everything about linux distro and not only
The previous chapter covered connecting with SSH — the commands, the file transfers, and the configuration. This chapter goes deeper into the authentication itself: the key pairs that replace the password with the cryptographic proof. A key pair is two mathematically linked files — the private key that stays on the client and the public…
Repository configuration is the layer that tells a package manager where to find software. On RHEL-based systems, the package manager (DNF or YUM) reads repository definitions from .repo files in /etc/yum.repos.d/ and from the [main] section of /etc/yum.conf . On Debian-based systems, APT reads from /etc/apt/sources.list and the drop-in directory /etc/apt/sources.list.d/, either in the one-line…
These three commands are the print management trio on Linux. lpstat tells you about the printers — which ones exist, which are accepting jobs, which is the default. lpq shows you the queue — what’s waiting to print. lprm lets you remove jobs from the queue. Key point: All three work with CUPS (Common UNIX…
The scp command copies files between hosts over SSH. It uses the SSH’s authentication and encryption, so the transfer is secure without any additional configuration. The command is the cp‘s remote’s version: the same source-and-destination shape, the same recursive’s -r, but the either side can be the remote’s and the transport is the encrypted’s. It…
Package verification and signing are the trust mechanisms of a Linux system. Without them, every dnf install or apt install is an act of faith: you are trusting that the package you receive came from the repository you configured, that it has not been modified in transit, and that it has not been tampered with…
A shell script is a plain-text file full of shell commands that the system runs for you, in order, automatically. Instead of typing the same sequence of commands over and over, you write them once and run the script. It’s the simplest form of programming on Linux — and one of the most useful. Key…
The previous chapter covered scp — the one-shot copy where the source and destination are given on the command line, the transfer runs, and the command exits. That model works when you know exactly which file you want and where it should go. It breaks down when you need to look around first. The sftp…
Process viewing is the first skill of system troubleshooting. Before you can diagnose a slow server, a runaway service, or a memory leak, you need to see what is running, who owns it, and how much of the system’s resources it is consuming. Linux provides three tools that cover this need at different levels of…
Variables are the foundation of any shell script. They let you store values, pass data around, and make your scripts flexible instead of hardcoded. Shell scripts also come with a set of special variables that the shell fills in automatically — the script name, arguments, process ID, and exit status. Key point: In shell scripting,…
The scp copies the whole file every time, and the sftp transfers interactively but also sends the whole file. The rsync is different. It computes the differences between the source and the destination, transfers only the changed blocks, and leaves everything else alone. That is the delta algorithm, and it is what makes rsync the…