🐧Linux

What Red Hat Enterprise Linux is — how open source licensing works, how Linux distributions differ from the kernel itself, and how RHEL's subscription model provides support, updates, and certifications for enterprise workloads running on the same Fedora/CentOS-derived codebase.

How to work efficiently at the Linux command line — understanding Bash shell command syntax, navigating and reusing command history, and using keyboard shortcuts that save time when typing long commands, editing mistakes, or searching for previous commands.

How Linux organises files into a single unified directory tree rooted at / — the purpose of each major directory in the Filesystem Hierarchy Standard, how to navigate and manipulate files from the command line, the difference between hard links and symbolic links, and how glob patterns match multiple files at once.

How Linux connects programs together and processes text — using I/O redirection to send output to files and capture errors separately, piping the output of one command as input to another, editing files with Vim's modal interface, and controlling shell behaviour through environment variables and startup files.

How Linux manages user identities through the /etc/passwd and /etc/shadow databases, the commands for creating and modifying user accounts, how groups enable shared access to resources, and how sudo grants controlled privilege escalation without sharing the root password.

How Linux controls access to files and directories through a nine-bit permission model — reading permission strings from ls -l output, changing permissions with chmod in symbolic or octal notation, setting ownership with chown, applying special bits like SUID and sticky bit, and controlling default permissions with umask.

How Linux manages running programs as processes — identifying processes with ps and top, controlling foreground and background jobs within a terminal session, sending signals to communicate with processes including terminating unresponsive ones, and understanding load average as a measure of system demand.

How systemd manages the Linux system from boot to shutdown — organising daemons and resources as units with declarative configuration files, controlling services with systemctl, and using targets as dependency-based milestones that replace traditional SysV runlevels.

OpenSSH client and server on RHEL 9 — key-based authentication, sshd_config hardening, ssh-keygen, scp, and sftp.

systemd-journald and rsyslog on RHEL 9 — journal persistence, journalctl filtering, log facilities, priorities, and /var/log structure.

How to configure and troubleshoot network interfaces on RHEL — inspecting current network state with ip commands, managing connections persistently with NetworkManager and nmcli, setting hostnames, and controlling how the system resolves DNS names.

How to archive and transfer files on Linux — creating and extracting compressed archives with tar, securely copying files between systems with scp and sftp, and efficiently synchronising directories between hosts with rsync including its important trailing-slash behaviour.

RPM package management on RHEL 9 — DNF commands, repositories, modules and AppStreams, and subscription-manager basics.

Block device management on RHEL 9 — partitioning with fdisk/parted, XFS and ext4 filesystems, mount, /etc/fstab, and LVM basics.

Cockpit web console for RHEL 9 administration — enabling Cockpit, its management features, and Red Hat support tools including sosreport and insights-client.