Mount Multiple Data Volumes and Multiple Data Volume Containers in Docker

Multiple Data Volumes from a Single Container

Create and run multiple data volumes in a container:

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$ docker run -d --name vol -v /vol1 -v /vol2 ubuntu

Mount the data volumes in a new container:

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$ docker run -it --rm --name foo --volumes-from=vol ubuntu

Both volumes will be mounted under the root directory as /vol1 and /vol2.

Multiple Data Volume Containers

Create and run multiple data volume containers:

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$ for i in {1..2}; do docker run -d --name vol${i} -v /vol${i} ubuntu; done

Mount multiple data volume containers:

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$ docker run -it --rm --name foo --volumes-from=vol1 --volumes-from=vol2 ubuntu

Now there are also two volumes mounted under the root directory as /vol1 and /vol2, one from each container.

Multiple Data Volume Containers But Sharing the Same Data Volume Name

Create multiple data volume containers with the same data volume name /vol:

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$ for i in {1..2}; do docker run -d --name vol${i} -v /vol ubuntu; done

Mount multiple data volume containers:

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$ docker run -it --rm --name foo --volumes-from=vol1 --volumes-from=vol2 ubuntu

Well, it appears to be successful without any error. But there is only one shared data volume /vol. The question is which container this data volume is from? To find out, we can create a file inside the data volume and then mount the data volume containers one at a time.

Create a file inside the shared data volume:

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[email protected]:/# touch /vol/file

Mount data volume container vol1:

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$ docker run -it --rm --name foo --volumes-from=vol1 ubuntu
# ls /vol
total 0
# exit

Well, it is not in data volume container vol1.

Mount data volume container vol2:

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$ docker run -it --rm --name foo --volumes-from=vol2 ubuntu
file

It is in data volume container vol2. Therefore, when mounting two data volume containers, if both share the same data volume name, later will override former, for example, in this command:

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$ docker run -it --rm --name foo --volumes-from=vol1 --volumes-from=vol2 ubuntu

Data volume vol from container vol2 will override the one from vol1.