How to use Linux under Help

As a beginner of Linux systems, it is important to learn to use the Get help command. In the following article, I summarize some commonly used methods to obtain help information, I hope I can help you in the future.

I. Use of Whatis

Whatis: Forquery what function a command performs and print the execution results to the terminal1. Database-based lookups
Advantages: Fast Search Speed
Cons: No real-time sex2. Database Files
Centos6:/var/cache/man/whatis
Centos7:/var/cache/man/index.db
3. Updating database files
Centos6:makewhatis
Centos7:mandb

Two. Use of Help

Help: Useful information for displaying commands inside the shell. The help command can only display command assistance information inside the shell. The Help information for external commands can only be viewed using the man or Info command. You can use the type command to see the types of commands before using them, and refer to different usages. Usage: type command If Output XXX is a shell builtin is an internal command, the other output is an external command.

1. External command:
Command–help or Command-h

2. Internal command:
Help command or Man bash

Three. Use of man

The practicality of the man command is very high, basically all UNIX-like systems are supported, so the use of man learning is very important. The reason we can man to help documentation is because there are help documents in the system, the files that provide the man command help exist in the/usr/share/man directory.
1. Man's help document classification

  1. Man1 executable programs or shell commands user commands and applications
2. MAN2 systems calls (functions provided by the kernel) system call and kernel error codes
3. MAN3 Library calls (functions within program libraries) libraries call
4. Man4 special files (usually found In/dev) device drivers and network protocols
5. man5 file formats and conventions EG/ETC/PASSWD standard files format
6. Man6 Games Game and demo
7. Man7 Miscellaneous (including macro packages and conventions), e.g. man (7), Groff (7) various files and documents
8. MAN8 System administration commands (usually only for root) administration commands
9. Man9 Kernel routines [Non standard] vague kernel specifications and interfaces

2.man Help paragraph description

–name Name and brief description
–synopsis Usage Format description
? [] Optional content
? <> Required Content
? A|b two Choose one
? {} grouping
?                                  ... The same content can appear multiple times
–description Detailed description
–options option Description
–examples Example
–files Related Documents
–author author
–copyright Version Information
–reporting BUGS Bug Information
–see ALSO Other Help reference

3.man Operation Button

SPACEBAR to turn down one page

Page DOWN pages

Page UP pages up

Y,k a line to the file header

E,j a line to the end of a file

B Flip screen to file header

U turn half screen to file header

D turn half screen to file tail

Home Direct to homepage

End goes directly to the end

1G back to file header

G turn to the end of the file

: Jump To Line #

/keywords search for a keyword from top to bottom

？ Keywords from bottom to top search for a keyword

N Navigate to the next search keyword

N navigates to the previous search keyword

Q Launch Help documentation

Four. Use of info

Man is often used for command reference, GNU tool info is more suitable for general document reference. Info page structure is like a website, no parameters, list all pages, each page is divided into "node", link node before there is "*" character hint. The info help document is stored under the/usr/share/info path. Usage: info command

The Operation button of info

？ Displays the common shortcut keys for info.

N Displays the document contents of the next node (relative to this node)

P Displays the document contents of the previous node (relative to this node)

U Enter the subject of the current command

M to enter the name of the command to see the help document for the command after tapping the M key

G Enter the subject name after tapping the G key to enter the topic

L go back to the last visited page

SPACE Scrolls forward one page

Backup or del scrolls back one page

Q Exit Info

Five. Other types of ways to get help

1. Local Help documentation

Through the local documentation to see the help, no network can also obtain the information, there are many internal Linux documents, these documents can not be viewed with the man or info command, only into the/usr/share/doc directory to view, the contents of the file is very detailed. And a lot of it, just/usr/share/doc/there are 1012 directories, which are not included under this subdirectory.
The following content is primarily included in the/usr/share/doc directory.
-a subdirectory of most of the installed packages, including a description of the relevant principles of these software
-Common documentation: README INSTALL changes
-Location of documents not suitable for other places
Configuration file Example
Documents in HTML/PDF/PS format
Details of the authorization letter

2. Online documentation Help

Getting help through online documentation is also a common way to solve problems. Usually go to the official website of the system distribution or third party software publisher to find the official information. By the way two Google search tips:
1.Openstack file type:pdf Filter Files of the specified type
2.rhcasite:redhat.com/docs search documents only on specified sites
Common third-party applications official documentation
http://www.nginx.org
http://tomcat.apache.org
http://httpd.apache.org
http://www.python.org

Installation guides, deployment guides, virtualization guides, and more can be obtained from the official website of the release version
Red Hat Knowledgebase and official online documentation Links:
Http://kbase.redhat.com
Http://www.redhat.com/docs
Http://access.redhat.com

Compare professional websites and search:
http://tldp.org
Http://www.slideshare.net
http://www.google.com

3. Red Hat Knowledgebase website

? rhn.redhat.com or local satellite server/proxy Server
– Network management-based servers
–RHN Proxy Server provides cache for portal traffic
–RHN Satellite Server provides autonomous portal
? Portal Account
– for its registered and web-based management of customer portal users
– System ID for automatic system validation
? Sosreport
A tool that collects log information on all systems and automatically compresses the package to facilitate technical support
People and Red Hat Global support to provide analysis based on

How to use Linux under Help