docker exec — Drop Into Running Container

# Interactive shell in a running container
docker exec -it myapp_web_1 sh
docker exec -it myapp_web_1 bash       # if bash is installed

# Run a one-off command (no TTY needed)
docker exec myapp_db_1 mysqldump -u root -p"$PW" app > backup.sql

# Run as a different user
docker exec -u root -it myapp_web_1 apt-get update

# Get env vars from inside
docker exec myapp_web_1 env | sort

# Find which compose service is which container
docker compose ps                                # human-readable table
docker compose ps -q web                         # just the container ID for the 'web' service