Summary from the Kali Linux Guide by OnWorks

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3.5. Summary‌

In this section, we took a whirlwind tour of the Linux landscape. We discussed the kernel and user space, reviewed many common Linux shell commands, discussed processes and how to manage them, reviewed user and group security concepts, discussed the FHS, and toured some of the most common directories and files found on Kali Linux.

Summary Tips:

• Linux is often used to refer to the entire operating system but in reality Linux itself is the operating system kernel that is started by the boot loader, which is itself started by the BIOS/UEFI.

• User space refers to everything that happens outside of the kernel. Among the programs running in user space, there are many core utilities from the GNU project2, most of which are meant to be run from the command line (a text-based interface that allows you to enter commands, execute them, and view the results). A shell executes your commands within that interface.

• Common commands include: pwd (print working directory), cd (change directory), ls (list file or directory contents), mkdir (make directory), rmdir (remove directory), mv, rm, and cp (move, remove, or copy file or directory respectively), cat (concatenate or show file), less/more (show files a page at a time), editor (start a text editor), find (locate a file or directory), free (display memory information), df (show disk free space), id display the identity of the user along with the list of groups they belong to), dmesg (review kernel logs), and journalctl (show all available logs).

• You can inspect the hardware on a Kali system with several commands: lspci (list PCI de- vices), lsusb (list USB devices), and lspcmcia lists PCMCIA cards.

• A process is a running instance of a program, which requires memory to store both the pro- gram itself and its operating data. You can manage processes with commands like: ps (show processes), kill (kill processes), bg (send process to background), fg (bring background process to foreground), and jobs (show background processes).

• Unix-like systems are multi-user. They support multiple users and groups and allow con- trol over actions, based on permissions. You can manage file and directory rights with sev- eral commands, including: chmod (change permissions), chown (change owner), and chgrp (change group).

• As with other professional Linux distributions, Kali Linux is organized to be consistent with the Filesystem Hierarchy Standard (FHS), allowing users coming from other Linux distributions to easily find their way around Kali.

• Traditionally, application configuration files are stored under your home directory, in hid- den files or directories starting with a period (or dot).