Linux Basics: A must-have for full-stack developers

Introduction

Linux is almost everywhere, whether it is server construction or client development, the basic skills of the operating system are necessary for the full stack.

System selection

Linux distributions can be roughly divided into two categories, one is the distribution maintained by commercial companies, and the other is the distribution maintained by community organizations. The former is represented by the famous Redhat (RHEL), and the latter is represented by Debian. .

Redhat should be called the Redhat series, including RHEL, Fedora, and CentOS (the community clone version of RHEL, free). Strictly speaking, Ubuntu cannot be considered an independent distribution. Ubuntu is enhanced based on Debian, a nearly perfect Linux desktop system that has all the advantages of Debian and its own enhanced advantages. The Ubuntu community values ​​practicality and innovation above all else.

If you need a relatively stable server system, then the best choice is CentOS. After the installation is completed, it can provide very stable services after simple configuration. But for cloud environments, unbantu may be good. Hadoop was first developed on ubantu.

Architecture

Understanding the architecture can give you a better sense of direction. Linux has two modes: kernel and user. The kernel, shell and file system together form the basic operating system structure. The Linux kernel consists of the following parts: memory management, process management, device driver, file system and network management, etc.

Linux kernel

Understanding the Linux kernel can make full use of resources and have a sense of purpose when tuning the system.

Linux divides memory into manageable "memory pages" and provides abstractions for 4KB buffers, such as the slab allocator. A process is actually a running entity of a specific application, and process scheduling controls the process's access to the CPU. Common inter-process communication mechanisms in Linux include signals, pipes, shared memory, semaphores, sockets, etc. The kernel provides an API through SCI to create a new process (fork, exec or POSⅨ), stop the process (kill, exit), and communicate and synchronize between them (signal or POSⅨ mechanism).

The Linux operating system combines independent file systems into a hierarchical tree structure, and a single entity represents this file system. Since Linux supports many different file systems and organizes them into a unified virtual file system, the device driver provides a set of abstract interfaces that the operating system can understand to complete the interaction with the operating system, while the specific hardware-related The details of operation are done by the device driver. The network portion of the Linux kernel consists of BSD sockets, network protocol layers, and network device drivers. Network device drivers are responsible for communicating with hardware devices, and there is a corresponding device driver for every possible hardware device.

linux file system

Linux system can support a variety of currently popular file systems, and EXT4 is recommended.

The main file types under Linux are:
1) Ordinary files are divided into plain text and binary.
2) Directory file, where files are stored.
3) Link files, files pointing to the same file or directory.
4) Device files are divided into block devices and character devices.
5) Pipe files provide inter-process communication
6) Socket file, related to network communication

Linux uses a standard directory structure. The installation program has already created a file system and a complete and fixed directory composition for the user, and specified the role of each directory and the file types in it.

Directory name	A brief description
/bin	Binary executable command
/dev	Device special files
/etc	System management and configuration files
/etc/rc.d	Startup configuration files and scripts
/home	The base point of the user's home directory. For example, the home directory of user abc is /home/user, which can be represented by ~abc
/lib	Standard Programming Library
/sbin	System management commands, the management programs used by system administrators are stored here
/tmp	Public temporary file storage point
/root	System administrator’s home directory
/mnt	The system provides this directory to allow users to temporarily mount other file systems.
/lost found	This directory is usually empty. The system shuts down abnormally and leaves "homeless" files
/proc	Virtual directory is a mapping of system memory. This directory can be accessed directly to obtain system information.
/var	The overflow area of ​​certain large files, such as log files of various services
/usr	The largest directory, almost all the applications and files to be used are in this directory. Contains: /usr/X11R6 directory where X window is stored /usr/bin Numerous Applications /usr/sbin Some management programs for super users /usr/doc linux documentation /usr/include Header files required to develop and compile applications under Linux /usr/lib Commonly used dynamic link libraries and software package configuration files /usr/man Help Document /usr/src source code, the source code of the Linux kernel is placed in /usr/src/linux /usr/local/bin Locally added commands /usr/local/lib Locally added libraries

Shell is the user interface of the system, providing an interface for users to interact with the kernel. It receives commands entered by the user and sends them to the kernel for execution. It is a command interpreter. There are many types of shells, but BASH is recommended here. BASH is GNU's Bourne Again Shell, which is the default shell on the GNU operating system. Most Linux distribution packages use this shell. Linux Shell and Commands

Linux has many commands. A simple classification is given below.

Organizing Linux commands in the shell to complete a series of tasks is shell programming. Shell, Perl and Python are the most commonly used scripting languages ​​on Linux, and I still recommend using Python.

Linux Application

Standard Linux systems generally have a set of programs called applications, which include text editors, programming languages, X Window, Internet tools, databases, etc.

For text editing, Emacs and vim have their own merits. They can even be used as IDEs through plug-ins. Personally, I feel that VIM should be a necessary skill. There are also many commands in vim, which are summarized as follows:

As far as application management is concerned, ubuntu needs to be familiar with the apt command, and centos needs the yum command. Of course, source code compilation and installation are necessary. The writing of makefile and the usage of configure/autoconfig/make must be familiar to you.

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