How can you configure DNS resolution for Docker containers?

The main difference between Docker and traditional virtualization lies in the processing and resource usage of the operating system layer. 1. Docker containers share the host OS kernel, which is lighter, faster startup, and more resource efficiency; 2. Each instance of a traditional VM runs a full OS, occupying more space and resources; 3. The container usually starts in a few seconds, and the VM may take several minutes; 4. The container depends on namespace and cgroups to achieve isolation, while the VM obtains stronger isolation through hypervisor simulation hardware; 5. Docker has better portability, ensuring that applications run consistently in different environments, suitable for microservices and cloud environment deployment.

When encountering Docker problems, you should first locate the problem, which is problems such as image construction, container operation or network configuration, and then follow the steps to check. 1. Check the container log (dockerlogs or docker-composelogs) to obtain error information; 2. Check the container status (dockerps) and resource usage (dockerstats) to determine whether there is an exception due to insufficient memory or port problems; 3. Enter the inside of the container (dockerexec) to verify the path, permissions and dependencies; 4. Review whether there are configuration errors in the Dockerfile and compose files, such as environment variable spelling or volume mount path problems, and recommend that cleanbuild avoid cache dryness

There are three main ways to set environment variables in PHP: 1. Global configuration through php.ini; 2. Passed through a web server (such as SetEnv of Apache or fastcgi_param of Nginx); 3. Use putenv() function in PHP scripts. Among them, php.ini is suitable for global and infrequently changing configurations, web server configuration is suitable for scenarios that need to be isolated, and putenv() is suitable for temporary variables. Persistence policies include configuration files (such as php.ini or web server configuration), .env files are loaded with dotenv library, and dynamic injection of variables in CI/CD processes. Security management sensitive information should be avoided hard-coded, and it is recommended to use.en

There are three common ways to set environment variables in a Docker container: use the -e flag, define ENV instructions in a Dockerfile, or manage them through DockerCompose. 1. Adding the -e flag when using dockerrun can directly pass variables, which is suitable for temporary testing or CI/CD integration; 2. Using ENV in Dockerfile to set default values, which is suitable for fixed variables that are not often changed, but is not suitable for distinguishing different environment configurations; 3. DockerCompose can define variables through environment blocks or .env files, which is more conducive to development collaboration and configuration separation, and supports variable replacement. Choose the right method according to project needs or use multiple methods in combination

To expose Docker container ports, the host needs to access the container service through port mapping. 1. Use the dockerrun-p[host_port]:[container_port] command to run the container, such as dockerrun-p8080:3000my-web-app; 2. Use the EXPOSE instruction to mark the purpose in the Dockerfile, such as EXPOSE3000, but the port will not be automatically published; 3. Configure the ports segment of the yml file in DockerCompose, such as ports:-"8080:3000"; 4. Use dockerps to check whether the port map is generated after running.

A common way to create a Docker volume is to use the dockervolumecreate command and specify the volume name. The steps include: 1. Create a named volume using dockervolume-createmy-volume; 2. Mount the volume to the container through dockerrun-vmy-volume:/path/in/container; 3. Verify the volume using dockervolumels and clean useless volumes with dockervolumeprune. In addition, anonymous volume or binding mount can be selected. The former automatically generates an ID by Docker, and the latter maps the host directory directly to the container. Note that volumes are only valid locally, and external storage solutions are required across nodes.

When running PHP, you need to pay attention to the environment configuration and container stability when running Docker. First, prepare a PHP project with a clear structure, ensure that there are dependent files such as composer.json, and place the code in a separate directory for mounting; second, use the official PHP image to quickly start container testing, such as using the CLI image to execute simple scripts; then write a custom Dockerfile image, copy the code, install the extensions, and enable the necessary modules; finally handle debugging and common problems, including permissions, missing dependencies, Apache operation and log viewing. It is recommended to build a custom image and optimize the configuration when deploying and launching it online.

The key to debugging code with VSCode in Docker containers is to configure the development environment and connection methods. 1. Prepare a mirror with development tools, install necessary dependencies such as debugpy or node, and use the official devcontainers image to simplify configuration; 2. Mount the source code and enable the Remote-Containers plug-in, create .devcontainer folders and configuration files, and realize in-container development; 3. Configure the debugger, add debug settings for the corresponding language in launch.json, and enable the listening port in the code; 4. Solve common problems, such as exposing the debug port, ensuring the host is 0.0.0.0, and use postCreateC