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Build docker image tools12/18/2023 However, they provide no isolation to that software and dependency conflicts occur often. Package tools like apt-get make installing and uninstalling software easier than if you have to do everything by hand. When it is finished, you can test the installation by running the “git” program: git version This will tell APT to download and install Git and all of its dependencies on the container’s file system. You can do that by running the following command: apt-get –y install git Next you need to install Git in the container. You should now have an interactive shell running with your container. Ubuntu ships with a Linux tool for software installation called “apt-get.” This will come in handy for acquiring the software that you want to package in a Docker image. From this prompt you can issue commands to customize your container. This will start a new container running the Bash shell. To get started building your own image, the first thing you will need is a container created from an appropriate base image: docker run -it -name image-dev At the moment, however, you only need to know that it is a program that you are going to install onto an Ubuntu image. If you are unfamiliar with it I recommend that you spend some time learning how to use it. Whole books have been written about the topic. Git is a popular distributed version control tool. In this case, you’ll be packaging a program called Git. Now that you’ve gotten an idea of the workflow, you should try to build a new image with real software. However, the basic steps will always be the same. If that seems stunningly simple, you should know that it does become a bit more nuanced as the images you produce become more sophisticated. # Test the new image docker run -rm hw_image # Commit the changes you made in that container With these steps in mind, work through the following commands to create a new image named, “hw_image.” # Modify a new containerĭocker run -name hw_container ubuntu:latest Figure 1 illustrates this workflow.įigure 1: Building an image from a container Once the changes are committed, you will be able to create new containers from the resulting image. The relationship between images, layers, and repositories will be revisited again in this chapter.įinally, once the changes have been made the last step is to commit those changes. These changes will be written to a new layer on the union file system for the container. The second step is to actually modify the file system of the container. You will choose the image based on what you want to be included with the new finished image and the tools you will need to make the changes. First, you need to create a container from an existing image. The basic workflow for building an image from a container includes three steps. A union file system (UFS) mount provides a container’s file system so any changes that you make to the file system inside a container will be written as new layers that are owned by the container that created them.īefore you work with real software, this article will detail the typical workflow using a Hello World example. It is easy to get started building images if you are already familiar with using containers. This article is excerpted from the book Docker in Action
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