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3.1. What Is Linux and What Is It Doing?
The term ”Linux” is often used to refer to the entire operating system, but in reality, Linux is the operating system kernel, which is started by the boot loader, which is itself started by the BIOS/UEFI. The kernel assumes a role similar to that of a conductor in an orchestra—it ensures coordination between hardware and software. This role includes managing hardware, processes, users, permissions, and the file system. The kernel provides a common base to all other programs on the system and typically runs in ring zero, also known as kernel space.
The User Space We use the term user space to lump together everything that happens outside of the kernel.
Among the programs running in user space are many core utilities from the GNU project1, most of which are meant to be run from the command line. You can use them in scripts to automate many tasks. Refer to section 3.4, “Useful Commands” [page 56] for more information about the most important commands.
The User Space We use the term user space to lump together everything that happens outside of the kernel.
Among the programs running in user space are many core utilities from the GNU project1, most of which are meant to be run from the command line. You can use them in scripts to automate many tasks. Refer to section 3.4, “Useful Commands” [page 56] for more information about the most important commands.
Let’s quickly review the various tasks handled by the Linux kernel.