Summary of linux related commands

I have been studying for a while and want to sort out what I have written before. If there is any incompleteness, I will slowly add it later

[1]Linux Notes:

• Strictly case-sensitive

• Linux commands are distinguished; file names are also strictly case-sensitive;

• Linux is all Lowercase;

• All content in Linux is saved in file form, including hardware

Hardware file/dev/sd[a-p]

The CD file is /dev/sr0

• Linux has no extension

1. #Compressed package: .gz, .bz , .tar.bz2,

2. Script: .sh

3. Configuration file: .conf

4. Webpage files: .html, .php

5. Webpage files: .html, .php

## All Linux storage devices must be mounted before they can be used, including hard disks, U disks and optical disks

【2】Linux directory:



• /bin：
  bin is Abbreviation for Binary, this directory stores the most frequently used commands.

• /boot:
  Stored here are some core files used when starting Linux, including some connection files and image files.

• /dev:
  dev is the abbreviation of Device. This directory stores Linux external devices. Access the device in Linux. The way to access files is the same.

• /etc:
  This directory is used to store all configuration files and subdirectories required for system management.

• /home:
  The user’s home directory. In Linux, each user has his own directory. Generally, the directory name is based on the user named after the account.

• /lib:
  This directory stores the most basic dynamic link shared library of the system, and its function is similar to the DLL file in Windows. Almost all applications require these shared libraries.

• /lost+found:
  This directory is usually empty. When the system is shut down illegally, some files are stored here.

• /media：
  The Linux system will automatically recognize some devices, such as U disks, optical drives, etc. After recognition, Linux will Mount it in this directory.

• /mnt:
  The system provides this directory to allow users to temporarily mount other file systems. We can mount the optical drive in /mnt /, and then enter the directory to view the contents of the CD-ROM drive.

• /opt：
  This is the directory where additional software is installed for the host. For example, if you install an ORACLE database, you can put it in this directory. The default is empty.

• /proc:
  This directory is a virtual directory, which is a mapping of system memory. We can obtain system information by directly accessing this directory. .
  The content of this directory is not on the hard disk but in the memory. We can also directly modify some files in it. For example, we can use the following command to block the ping command of the host so that others cannot ping your machine:

  echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_all

• /root:
  This directory is the user home directory of the system administrator, also known as the super authority.

• /sbin:
  s means Super User. The system management program used by the system administrator is stored here.

• /selinux：
  This directory is unique to Redhat/CentOS. Selinux is a security mechanism, similar to the Windows firewall, but this The mechanism is more complicated. This directory stores selinux-related files.

• /srv:
  This directory stores some data that needs to be extracted after the service is started.

• /sys：
  This is a big change in the linux2.6 kernel. A new file system sysfs that appeared in the 2.6 kernel is installed in this directory.

  The sysfs file system integrates the information of the following three file systems: the proc file system for process information, the devfs file system for devices, and the devpts file system for pseudo terminals.

  This file system is an intuitive reflection of the kernel device tree.

  When a kernel object is created, the corresponding files and directories are also created in the kernel object subsystem.

• /tmp:
  This directory is used to store some temporary files.

• /usr：
  This is a very important directory. Many of the user's applications and files are placed in this directory, similar to Windows. program files directory.

• /usr/bin:
  Applications used by system users.

• /usr/sbin:
  A relatively advanced management program and system daemon used by super users.

• /usr/src: The default placement directory for kernel source code.

• /var:
  This directory stores things that are constantly expanding. We are used to placing directories that are frequently modified in this directory. . Includes various log files.

In the Linux system, there are several directories that are relatively important. You need to be careful not to accidentally delete or change internal files at will.

/etc: As mentioned above, this is the configuration file in the system. If you change a file in this directory, the system may not start.

/bin, /sbin, /usr/bin, /usr/sbin: This is the system’s default directory for placing executable files. For example, ls is in the /bin/ls directory.

It is worth mentioning that /bin and /usr/bin are commands for system users (normal users except root), while /sbin and /usr/sbin are commands for root.

/var: This is a very important directory. There are many programs running on the system, so each program will have corresponding logs, and these logs are recorded in this directory, specifically in the /var/log directory Next, the default placement of mail is also here.




【3】lsCommand

• ls View the current File

• ls -a View all files, including . and .. File

• ls -A View all files, excluding . and .. files

• ls -l View files to display file attributes, including file owners, all groups , permissions, creation time, etc.

Example: -rw-------. 1 root root 1191 May 21 17:45 anaconda- ks.cfg

1. -: represents ordinary file

2. d: file directory

3. l: Soft link

rread w write x execute

three bytes per permission

rw-	r--	r--
u Owner user	g Group to which group	o others other

1) 1 represents the citation coefficient

3) The third part is the owner

4) The fourth part is Group to which it belongs

5) The fifth part of the file size in bytes

6) The last modification time of the file

7) Part of the file name

• The difference between ls -lh and ls -l is the size of the file

Example: -rw-------. 1 root root 1.2K May 21 17:45 anaconda-ks.cfg

• ls -i query File i node, file unique identifier

Example: 262497 anaconda-ks.cfg 262147 install.log 262148 install.log.syslog

【4】Directory processing command

• mkdir creates directory

• mkdir -pCreate multi-level directories

• touch create files

• ##rmdir Delete directory

• rm -r Delete directory

• rm Delete file

• rm -rf force deletion, no confirmation required

• cp Copy the file: cp to The destination directory for the copied files to be copied

• cp -rCopy the file and rename it

• mv Switch filemv Switch the file to the switching destination

• pwd Display the current directory

• file: Read r: cat, more, less, head, tail

## Write w: vim
Execute x: scrip, command
directory Read: ls
Write: touch, mkdir , rmdir, rm
Execution: cd

【5】

Permission management command

1. chmod [ugoa +-=] [file or directory]

chmod 777 file name
chgrp changes the group to which the file belongs chgrp [user group] [file or directory]
umsk -S displays the default permissions of the file

5. 
   

u:userowner
g: The group to which group belongs
o:otherOthers
a:allEveryone
Use Numbers represent permissions: r--4 w--2 x--1 rwx:[421]:7 rw-[420]:6 r--[400]:4

【6】

File search command

find [Search range] [Matching conditions]

• find / etc -name init: Only init

appears in the file name find /etc -name *init*: The file name contains init
find /etc -name init*: The file name starts with init
find /etc -name init???: The file name starts with init and is followed by three characters
find /etc -iname init???: File name search is not case sensitive
find /etc -size +204800: By file name Size search + means the search element is greater than - means the search is less than the file size. According to the data block, one data block is 0.5k, then 100M=102400k=204800 data blocks

[7 】

Help command

• man [Command or configuration file]

• man ls

• ## /Configuration options

• more /etc/services: View configuration file

• man services

• whatis Command: Check the fate

• apropos configuration file: only view the configuration file content

• Command--help

【8】

Change the system time

• 1. Date: View the system time

• 2 ,[root@localhost ~]# date 020612214317.33

##Tue Feb 6 12:21:33 CST 4317
• [root@ localhost ~]# date 0612214317.33//////month, day, hour, minute, year.second

##Mon Jun 12 21:43:33 CST 2017

• 【9】
File compression format

1, .gz compression format

• Compressed file: gzip file name

• Decompressed file: gunzip file name

• gzip -d file

• Compressed directory: tar -cvf generated directory Directory to be packaged

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