Unix / Linux for Beginners | Notion

What is Unix ?

The Unix operating system is a set of programs that act as a link between the computer and the user.
The kernel is responsible for managing system resources and coordinating the various aspects of a computer's internal operations.
Users communicate with the kernel through a program known as the shell.
The shell is a command line interpreter.

System Shutdown

The most consistent way to shutdown a Unix system properly via the command line is to use one of the following commands −

Sr.No.	Command & Description
1	`halt`
Brings the system down immediately
2	`init 0`
Powers off the system using predefined scripts to synchronize and clean up the system prior to shutting down
3	`init 6`
Reboots the system by shutting it down completely and then restarting it
4	poweroff
Shuts down the system by powering off
5	`reboot`
Reboots the system
6	`shutdown`
Shuts down the system

`ls -l` Commands Output

Every file line begins with a d, -, or l. These characters indicate the type of the file that's listed.

Sr.No.	Prefix & Description
1	`-`
Regular file, such as an ASCII text file, binary executable, or hard link.
2	`b`
Block special file. Block input/output device file such as a physical hard drive.
3	`c`
Character special file. Raw input/output device file such as a physical hard drive.
4	`d`
Directory file that contains a listing of other files and directories.
5	`l`
Symbolic link file. Links on any regular file.
6	`p`
Named pipe. A mechanism for interprocess communications.
7	`s`
Socket used for interprocess communication.

Metacharacters