What is docker compose exec ?
Docker compose can be used to both build and run your application. As a matter of fact, the way you use docker compose is entirely up to you. It is a very flexible tool in that sense, and it only needs to be configured once. After that all that remains is running the commands, which we will get into later in this article.
With docker compose you can create a multi-container application that can segment your application. For the purposes of this article I will create a simple single-page app, but it could be anything else that you want. You can use this multi-container approach to scale, or isolate, your service. Also you will be able to use the same code in multiple containers so if something goes wrong one of the containers can be quickly replaced with another version.
The first thing to do is install docker compose. It comes with the docker command and can be installed using:
If you want, you can also run this as a standalone program. If it is installed, run:
How to use docker compose exec ?
The docker compose command has three modes of operation. As a matter of fact, these modes are used in different situations. In the simplest scenario you can use docker-compose up when you want to try out your application. When you start the first time, it will launch a container of your application and serve it on port 8080. To run your application as a daemon, simply launch it with the name of your service in the compose file and make sure that the port you specified is open: docker-compose up -d . Another way to use docker-compose is to launch your application with the name of your service. This will make sure that the port you specified in your compose file is not available, so it will create a new container. When you start this new instance, a connection will be created between the two containers and they will share the same filesystem. This mode is great if you want to share between two containers or when you want to run multiple containers at once on a single host. For example: docker-compose up -d . The docker-compose command can also be used to create a clone of your application. For example: docker-compose up -d –build will do just that.
To use this mode, you need to make sure that the volume you want to clone on exists already. This can be a volume on your host or you can use the docker volume create command.
Examples of how docker compose exec can be used
There are many ways, but in this article we will go over one common use case of docker-compose exec . In short, it is used to run multiple applications on a single Docker host. The main benefit is that the same set of commands can be used to run multiple containers, so there is less configuration needed since each container gets its own command line. Also, you will not need to specify ports or volumes, since they are already part of each container. To use this function in your compose file, you only need to specify the application’s name. The example below is the simplest way to start up a web service. In this case we are starting up an instance of Nginx and MySQL with a single command – docker-compose exec .
version: ‘2’ services: nginx: image: nginx volumes: – ./nginx/conf:/etc/nginx/conf.d/default.conf mysql: image: mysql environment: – MYSQL_ROOT_PASSWORD=mypassword
The benefits of using docker compose exec
The great thing about docker compose exec is that it is a very efficient way of starting up multiple instances of the same application. The main benefit is that you don’t have to write the same command line for each container, so the complexity of your startup commands are greatly reduced. You only need to write one command, and it will start all the containers in the same directory. The structure of your compose file is greatly simplified, so it takes less time to build. It also allows you to run multiple instances of your application on a single host which is great for testing and development environments.