' logs are stored. We use journalctl to interact with journals.

Erick Lumunge
Linux

SSH passwordless login in Linux

Passwordless login is useful in cases whereby we want to automate server administration tasks. We discuss how to configure ssh passwordless login in Linux.

Erick Lumunge
Linux

Accessing a remote server using SSH

Secure Shell(ssh) is a cryptographic protocol for networking which encrypts communication between two remote hosts. In this article we learn how to safely access a remote server using ssh.

Erick Lumunge
Linux

Managing packages with yum/dnf in RHEL

Package management involves managing software on a system. This includes installing, upgrading, downgrading, updating, removing, etc. We discuss package management in Red Hat Enterprise Linux Distros using yum and dnf.

Erick Lumunge
Linux

Managing Debian packages with dpkg

In Linux software is considered a package and is distributed using remote repositories. As end-users, to access it we use package managers. We discuss the dpkg package manager for Debian-based Linux distros.

Erick Lumunge
Linux

Managing Debian packages with apt

apt(Advanced Package Tool) is a package management tool. It is used to install, configure, search for, update and remove software in a Debian based Linux system.

Erick Lumunge
Linux

Bash until loop

Loops are an important aspect in any programming language. In this article we look at the until loop that is used for looping in shell scripts.

Erick Lumunge
Operating System

Secure boot

Secure boot is a security standard implemented in the advanced UEFI to prevent malware from attacking the computer during boot up when the computer is most vulnerable.

Erick Lumunge
Computer Architecture

UEFI and Legacy boot

Both UEFI and BIOS are firmware that specify an interface between the computer operating system and the underlying firmware. Legacy boot involves booting the computer using legacy firmware such as BIOS and UEFI boot involves booting a computer using the more advanced UEFI.

Erick Lumunge
Computer Architecture

UEFI (Unified Extensible Firmware Interface)

UEFI(Unified Extensible Firmware Interface) is the interface between the operating system and the low-level initialization firmware. It initializes hardware components and is responsible for executing the OS stored in a boot device.

Erick Lumunge
Computer Architecture

Firmware

In this article we discuss firmware - software that is directly programmed into hardware devices such as routers, cameras, network cards etc.

Erick Lumunge
Computer Architecture

BIOS (Basic Input Output System)

We discuss BIOS - firmware stored in non-volatile memory e.g EPROM, responsible for startup procedures such as POST before passing control to the bootloader which loads the OS.

Erick Lumunge
Linux

Types of Boot loaders

A boot-loader is responsible for loading the operating system to the Linux kernel and the Linux initial RAM disk. In this article we discuss different boot loaders for the Linux operating system.

Erick Lumunge
Linux

GRUB bootloader

GRUB is one of the many Linux boot loaders responsible for loading an operating system into memory during startup. In this article we discuss the booting process involving GRUB and how to configure and customize GRUB.

Erick Lumunge
Linux

Run levels in Linux

Run levels are modes of operation for computer operating systems. We discuss the different run levels in the Linux OS and demonstrate how to change the default run level.

Erick Lumunge
Linux

Systemd Components

Systemd is a suite of utilities that provide an array of system components for the Linux OS. We look at various components within systemd.

Erick Lumunge
Linux

Unit files in Linux

A unit file is responsible for specifying how systemd starts and runs. In this article, we discuss unit files, the contents of these files, service and target unit and unit files and how to create and edit unit files.

Erick Lumunge
Linux

Systemctl and Systemd in Linux

The systemctl command is a systemd utility used to manage services, get information about service unit files and service states and therefore a useful utility to know for managing services on the server while systemd is an array of components for Linux OS.

Erick Lumunge
Compiler Design

Data-flow analysis in Compiler Design

All optimizations in a compiler depend on data-flow analysis. We discuss three instances of data-flow problems, reaching definitions, live variables and available expressions.

Erick Lumunge
Compiler Design

Sethi Ullman algorithm

The Sethi-Ullman algorithm is an optimal algorithm used for finding an optimal ordering of a computation tree. We discuss two generalizations that increase its applicability without increasing the cost.

Erick Lumunge
Compiler Design

L-Attributed and S-Attributed definitions and grammar

We have discussed two classes of definitions that can efficiently be implemented in connection to top-down or bottom-up parsing in compilers and corresponding attribute grammars that result from serious restrictions.

Erick Lumunge
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