Linux Learning Summary--linux program management, terminal type and command get help way

This chapter blog related Linux knowledge points

Computer = hardware + software.

Von Neumann theory, five parts: cpu--arithmetic, controller, memory, input device, output device.

The Shell environment configuration is configured through environment variables, and environment variables are saved to the application's configuration and are valid in the current process. If it is valid for a long time, it must be saved to the configuration file.

Language classification:

Interpreted language-the written program requires a specialized compilation process to compile the program into a machine-language file before it is executed, and the compiled language: the explanatory language is translated when the program is run and is less efficient. The two ways are only a different time to translate

The relationship between the program and the process:

The program runs-the process starts, the process-from the shell parent process fork itself. Process: is a program that can execute concurrently on a data set of the process, is the system for resource allocation and scheduling of independent units, the process and the program is not one by one corresponding, a program execution on different datasets become a different process. In general, a process must have a corresponding program, and only one. While a program may not have a corresponding process, there may be multiple processes corresponding to it.

Bash:

Administrator: Prompt #

Normal User: Prompt $

Environment variable: Only the current process is valid, named memory space

Reference environment variable: echo ${variable} #echo $PS 1

[\[email protected]\h \w]\$: \u represents the logged-in user name, \h represents the hostname, and \w represents the path base name of the working directory

For Linux, the path delimiter:/

Relative path: The path starting at the current position

Absolute path: The path starting from the top level

Linux File system features:

Filenames can use any character except/extra, but cannot exceed 255 characters in length

Strictly case-sensitive

Two command types in bash, you can use the #type command to determine the type of command

Builtin: Commands implemented inside the shell program are built-in commands

External command: There is an executable file with the same command at a location in the file system

Shell:

Multiple paths are set up in advance with a variable, and when the user enters a command, the shell automatically checks to these paths (left to right) to see the executable file with the same name as the command will be saved to a hash lookup table, #hash look at the hash table

Command format:

Command Options arguments

Command option Parameters

Options: Adjust the execution characteristics of a command

Option can have multiple

Short option:-char, can be merged; Long option:--word, multiple options must be separated by a space;

Some options require parameters;

Parameters: The Action object of the command

Some commands can take multiple parameters, and each parameter is separated by a space;

Program four elements: binary files, configuration files, library files, and Help files

Linux Program Manager

Binary programs, configuration files, library files, Help files

Debian Manager: Deb

SuSE, Redhat Manager: rpm

General Software

Kernel: FileSystem (file system), network protocol stack, process management, encryption and decryption mechanism, driver, create index encryption, decryption function, TCP/IP protocol (kernel module)

Application software

System Management: Network configuration, file system (partition, RAID), user, file (create, delete, move, permissions), encrypt decrypt, kernel (compile), boot process, package management

Network Service Management: Web (apache,nginx,mysql,php), NFS, DNS, FTP, postfix/d: Ovecot, network Security (Iptables, Tcp_wrapper)

Mysql:crud, indexing, storage engine, backup recovery, clustering, sharding

Clusters: LB, HA, Hadoop, GFS

Web:nginx, Haproxy, keeplived, Tomcat, Distributed File System, CDN, Nosql

Virtualization: Xen, KVM, Lxc/openvz

Laas:openstack

Automated operations: Zabbix, Nginos, Python

Massively parallel processing platform: Hadoop

Linux terminal type

Serial terminals, such as/dev/ttys/#

Physical terminals, such as/dev/console

Virtual terminal, ctrl+alt+f "1-6", Ctrl+alt+f7 start graphical interface (first start the graphics function #startx), such as/dev/tty/#

Pseudo terminal (analog terminal), remote connection, graphical environment open remote interface.

Ctrl +c cancels the current program, such as: #startx & indicates running in the background

Shift +pageup/pagedown screen to see the number of previous command interfaces

Linux command Help information

Built-in commands:

# Help command get internal command assistance

External command:

# command--help Get External command help

# Man Command view command manual

# info COMMAND online documentation

Documentation from the application:/usr/shared/doc Help documentation

Google Web view Help

Add: Man can actually provide help for commands (common commands, administrative commands), program configuration file formats, system calls, library calls, games, and other inconvenient files.

Man's use mechanism:

Flip Screen:

Space to flip a screen to the end of the file

b Flip a screen to the file header

Enter: Flip a line to the end of the file

K Flipping a line to the file header

Ctrl +d half screen to the end of the file

Ctrl +u half screen to file header

Text Search:

/keyword searching the end of a file

Keyword to file header search

n the same direction as the Search command (next)

N the opposite direction of the search command (previous)

Q: Exit

Man segmentation mechanism: 1-8

1. User Commands 2. System call 3. Library call 4. device file 5. file format 6. Games 7. Miscellaneous 8. Administrative commands

Linux Learning Rollup a common command:

# TTY: Displays the terminal device file for the current terminal, which is the end access type

# Who: View all users and their information for the current system login

# Hash: View Hash table

# Whatis Keyword: see which paragraphs in which a keyword is used help

# type command: Displays the specified command type

# dirname Path: View Path directory name

# basename Path: View Path base name

# Hash: View Hash table

# which command: View the specific path of an executable program, that is, the location of the external command

# Help Builtincommand: View the built-in command helper information

# command--help: Get External command Help

# Man command: View command manual

# info COMMAND online documentation

Linux Learning Summary--linux program management, terminal type and command get help way