Let's talk about the login method of docker container

Docker is a popular containerization technology that makes it easier for applications to run in different environments. Docker is a very convenient tool for developers because it allows them to quickly build, test and debug containers on their local machine. In this article, we will learn how to log into a Docker container.

1. Use the docker exec command to log in to the container

Docker provides a command line tool docker exec, which allows us to log in to the running container. The following is the syntax to log in to a container using the docker exec command:

docker exec -it container_name_or_id /bin/bash

where container_name_or_id is the name or container ID of the container. /bin/bash is the command to be run in the container. It starts a bash shell so that we can execute commands within the container.

For example, assuming we have a running container named my_container, you can use the following command to log in to inside the container:

docker exec -it my_container /bin/bash

Of course, if you want to To run other commands in the container, you can replace /bin/bash with the path of other commands.

2. Use the docker attach command to log in to the container

In addition to using the docker exec command to log in to the container, we can also use the docker attach command to connect to the container and view the output in the container.

The syntax for using docker attach is as follows:

docker attach container_name_or_id

This command will connect you to the specified Docker container, allowing you to view the stdout and stderr output inside the container. But it should be noted that when you use docker attach to connect to a container, it will connect the standard input and standard output to the inside of the container, which means that you can only see the output in the container, but not execute it in the console Other commands.

3. Use SSH to log in to the Docker container

If you want to perform more operations in the Docker container, such as system management, modifying configuration files, etc., then use SSH Logging into the container might be a better option.

Using SSH to log in to the Docker container requires completing the following two steps:

Step 1: Install the SSH service in the container

First, we need to install the SSH service in the container. For Debian or Ubuntu-based containers, you can install SSH using the following command:

apt-get install -y openssh-server

For CentOS or RHEL-based containers, you can install SSH using the following command:

yum install -y openssh-server

Step 2: Use the SSH client Connect to the container

After installing the SSH service, you can use the SSH client to connect to the container. The information you need is:

• The IP address of the container: You can use the docker inspect command to view the user name and password of the SSH service in the
• container: If you have not set a user for the SSH service name and password, then you can use the default username and password in the container (such as root/root) when logging in

For example, run the following command in the container to view the IP address of the container:

docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' container_name_or_id

After obtaining the IP address of the container, you can use the SSH client to connect to the container:

ssh root@container_ip_address

When you use SSH to connect to the container for the first time, you will be prompted to accept the RSA key. Enter yes and press Enter.

Then enter the password of the container to log in to the container.

Summary

Logging in a Docker container is a very basic operation. We can use docker exec, docker attach or SSH to log into the container. They each have their own merits, and we need to choose the method that suits our needs. No matter which method you use, you can debug, run commands, modify configuration files, etc. in the container, which provides more convenience for containerized application development and deployment.

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