Introduction to Linux system installation and Linux connection finalshell

operating system （Operating System, OS） It's part of the software , It's the first layer of software based on hardware , It's a bridge between hardware and other software （ Or interface 、 A middleman 、 Agency, etc ）.

The operating system will control other programs , Manage system resources , Provide the most basic computing functions , Such as managing and configuring memory 、 Determine the priority of supply and demand of system resources , It also provides some basic service procedures , for example ： file system 、 Device drivers 、 The user interface 、 System services, etc .

The operating system makes it impossible for applications to deal directly with hardware , Instead, it must pass through the kernel of the operating system , Coordinate the running of multiple programs to prevent malicious programs from damaging other processes and monopolizing resources , Ensure the smooth operation of multi tasks .

The operating system provides external system calls , Then the system call is encapsulated into a library, and the library call is provided to the outside , The programmer only needs to base the library on API Interface to program , Don't care about the difference of the underlying hardware , It is convenient for program transplantation .

Linux Main characteristics of the system

Installation preparation

*Centos 7

Download address : http://isoredirect.centos.org/centos/7/isos/x86_ 64/CentOS-7-x86_ 64- DVD-1708.iso

*VMware workstation 15

First step ： Create a virtual machine

The second step ： Set the virtual machine file location ： 

The third step ： Configure processor and memory

Step four ： Configure network and hard disk

 

Step five ： Set the memory size of the virtual machine

Step six ： Choose install image  

 

Step seven ： Click on the install , Set up root password ： 

 

Linux Characteristics

It consists of small programs with single purpose ; Combining applets to accomplish complex tasks ;

Everything is a document ;

Try to avoid capturing user interfaces ;

The configuration file is saved in plain text format ;

Linux Of shell, Man machine interface .Linux Of shell Include GUI and CLI Two types of .

GUI Refers to the graphical interface , And windows similar . The more common ones are gnome、KDE and xface etc. .

CLI It's the command line interface . The more common ones are bash、csh、zsh、ksh and tcsh etc. , We usually use bash.

The first 2 course - Command line Basics
We can press Ctrl + Alt+ F2 Switch to the command line . When switching to command line login , Note that when entering the password , The screen is not echoed .

We can press Ctrl + Alt+ F1 Switch back to the GUI .

Linux The prompt at the end of the command line is “#” and ”$” Two different symbols

• $ No. is the prompt after logging in with an ordinary user
• # Number is to use super user root Prompt after login

Command line shortcuts

• CtrI+C： Terminate the current input , If you enter a lot of content on the command line , Incorrect input found , Or perform other tasks . Press down Ctrl+C after , Will automatically terminate the current input , Jump to the next line .
• TAB key ： Complete the current command ,Linux There are many commands or long paths in , Beginners can't remember , We can use TAB Key to complete .
• Ctrl+A： Move the cursor to the front ;
• Ctrl+E： Move the cursor to the last ;
• Ctrl+D： Exit the current terminal ;
• Ctrl+L： Clear current screen ;
• Ctrl+Z： Pause the current process , And CtrI+C No - What it looks like is Ctrl+ Z After pausing, the process can be resumed .

Log in through the network Linux

• ifconfig： View the current interface status , The default is auto get IP, The default network port name is ens33
• Centos7 Has been allowed by default SSH Sign in , We can go through .ss -Int： View the currently open tcp port , It already includes 22 Port no. , By allowing SSH Sign in .

Finalshell Use

Linux Command basic syntax format

• Sometimes commands have one or more options .
• Usually options consist of a single letter , And add a connector before the letter "-"
• Sometimes because there are too many options , We can use simpler expressions such as ：
  Is -a -l -t and Is -alt Is a meaning
• Some options can also be a continuous word , We call it the long option , Use two connectors to add a complete word, such as ：Is --help
• --help Most commands Help options for , You can view the basic usage of the command
• meanwhile , Most commands can be followed by arguments , Parameters usually refer to file names 、 Catalog 、 user name 、 equipment . It can be interpreted as The order is to
• The object of the operation .
• To sum up , The option is to tell the command ” What about? ” perform , Parameters tell the command " To whom ” perform

linux Command history

• Shell History Is a list of previously entered commands
• adopt history Command to view previously executed commands
• ! Numbers   perform history Command number specified in
• !! Execute the last order
• !?is? perform history Contained in the is The order of
• You can also select historical commands from the top and bottom of the key head

The first 3 course - File system and directory

/ yes Linux Start of all paths , Is the root of all directories

Linux The whole directory is a tree structure , Pictured

System start-up must be

• /boot： Start of storage Linux The kernel file used when , Including connection files and image files .
• /etc： Store all configuration files and subdirectories required by the system , Changing the files in the directory may cause the system to fail to start .
• /lib： Store the base code base （ such as C++ library ）, Its function is similar to Windows Inside DLL file . These shared libraries are required for almost all applications .
• /sys： This is a linux2.6 A big change in the kernel . This directory has 2.6 A new file system in the kernel sysfs.sysfs The file system integrates the following 3 File system information ： For process information proc file system 、 For equipment devfs File system and for pseudo terminal devpts file system . The file system is an intuitive reflection of the kernel device tree . When a kernel object is created , The corresponding files and directories are also in the kernel object subsystem .

Instruction sets and ：

• /usr/bin： Application programs and instructions used by system users .
• /usr/sbin：s Namely Super User It means , yes Superuser Binaries（ Super user binaries ） Abbreviation , Here is the system management program used by the system administrator .

External document management ：

• /dev：Device（ set up To prepare ） Abbreviation , Deposit is Linux External equipment of . Be careful ： stay Linux The way to access devices and files in is the same .
• /media： class windows Other equipment , for example U disc 、 Optical drive and so on , After identification linux Will put the device in this directory .
• /mnt： Temporarily mount other file systems , We can mount the CD-ROM drive on /mnt/ On , Then enter the directory and you can view the contents of the CD-ROM drive .

The temporary file ：

• /run： It's a temporary file system , Information since the storage system started . When the system restarts , The files in this directory should be deleted or erased . If you have /var/run Catalog , It should point to run.
• /lost+found： It's usually empty , After the system is shut down illegally , Here are some files .
• /tmp： This directory is used to store some temporary files .

Account ：

• /root： System administrator's user home directory .
• /home： User's home directory , Named after the user's account .
• /usr： Many of the user's applications and files are in this directory , Be similar to windows Under the program files Catalog .
• /usr/src： The default placement directory for kernel source code .

Use... During operation ：

• /var： Store frequently modified data , For example, the log file of program running （/var/log Under the table of contents ）.
• /proc： Manage memory space ！ Virtual directory , Is a mapping of system memory , We can access this directory directly , Get system information . The contents of this directory are not on the hard disk but in memory , We can also directly modify some of the files to make changes .
• proc The contents of the directory are not on the hard disk, but in memory , We can also modify some files directly , For example, you can use the following command to shield the host ping command , Make it impossible for others to ping Your machine ：echo 1 > /proc/sys/net/ipv4/icmp_ echo. ignore_ all; recovery ping Same as ：echo 0 > /proc/sys/net/ipv4/icmp_ echo. ignore_ all

Create and delete ：

• Create directory ：mkdir
• Delete directory or file ：rm
• Delete non empty directory ：rm -rf file Catalog
• Delete log rm *log （ Equivalent $find ./ -name“*log" -exec rm {} ;）
• Move （ shear ）：mv The original document Target file
• Copy file ：cp The original document Target file
• duplicate catalog ：cp -r Original catalogue Target directory

Directory switching ：

• file found / Directory location ：cd
• Switch to the previous working directory ：cd -
• Change to parent directory ：cd
• Switch to home Catalog ：cd or cd ~
• Switch to /root Catalog ：cd /root
• Show current path ：pwd
• Change the current working path to path：$cd path

Absolute path ： from Linux Root directory / Start writing , such as /var/log, Get into /var/log

Relative paths ： The path is not written from the root directory , But relative to the current pwd The catalog of

For example, enter /var/log Catalogues can be written

cd /var： here /var It's the absolute path

cd log：log Is a relative path , be relative to var/ for

List the contents ：

• ls： Show files in current directory , Common options ：
• -a   List all files , Contains hidden files
• -l   It is displayed as a list
• -1 （ Numbers 1） Display in branches
• -t  Sort by time
• -r  Reverse order
• -R  Include subdirectories and files of the directory

Sort by time , Show directory entries as a list ls -lrt

If ls -lrt Use it very often , We can give him an alias , stay .bashrc Set command alias in ：alias lsl='ls -lrt'

View file type ：ls -l

ln command ： Create link file

ln -s file A file B

file type ：

• -： Represents a common file
• d： Represents a catalog file
• b： Represents a block device file , such as /dev/sda
• C： Represents a character device file , such as /dev/tty
• l： Represents a soft link file , such as /etc/rc.local
• p： Represents a pipeline file
• s： Represents a socket file