everything about linux distro and not only
The Linux boot process is a sequence of handoffs: firmware to bootloader, bootloader to kernel, kernel to initramfs, and initramfs to the real root filesystem where systemd takes over as PID 1. For the LFCS exam, the objective is not to memorize every driver load but to understand the stages, the components responsible for each,…
Shell scripts use operators to perform operations on variables, strings, numbers, and files. They fall into a handful of categories — arithmetic, relational, logical, assignment, file test, string, and bitwise. Knowing which operator to use in which context is half the battle in shell scripting. Key point: The operator you use depends on where you…
The previous chapter covered tar — the archive tool that bundles files into a single stream. This chapter covers rsync — the synchronization tool that copies only what changed. They solve different problems. tar creates a portable archive that can be stored, moved, and restored as a single file. rsync keeps two directories in sync,…
Systemd targets are the replacement for SysV runlevels. They are synchronization points that group units together, defining what services and capabilities the system should have at a given stage of boot or operation . For the LFCS exam, the key distinction is between the default target (what the system boots into next time) and the…
Bash arithmetic is integer-only. 10 / 3 gives 3, not 3.33. If you need decimals, square roots, or trigonometric functions, bc is the tool. It’s an arbitrary-precision calculator that reads expressions from stdin and writes results to stdout. Key point: bc is a full calculator language — variables, functions, loops, conditionals. But in shell scripts…
The previous chapters covered tar and rsync — the tools that create backups. This chapter covers the step that matters most: restoring. A backup that has never been restored is not a backup. It is an unverified copy of data that may or may not be usable when you need it. The LFCA exam places…
The default target is the systemd state the machine reaches after boot completes. Changing it is a persistent configuration decision: the new target governs the next startup, not the current session. The command that performs this change is systemctl set-default, and it works by replacing a single symbolic link at /etc/systemd/system/default.target . Everything else follows…
Arrays let you store multiple values under a single variable name. Instead of juggling file1, file2, file3, you have one array files with three elements. Bash arrays are zero-indexed, flexible, and — with associative arrays — can even be keyed by strings. Key point: Bash has indexed arrays (numbered slots) and associative arrays (named keys)….
Cloud computing is the delivery of computing resources — servers, storage, databases, networking, software — over the internet as a service. Instead of buying and maintaining physical hardware, you rent what you need from a provider and pay for what you use. The LFCA exam places this topic under Cloud Computing Fundamentals, which carries 18–20%…
Single-user mode is the boot state in which the system starts with minimal services and presents a root shell without requiring the normal multi-user login sequence. On systemd systems, the equivalent states are rescue.target (single-user mode, local filesystems mounted, networking stopped) and emergency.target (root mounted read-only, almost nothing else). The distinction matters for recovery: rescue.target…