Some common commands for Linux beginners (3)

pipeline | 
  An important concept that uses the output of one command as input to another command
  For example:
   find 192.168 strings in ifconfig results
   Ifconfig | grep 192.168

   find Java-related processes
  ps-ef | grep java
   Find and 3306 related information
  ps-ef | grep 3306
 
   
system administration Command
 date Display or set the system time
  date  display the current system time
  date-s "2014-01-01 10:10:10"   Set the system time
    
 clear Clear Screen
  ctrl+l
  
 ps Status of a process that is running
  ps–ef  view all processes
  ★ps–ef | grep ssh finds a process
 
 kill Kill a process
  kill 2868  kill 2868 numbered process
  ★kill-9 2868  Force kill process

Network management
Ifconfig: View all network settings
Ifconfig nic name down: Disable NIC
Ifconfig nic name up: Enable NIC

Ping: Same as in window
Cancel with Ctrl + C

Netstat view the network ports.
Netstat-an | grep 3306 Query 3306 port occupancy

User Management
Add to
Useradd Username: The default is to create a directory for a user in the home directory
passwd User name: Enter password

Useradd User name-d/home/directory: Create a user and then specify the user's home directory

Delete
Userdel User name: Just delete the user but do not delete the home directory
Userdel-r User name: Delete user with home directory delete

To switch users:
Ssh-l User name-P 22 Host
Example: Ssh-l tom-p 22 192.168.17.131
Su-user name

Group Management
Add to
Groupadd Group Name
Useradd User name-G group name
Delete
Groupdel Group Name
Attention:
If there are users under the group, can not delete

permissions for the file:
Normal files: Include text files, data files, executable binaries, and so on.
Catalog files: The Linux system sees the directory as a special kind of file, which makes up the tree structure of the file system.
Device files: The Linux system sees every device as a file

List by LL show
Starting with D is the catalog file
To-start with a normal file

Permissions for a file 9 letters three three a group
The first group represents the permissions of the current user
The second group represents the permissions of the group
The third group represents the rights of other users

R: Read 4
W: Write 2
X: Perform 1

chmod Change the permissions of a file or directory.
chmod 755 A.txt
chmod U=rwx,g=rx,o=rx A.txt
chmod a.txt/
★chmod 777 A.txt

Chown changing a file or directory to the user and group to which the file belongs
Chown u1:public a.txt: Change the owning user and group of the current directory or file
Chown-r u1:public dir: Change the user and group of all subdirectories and files in the directory
Format:
Chown User: Group file

Some common commands for Linux beginners (3)