Docker has been installed and the execution command does not take effect.

With the development of modern software development, containerization technology has also become rapidly popular. As a popular containerization solution, Docker is widely used in the development and deployment of various applications. However, sometimes when using Docker, you will encounter some problems. This article will discuss one of the common problems: Docker has been installed, but the executed command does not take effect, and provide some solutions.

1. Problem description

When using Docker, sometimes you will encounter the following situation:

1. Docker has been installed, but when executing the command, you will be prompted to find The command cannot be found;
2. When executing the Docker command, a prompt of insufficient permissions will be displayed.

These problems may seem simple, but they have a greater impact on development and deployment work. Next, we’ll explore solutions to these problems in detail.

2. Cause of the problem

1. The problem of not finding the command

After installing Docker, many users will directly enter the Docker command in the terminal . However, sometimes a prompt such as "command not found" will appear, indicating that the command cannot be found.

The root cause of this problem is that the system does not correctly set the Docker environment variables. When Docker is installed, Docker binary files will be generated, and these files will be placed in /usr/bin/docker by default. However, if the system's environment variables are not set correctly, the system cannot find these files, resulting in a "command not found" error message.

2. The problem of insufficient permissions

When executing Docker commands, sometimes there will be insufficient permission problems, such as "permission denied" and other prompts. The cause of this problem is that the current user does not have sufficient permissions to execute Docker commands.

Docker needs to run under the permissions of the root user, but after installing Docker, many users may directly use non-root users to operate. This will lead to the problem of insufficient permissions.

3. Solution

1. Solution for command not found

First, we need to check whether the system environment variables are set correctly. In Linux systems, you can use the following command to view all environment variables:

printenv

After using the above command, you can see the list of environment variables of the current system. We need to check if the PATH variable contains the Docker binary path. If it is not included, you will need to manually add the path to the PATH variable.

For example, if your Docker binary path is /usr/bin/docker, you can use the following command to add the PATH variable:

export PATH=$PATH:/usr/bin/docker

This command will put /usr/bin/docker The path is added to the end of the PATH variable. In this way, the system can correctly find the Docker command.

In order to avoid having to manually add the path every time we need to use Docker, we can add the above command to the Bash configuration file, such as the .bashrc file. In this way, the system will automatically add the path every time you open the terminal.

If you still cannot find the Docker command after the above operations, please try restarting the terminal or restarting the system.

2. Solution to Insufficient Permissions

First, we need to ensure that the current user has been added to the Docker user group. In Linux systems, you can use the following command to view the user groups to which the current user belongs:

groups

After using the above command, you can view all user groups to which the current user belongs. If the current user has not been added to the Docker user group, you need to add it to the user group. You can use the following command to add a user to the Docker user group:

sudo usermod -aG docker <username>

In the above command, "" is the username of the user who needs to join the Docker user group. It should be noted that this operation needs to be performed with sudo permissions.

After executing the above command, you need to log in again as the current user for the operation to take effect. After that, when executing Docker commands, there will be no problem of insufficient permissions.

It should be noted that joining the Docker user group may have certain security risks. Therefore, the associated security risks need to be carefully considered before joining.

4. Summary

During the use of Docker, Docker commands may not take effect due to various reasons. In this article, we explain the causes of this problem and provide solutions. If you encounter similar problems, you can solve them according to the methods provided in this article.

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