Understanding Linux
CyberStart Essentials Glossary
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All professions have their own termoniolgy and acronyms. Sometimes, it can be daunting to try and understand what feels like a whole new language (no pun intended). Cyber security is no different so, we’ve put together a series of glossaries to help you get to grips with the phrases and words you’ll need to know to get ahead.
Here are the terms, phrases, and words you’ll hear when learning about Linux. There’s a lot to learn, but bear with us and by the end of the glossary, you’ll be able to talk about Linux like a pro!
Aptitude / RPM: Aptitude and RPM are both package managers. Depending on which distribution of Linux you are running, you will be running a certain package manager. They effectively do the same thing — allow the user to install new software on to the machine. For example, if you wanted to install an Apache2 web server on to your computer, you could do: “apt-get install apache2”.
Bash Script: A Bash Script is a file that contains a series of commands to be executed. Internally, it can be reminiscent of a programming language, as it has the capability to be a lot more than just a list of commands. Effectively a bash script is a file that will be interpreted and executed by the shell.
Binary / Binaries: Loosely speaking, a “binary” is a file that can be executed by a computer or Operating System. A “Windows Binary” would refer to an EXE file. In Linux, a binary refers to an ELF (Executable Linking Format) File, which is a file that can be executed by Linux. Firefox on Linux is an ELF file, for example.
Compile: The process of converting code from a human-readable format into a machine-readable format — compiling “compiles” human-written code into code that the computer can understand and further process.
Cron: A robust tool for scheduling periodic tasks.
Desktop Environment: A collection of software that works together to provide a graphical interface for the user. The main software used for this purpose is KDE and Gnome.
Hidden Files: A Hidden File in Linux is a file which has a filename starting with the character “.”. For example, “.thisisafilename”, would be a hidden file, and would not be shown under the normal operation of the file manager or utility. In order to see a hidden file, you must explicitly state that you wish to see them by using the “ls” command with the “-a” flag. “ls -a” will list *all* files in the current directory, including hidden ones.
Linux Distribution / Distro: An Operating System that uses the Linux Kernel (e.g. Ubuntu). There are many Distributions and each one is different — the Distribution you use is based on personal preference.
Linux Kernel: The core code of any Linux-based Operating System, created and maintained by Linus Torvalds.
Network Interface: A device that represents a physical or virtual network connection (E.g. Ethernet Port.) This device can be used to configure certain networking settings. Interfaces can be listed using the “ifconfig” command from the terminal.
Package: A package is a bundle of software that can be installed on Linux by using your package manager.
Permissions: Permissions are attributes associated with a file that describes who is allowed to access it and what they are allowed to do. Permissions and ownership can be modified using the “chmod” and “chown” commands respectively.
Root: The administrator account on the Linux Operating System. It comes installed by default and initially allows you to elevate your privileges to perform administrative tasks by using the “sudo” command (super user do) and the password for your user.
Runlevel: A runlevel describes the mode that the Linux Operating System will run in. There are 7 runlevels, numbered from 0–6, each describing an environment with different services running and providing granularity over what is running in the background. Runlevel 6 for example, causes a system reboot, runlevel 3 runs the system with multi-user capability and networking, and runlevel 2 does the former, but without networking capability.
Service / Daemon: A Service or Daemon is a program that runs in the background and waits to be used to carry out certain tasks.
Sudo: A command that allows you to temporarily assume the privileges of another user by using your password to login. In order for this to be permitted, an entry must be created in the “sudoers” file explicitly permitting this access. The sudoers file is located at: /etc/sudoers.
Systemd: Systemd is a suite of software used to manage services on the Linux Operating System. You can use it to automatically start programs and services on startup, restart on crash and much more.
Terminal / Console / Shell: A powerful utility that allows you to perform many tasks by issuing series of “commands”. There are many types of shell, but the main one in use today is “bash” (Bourne Again Shell). It’s important to be familiar with the Linux Terminal, as some Linux Operating Systems are console only so that all resources can be dedicated for a specific purpose, i.e. A Web Server.
X / X-Window: A piece of software that provides the basic graphical functionality that most Desktop Environments use.
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