Linux network related, FIREWALLD and netfilter, NETFILTER5 table 5 chain Introduction, IPTA

Linux Network related

Ifconfig View network card IP (need to install Net-tools package) IP Add can also view network card IP
yum install -y net-tools

When your network card does not have an IP, it is not displayed, but plus-a can be viewed.
ifconfig -a

Turn off the specified network card (if you are connecting this network card using this command will disconnect, so do not use this command to close the network card in use) (Ens33 is the network card name, based on the current server network card name)
ifdown ens33

Start the specified NIC
ifup ens33

Specifies that the network adapter being used is restarted
ifdown ens33 && ifup ens33

To set the virtual network card method:
First to the NIC directory
cd /etc/sysconfig/network-scripts/

Copy the network card (plus backslash \ is to drag the meaning:, ens33:0 for the new NIC name)
cp ifcfg-ens33 ifcfg-ens33\:0

Then edit it, change the red part, and the green section can not. (This place ens33:0 does not need to add anti-slash drag meaning)
vi ifcfg-ens33:0

Save exit, and then restart the NIC
ifdown ens33:0 && ifup ens33:0

Then use Ifconfig to see the virtual network card.
ifconfig

Then we can try to ping.

Check whether the network card is connected (Ens33 is the name of the network card, if the end is link OK is connected, no link is not connected, sometimes will not show support)
mii-tool ens33

If not, we can use Ethtool Ens33 (Ens33 as the NIC name) (and then look at the last line link detected if yes is connected, no is no connection.) ）
ethtool ens33

Change host name (Shuaiyangyang is the modified host name)
hostnamectl set-hostname shuaiyangyang

You can use hostname to view it, but you need to log back in to change it, or you can use the Bash command to enter the child shell as well.
hostname

Host Name Master profile location
cat /etc/hostname

DNS配置文件位置（该配置文件只能临时修改，重启网卡后失效）

cat /etc/resolv.conf

Custom domain name, change resolution address, ping URL specified IP (only valid on this computer)
cat /etc/hosts

For example, we visit www.baidu.com, (we use ping) to access the IP is Baidu's IP, but we now want to let him access to 192.168.71.134 this IP, we will modify this configuration file

Vim opens this configuration file
vim /etc/hosts

Under another line, make the following edits

Save the exit, we will ping the Baidu can see, it has automatically jumped to 192.168.71.134 this IP came up

Support for more domain names after one IP, split with spaces. If a domain name sets multiple IPs, it will take effect with the last IP setting

Firewalld and NetFilter

SELinux Shutdown method (General enterprise is closed)

Temporarily closed
setenforce 0

Permanently closed, you need to go to the configuration file to close

Enter configuration file
vi /etc/selinux/config

Change the red position of the word enforcing to the green part of the word disabled

After saving the reboot, we can use Getenforce to see if SELinux is off
The enforcing is on, permissive is off state. (Because a reboot is required to take effect, I do not restart)

NetFilter Firewall and FIREWALLD firewall

Linux network related, FIREWALLD and netfilter, NETFILTER5 table 5 chain Introduction, IPTA