How do you use persistent storage in docker containers?
I am currently using this approach: build the image, e.g. for PostgreSQL, and then start the container with
docker run --volumes-from c0dbc34fd631 -d app_name/postgres
This has the drawback that i must not delete container c0dbc34fd631
Another idea would be to mount host volumes "-v" into the container, however, the userid within the container does not necessarily match the userid from the host, and then permissions might be messed up.
Note: Instead of
--volumes-from 'cryptic_id' you can also use
--volumes-from my-data-container where
my-data-container is a name you assigned to a data-only container, e.g.
docker run --name my-data-container ... (see the accepted answer)
Docker 1.9.0 and above
Use volume API
docker volume create --name hello docker run -d -v hello:/container/path/for/volume container_image my_command
This means the data-only container pattern must be abandoned to the new volumes
Actually the volume api is only a better way to achieve what was the data-container pattern.
If you create a container with a
-v volume_name:/container/fs/path Docker will automatically create a named volume for you that can.
- Be listed through the
docker volume ls
- Be identified through the
docker volume inspect volume_name
- Backed up as a normal directory
- Backed up as before through a
The new volume api adds a useful command which helps you identify dangling volumes
docker volume ls -f dangling=true
And then remove it through its name.
docker volume rm <volume name>
As @mpugach underlines in the comments, you can get rid of all the dangling volumes with a nice one-liner.
docker volume rm $(docker volume ls -f dangling=true -q) # Or using 1.13.x docker volume prune
Docker 1.8.x and below
The approach that seems to work best for production is to use a data only container .
The data only container is run on a barebones image and actually does nothing except exposing a data volume.
Then you can run any other container to have access to the data container volumes.
docker run --volumes-from data-container some-other-container command-to-execute
- Here you can get a good picture of how to arrange the different containers.
- Here there is a good insight on how volumes work.
In this blog post there is a good description of the so-called container as volume pattern which clarifies the main point of having data only containers .
Following is the backup/restore procedure for Docker 1.8.x and below.
sudo docker run --rm --volumes-from DATA -v $(pwd):/backup busybox tar cvf /backup/backup.tar /data
- --rm: remove the container when it exits
- --volumes-from DATA: attach to the volumes shared by the DATA container
- -v $(pwd):/backup: bind mount the current directory into the container; to write the tar file to
- busybox: a small simpler image - good for quick maintenance
- tar cvf /backup/backup.tar /data: creates an uncompressed tar file of all the files in the /data directory
# Create a new data container $ sudo docker run -v /data -name DATA2 busybox true # untar the backup files into the new container᾿s data volume $ sudo docker run --rm --volumes-from DATA2 -v $(pwd):/backup busybox tar xvf /backup/backup.tar data/ data/sven.txt # Compare to the original container $ sudo docker run --rm --volumes-from DATA -v `pwd`:/backup busybox ls /data sven.txt
Here is a nice article from the excellent Brian Goff explaining why it is good to use the same image for a container and a data container.