How to save a Docker container state
The usual way is at least through a docker commit: that will freeze the state of your container into a new image.
Note: As commented by anchovylegend, this is not the best practice, and using a Dockerfile allows you to formally modeling the image content and ensure you can rebuild/reproduce its initial state.
You can then list that image locally with docker images, and run it again.
Example:
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
c3f279d17e0a ubuntu:12.04 /bin/bash 7 days ago Up 25 hours desperate_dubinsky
197387f1b436 ubuntu:12.04 /bin/bash 7 days ago Up 25 hours focused_hamilton
$ docker commit c3f279d17e0a svendowideit/testimage:version3
f5283438590d
$ docker images
REPOSITORY TAG ID CREATED SIZE
svendowideit/testimage version3 f5283438590d 16 seconds ago 335.7 MB
After that, if you have deployed a registry server, you can push your image to said server.
The usual way is at least through a docker commit: that will freeze the state of your container into a new image.
But know that there is no reliable way to "save state" of container unlike virtual machine save state in Hyper-V or VMware. This is a downside also to docker.
It seems it only saves the changes made to the persistent file changes. So when you spin up the container again from new images, the dependencies and all the run commands executed will not have same effect.
That's why its ideal to have to changes in docker file and in short, there is no save state feature in docker system like we have in virtual machines. The memory contents are always lost.
It's possible (but not recommended) by using docker commit command.
You can check the following clear example:
https://phoenixnap.com/kb/how-to-commit-changes-to-docker-image