Shulou(Shulou.com)05/31 Report--

This article introduces the relevant knowledge of "what are the basic knowledge points of the Linux system". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Preface

Linux is an open source, free operating system, its stability, security, handling concurrency has been recognized by the industry, at present, many enterprise projects will be deployed to the Linux/unix system. Linux can be installed in a variety of computer hardware devices, such as mobile phones, tablets, routers, video game controls, desktops, mainframes and supercomputers. Strictly speaking, the word Linux itself only refers to the Linux kernel, but in fact people have become accustomed to using Linux to describe this operating system based on the Linux kernel and using GUN to project various tools and databases. It is professional, mainly used in servers, embedded systems, mobile terminal systems, etc., but the personal desktop is not as good as Windows.

1. System introduction of Linux.

"system administrator:"

Root is the system administrator under Linux.

Ordinary users can use su- to switch to system administrator after logging in.

"basic command:"

Command

Shutdown command shutdown-r now now restart the computer reboot now restart the computer logout shutdown-h now immediately shut down and log out cd.. Go back to the up directory to save the file ESC: wq! Do not save ESC: Q! Browse the files under the current directory ls to clear the desktop clear

Vi Editor

Vi editor is the most famous editor under Linux, and it is also a tool that must be mastered to learn Linux.

Vi can also be used to develop programs under unix.

"Linux can do java/c development:"

Write the simple java program "hello,world" in the vi editor of Linux

1. Vi Hello.java 2, enter I [enter insert mode] public class hello {public static void main (String [] args) {System.out.println ("hello,world");}} 3, enter esc key [enter command mode] 4, type wq to save exit / Q! Exit without saving 6, compile javac hello.java javac Hello.java 7, run java Hello [java is running a class file] ls command display current file ls-l command display detailed file list

"develop c programs or C++ (cpp) programs under Linux:"

Establish vi hello.cpp

# include int main () {printf ("hello!"); return 0;} gcc hello.cpp compiled with gcc compiler unnamed will be a.out file gcc-o [file name] [source text name] compiled with gcc compiler file name / a.out run c program under linux as long as input / can be run

2. File directory under Linux

"File directory:"

Linux's file system uses a hierarchical tree directory structure, in which the top level is the root directory "/", and then create other directories under this directory. It is very important to have a deep understanding of the Linux file directory.

The important directories in the root directory under linux are as follows: root directory, home directory, bin directory, sbin directory, mnt directory, etc directory, var directory, boot directory, usr directory, Tmp directory (all at the same level) root directory: directory used to store files related to root users home directory: directory used to store related files of ordinary users bin directory: directory used to store common commands sbin directory: used to store commands that can only be used with certain permissions mnt directory: used to mount floppy drive by default, Directory of the optical drive this directory can be used to mount files or use shared files etc directory: directory used to store configuration-related files var directory: directory used to store frequently changed files boot directory: directory used to store system boot files (important) usr directory: the default directory for installation (installation files will be installed in the usr directory by default) tmp directory Record: directory used to store temporary files cd / return to the home directory ls has the same function as dir to display the directory name

Displays the path under which the pwd command shows which path it is currently under

3. User management of Linux (ordinary users cannot use it)

User management commands:

Useradd command: useradd username (add user) passwd command: passwd username (change user password) userdel command: userdel username (delete user) userdel-r username (delete user and user home directory)

4. Common commands of Linux

"Common command 1:"

Specify run level command: init [012356] run level 0: shutdown 1: single user 2: multi-user state no network service 3: multi-user state has network service 4: system is not used reserved for user 5: graphical interface 6: system restart common run levels are 3 and 5 To change the default run level to change the id:5:initdefault of the file / etc/inittab: the numbers in this line press e to enter editing when you start the boot interface, enter e when entering the grub boot interface, press e when the second option is selected, enter 1 [single user level] at the end, and then press b to enter single user mode. *: the password of linux user can be modified by this method

"Common Command 2:"

Command pwd [Show current working directory] command cd [change directory] command ls [list files and directories] ls-a show hidden files ls-l display long list format command mkdir [create directory] command rmdir [delete empty directory] rm-f file delete is the file rm-rf folder delete directory

"Common Command 3:"

Tab key can complete the corresponding content command touch [create empty file] command cp [copy command] cp-r dir1 dir2 recursive copy command (copy subdirectory information) command mv [move file and change file name] command rm [delete files and directories] rm-rf * [delete all contents (including directories and files) r recursive f force]

"Common Command 4:"

Command more [display file contents with paging] command less [display file contents with paging] command grep [query contents in text] grep-n "find contents" [file name] command | [pipe command] in linux and unix systems | pipe command Send the result of the last command to | the latter command for processing command man [equivalent to help under dos] example: display information about the grep command man grep view port usage netstat-apn | grep port number kills the process using the port kill-9 process number enters the root directory cd / no matter which directory it goes to the root directory

"Common command 5:"

The command find [search for files and directories] in linux, because the file system is made up of hierarchical structures, it is not easy to find specific files and directories throughout the system. The "find" command can solve the above problem. 1. Search for and display files and directories with the specified name find /-name man in a specific directory: it means to search for files or directories with the name man from the root directory, and to search for files or directories that have been accessed / changed within a period of time. Find / home-amin-10: files or directories accessed within ten minutes find / home-atime-10: files or directories accessed within ten hours find / home-cmin-10: files or directories changed within ten minutes find / home-ctime + 10: files or directories changed ten hours ago, search for files of a specified size. Find / home-size + 10k: it means to find a file with a size of 10k in the / home directory. Find file directly looks for file find-name "* keyword *" fuzzy search.

"Common command 6:"

The file type is determined by the file header field, not by the file suffix. Redirect command: pipe direction command ">" overwrite, "> >" append the contents of the ls-l > a.txt list written after the contents of the original file to the file a.txt (overwrite) ls-al > > aa.txt list append to the end of the file aa.txt input information database_program from the file

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