Linux Interview Questions

Linux is an operating system, which is based on Linux Kernel. It is an open-source operating system where it can run on different hardware platforms. It provides a free and low-cost operating system for users. It is a user-friendly environment where they can easily modify and create variations in the source code.

Difference between Linux and Unix

And some other differences.

Linux is a Unix clone But if you consider Portable Operating System Interface (POSIX) standards then Linux can be considered as UNIX.

Linux Is Just KernalAll Linux distributions include GUI system, GNU utilities, installation & management tools, GNU c/c++ Compilers, Editors (vi), and various applications like OpenOffice, Firefox.

UNIX operating systems are considered as a complete OS as everything come from a single vendor.

Security And Firewall

Linux comes with an open source Netfilter and IPTables based firewall tool to protect your server and desktop from crackers and hackers. UNIX operating systems come with their own firewall products.

Backup And Recovery UNIX and Linux come with their own set of tools for backing up data to tape and other backup media. However, both Linux and UNIX share some common tools such as tar, dump/restore, and cpio etc.

The kernel is the core for Linux operating system.

Linus Torvalds created Linux.

Kernel is the heart of the operating system. It acts as a bridge between software and hardware. If Software requests the hardware, then kernel delivers the data between software and hardware. For example, if you want to play a song you should launch your default player, it requests the kernel to play a song, now kernel will contact the hardware to seek the permissions or to seek the hardware components like if you plugged in any headset to the device. Most of the Android phones use Linux kernels.

Yes, the kernel can edit, because it is released under General Public License.

Linux Torvalds was a student at the University of Helsinki, Finland in 1991. He started writing code on his own to get the academic version of Unix for free. Later on, it became popular as Linux Kernel.

Shell is a computer program that acts as an interface between the user and the kernel. Users can communicate with the kernel by writing programs, commands, and scripts on the shell. It accepts human-readable commands and converts them into the kernel understandable language.

They are five Shells in Linux: C Shell (csh): It is like C syntax and provides spelling checking and job control.

Korn Shell (ksh): Is a high-level programming language shell.

Z Shell (Zsh): It provides some unique nature like it observes login/logout watching, file name generating, startup files, closing comments.

Bourne Again Shell (bash): It is the default to Linux distributions. Friendly Interactive Shell (Fish): It provides web-based configuration, auto-suggestions, etc.

9. What are the basic components of Linux?

Launch your terminal by pressing CTRL+ALT+T or by giving terminal in the menu search bar.

Bash is a Unix shell and command processor written by Brian Fox for the GNU project. It is free software and acts as a replacement for Bourne Shell. It is an interpreted and not compiled process which can also be run in the terminal window. This allows users to write commands and cause actions. Bash is capable of reading commands from shell scripts.

LILO means Linux Loader is a boot loader that is used for the Linux operating system. Most of the Linux Operating systems use LILO, to boot the operating system into the main memory to start the operations.

Ans: Swap Space is used when then physical Ram memory is running out. It will move the Ram inactive pages to the swap space. It can consider in the form of a dedicated swap partition or a swap file.

CLI means Command language Interpreter. It interacts with the computer program, where the user issues command in the form of text lines. It Interacts with the computer terminals also, the interface accepts the text lines and converts them as a command to the operating system.

GUI means Graphical User Interface. It is a human-computer interface that uses windows, images, icons, and menus which can be manipulated by using a mouse. Most of the modern applications in electronic gadgets communicate with the user through GUI. GUI is a combination of graphical and textual interaction that uses buttons, menus, message boxes, etc.

Each file or directory has 3 permissions

They are

1. Read--It refers that only they can read the file.
2. Write--It refers that they can write the file or modify the file of a directory.
3. Execute-- It affects the user’s capability to execute the file or to view the file of a directory.

They are dynamic values that affect the process of programs on a computer. They exist in every operating system and their types may vary. They can be created, edited, saved, and deleted and they also give information about the system behavior.

Linux was one of the first open-source technologies, many programmers added software that was completely open to the users, which means you can download the file and change the code as you like. It has a wide range of options for the users and increased security.

Disadvantages of Open Source Operating System mentioned below

1. Difficulty of use
2. Compatibility Issues
3. Liabilities and warranties
4. Hidden costs

It will be redirected to another file using its path. Target files do not contain any data. Symbolic links redirect to another entry somewhere in the file system. If the target file is deleted, the link to that file is removed, but not the file.

A hard link is another name for an existing file on Linux. We can create so many hard links, for any file. They can create links for other hard links.

Redirection can be defined as changing the standard input and output devices. To redirect metacharacters are used, you can redirect the file or program.

A Daemon is a background process that accepts the requests for service from other computers, most of the operating systems use daemons in other forms.

The root is the user name, that default has access to all files and commands. The root user can do many things, but an ordinary user cannot do like installing software, change file permissions, etc.

Virtual Desktop is a user interface when you are facing the problem of how to manage multiple windows on your desktop, virtual desktop serves as an alternative. Virtual desktop stores remote server and allow you to use one or more programs on a clean slate.

There are three kinds of modes in vi editors. They are

• Command Mode/ Regular Mode
• Insertion Mode/Edit Mode.
• Ex Mode/ Replacement Mode.

An inode is a unique name given to each file and process id is a unique name given to each process.

Five process states in Linux. They are

1. New/ Ready: A new process is created and ready to run.
2. Running: The process is being executed.
3. Blocked/ Wait: The process is waiting for input from the user.
4. Terminated/ Completed: The process completed the execution or terminated by the operating system.
5. Zombie: The process is deleted, but still the information regarding the process exists in the process table.

The process management system calls in Linux:

• fork(): Used to create a new process.
• exec(): Execute new process.
• wait(): wait until process execution.
• exit(): exit from the process.
• System calls to get the Process id :
• getpid(): to find the unique process id.
• getppid(): to find the unique parent process id.

There are three user-based permission groups for each file and directory.

They are:

1. Owner: Owners only will have to access the file or directory, they will not impact the actions of other users.
2. Group: These permissions apply only to the group, that has been assigned to the file or directory. They will not impact the actions of other users.
3. All Users: These permissions are applied to all users on the system.