Creating an image without dockerfile

• Even though the conventional way to create a docker image would be through a dockerfile, it is possible to create an image from an existing container.
• Basically the image will be a snapshot of the container along with changes that have been made to it.
• Let’s pull latest Alpine to start with:

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docker pull alpine:latest

• Create a container from the Alpine:latest image, name it chan-alpine and start a bash shell into the container

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docker container run -it --name chan-alpine alpine:latest /bin/sh

• Container shows up in the list of started containers
• Let’s install git on this container by running the command below on the shell:

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apk add git

• Now that we have a container running alpine and git installed, let’s create an image of this set up using docker container commit and passing it the name of the alpine container and a name for the resulting image which we will call chan-alpine-image

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docker container commit chan-alpine chan-alpine-image

• Listing the images now show our custom image:

• At this stage, let’s create a container from our custom image and confirm that it comes pre-installed with git by simple running the git CLI:

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docker container run chan-alpine-image git

And the output shows the help menu of the Git CLI: