Linux is currently the most widely used server operating system, based on Unix, open source and free. Due to the stability and security of the system, the market share is very high, almost becoming the best system environment for program code operation. Linux can not only run the program code we have written for a long time, but also can be installed in various computer hardware devices, such as mobile phones and routers. The bottom layer of the Android program is run on the Linux system.

First, the directory structure of Linux

/ Subordinate directory structure

bin (binaries) stores binary executable files
sbin (super user binaries) stores binary executable files, only root can access
etc (etcetera) stores system configuration files
usr (unix shared resources) is used to store shared system resources
home The root directory where user files are stored
root super user directory
dev (devices) is used to store device files
lib (library) stores shared libraries and kernel modules needed to run programs in the file system
mnt (mount) The installation point where the system administrator installs the temporary file system
boot stores various files used for system boot
tmp (temporary) is used to store various temporary files
var (variable) is used to store files that need to change data at runtime

Second, linux commonly used commands

Command format: command-option parameters (options and parameters can be empty)

如：ls -la /usr

2.1 Operation files and directories

2.2 Common system commands

2.3 Compression and decompression

2.4 File permission operation

Interpretation of the description format of linux file permissions

r read permission, w write permission, x executable permission (also can be expressed in binary 111 110 100-> 764)
Bit 1: File type (d directory,-ordinary file, l link file)
Bits 2-4: user rights, represented by u (user)
Bits 5-7: Group permissions, represented by g (group)
Bits 8-10: Other user rights, indicated by o (other)
Bits 2-10: indicates all permissions, with a (all)

3. Commonly used shortcut keys and symbol commands in Linux system

Four, vim editor

vi / vim is the most commonly used text editor on Linux and is very powerful. There are only commands and no menus. The following figure shows the various modes of the vi command.