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Interactive mode

Learn the interactive terminal with -it flags.

Interactive mode

To work with a shell inside a container, two flags are used together: -i (interactive) keeps standard input open, -t (tty) allocates a terminal. They are usually written as -it:

$ docker run -it ubuntu:24.04 bash
root@3a4b5c6d7e8f:/# ls
bin  boot  dev  etc  home  ...
root@3a4b5c6d7e8f:/# exit

Here the main process is bash; typing exit closes the shell and the container stops.

Detaching and reattaching

To leave an interactive container's terminal without stopping it, press Ctrl+P, Ctrl+Q. Later, docker attach reconnects to the main process. For debugging, docker exec -it, which opens a new shell, is usually safer:

docker run -dit --name kutu alpine sh   # in the background with -d, but with a TTY
docker attach kutu                      # attach to the main process
docker exec -it kutu sh                 # open a separate shell

Practice A temporary shell

Write the command that opens an interactive sh shell in the alpine:3.20 image and deletes the container on exit.

Starter code

terminal
# buraya yaz

Expected output

/ #

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 What happens when you type exit in a bash shell opened with docker run?

  • A new shell opens
  • The container stops because the main process ended Correct answer
  • The container keeps running in the background
  • The container is removed

Explanation: Unlike a shell opened with exec, here bash is the main process.

2 Open an interactive shell.

Question 
docker run ____ ubuntu:24.04 bash
Answer 
docker run -it ubuntu:24.04 bash

Explanation: -i keeps input open, -t allocates a terminal.

3 Match.

Term Meaning
-i Keeps input open
-t Allocates a terminal
Ctrl+P, Ctrl+Q Detach without stopping
docker attach Attach to the main process

All lessons in Beginner

1 What is Docker?

  1. What is Docker?
  2. Containers and virtual machines
  3. Images and containers
  4. Docker architecture
  5. Use cases
  6. Summary - What is Docker

2 Installation and first commands

  1. Installing Docker
  2. docker version
  3. docker info
  4. The hello-world container
  5. Docker Desktop
  6. Summary - Installation

3 First container

  1. docker run basics
  2. Running in the background
  3. docker ps
  4. docker stop and rm
  5. docker logs
  6. Summary - First container

4 Dockerfile basics

  1. What is a Dockerfile?
  2. The FROM instruction
  3. The RUN instruction
  4. COPY and ADD
  5. CMD and ENTRYPOINT
  6. Summary - Dockerfile

5 Build and images

  1. docker build
  2. Tagging images
  3. Build context
  4. Layers and cache
  5. .dockerignore
  6. Summary - Build

6 docker run options

  1. Interactive mode
  2. Naming containers
  3. Restart policy
  4. Working directory
  5. Switching users
  6. Summary - docker run

7 Image management

  1. docker images
  2. docker rmi
  3. docker pull
  4. docker push
  5. docker tag
  6. Summary - Image management

8 Port mapping

  1. The port concept
  2. The -p flag
  3. Multiple ports
  4. Random ports
  5. IP binding
  6. Summary - Port mapping

9 Volumes and data

  1. Data persistence
  2. Named volumes
  3. The -v flag
  4. Bind mounts
  5. Volume management
  6. Summary - Volumes

10 Environment variables

  1. The -e flag
  2. The ENV instruction
  3. The ARG instruction
  4. env-file
  5. The WORKDIR instruction
  6. Summary - Environment

11 Project: docker-compose

  1. Compose design
  2. Service definition
  3. Database service
  4. Volume and network
  5. Putting it together - compose

12 Docker Hub and registry

  1. What is Docker Hub?
  2. docker login
  3. Searching images
  4. Official images
  5. Private registry
  6. Summary - Registry

13 Network basics

  1. Network drivers
  2. docker network ls
  3. Bridge network
  4. Container connectivity
  5. Publishing ports
  6. Summary - Network

14 Beginner final

  1. Challenge - Dockerfile
  2. Challenge - Build and run
  3. Challenge - Volume
  4. Challenge - Compose
  5. Challenge - Beginner project