Basic Docker Commands

In this lesson you’ll learn commonly used Docker commands for creating, running, inspecting, and cleaning up containers and images. A short hands-on quiz follows the conceptual overview to help you practice. Table of contents:

docker run — create & start containers
docker ps — list containers
stop & remove containers
docker images, docker rmi, docker pull — image management
why some containers (like ubuntu) exit immediately
running specific commands and docker exec
foreground vs detached mode
quick tips and references

docker run — Create and start a container

The docker run command creates a container from an image and starts it. If the image is not available locally, Docker pulls it from Docker Hub on first use and reuses the downloaded image for subsequent runs. Example: starting the official nginx image

$ docker run nginx
Unable to find image 'nginx:latest' locally
latest: Pulling from library/nginx
fc71811084d0: Already exists
d2e987ca2267: Pull complete
0b760b431b11: Pull complete
Digest: sha256:96fb261b66270b900ea5...
Status: Downloaded newer image for nginx:latest

A graphic titled "Heads‑Up — Docker Hub Rate Limits" showing three tiers: Anonymous (100 pulls/6 hrs per IP), Free (200 pulls/6 hrs per account), and Paid (unlimited/no rate limit).

Docker Hub enforces pull rate limits for unauthenticated and authenticated accounts. If you see “too many requests” errors while following this lesson, log in with docker login or use a paid plan to avoid interruptions.

docker ps — List running (and all) containers

docker ps lists running containers and shows columns such as CONTAINER ID, IMAGE, COMMAND, CREATED, STATUS, PORTS, and NAMES.
Docker auto-generates a friendly container name (for example, silly_sammet) unless you set one with --name.

To include stopped/exited containers, add -a:

docker ps -a

Example outputs:

$ docker ps
CONTAINER ID   IMAGE     COMMAND                  CREATED         STATUS         PORTS    NAMES
796856ac413d   nginx     "nginx -g 'daemon of...'" 7 seconds ago  Up 6 seconds    80/tcp   silly_sammet

$ docker ps -a
CONTAINER ID   IMAGE     COMMAND                  CREATED          STATUS                        NAMES
796856ac413d   nginx     "nginx -g 'daemon of...'" 7 seconds ago   Up 6 seconds                  silly_sammet
12a0f4b2c8d3   redis     "redis-server"           2 minutes ago    Exited (0) 30 seconds ago     eager_curie
8e5d92ab1f7c   ubuntu    "/bin/bash"              5 minutes ago    Exited (0) 4 minutes ago      hopeful_ada

Stop and remove containers

Stop a running container:

docker stop <container-name-or-id>

You can provide the full container ID or the first unique characters.

After stopping, the container will appear in docker ps -a with Exited status.
Remove a stopped container permanently:

docker rm <container-name-or-id>

Example sequence:

$ docker ps
CONTAINER ID   IMAGE    STATUS        NAMES
796856ac413d   nginx    Up 6 seconds  silly_sammet

$ docker stop silly_sammet
silly_sammet

$ docker ps
$ docker ps -a
CONTAINER ID   IMAGE   STATUS                      NAMES
796856ac413d   nginx   Exited (0) 4 seconds ago    silly_sammet

$ docker rm silly_sammet
silly_sammet

$ docker ps -a
# container no longer present

Before removing an image with docker rmi, stop and remove any containers that depend on it. Removing an image in use will fail.

docker images, docker rmi, and docker pull — Image management

docker images lists images on the host including repository, tag, image ID, creation time, and size.
Remove an image with:

docker rmi <image>

(Stop and remove containers that use the image first.)

Pull an image without running it:

docker pull <image>

Example:

$ docker images
REPOSITORY   TAG      IMAGE ID       CREATED         SIZE
nginx        latest   f68d6e55e065   4 days ago      109MB
redis        latest   4760dc956b2d   15 months ago   107MB
ubuntu       latest   f975c503748d   16 months ago   112MB
alpine       latest   3fd9065eaf02   18 months ago   4.14MB

$ docker rmi nginx
Untagged: nginx:latest
Deleted: sha256:f68d6e55e065...

$ docker pull ubuntu
Using default tag: latest
Status: Image is up to date for ubuntu:latest

Why an `ubuntu` container often exits immediately

Containers run the command specified in the image’s CMD or ENTRYPOINT. Base images like ubuntu usually don’t run a long-lived process, so the container starts, runs the default command (often non-interactive or nothing), then exits. Example:

$ docker run ubuntu

$ docker ps -a
CONTAINER ID   IMAGE    COMMAND       STATUS                     NAMES
45aacca36850   ubuntu   "/bin/bash"   Exited (0) 41 seconds ago  distracted_mcclintock

To keep a container alive, run a long-running command or service (for example, sleep, a shell with interactive mode, or an actual daemon).

Run a specific command when starting a container

You can override the image’s default command by appending a command to docker run:

docker run ubuntu sleep 5

This starts the container, runs sleep 5, then the container exits after 5 seconds. If you want an interactive shell:

docker run -it ubuntu /bin/bash

Execute commands inside a running container: docker exec

docker exec runs a command inside an already-running container. This is handy for debugging, inspecting files, or running a shell. Example: viewing /etc/hosts inside a container

$ docker ps
CONTAINER ID   IMAGE    COMMAND       STATUS         NAMES
538d037f94a7   ubuntu   "sleep 100"   Up 4 seconds   distracted_mcclintock

$ docker exec distracted_mcclintock cat /etc/hosts
127.0.0.1       localhost
::1             localhost
# (example output)

To get an interactive shell inside a running container:

docker exec -it <container-name-or-id> /bin/bash

Foreground (attached) vs detached mode

By default docker run attaches the container’s stdout/stderr to your terminal (foreground). Pressing Ctrl-C will stop the container.
To start a container in the background, use -d (detached):

docker run -d --name myweb codecloud/simple-web-app

Reattach to a container’s streams with:

docker attach <container-name-or-id>

Example:

# foreground (attached)
$ docker run codecloud/simple-web-app
# detached (background)
$ docker run -d --name myweb codecloud/simple-web-app
# back at prompt immediately
$ docker ps
CONTAINER ID   IMAGE                         COMMAND    STATUS     PORTS    NAMES
a1b2c3d4e5f6   codecloud/simple-web-app      "..."      Up 2s      80/tcp   myweb

# attach later if needed
$ docker attach myweb

Quick reference — common Docker commands

Command	Purpose	Example
`docker run`	Create & start a container	`docker run nginx`
`docker run -d`	Start container in background (detached)	`docker run -d --name myweb nginx`
`docker ps`	List running containers	`docker ps`
`docker ps -a`	List all containers, including stopped	`docker ps -a`
`docker stop`	Stop a running container	`docker stop \`docker ps -q“
`docker rm`	Remove stopped container	`docker rm \`docker ps -a -q“
`docker images`	List local images	`docker images`
`docker rmi`	Remove an image	`docker rmi nginx`
`docker pull`	Download an image without running	`docker pull ubuntu`
`docker exec`	Run a command in a running container	`docker exec -it myweb /bin/bash`
`docker attach`	Attach to container’s stdio	`docker attach myweb`

Note: In the examples above, when angle brackets are used for placeholders, use backticks around them. For example, docker stop <container-name-or-id>`

Tips and reminders

You only need the leading unique characters of a container ID to reference it.
Stop and remove containers before removing their images.
Authenticate with docker login to increase pull quotas and reduce rate-limit interruptions.
Use -it for interactive shells (-i keeps STDIN open; -t allocates a pseudo-TTY).

Links and references

Docker Hub: https://hub.docker.com
Docker CLI reference: https://docs.docker.com/engine/reference/commandline/cli/
Docker run reference: https://docs.docker.com/engine/reference/commandline/run/

Next: practice these commands in the hands-on exercises to reinforce the concepts covered.

Docker Basics

Basic Docker Commands

docker run — Create and start a container

docker ps — List running (and all) containers

Stop and remove containers

docker images, docker rmi, and docker pull — Image management

Why an `ubuntu` container often exits immediately

Run a specific command when starting a container

Execute commands inside a running container: docker exec

Foreground (attached) vs detached mode

Quick reference — common Docker commands

Tips and reminders

Links and references

Watch Video

Practice Lab

​docker run — Create and start a container

​docker ps — List running (and all) containers

​Stop and remove containers

​docker images, docker rmi, and docker pull — Image management

​Why an ubuntu container often exits immediately

​Run a specific command when starting a container

​Execute commands inside a running container: docker exec

​Foreground (attached) vs detached mode

​Quick reference — common Docker commands

​Tips and reminders

​Links and references

Watch Video

Practice Lab

docker run — Create and start a container

docker ps — List running (and all) containers

Stop and remove containers

docker images, docker rmi, and docker pull — Image management

Why an `ubuntu` container often exits immediately

Run a specific command when starting a container

Execute commands inside a running container: docker exec

Foreground (attached) vs detached mode

Quick reference — common Docker commands

Tips and reminders

Links and references