docker revert changes to container - import

Question

I'm trying to snapshot my docker container so that I can revert back to a single point in time.
I've looked at docker save and docker export but neither of these seems to do what I'm looking for. Am I missing something?

Answer 1

You might want to use docker commit. This command will create a new docker image from one of your docker containers. This way you can easily create a new container later on based on that new image.
Be aware that the docker commit command won't save any data stored in Docker data volumes. For those you need to make backups.
For instance if you are working with the following Dockerfile which declares a volume and will write the date every 5 seconds to two files (one being in the volume, the other not):
FROM base
VOLUME /data
CMD while true; do date >> /data/foo.txt; date >> /tmp/bar.txt; sleep 5; done
Build a image from it:
$ docker build --force-rm -t so-26323286 .
and run a new container from it:
$ docker run -d so-26323286
Wait a bit so that the running docker container have a chance to write the date to the two files a couple of times.
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
07b094be1bb2 so-26323286:latest "/bin/sh -c 'while t 5 seconds ago Up 5 seconds agitated_lovelace
Then commit your container into a new image so-26323286:snapshot1:
$ docker commit agitated_lovelace so-26323286:snapshot1
You can now see that you have two images availables:
$ docker images | grep so-26323286
so-26323286 snapshot1 03180a816db8 19 seconds ago 175.3 MB
so-26323286 latest 4ffd141d7d6f 9 minutes ago 175.3 MB
Now let's verify that a new container run from so-26323286:snapshot1 would have the /tmp/bar.txt file:
$ docker run --rm so-26323286:snapshot1 cat /tmp/bar.txt
Sun Oct 12 09:00:21 UTC 2014
Sun Oct 12 09:00:26 UTC 2014
Sun Oct 12 09:00:31 UTC 2014
Sun Oct 12 09:00:36 UTC 2014
Sun Oct 12 09:00:41 UTC 2014
Sun Oct 12 09:00:46 UTC 2014
Sun Oct 12 09:00:51 UTC 2014
And witness that such a container does not have any /data/foo.txt file (as /data is a data volume):
$ docker run --rm so-26323286:snapshot1 cat /data/foo.txt
cat: /data/foo.txt: No such file or directory
Finally if you want to access to the /data/foo.txt file which is in the first (still running) container, you can use the docker run --volumes-from option:
$ docker run --rm --volumes-from agitated_lovelace base cat /data/foo.txt
Sun Oct 12 09:00:21 UTC 2014
Sun Oct 12 09:00:26 UTC 2014
Sun Oct 12 09:00:31 UTC 2014
Sun Oct 12 09:00:36 UTC 2014
Sun Oct 12 09:00:41 UTC 2014
Sun Oct 12 09:00:46 UTC 2014
Sun Oct 12 09:00:51 UTC 2014
Sun Oct 12 09:00:56 UTC 2014
Sun Oct 12 09:01:01 UTC 2014
Sun Oct 12 09:01:06 UTC 2014
Sun Oct 12 09:01:11 UTC 2014
Sun Oct 12 09:01:16 UTC 2014

Answer 2

Here is an example of how to do it with the hello-world image from Docker Hub
First run the hello-world image, thereby downloading the image:
docker run hello-world
Then get the hash of the image you want to get the has of
docker history hello-world
You will see something like:
IMAGE CREATED
fce289e99eb9 15 months ago
fce289e99eb9 is your hash-code.
To tag this image, you run:
docker tag fce289e99eb9 hello-world:SNAPSHOT-1.0
To list all the tags for a repository, use:
docker image ls hello-world
And you will get something like:
REPOSITORY TAG IMAGE ID CREATED SIZE
hello-world SNAPSHOT-1.0 fce289e99eb9 15 months ago 1.84kB
hello-world latest fce289e99eb9 15 months ago 1.84kB