Run ifconfig to view the NETWORK adapter IP address
Netstat Displays the network port number
Netstat-tulpn or netstat-ano
Netstat Common options
T Displays the TCP connection status
U Displays the udp connection status
L Displays network connections in the listening state
P Displays the application PID and program name
N Displays the IP address
A Displays all connections
O Display timer
View process && Kill process
ps -ef
kill -9 PID
systemctl
Start Starts the service.
Stop Stop the service
Restart Restart the service.
Enable Enables startup upon startup
Disable Disables startup
Status Displays the service status
Daemon-reload Reload the service configuration file
List-unit-files Lists all services
Common commands used by users and user groups
Useradd creates a new user
Passwd Changes the password
Usermod Modifies user information/assignment group (overwrites the original group)
Groupadd Creates a user group
Chown Changes the owner or owner group of a file
Chmod Changes the access permission of a file
Newgrp Switches the current user group
sudo
Sudo allows ordinary users to have execution privileges as super administrators
Common users must be authorized by the super administrator
Authorization command: visudo
A firewall
A firewall is a measure to protect the internal and external network environment by means of hardware and software
CentOS 7 uses firewall to implement application-layer firewall, and CentOS 6 uses iptables
Firewall-cmd is the core firewall command
Linux shell classification
Bourne Shell /usr/bin/sh or /bin/sh
Bourne Again Shell /bin/bash (default)
C Shell /usr/bin/csh
K Shell /usr/bin/ksh
Shell for Root /sbin/sh