igralni The EXPOSE keyword indicates which TCP/IP ports viewed from inside the Docker container should be accessible from outside the Docker container when it runs. By default you canât access any of the ports inside the Docker container – this means itâs secure by default and you have to choose what you want to expose and when. So what Iâm doing in the next three commands is updating the current Ubuntu image to the latest set of fixes and updates from Ubuntu, and then installing the default Java JDK and the wget utility. As I mentioned earlier, there are two steps to get a running container: you build the Dockerfile into an image, and then run the image as a container. The CMD instruction executes whatever comes after the CMD keyword when the Docker image created by this Dockerfile is run. A RUN command is exactly the same as executing a command at the Linux command line. My next command creates a file named eula.txt that shows that the user of this server has accepted the EULA agreement.