What should I do if docker is created successfully but cannot connect?

Written in front:
This article mainly talks about the reasons and solutions when docker is successfully created but cannot be connected. It is a practical article for docker beginners. The operations and solutions in the article are based on the Ubuntu system environment.

In the process of using docker, there are some situations where even if your container is successfully created, it cannot be connected. This situation often makes people very distressed and cannot find the problem. This article will use a practical case to explain the reasons and solutions for why docker is successfully created but cannot be connected.

Case description:

We used docker to create an nginx container on the local computer, but when accessing it, we could not connect successfully.
The steps are as follows:

1. Install docker on the Ubuntu system

Enter the following instructions on the command line:

sudo apt-get install docker. io

After the installation is complete, use the following command to start docker:

sudo systemctl start docker

2. Create nginx container on docker

Enter the following command on the command line:

sudo docker run --name mynginx -p 80:80 -d nginx

This command means: use the nginx image to create a new container, container The name is mynginx, which maps port 80 to the local port 80 and runs in the background.

3. Verify whether the container is created successfully

Enter the following instructions on the command line:

sudo docker ps

If the following content is displayed, Indicates that the container is created successfully:

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
aaed7c1b cccf nginx "/docker-entrypoint.…" 21 seconds ago Up 20 seconds 0.0.0.0:80->80/tcp mynginx

4. Visit nginx in the browser

Enter localhost or 127.0.0.1 in the browser to see the nginx welcome interface.

However, in some cases, nginx cannot be accessed.

Problem analysis:

First of all, we need to confirm where the problem lies.

1. View system firewall configuration

The default firewall tool of Ubuntu system is ufw, you can use the following command to view its configuration:

sudo ufw status

If the output is as follows, it means that the system firewall is on:

Status: active

To                         Action     From

22/tcp                               ’ ALLOW ’           ’ s ’s ’ s ’s ’ s ’ t - ----- ,                                                                      ##80/tcp ALLOW Anywhere
22/tcp (v6) ALLOW Anywhere (v6)
80/tcp (v6) Anywhere (v6)

Network connection status

Is the local network address correct?

listen 80 default_server;
listen [::]:80 default_server;

server_name localhost;

root /var/www/html;
index index.html index.htm;

location / {
    try_files $uri $uri/ =404;
}

# 新增的本机IP节点
server {
    listen 80;
    listen [::]:80;

    server_name <本机IP>;

    root /var/www/html;
    index index.html index.htm;

    location / {
        try_files $uri $uri/ =404;
    }
}

The problem that docker is successfully created but cannot be connected may be related to the network connection status, system firewall configuration, local network address settings, etc. By troubleshooting the problem and taking appropriate solutions, it can be resolved smoothly. In the future use of docker, don't panic when you encounter problems. You must calm down, check the logs carefully, determine the problem, and then formulate a solution. Only in this way can you better master docker technology and improve development efficiency.

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