Volume Management

Volume Management

Bind mount

• Map a local directory into the container
• Easy to exchange data with non-containerized processes
• Remote bind mount to not work

Volume

• Managed by Docker daemon
• Works well for processing data from containers only

tmpfs

• Real temporary data
• Removed with containers

Bind Mounts

Map host-local directory into container

Old syntax

docker run --volume $(pwd):/src alpine

Silently creates source if it does not exist

New syntax

docker run --mount type=bind,source=$(pwd),target=/src alpine

Throws error if source does not exist

–

Demo: Bind Mounts /1

Bind mount using old syntax

docker run -it --rm \
  --volume $(pwd):/src \
  alpine

Local directory will be created silently:

docker run -it --rm \
  --volume $(pwd)/missing:/src \
  alpine

–

Demo: Bind Mounts /2

Bind mount using new syntax

docker run -it --rm \
  --mount type=bind,source=$(pwd),target=/src \
  alpine

Fails of local directory does not exist:

docker run -it --rm \
  --mount type=bind,source=$(pwd)/missing,target=/src \
  alpine

–

Demo: Volume Mount

docker volume create myvol
docker volume ls
docker volume inspect myvol
docker -it --rm --volume myvol:/src alpine

File Permissions

Bind mounts are useful for development:

docker run \
    --mount type=bind,source=$(pwd),target=/src \
    --workdir /src \
    maven

But this creates root-owned files

Fix file permissions:

docker run \
    --mount type=bind,source=$(pwd),target=/src \
    --workdir /src \
    --user $(id -u):$(id -g) \
    maven

–

Demo: File Permissions

Access permissions:

docker -it --rm --volume myvol:/src:ro alpine

Works for bind mounts as well

Real temporary data:

docker run -it --rm --tmpfs /src alpine