docker compose exec Command Reference
Run a command in an already-running service container.
docker compose exec runs a command inside a service container that compose up already started, unlike compose run which creates a fresh container. In CI it executes migrations, health probes, or admin commands against the live stack.
Common flags
-T- disable pseudo-TTY allocation (required in CI)-e KEY=value- set an environment variable for the command-w, --workdir- working directory inside the container-u, --user- user to run as--index- target a specific replica when scaled
Example
shell
docker compose up -d --wait
docker compose exec -T db pg_isready -U postgres
docker compose exec -T -e RAILS_ENV=test app bin/rails db:migrateIn CI
Always pass -T in pipelines or compose exec fails with "the input device is not a TTY". Use exec (not run) against services already started by compose up so migrations operate on the same database the tests will hit.
Key takeaways
- -T disables the TTY so compose exec works in CI.
- exec targets a running service; run creates a new container.
- Use it for migrations and probes against the live stack.
Frequently asked questions
docker compose exec Command Reference?
docker compose exec runs a command inside a service container that compose up already started, unlike compose run which creates a fresh container. In CI it executes migrations, health probes, or admin commands against the live stack.
In CI?
Always pass -T in pipelines or compose exec fails with "the input device is not a TTY". Use exec (not run) against services already started by compose up so migrations operate on the same database the tests will hit.
Related guides
docker compose run Command ReferenceReference for docker compose run in CI: run a one-off command in a service container with --rm, -e, and
docker compose up Command ReferenceReference for docker compose up in CI: start services from a compose file with -d, --build, and --wait so
docker exec Command ReferenceReference for docker exec in CI: run a command inside a running container with -e, -w, -u, and -i to drive