User Space and Kernal Space & types of Processes in Linux

User and kernel spaces in Linux:

Kernal Space:

The Kernal is the heart of the operating system.

It is responsible for scheduling and running programs, file management, and security. The kernel's job is to support the user's programs which are running in the user's space like a web browser or similar programs.

User's Space:

User's space programs interact with the kernel through special devices or system calls that they make.

An individual running program is called a process and each process has its own private virtual memory space. It runs as a particular user and a set of groups so that it can access files in the file system.

A process also has its state that describes whether it is currently running, waiting to run, waiting for a resource user by other processes, or maybe in a blocked state.

How do we identify the process? A process is identified by its unique ID which we commonly call a PID.

Types of processes in Linux:

There are different types of processes in Linux systems:

User Processes:

User Processes are processes that are associated with a particular user. They are started through a shell prompt, They print the output to the terminal and the input from the terminal.

If they are taking input from the terminal then we call that process a full grunt process, because they control the shell prompt.

It is possible for a process to be put in the background, in that case, they are not taking any input from the terminal but they can display output to the terminal.

Daemon Processes:

We have a second class of processes called daemon processes. These processes are not associated with the terminal at all. They are started when the system starts and provide services like networking, or other types of special tasks to keep the system running.

Kernal Threads:

We have a third class of processes called kernel threads. These are the parts of the kernel that are running as if they are regular user processes or system demons but are not associated with the terminal. They are the parts of the kernel but they are still scheduled as if they were regular processes.

We can get information about the processes running in a system by using the ps command in Linux.

Type ps you will see processes associated with the shell.

You will see PID (process ID) TTY (Tele Type) Time and the command that represents the particular process id.

These are not all the processes that are running on your system. You can use different options with the ps command in order to display different processes.

ps -ef

e shows us information about all the processes, the f provides us detailed information, it displays the data (formats the data) in different columns

You will see:

UID It is a user ID it may be the root or other user

PID Process

PPID Parent Process ID

C

STIME

TTY if you see? below the running process then it represents the demon process. It means that this process is not attached to the terminal.

TIME

CMD /usr/lib/systemd/system

These are the third class of kernel threads, that still appear in the output of the ps command.

I will add more information later....