How To Remove Docker Images, Containers, and Volumes

Introduction

Docker makes it easy to wrap your applications and services in containers so you can run them anywhere. However, as you work with Docker, it’s also easy to accumulate an excessive number of unused images, containers, and data volumes that clutter the output and consume disk space.

Docker gives you all the tools you need to clean up your system from the command line. This cheat sheet-style guide provides a quick reference to commands that are useful for freeing disk space and keeping your system organized by removing unused Docker images, containers, and volumes.

How to Use This Guide:

• This guide is in cheat sheet format with self-contained command-line snippets.
• Jump to any section that is relevant to the task you are trying to complete.

If you want a 1-click way to deploy a Docker application to a live server, take a look at DigitalOcean App Platform.

Purging All Unused or Dangling Images, Containers, Volumes, and Networks

Docker provides a single command that will clean up any resources — images, containers, volumes, and networks — that are dangling (not tagged or associated with a container):

docker system prune

To additionally remove any stopped containers and all unused images (not just dangling images), add the -a flag to the command:

docker system prune -a

Removing Docker Images

Remove one or more specific images

Use the docker images command with the -a flag to locate the ID of the images you want to remove. This will show you every image, including intermediate image layers. When you’ve located the images you want to delete, you can pass their ID or tag to docker rmi:

List:

docker images -a

Remove:

docker rmi Image Image

Remove Dangling Docker Images

Docker images consist of multiple layers. Dangling images are layers that have no relationship to any tagged images. They no longer serve a purpose and consume disk space. They can be located by adding the filter flag -f with a value of dangling=true to the docker images command. When you’re sure you want to delete them, you can use the docker image prune command:

List:

docker images -f dangling=true

Remove:

docker image prune

Removing images according to a pattern

You can find all the images that match a pattern using a combination of docker images and grep. Once you’re satisfied, you can delete them by using awk to pass the IDs to docker rmi. Note that these utilities are not supplied by Docker and are not necessarily available on all systems:

List:

docker images -a |  grep "pattern"

Remove:

docker images -a | grep "pattern" | awk '{print $1":"$2}' | xargs docker rmi

Remove all images

All the Docker images on a system can be listed by adding -a to the docker images command. Once you’re sure you want to delete them all, you can add the -q flag to pass the image ID to docker rmi:

List:

docker images -a

Remove:

docker rmi $(docker images -a -q)

Removing Containers

Remove one or more specific containers

Use the docker ps command with the -a flag to locate the name or ID of the containers you want to remove:

List:

docker ps -a

Remove:

docker rm ID_or_Name ID_or_Name

Remove a container upon exiting

If you know when you’re creating a container that you won’t want to keep it around once you’re done, you can run docker run --rm to automatically delete it when it exits:

Run and Remove:

docker run --rm image_name

Remove all exited containers

You can locate containers using docker ps -a and filter them by their status: created, restarting, running, paused, or exited. To review the list of exited containers, use the -f flag to filter based on status. When you’ve verified you want to remove those containers, use -q to pass the IDs to the docker rm command:

List:

docker ps -a -f status=exited

Remove:

docker rm $(docker ps -a -f status=exited -q)

Remove containers using more than one filter

Docker filters can be combined by repeating the filter flag with an additional value. This results in a list of containers that meet either condition. For example, if you want to delete all containers marked as either created (a state which can result when you run a container with an invalid command) or exited, you can use two filters:

List:

docker ps -a -f status=exited -f status=created

Remove:

docker rm $(docker ps -a -f status=exited -f status=created -q)

Remove containers according to a pattern

You can find all the containers that match a pattern using a combination of docker ps and grep. When you’re satisfied that you have the list you want to delete, you can use awk and xargs to supply the ID to docker rm. Note that these utilities are not supplied by Docker and are not necessarily available on all systems:

List:

docker ps -a |  grep "pattern”

Remove:

docker ps -a | grep "pattern" | awk '{print $1}' | xargs docker rm

Stop and remove all containers

You can review the containers on your system with docker ps. Adding the -a flag will show all containers. When you’re sure you want to delete them, you can add the -q flag to supply the IDs to the docker stop and docker rm commands:

List:

docker ps -a

Remove:

docker stop $(docker ps -a -q)
docker rm $(docker ps -a -q)

Removing Volumes

Remove one or more specific volumes

Use the docker volume ls command to locate the volume name or names you wish to delete. Then you can remove one or more volumes with the docker volume rm command:

List:

docker volume ls

Remove:

docker volume rm volume_name volume_name

Remove dangling volumes

Since the point of volumes is to exist independent from containers, when a container is removed, a volume is not automatically removed at the same time. When a volume exists and is no longer connected to any containers, it’s called a dangling volume. To locate them to confirm you want to remove them, you can use the docker volume ls command with a filter to limit the results to dangling volumes. When you’re satisfied with the list, you can remove them all with docker volume prune:

List:

docker volume ls -f dangling=true

Remove:

docker volume prune

Remove a container and its volume

If you create an unnamed volume, it can be deleted at the same time as the container with the -v flag. Note that this only works with unnamed volumes. When the container is successfully removed, its ID is displayed. Note that no reference is made to the removal of the volume. If it is unnamed, it is silently removed from the system. If it is named, it silently stays present.

Remove:

docker rm -v container_name

docker rm vs docker rmi vs docker prune

Note: The -f flag is used to force the removal of resources without prompting for confirmation. The -a flag is used to remove all unused resources, including dangling ones.

Common Errors and Debugging

Handling thread synchronization issues when multiple containers share volumes

When multiple containers share volumes, thread synchronization issues can arise, leading to data corruption or unexpected behavior. To handle these issues, you can use the following strategies:

• Use Named Volumes: Named volumes provide better control and management over shared data. Here’s an example of how to use named volumes in a Docker Compose file:

version: '3.8'
services:
  app:
    image: myapp
    volumes:
      - myvolume:/app/node_modules
volumes:
  myvolume:

• Implement File Locks: Use file locking mechanisms to ensure that only one container can access a file at a time. This can be achieved using tools like flock or lockfile within your application code.

• Use Docker Compose: Docker Compose allows you to define and manage multi-container applications, ensuring proper synchronization and volume sharing. Here’s an example of a Docker Compose file that defines a service with a named volume:

version: '3.8'
services:
  app:
    image: myapp
    volumes:
      - myvolume:/app/node_modules
    depends_on:
      - db
  db:
    image: mydb
    volumes:
      - myvolume:/var/lib/mysql
volumes:
  myvolume:

Debugging performance bottlenecks caused by excess image layers

Excess image layers can lead to performance bottlenecks, especially during the build and deployment process. To debug and resolve these issues, follow these steps:

• Analyze Image Layers: Use the docker history <image> command to inspect the layers of an image and identify unnecessary layers. For example:

docker history myapp

• Optimize Dockerfile: Combine multiple RUN instructions into a single instruction to reduce the number of layers. For instance, instead of:

RUN apt update && apt install -y python3
RUN apt install -y python3-pip

Use:

RUN apt update && apt install -y python3 python3-pip

• Use Multi-Stage Builds: Multi-stage builds allow you to create smaller and more efficient images by copying only the necessary artifacts from intermediate stages. Here’s an example:

FROM scratch AS base
WORKDIR /app
COPY go.mod ./
COPY go.sum ./
RUN go mod download

FROM base AS builder
RUN go build -o myapp

FROM scratch
COPY --from=builder /app/myapp .
CMD ["./myapp"]

Fixing container is running errors when attempting to remove an active container

When you try to remove an active container, you may encounter the container is running error. To fix this issue, you have several options:

1. First stop the container, then remove it:

   docker stop <container_id>
   docker rm <container_id>
   

   Copy

2. Force remove the container in a single command:

   docker rm -f <container_id>
   

   Copy

3. Stop and remove all containers:

   docker stop $(docker ps -a -q)
   docker rm $(docker ps -a -q)
   

   Copy

4. Use Docker Compose to stop and remove containers:

   docker-compose down
   

   Copy

5. If you’re using Docker Desktop, you can also use the GUI to stop and remove containers by right-clicking on the running container and selecting “Stop” and then “Remove”.

FAQs

1. How do I delete all stopped containers in Docker?

To delete all stopped containers in Docker, use the following command:

docker-compose down

This command will stop and remove all containers defined in your docker-compose.yml file. If you want to remove all stopped containers without using docker-compose, you can use:

docker system prune -a

2. What happens when I run docker system prune?

When you run docker system prune, Docker will remove all stopped containers and all networks not used by at least one container. Additionally, if you use the -a flag, Docker will also remove all unused images. This command is useful for freeing up disk space and cleaning up your Docker environment.

3. Can I remove a running Docker container?

Yes, you can remove a running Docker container using the -f flag with the docker rm command. This will force the removal of the container without stopping it first. Here’s an example:

docker rm -f <container_id>

4. How do I free up disk space used by Docker?

To free up disk space used by Docker, you can use the following commands:

• docker system prune -a to remove all unused images.
• docker system prune -a -v to remove all unused images and volumes.
• docker volume prune -a to remove all unused volumes.
• docker network prune -a to remove all unused networks.

5. What is the difference between docker rm and docker rmi?

docker rm is used to remove a container, while docker rmi is used to remove an image. docker rm will delete a container and its associated resources, but it will not delete the image that the container was based on. docker rmi, on the other hand, will delete an image, but it will not delete any containers that are based on that image.

6. How do I completely remove Docker images?

To completely remove a Docker image, use the following command:

docker rmi <image-id>

Replace <image-id> with the ID or name of the image. If the image is in use by a container, you must first remove the container before removing the image.

7. How do I remove unused Docker images?

Unused images (dangling and untagged) can be removed using the following command:

docker image prune

To remove all unused images, use the --all flag:

docker image prune --all

8. How do I clear all Docker images and cache?

To remove all Docker images, containers, volumes, and networks, use this command:

docker system prune --all --volumes

9. How do I remove files from a Docker image?

You cannot directly modify a Docker image. Instead, create a new image without the unwanted files. Here’s how:

Start and login inside the container from the image:

docker run -it <image-id> /bin/bash

Now, remove files within the container as needed.

Next, commit the changes to a new image:

docker commit <container-id> <new-image-name>

10. How to remove all stopped Docker containers?

To remove all stopped containers, use:

docker container prune

You will be prompted for confirmation. To skip the prompt, use:

docker container prune -f

11. How do I remove old Docker containers?

To remove containers that have been inactive for a specified time, use the following:

docker ps -a --filter "status=exited" --filter "status=created"
docker rm $(docker ps -a -q --filter "status=exited" --filter "status=created")

This removes containers with exited or created status. Adjust the filter based on your needs.

12. Where are Docker images stored?

Docker images are stored in the Docker directory of your system. By default:

• Linux: /var/lib/docker
• MacOS: In Docker Desktop’s VM
• Windows: In Docker Desktop’s WSL2 VM or the C:\ProgramData\DockerDesktop

You can verify the storage driver and path using:

docker info | grep "Docker Root Dir"

13. How do I remove a container when Docker is finished?

To automatically remove a container after it exits, use the --rm flag when starting the container:

docker run --rm <image-id>

This ensures the container is removed as soon as it stops.

Conclusion

This guide covers some of the common commands used to remove images, containers, and volumes with Docker. There are many other combinations and flags that can be used with each. For a comprehensive guide to what’s available, see the Docker documentation for docker system prune, docker rmi, docker rm, and docker volume rm. If there are common cleanup tasks you’d like to see in the guide, please ask or make suggestions in the comments.

For a detailed look at the different components of a Docker container, check out The Docker Ecosystem: An Introduction to Common Components. Additionally, explore more Docker-related topics with these tutorials:

• Working with Docker Containers.
• How to Install and Use Docker on Ubuntu.
• How to Automatically Update Docker Container Images with Watchtower on Ubuntu.