How to migrate Docker volume between hosts?

Question

Docker's documentation states that volumes can be "migrated" - which I'm assuming means that I should be able to move a volume from one host to another host. (More than happy to be corrected on this point.) However, the same documentation page doesn't provide information on how to do this.

Digging around on SO, I have found an older question (circa 2015-ish) that states that this is not possible, but given that it's 2 years on, I thought I'd ask again.

In case it helps, I'm developing a Flask app that uses [TinyDB] + local disk as its data storage - I have determined that I didn't need anything more fancy than that; this is a project done for learning at the moment, so I've decided to go extremely lightweight. The project is structured as such:

/project_directory
|- /app
   |- __init__.py
   |- ...
|- run.py  # assumes `data/databases/ and data/files/` are present
|- Dockerfile
|- data/
   |- databases/
      |- db1.json
      |- db2.json
   |- files/
      |- file1.pdf
      |- file2.pdf

I have the folder data/* inside my .dockerignore and .gitignore, so that they are not placed under version control and are ignored by Docker when building the images.

While developing the app, I am also trying to work with database entries and PDFs that are as close to real-world as possible, so I seeded the app with a very small subset of real data, that are stored on a volume that is mounted directly into data/ when the Docker container is instantiated.

What I want to do is deploy the container on a remote host, but have the remote host seeded with the starter data (ideally, this would be the volume that I've been using locally, for maximal convenience); later on as more data are added on the remote host, I'd like to be able to pull that back down so that during development I'm working with up-to-date data that my end users have entered.

Looking around, the "hacky" way I'm thinking of doing is simply using rsync, which might work out just fine. However, if there's a solution I'm missing, I'd greatly appreciate guidance!

Answer 1

you can use this trick :

docker run --rm -v <SOURCE_DATA_VOLUME_NAME>:/from alpine ash -c "cd /from ; tar -cf - . " | ssh <TARGET_HOST> 'docker run --rm -i -v <TARGET_DATA_VOLUME_NAME>:/to alpine ash -c "cd /to ; tar -xpvf - " '

more information

Answer 2

According the Docker docs you could also create a Backup and Restore it:

Backup volume

docker run --rm --volumes-from CONTAINER -v \
$(pwd):/backup ubuntu tar cvf /backup/backup.tar /MOUNT_POINT_OF_VOLUME

Restore volume from backup on another host

docker run --rm --volumes-from CONTAINER -v \
$(pwd):/LOCAL_FOLDER ubuntu bash -c "cd /MOUNT_POINT_OF_VOLUME && \
tar xvf /backup/backup.tar --strip 1"

OR (what I prefer) just copy it to local storage

docker cp CONTAINER:/MOUNT_POINT_OF_VOLUME ./LOCAL_FOLDER

then copy it to the other host and start with e.g.

docker run -v ./LOCAL_FOLDER:/MOUNT_POINT_OF_VOLUME some_image