Starting with Linux shell

1.You can see the current status of the virtual memory on your Linux system by viewing
   the special /proc/meminfo file.
cat /proc/meminfo

2.By default, each process running on the Linux system has its own private memory pages.
   One process cannot access memory pages being used by another process. The kernel
   maintains its own areas. For security purposes, no process can access memory used by
   the kernel processes.

3.To facilitate data sharing, you can create shared memory pages. Multiple processes can
   read and write to and from a common shared memory area. The kernel maintains and
   administers the shared memory areas and allows individual processes access to the
   shared area.

4.The special ipcs command allows you to view the current shared memory pages on the
   system.
ipcs -m

5.The kernel creates the first process, called the init process, to start all other processes
   on the system. When the kernel starts, it loads the init process into virtual memory, As
   the kernel starts each additional process, it gives it a unique area in virtual memory to
   store the data and code that the process uses.

6.Some Linux implementations contain a table of processes to start automatically on bootup.
   On Linux systems, this table is usually located in the special file /etc/inittabs.
   Other systems(such as the popular Ubuntu Linux distribution) utilize the /etc/init.d folder,
   which contains scripts for starting and stopping individual applications at boot time. The
   scripts are started via entries under the /etc/rcX.d folders, where X is a run level.
we can use runlevel command get the run level:
digdeep@ubuntu:~$ runlevel
N 2

7.The Linux kernel interfaces with each filesystem using the Virtual File System(VFS).This 

  provides a standard interface for the kernel to communicate with any type of filesystem.

  VFS caches information in memory as each filesystem is mounted and used. 

8.The GNU Utilities were developed under a software philosophy called open source software

  (OSS). The concept of OSS allows programmers to develop software and then release it to

  the world with no licensing fees attached. Anyone can use the software, modify it, or

  incorporate it into his or her own system without having to pay a license fee.

9.