How to save a Docker container state
DockerDocker Problem Overview
I'm trying to learn the ins and outs of Docker, and I'm confused by the prospect of saving an image.
I ran the basic Ubuntu image, installed Anaconda Python and a few other things...so now what's the best way to save my progress? Save, commit, export?
None of these seem to work the same way as VirtualBox, which presents an obvious save-state file for your virtual machine.
Docker Solutions
Solution 1 - Docker
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.
Solution 2 - Docker
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.
Solution 3 - Docker
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
Solution 4 - Docker
Use a Docker file for these kind of scenarios.
An example case for an Ubuntu image with MongoDB:
FROM ubuntu
MAINTAINER Author name
RUN apt-key adv --keyserver keyserver.ubuntu.com --recv 7F0CEB10
RUN echo "deb http://downloads-distro.mongodb.org/repo/ubuntu-upstart dist 10gen" | tee -a /etc/apt/sources.list.d/10gen.list
RUN apt-get update
RUN apt-get -y install apt-utils
RUN apt-get -y install mongodb-10gen
#RUN echo "" >> /etc/mongodb.conf
CMD ["/usr/bin/mongod", "--config", "/etc/mongodb.conf"]
Also see Best practices for writing Dockerfiles.