Docker is a software containerization tool created by Docker Inc. Containers let you run programs inside of them, rather than installing software on your own machine. These containers can be updated in an automated fashion so that they are always running the latest release with no manual intervention needed. In this tutorial we will show how to update Docker images and how it differs from updating docker-compose files or job scripts.,
The “docker update image to latest” is a command-line tool that allows users to update their docker images with the latest version.
Docker containers are built on Docker images. Have you ever pondered how to update Docker containers when a new version of an image is available, since images are the foundation?
No longer be perplexed! This guide will show you how to upgrade your local Docker image repository and your containers to a new version without breaking anything!
Prerequisites
This will be a hands-on presentation in this course. If you want to follow along, make sure you have the following items on hand:
- The guide utilizes Linux (Ubuntu Focal) to run Docker, but the same fundamental methods may be used to Windows or macOS as well.
- Install Docker desktop 3.5.2 or Docker engine 20.10.8 (Linux) (macOS and Windows).
Docker Images That Are Idempotent
A Docker image includes all of the software needed to execute the application, including OS packages and dependencies. Docker creates images by following the instructions in a Dockerfile file, which provides idempotent installation instructions.
An idempotent instruction means that the image created by running the installation command always produces the same outcome.
Building idempotent pictures has the benefit of being system-independent: the resultant image will always be the same. No matter where the container is executed, the execution will always be the same.
A new image version generally entails some changes to the instructions for constructing the Docker container basis, such as:
- The previous version of the application source code may be replaced with a newer version;
- Better dependency management: less space needed or improved performance;
- Better security: security patches have been applied to the image to prevent vulnerabilities.
To get the most out of each Docker image update, you must first learn how to update it and then apply it to your containers.
Start by upgrading a Docker image on your local machine. Python code applications are executed by the application in the example python container. Applications may depend on the newly updated Docker image after updating the local Docker image.
To begin, you must first determine whether photographs are presently accessible in your local area. To check your local images, use the command below. The TAG column shows which image versions are available.
An example of a command that may be used to get a list of available Docker images.
After you’ve obtained your local copy of the picture, you’ll need to locate the most recent image on a distant registry. The Docker engine checks various external Docker registries (image repositories) to keep your local images up to date. Docker uses DockerHub by default, although there are many other options, the most of which are private. The following are some alternative repositories.
Navigate to the repository page and seek for the image you want to update: an official Python image, for example. To discover the appropriate image on DockerHub, type python and open it to see the available tags. This lesson uses a Python picture as an example.
Every tag has a push date as well. The image’s push date is the date it was posted to the registry. Take note of the picture tag and name, since you’ll need them in the next stages.
In the DockerHub website, I’m looking for particular tags.
It’s time to update the picture now that you have the newest version tag. You must first fetch the updated version in order to upgrade to a newer image. Execute the docker pull command, followed by a colon, and the name and tag of the updated image: the name and tag you noted earlier. The example’s name and tag are python:slim-buster. The whole command and its output are presented below.
slim-buster docker pull python
Using the DockerHub registry to get a newer Python image.
Instead, you must give the whole image URI to fetch the image from the non-default Docker image repository (DockerHub). Run dockerpull public.ecr.aws/bitnami/python:3.7 to get Python from the (AWS) ECR Public Gallery.
Troubleshooting Docker Permission Denied Issues is a related topic.
Getting to Know Docker Containers and How to Update Them
The container image cannot be changed after it has been created. You can’t genuinely update a running container since the image can’t change. You need to replace any running containers with updated image version replacement containers.
Because you already have the latest version, it’s time to recreate the containers with the outdated images.
To figure out which containers you need to rebuild, make a list of all the ones that are still running the old image. Containers are listed using the docker ps command. You may define which containers to list with the —filter parameter. The ancestor flag filters by the picture used as a foundation to generate the container, and there are many more possibilities for filtering. In the examples, the starting containers are for Python 3.7.2, which you will use as a filter. The -a switch displays all of the containers that are available.
—filter “ancestor=python:3.7.2” docker ps -a
Make a list of all the containers that were generated using the old image.
The output of docker ps can be used to perform the docker stop command on all the containers mentioned. Because the -q argument is used, the listing command just provides the container IDs. The list of IDs of the halted containers is the command’s output.
$(docker ps -aq —filter “ancestor=python:3.7.2”) docker stop
Stopping any containers that are still using the previous image
Related:How to Use Docker Stop Containers Without Getting Everything Wrong!
Before uninstalling the old image, you must first ask Docker to effectively remove the containers from the system.
$(docker ps -aq —filter “ancestor=python:3.7.2”) docker rm
Getting rid of the halted containers that were generated with an old image.
After deleting all containers associated with the deprecated image, use the docker rmi command to delete the old image.
Using the docker rmi command to remove a deprecated image.
Using the Update Images to Create New Containers
It’s now time to replace the old containers, which were previously removed, with new containers that are based on the updated image. This time, you’ll use the updated picture version to make the containers. You may expect everything to operate as previously since the containers are idempotent.
Using the docker run command and the name and tag of the updated image that the container requires, start the new container. In this case, the -it parameter instructs Docker to run the container in interactive mode, allowing you to test any enhanced functionality by running commands within the container.
python:slim-buster docker run -it
Using the Docker container that has been updated.
It’s worth noting that the new Docker container uses a newer Python version: 3.9.7.
Conclusion
You got a sneak peak behind the curtain and discovered the magic behind how to update Docker containers in this tutorial: smoke and mirrors! There is no way to update! Remove all remnants of the old version and replace them with new containers that use the updated version instead. And, owing to idempotency, containers continue to function normally: TA-DA!
So, what are the next containers you’re going to update?
The “docker update image from dockerfile” is a command-line tool that allows users to update Docker images to the latest version. These updates can be done by using the docker build, which will create a new image and then use the docker commit to save it as a new layer in the Docker repository.
Related Tags
- how to update docker image with new code
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- docker-compose update images
- docker pull latest image
