20 IMPORTANT LINUX QUESTION

1) What is Linux?

Linux is an operating system based on UNIX and was first introduced by Linus Torvalds. It is based on the Linux Kernel and can run on different hardware platforms manufactured by Intel, MIPS, HP, IBM, SPARC, and Motorola. Another popular element in Linux is its mascot, a penguin figure named Tux.

2) What is Linux Kernel?

The Linux Kernel is a low-level systems software whose main role is to manage hardware resources for the user. It is also used to provide an interface for user-level interaction.

3) How can you find out how much memory Linux is using?

From a command shell, use the "concatenate" command: cat /proc/meminfo for memory usage information. You should see a line starting something like Mem: 64655360, etc. This is the total memory Linux thinks it has available to use.

COMMAND 
free - m

vmstat

 top

 htop

 4) Permissions under Linux?

 5)What is the pwd command?

The pwd command is short for print working directory command.

 6) What are daemons?

Daemons are services that provide several functions that may not be available under the base operating system. Its main task is to listen for service request and at the same time to act on these requests. After the service is done, it is then disconnected and waits for further requests.

 7) What is grep command?

grep a search command that makes use of pattern-based searching. It makes use of options and parameters that are specified along with the command line and applies this pattern in searching the required file output.

8) What is the difference between UNIX and Linux?

UNIX was originally started as a propriety operating system for Bell Laboratories, which later release their commercial version while Linux is a free, open source and a non-propriety operating system for the mass uses.

9) What is LILO?

LILO is a boot loader for Linux. It is used to load the Linux operating system into the main memory to begin its operations.

10) Define shell

It is an interpreter in Linux.

11) Define inode.

Each file is given a unique name by the operating system which is called as the inode.

12) Name some Linux variants.

Some of the Linux commands are:

• CentOS
• Ubuntu
• Redhat
• Debian
• Fedora

13) What is Swap Space?

Swap space is used to specify a space which is used by Linux to hold some concurrent running program temporarily. It is used when RAM does not have enough space to hold all programs that are executing.

14) What is BASH?

BASH is a short form of Bourne Again SHell. It was a replacement to the original Bourne shell, written by Steve Bourne.

15) What is the basic difference between BASH and DOS?

• BASH commands are case sensitive while DOS commands are not case sensitive.
• DOS follows a convention in naming files. In DOS, 8 character file name is followed by a dot and 3 characters for the extension. BASH doesn't follow such convention.

16) What is the GUI?

GUI stands for Graphical User Interface. It uses the images and the icons which are clicked by the users to communicate with the system. It is more attractive and user-friendly because of the use of the images and icons.

17) What are the basic commands for user management?

• last,
• chage,
• chsh,
• lsof,
• chown,
• chmod,
• useradd,
• userdel,
• newusers etc.

18) Is Linux Operating system virus free?

No, There is no operating system till date that is virus free, but Linux is known to have less number of viruses.

19) What are the file permissions in Linux?

There are 3 types of permissions in Linux OS that are given below:

• Read: User can read the file and list the directory.
• Write: User can write new files in the directory .
• Execute: User can access and run the file in a directory.

20) How to exit from vi editors?

The following commands are used to exit from vi editors.

1. :wq saves the current work and exits the VI.
2. :q! exits the VI without saving current work.