How to run commands inside a Docker container

If you run your API using Docker Compose, with the docker compose up command, you may also want to be able to execute arbitrary shell commands in the container.

For example, later on in the course we will look at database migrations.

To execute a database migration, we need to run a specific command, flask db mgirate.

If we use Docker Compose, we'll need to run the command inside the running container, and not in a local terminal.

You can run any arbitrary command in a running container like so:

docker compose exec web flask db migrate

This command is split into 4 parts:

• docker compose: uses the Docker Compose part of the Docker executable
• exec: used to run a command in a specific Docker Compose service
• web: which Docker Compose service to run the command in
• flask db migrate: the command you want to run

That's all! Just remember while following the course, that if I run any commands in my local terminal and you are using Docker Compose, you should precede the commands with docker compose exec web.