everything about linux distro and not only
Permissions decide what can be done to a file. Ownership decides who the permissions apply to. Every file has an owner and a group, set when the file is created to the creating user and their primary group. When a file needs to belong to someone else — a web server that runs as www-data,…
The previous chapter established the concepts: a network namespace is a logical copy of the kernel network stack, isolated from the default namespace and from every other namespace. This chapter is the practical application. It covers the four patterns that account for nearly every real-world use of network namespaces: connecting two namespaces with a veth…
Every command on Linux has three streams: the standard input, the standard output, and the standard error. The pipe is the operator that connects the standard output of one command to the standard input of the next. The ls -l | grep ‘.txt’ takes the listing from the ls, feeds it to the grep, and…
A package manager is a tool that automates installing, upgrading, configuring, and removing software. Each package manager maintains a list of software packages that can be installed, updated, and removed from the system. Package managers also provide tools to search for packages, install dependencies, manage configurations, and automate updates. Almost all packages can be found…
Software on a Linux system does not arrive as a single downloaded installer, the way it does on Windows or macOS. It arrives as a package: a file that contains the program’s binaries, its configuration templates, its documentation, and a manifest of what it needs to run. A package manager is the tool that finds…
TUN and TAP are virtual network kernel drivers that move packets between the kernel’s network stack and a userspace program. They are not physical interfaces, but they appear to the kernel as if they were, and they can be assigned IP addresses, added to routes, and used by any application that opens a socket. The…
Some commands read their input from the standard input. The grep, the sed, the awk, and the sort are the line-oriented, and the pipe is the natural. Other commands expect the arguments on the command line. The rm, the cp, the mv, the mkdir, and the chmod take the file names as the arguments, and…
The mount command attaches a filesystem or device to a directory (the mount point) so its contents become accessible. The umount command detaches it. Key point: A device must be mounted before you can read or write to its files. Linux treats everything as a file — including devices and filesystems. a – mount options…
Installing packages is the daily work of Linux administration. The previous chapter covered what package managers are and the full set of operations. This chapter is about the install operation specifically — the command, what happens when it runs, how dependency resolution works, the difference between installing from a repository and installing a local file,…
A veth pair is a virtual Ethernet cable with exactly two ends. A packet transmitted on one end is immediately received on the other. This simplicity is the entire mechanism, and it is also the reason veth pairs are the foundation of every modern Linux virtualization and container network. Unlike a TUN or TAP device,…