![]() Scroll back to the beginning of this post to see the output of docker ps a to see the mappings. The output from these four commands shows us that Docker has mapped three of the containers to ports 8083, 8082, and 8081. ![]() So, xargs transforms command docker port ‘ID’ 80 into these four commands:ĭocker port 344bf90e09e7 80 docker port 8667dc69816a 80 docker port 322f55c7b223 80 docker port c5df9ef22d09 80 This tells xargs that when it sees ‘ID’ in the command that follows, replace it with the input from the pipe. ![]() Then it pipes ( |) the output to xargs with -I ‘ID’ as the first two arguments. Here’s how to examine port 80 on all four containers.įirst, this command line runs docker ps -aq. So, we need to tell xargs how to run this command. You need to pass it the container ID and the port you’re interested in. So, let’s get fancy.ĭocker port lists information about network ports in a container. Since you didn’t tell echo to add a carriage return, it printed all four IDs on one line. This command transformed the output of docker ps to:Įcho 344bf90e09e7 echo 8667dc69816a echo 322f55c7b223 echo c5df9ef22d09 When you pass it to xargs without any additional arguments, it defaults to /bin/echo for its command, and it appends its input to the end of the command you specify: Here’s an example that gives you an idea of what’s happening when you pipe the output of docker ps -aq to xargs. Xargs is a Linux utility that accepts entries from its input and executes the command you specify for each entry. The next two parts of the command to stop and remove all containers start with xargs. So, if you want to stop all of the running containers and remove everything, regardless of its previous state, provide the - a to docker ps. That’s because one of them isn’t currently running. If you drop the a, you only see three containers: ![]() You can combine the two arguments after a single dash ( -). The -aq option tells docker ps to list all containers ( -a) by container ID ( -q). Here’s a screenshot of a system with four containers: The first part of the command lists all of the containers on the system. How does this command work? Let’s take a closer look. $ docker ps -aq | xargs docker stop | xargs docker rm Here’s a command that will stop and remove all of the containers on your system, assuming the user running it is root or a member of the docker group. Stopping and Removing All Containers For the Impatient You’ll need to have Docker installed, as well as docker-compose. These examples will be for systems that use Docker’s shell-based tools, including macOS, Linux, and Windows with WSL. Then, we’ll look at Docker Compose, another tool that makes managing smaller collections of containers easier. We’ll focus on stopping and removing containers. Let’s look at how to make the Docker command line easier to use. And stopping and removing 10 containers is-well, you get the idea. Stopping and removing two containers is four. Stopping and removing a container from the command line takes two steps. Managing containers from the command line can be painful, but setting up an orchestration tool like Kubernetes or Docker Swarm is overkill for smaller systems. But as containers proliferate, controlling them gets more complicated, too. You can run almost any application with a single command and customize it for your environment via a consistent container-based interface. It’s an understatement to say that Docker is a game-changer for systems engineers and developers.
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