Analysis and description of network configuration files under Ubuntu system

I encountered a strange network problem today. I recorded the research process and some configuration situations, and learned about the network environment configuration under Linux.

Network Configuration Files

This file configures the network card information vi /etc/network/interfaces

auto lo
iface lo inet loopback
# Configure eth0 dhcp to obtain IP address auto eth0
iface eth0 inet dhcp

The role of configuration

There may be some configurations in /etc/network/interfaces, such as

auto lo
iface lo inet loopback

These two lines indicate that the auto lo system automatically configures the lo interface when it starts, and then configures a local loopback address for the lo interface.

If you want to configure a static address for the network card

auto eth0
iface eth0 inet static
 address 192.168.2.100
 network 192.168.2.0
 netmask 255.255.255.0
 broadcast 192.168.0.255
 gateway 192.168.0.1

The following lines represent the IP, network number, mask, broadcast address and gateway of the eth0 interface respectively.

If you want to configure DHCP to automatically obtain an IP address

auto eth0
iface eth0 inet dhcp

For more configuration information, see man interfaces

Go to the /etc/network directory and you will find many interesting directories.

if-down.d
if-post-down.d
if-pre-up.d
if-up.d

These directories are all network configurations implemented in Debian. When if-up occurs, the scripts placed in the if-up.d directory will be executed. This can be used to achieve some interesting things. For example, if you write a sign-in script, you can automatically sign in when the laptop is connected to the Internet, or start the VPN after connecting to the Internet.

Add execute permissions

chmod 755 /etc/network/if-up.d/YOUR_SCRIPT

Note that scripts are executed in lexicographic order.

Another way is to define the script in /etc/NetworkManager/dispatcher.d/, which can do the same thing, but it depends on NetworkManager.

Configure DNS

The DNS configuration file is in the /etc/resolv.conf file, which is usually

search domain
nameserver 127.0.0.53

Restart the network card

sudo ifup eth0
sudo ifdown eth0
# or
sudo ifconfig eth0 down
sudo ifconfig eth0 up

Restart the network

sudo /etc/init.d/networking restart
sudo /etc/init.d/network-manager restart

Summarize

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