Manage data in Docker

13 Apr 2019

Default

all files created inside a container are stored on a writable container layer, therefor:

• the data doesn’t persist when that container no longer exists, difficult to transport data to another process out of the container;
• can not move data when running
• requires a storage driver to manage the filesystem

options to store files

• volumes are stored in a part of the host filesystem which is managed by Docker (/var/lib/docker/volumes/ on Linux), best way to store; Non-Docker processes should not modify this part of the filesystem.
• bind mounts: Non-Docker processes on the Docker host or a Docker container can modify them at any time
• (or tmpfs in linux system) are stored in the host system’s memory only and are never written to host ystem’s filesystem.

Usage

Volume:

• use docker volume create command;
• When you create a volume, it is stored within a directory on the Docker host.
• When you mount the volume into a container, this directory is what is mounted into the container. This is similar to the way that bind mounts work
• -v or --volume and --mount
• --mount is easier and can use on services

Create and manage volumes:

• docker volume create my-vol
• docker volume ls
• docker volume inspect mu-vol

Start a container with a volume:
f you start a container with a volume that does not yet exist, Docker creates the volume for you. The following example mounts the volume myvol2 into /app/ in the containe

docker run -d \
  --name devtest \
  -v myvol2:/app \
  nginx:latest

bind mounts