Linux - System managers

The Linux kernel is a free and open-source , [6] [7] monolithic , modular , [8] multitasking , Unix-like operating system kernel . [9] It was conceived and created in 1991 by Linus Torvalds [10] for his i386 based PC, and it was soon adopted as the kernel for the GNU Operating System , [11] which was created as open source and free software , and based on UNIX as a by-product of the fallout of the Unix wars . [12] Since then, it has spawned a plethora of operating system distributions , commonly also called Linux . Linux is deployed on a wide variety of computing systems, such as embedded devices , mobile devices (including its use in the Android operating system), personal computers , servers , mainframes , and supercomputers . [13] It can be tailored for specific architectures and for several usage scenarios using a family of simple commands (that is, without the need of manually editing its source code before compilation); [14] [15] [16] privileged users can also fine-

Linux Shell The shell is an interface for you to interact with your operating system (OS). As you type commands into the shell, it's responsible for interpreting those commands. Operations like copying files, piping, listing files are all within a shell's remit. Several Linux shells are available. To find out all the shells that are available on your system, open the terminal and type:    cat /etc/shells To find out what shell you're currently using type:      echo $0 Other  shells   are tsch, fish, KornShell, and Z Shell. How to change the shell to use another one? If you want to use a different shell, you can simply type its name and you’ll be logged into the new shell. For example, if you install fish (sudo apt install fish) and want to use it, you can simply use:                                                                  to use  fish You can enter exit to exit from the new shell and return to the previous one. 2 Ways to Change a Users Default Shell in Linux: u

In this link, you can learn about directories and files systems. On Linux and Unix everything is a file. more