01 / LINUX
Kernel
The Linux kernel is the core component of the operating system, responsible for managing CPU
scheduling, memory, processes, devices, filesystems and networking. It provides the interface
between user-space programs and the underlying hardware through system calls and kernel
subsystems. The kernel is modular, allowing functionality such as device drivers and filesystems
to be loaded dynamically, while its architecture supports everything from embedded systems and
servers to desktops and large-scale cloud infrastructure.
02 / LINUX
Boot
The Linux boot process transforms a powered-off machine into a running operating system through
several distinct stages. Firmware such as UEFI initializes hardware and selects a bootloader,
commonly GRUB, which loads the Linux kernel and an initial RAM filesystem (initramfs). The
kernel initializes hardware and core subsystems before starting the first user-space process,
typically systemd on modern distributions. Understanding each stage is essential when diagnosing
boot failures, kernel problems and filesystem issues.
03 / LINUX
systemd
systemd is a system and service manager used by most modern Linux distributions. It starts and
supervises services, manages dependencies between units, handles device and mount events,
provides logging through journald and can manage timers, sockets, users and other system
resources. Administrators commonly interact with it using systemctl and journalctl, while unit
files define how services are started, stopped, configured and monitored.
04 / LINUX
Storage
Linux storage is built from several layers, ranging from physical devices and partitions to
filesystems and logical storage abstractions. Tools such as lsblk, fdisk, blkid and mount expose
the structure of storage devices, while filesystems such as ext4 and XFS provide persistent
organization of files and metadata. More advanced configurations can use LVM, RAID,
device-mapper and network storage, allowing administrators to create flexible storage
architectures that can be resized, replicated and managed independently of individual physical
disks.
05 / LINUX
Networking
Linux provides a comprehensive networking stack supporting Ethernet, wireless networking, IPv4,
IPv6, routing, VLANs, bridges, bonding, tunnels and network namespaces. Interfaces, addresses
and routes can be inspected with tools such as ip, while utilities such as ss, ping, traceroute
and tcpdump provide visibility into network connectivity and traffic. Modern Linux networking is
also fundamental to containers and Kubernetes, where namespaces, virtual interfaces, bridges and
routing are used to isolate and connect workloads.
06 / LINUX
Security
Linux security is implemented through multiple layers including Unix permissions, user and group
isolation, capabilities, mandatory access control and kernel security mechanisms. Systems may
use frameworks such as SELinux or AppArmor to restrict what processes are permitted to access,
while capabilities allow specific privileged operations without granting complete root access.
Additional controls such as sudo, namespaces, seccomp, firewalling, auditing and cryptographic
authentication provide further protection for systems and workloads.
07 / LINUX
Performance
Linux performance analysis involves understanding how CPU, memory, storage and network resources
are being consumed. Utilities such as top, vmstat, iostat, free, sar, ss and pidstat provide
different views of system activity, while tools such as perf can examine CPU-level performance
and application behaviour. Effective troubleshooting begins by identifying the constrained
resource, measuring its behaviour and determining whether the bottleneck originates in the
kernel, hardware, application or workload configuration.
08 / LINUX
Troubleshooting
Linux troubleshooting is a structured process of identifying symptoms, gathering evidence,
isolating the failing component and applying a controlled correction. Logs from journald and
traditional log files provide historical evidence, while commands such as systemctl, dmesg, ps,
ss, df, du and journalctl help establish the current state of the system. Effective
troubleshooting avoids assumptions and instead works from observable evidence, making it
possible to diagnose problems involving boot failures, services, networking, storage,
permissions, resource exhaustion and application faults.