docker-exec

Run command in container

$ docker exec [container] [command]

$ docker exec -it [container] /bin/bash

$ docker exec -u [root] [container] [command]

$ docker exec -e [VAR=value] [container] [command]

$ docker exec -w [/path] [container] [command]

docker exec [options] container command [args...]

docker exec runs a new command in a running container's existing environment, creating a new process within the container's namespaces and cgroups. This is fundamentally different from docker run, which creates an entirely new container.
The most common use case is opening an interactive shell for debugging with docker exec -it container /bin/bash, which provides direct access to the container's filesystem and running processes. Commands executed via docker exec inherit the container's environment but can be customized with user, working directory, and environment variable options.
The --privileged flag grants extended capabilities useful for system administration tasks, though it should be used cautiously as it reduces container isolation.

-d, --detach

Run command in background.

Keep STDIN open.

Allocate pseudo-TTY.

Username or UID.

Working directory inside container.

Set environment variables.

Give extended privileges.

docker-container-exec(1), docker-run(1)