Linux

In Linux, the expr command evaluates an expression passed to it and returns the corresponding value. We usually use it for basic arithmetic such as addition, subtraction, modulo operations, division, multiplication. We also use expr command to evaluate expressions.

We use the locate command to find files in Linux, unlike the find command that searches the entire file system, this command uses a local database to search for the file passed as an argument.

We use the read command to read from standard input or file descriptors. In this article, we learn to use the read command to get input from a user using a prompt, hiding input, limiting input, read command variables, arrays, timeouts, IFS, and more.

Linux is a multi-user system and as such there are occasions as system administrators we want to send a message to all logged in users seamlessly, in this case we use the wall command.

A here document is a special code block with multi-line strings that can be redirected to the command script or interactive program. In this article, we learn about here documents in Linux.

The finger command is used to get all information about system users. With it, we get information such as login name, user name, login time, idle time and much more. We look at commonly used finger commands 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.

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

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

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

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

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.

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.

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.

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.

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.

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.

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.

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.

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

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.

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.