Difference between save and export in Docker - Thomas Uhrig

Difference between save and export in Docker – Thomas Uhrig
How Docker works (in a nutshell)

Docker is based on so called images. These images are comparable to virtual machine images and contain files, configurations and installed programs. And just like virtual machine images you can start instances of them. A running instance of an image is called container. You can make changes to a container (e.g. delete a file), but these changes will not affect the image. However, you can create a new image from a running container (and all it changes) using docker commit <container-id> <image-name>.

Export

Export is used to persist a container (not an image). So we need the container id which we can see like this:

1	sudo docker ps -a

To export a container we simply do:

1	sudo docker export <CONTAINER ID> > /home/export.tar

The result is a TAR-file which should be around 2.7 MB big (slightly smaller than the one from save).

Save

Save is used to persist an image (not a container). So we need the image name which we can see like this:

1	sudo docker images

To save an image we simply do:

1	sudo docker save busybox-1 > /home/save.tar

The result is a TAR-file which should be around 2.8 MB big (slightly bigger than the one from export).

So what’s the difference between both? Well, as we saw the exported version is slightly smaller. That is because it is flattened, which means it lost its history and meta-data. We can see this by the following command:

1 2	# shows the layers of all images sudo docker images --tree

If we run the command we will see an output like the following. As you can see there, the exported-imported image has lost all of its history whereas the saved-loaded image still have its history and layers. This means that you cannot do any rollback to a previous layer if you export-import it while you can still do this if you save-load the whole (complete) image (you can go back to a previous layer by usingdocker tag <LAYER ID> <IMAGE NAME>).

Read full article from Difference between save and export in Docker – Thomas Uhrig