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Virtual Machines Articles
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How to execute a script when I terminate a Docker container?
Introduction Executing a script upon container termination is the process of running a script or command when a Docker container is stopped or removed. This can be useful in a variety of scenarios, such as cleaning up resources, logging information, or triggering other actions. Container termination refers to the process of stopping or removing a Docker container. This can be done manually using the docker stop or docker rm commands, or automatically through the use of container orchestration tools or container lifecycle management features. Example 1: ONBUILD To execute a script upon container termination using the ONBUILD Dockerfile command, follow ...
Read MoreHow to cache the RUN npm install instruction when docker builds a Dockerfile?
Introduction When building a Docker image, one of the most time-consuming and resource-intensive steps is running the "RUN npm install" instruction. This instruction installs all the dependencies listed in your package.json file. Caching the results of this instruction can greatly improve the build time of your image. In this article, we will explore different strategies for caching the "RUN npm install" instruction in a Dockerfile. Caching Strategies There are several strategies for caching the "RUN npm install" instruction in a Dockerfile. These include − Using a .dockerignore file − This strategy involves excluding the node_modules directory from being copied ...
Read MoreHow many CPUs does a docker container use?
Introduction Docker containers are a popular way to package and deploy applications. One of the key features of containerization is the ability to isolate resources and limit their usage. In terms of CPU, it is important to know how many CPUs a container can use, as this can greatly impact the performance of the application running inside the container. This article will cover the concepts of CPU resource allocation in Docker, determining the number of CPU available to a container, configuring CPU resources for a container, and advanced techniques for managing CPU resources. Understanding these concepts will help ensure that ...
Read MoreHow can I use a variable inside a Dockerfile CMD?
Introduction Using variables in a Dockerfile CMD can greatly improve the flexibility and maintainability of container configuration. Hardcoding values in a CMD instruction can make it difficult to update or modify the container's configuration in the future. Using variables allows for more dynamic and reusable configurations. Prerequisites The prerequisites for using variables inside a Dockerfile CMD depend on the method you choose to use − Using shell expansion − No specific prerequisites are required. Using the ENV instruction − No specific prerequisites are required. Using the ARG instruction − No specific prerequisites are required. Passing variable at runtime − ...
Read MoreDocker add network drive as volume on windows
Introduction When working with Docker on Windows, it is possible to use network drives as volumes. This allows you to store data on a network drive and access it from within a Docker container. This can be useful in situations where you need to share data between containers, or between the host and the container. With network drive as volume, you can easily store, manage and backup your data in a centralized location and use it with multiple Docker containers. In this article, we will explore the process of adding network drives as volumes in Docker on Windows, and the ...
Read MoreProtect the Docker daemon socket
Introduction The Docker daemon is a background process that manages Docker containers and is responsible for the creation, execution, and deletion of containers. One key component of the Docker daemon is the Docker daemon socket, which is used to communicate with the daemon from the Docker CLI and other applications. It is important to secure the Docker daemon socket to prevent unauthorized access to the Docker daemon and to protect sensitive information that may be exposed through the socket. In this article, we will discuss the location and default permissions of the Docker daemon socket, potential security risks, and best ...
Read MoreHow to run splash using Docker toolbox?
Introduction Splash is a powerful tool for rendering JavaScript-based websites, making it an essential tool for web scraping and data extraction. In this tutorial, we will show you how to run Splash using Docker Toolbox, an older version of Docker that is no longer being maintained but is still available for download. Prerequisites Before you can get started, you will need to install Docker Toolbox on your machine. Docker Toolbox is a version of Docker that is designed to run on older systems and/or systems without native virtualization. It is available for Windows, macOS, and Linux. Follow the steps ...
Read MoreHow to reference embedded Docker resource files using file path URL?
Introduction Embedded Docker resource files are files included in a Docker image rather than stored on the host file system or an external network location. These files can be useful for including configuration files, scripts, or other resources that are needed by the applications or processes running in the Docker container. You can reference embedded Docker resource files in several different ways, including using file path URLs. This article explains what file path URLs are and how to use them to reference embedded Docker resource files. We will also provide tips and examples to help you use file path URLs ...
Read MoreHow to change user config in Docker tomcat 8?
Introduction In a Docker Tomcat 8 container, you may want to change the user configuration to add or modify users and roles. This modification can be useful for tasks like securing access to the Tomcat 8 instance or setting up different levels of permissions for different users. This article explains how to change the user configuration in a Docker Tomcat 8 container. We cover the steps involved in modifying the tomcat-users.xml file, building a new Docker image with the modified configuration, and running a Docker container from the new image. Prerequisites Before changing the user configuration in a Docker Tomcat ...
Read MoreHow to access JMX interface in docker from outside?
JMX and its use in Java applications JMX (Java Management Extensions) is a Java technology that provides a way to manage and monitor Java applications. It exposes a set of APIs and MBeans (Java objects that represent resources to be managed) that can be used to monitor and control the behaviour of a Java application. JMX is commonly used in Java-based applications to monitor performance metrics such as memory usage, CPU utilization, and thread counts, as well as to manage and configure the application at runtime. Accessing JMX from outside a Docker container When running a Java application in a ...
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