everything about linux distro and not only
A shell session ends when the terminal closes or the SSH connection drops. Every process that was started from that shell receives a SIGHUP (hang-up signal), and unless the process is specifically designed to survive it, it terminates. This is the default behavior, and for a quick command it is correct. For a long-running task—a…
Part 1 covered how to define and call functions. Part 2 is about making them robust — how functions report success or failure, how to stop a script when something breaks, and how to catch errors before they cascade. These techniques separate a fragile script from one you can trust in production. Key point: In…
A script that does something once is a command. A script that does something to every file in a directory, every line in a log, every user in a list, or every server in a cluster is automation. Loops are what make that possible. The LFCA exam places shell scripting under Linux Fundamentals, which carries…
A signal is a limited form of inter-process communication: a notification delivered to a process by the kernel or by another process. It interrupts whatever the process is doing and invokes one of three dispositions—the default action, an ignore, or a handler function that the process installed. The default action is signal-specific. SIGTERM terminates the…
59 – shell functions flow control and if Flow control is what turns a script from a straight line of commands into a program that makes decisions. The if statement is the most important of these — it lets you run different code depending on whether a condition is true or false. Combined with operators…
Every process on a Linux system carries a small set of hidden values — strings like HOME=/home/alice, PATH=/usr/bin:/bin, LANG=en_US.UTF-8 — that shape how programs behave. These are environment variables. They are the reason ls finds your commands without a full path, the reason date prints in your language, and the reason sudo knows which home…
systemd is the init system and service manager that replaced SysVinit and Upstart on most modern Linux distributions. It is not just a boot script runner. It is a dependency-aware, parallel-starting, socket-activated service manager that also handles device management, mount points, timers, and resource control. The core abstraction is the unit: a resource that systemd…
The test command is the engine behind every if condition you’ve written so far. [ … ] is actually a synonym for test — they do exactly the same thing. Understanding test directly makes your scripts clearer and helps you avoid quoting bugs. Key point: test evaluates a conditional expression and returns an exit status…
Every time you open a terminal, log in via SSH, or start a new shell session, Bash reads one or more configuration files to set up your environment. These files control your PATH, define aliases, customize your prompt, export variables that programs rely on, and decide whether your favorite shortcuts exist at all. They are…
The LFCS exam tests systemd at the operational level: can you start a service, make it persist across reboots, verify its status, and read its logs? The commands are not complicated individually, but the exam is performance-based on a live system, and the most common failure is not a wrong command—it is a command that…