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This article mainly introduces "what are the Linux interview questions". In the daily operation, I believe many people have doubts about the Linux interview questions. The editor consulted all kinds of materials and sorted out simple and easy-to-use methods of operation. I hope it will be helpful for you to answer the questions of "what are the Linux interview questions?" Next, please follow the editor to study!

Overview of Linux

What is Linux?

Linux is a free-to-use and free-spread Unix-like operating system. It is a multi-user, multi-task, multi-threaded and multi-CPU operating system based on POSIX and Unix. It runs major Unix tools, applications, and network protocols. It supports 32 bit and 64 bit hardware. Linux inherits the design idea of Unix with network as the core, and is a multi-user network operating system with stable performance.

What's the difference between Unix and Linux?

Linux and Unix are both powerful operating systems and widely used server operating systems. There are many similarities, and some people even mistakenly think that Unix and Linux operating systems are the same. However, this is not the case. Here is the difference between them.

Open source

Linux is an open source operating system, which can be used without paying; Unix is a traditional commercial software that protects the intellectual property rights of the source code.

Cross-platform

Linux operating system has good cross-platform performance and can run on a variety of hardware platforms; Unix operating system has weak cross-platform performance and most of them need to be used with hardware.

Visual interface

In addition to command-line operations, Linux also has a form management system; Unix is just a system under the command line.

Hardware environment

Linux operating system has lower requirements for hardware, and installation methods are easier to master; Unix has more stringent requirements for hardware, which is more difficult.

User group

Linux has a wide user base, which can be used by both individuals and enterprises; Unix is used by large enterprises with high security requirements, such as banks, telecommunications departments, etc., or Unix hardware manufacturers, such as Sun, etc.

Compared with Unix operating system, Linux operating system is more loved by computer enthusiasts. The main reason is that Linux operating system has all the functions of Unix operating system, and can achieve all the Unix features on ordinary PC computers. Open source free features are easier to popularize!

What is the Linux kernel?

The core of the Linux system is the kernel. The kernel controls all the hardware and software on the computer system, allocates the hardware when necessary, and executes the software as needed.

System memory management

Application management

Hardware equipment management

File system management

What are the basic components of Linux?

Like any other typical operating system, Linux has all these components: kernel, shell and GUI, system utilities and applications. The advantage of Linux over other operating systems is that every aspect comes with other features, and all the code can be downloaded for free.

The architecture of Linux

In a big way, the Linux architecture can be divided into two parts:

User space (User Space): user space also includes user's application (User Applications), C library (C Library).

Kernel space (Kernel Space): kernel space also includes system call interface (System Call Interface), kernel (Kernel), platform architecture-related code (Architecture-Dependent Kernel Code).

Why is the Linux architecture divided into user space and kernel space?

1. Modern CPU implements different working modes, and CPU can execute different instructions and access registers in different modes.

2. From the perspective of CPU, Linux divides the system into two parts in order to protect the security of the kernel.

User space and kernel space are two different states of program execution. We can transfer user space to kernel space in two ways: 1) system call; 2) hardware interrupt.

What is the basic difference between BASH and DOS?

The main differences between the BASH and the DOS console are in three aspects:

The BASH command is case-sensitive, while the DOS command is not.

Under BASH, / character is the directory delimiter and\ is the escape character. Under DOS, / is used as the command parameter delimiter and\ is the directory delimiter

DOS follows the convention in named files that an 8-character file name is followed by a dot with a 3-character extension. BASH does not follow this convention.

Linux boot process?

Just get to know it.

1. Host power-on self-test, loading BIOS hardware information.

2. Read the boot files (GRUB, LILO) of MBR.

3. Boot the Linux kernel.

4. Run the first process init (process number is always 1).

5. Enter the corresponding running level.

6. Run the terminal and enter the user name and password.

What is the default run level of the Linux system?

Turn it off.

Stand-alone user mode.

Multi-user mode of the character interface (network is not supported).

Multi-user mode of the character interface.

Not allocated for use.

Multi-user mode of graphical interface.

Restart.

What is the mode of interprocess communication used by Linux?

Just get to know it. You don't need to go too deep.

1. Pipeline (pipe), flow pipeline (s_pipe), named pipeline (FIFO).

2. Signal (signal).

3. Message queue.

4. Shared memory.

5. Semaphore.

6. Socket (socket).

What Syslog files does Linux have?

More important is the / var/log/messages log file.

This log file is a summary of many process log files, from which you can see any attempted or successful intrusion.

In addition, if the fat friend's system has a centralized collection of ELK logs, it will also be collected.

Is it helpful for Linux systems to install multiple desktop environments?

Typically, a desktop environment, such as KDE or Gnome, is sufficient to run without a problem. Although the system allows switching from one environment to another, this is a priority for users. Some programs work in one environment but not in another, so it can also be seen as a factor in choosing which environment to use.

What is swap space?

Swap space is a certain amount of space used by Linux to temporarily store programs that run concurrently. This happens when RAM does not have enough memory to hold all the programs that are executing.

What is a root account

The root account is like a system administrator account that allows you to take complete control of the system. You can create and maintain user accounts here, assigning different permissions to each account. It is the default account every time you install Linux.

What is LILO?

LILO is the boot loader for Linux. It is mainly used to load the Linux operating system into main memory so that it can start running.

What is BASH?

BASH is the abbreviation of Bourne Again SHell. It is written by Steve Bourne as a substitute for the original Bourne Shell (represented by / bin / sh). It combines all the features of the original version of Bourne Shell, among other features, to make it easier to use. Since then, it has been adapted as the default shell for most systems running Linux.

What is CLI?

The command line interface (English * *: command-line interface**, abbreviation]: CLI) is the most widely used user interface before the graphical user interface was popularized. It usually does not support the mouse. Users enter instructions through the keyboard, and the computer receives the instructions and executes them. Some people call it a character user interface (CUI).

It is generally believed that the command line interface (CLI) is not as user-friendly as the graphical user interface (GUI). Because the software of the command line interface usually needs the user to remember the commands of the operation, but because of its own characteristics, the command line interface saves the resources of the computer system than the graphical user interface. Under the premise of memorizing commands, using a command-line interface is often faster than using a graphical user interface. Therefore, the optional command line interface is retained in the operating system of the graphical user interface.

What is GUI?

Graphical user interface (Graphical User Interface, referred to as GUI, also known as graphical user interface) refers to the graphical display of the computer operation user interface.

Graphical user interface (GUI) is an interface display format in which people communicate with computers, allowing users to use input devices such as a mouse to manipulate icons or menu options on the screen to select commands, invoke files, start programs, or perform other daily tasks. A graphical user interface has many advantages over a character interface that completes routine tasks by entering text or character commands through the keyboard.

What are the advantages of open source?

Open source allows you to distribute software (including source code) free of charge to anyone who is interested. People can then add functionality and even debug and correct errors in the source code. They can even make it run better and then be free to redistribute the enhanced source code again. This ultimately benefits everyone in the community.

What is the importance of the GNU project?

This so-called free software movement has many advantages, such as the freedom to run programs and the freedom to learn and modify programs according to your needs. It also allows you to redistribute copies of the software to others and to be free to improve the software and release it to the public.

Disks, directories, files

Simple Linux file system?

In the Linux operating system, all resources managed by the operating system, such as network interface cards, disk drives, printers, input and output devices, ordinary files or directories, are regarded as a file.

In other words, there is an important concept in Linux system * *: everything is a file * *. In fact, this is an embodiment of Unix philosophy, and Linux is a rewriting of Unix, so this concept has been passed on. In Unix system, all resources are regarded as files, including hardware devices. UNIX system regards each hardware as a file, which is usually called a device file, so that users can access the hardware by reading and writing files.

Linux supports five file types, as shown in the following figure:

What is the directory structure of Linux?

This question is not usually asked. More is the actual use, need to know.

The Linux file system is structured like an upside-down tree, with its root directory at the top:

Common catalog description:

/ bin: stores binary executable files (ls,cat,mkdir, etc.). Commonly used commands are usually here.

/ etc: stores system management and configuration files

/ home: the root directory where all user files are stored, which is the base point of the user's home directory. For example, the home directory of the user user is / home/user, which can be represented by ~ user.

* * / usr * *: used to store system applications

/ opt: the location where additional installed optional application packages are placed. In general, we can install tomcat and so on here.

/ proc: virtual file system directory, which is the mapping of system memory. You can access this directory directly to get system information

/ root: home directory of the superuser (system administrator) (privileged class o)

/ sbin: stores binary executables that can only be accessed by root. What is stored here are system-level management commands and programs used by system administrators. Such as ifconfig, etc.

/ dev: used to store device files

/ mnt: the mount point where the system administrator installs the temporary file system. The system provides this directory for users to mount other file systems temporarily.

/ boot: stores various files used for booting the system

* * / lib * *: store the library files related to the operation of the system

/ tmp: used to store all kinds of temporary files, which is a common temporary file storage point

/ var: used to store files that need to change data at runtime, and it is also an overflow area for some large files, such as log files for various services (system startup log, etc.). ), etc.

/ lost+found: this directory is usually empty, and the "homeless" file (.chk under windows) is here when the system is not shut down properly.

At this point, the study of "what are the Linux interview questions" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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