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Mount a single file as a Docker volume

Nov 25, 2022 · 1 min read · Post a comment

There are few ways to mount a single file as a Docker volume whatever you are trying to spin a single container using docker run or being a part of a Docker Compose stack. This scenario usually comes in mind when dealing with a single configuration file that needs to be stored under a certain Git repository, hence you want to keep track of all changes applied on the file itself.

Prerequisites

  • Docker

Solution(s)

docker compose

Mount a single file as a Docker volume code snippet:

version: "3.9"
services:
  redis:
    ...
    volumes:
    - ./conf/redis.conf:/etc/redis/redis.conf

./ refers to the relative path which could be achieved using ${PWD} as well. For instance:

volumes:
  - ${PWD}/conf/redis.conf:/etc/redis/redis.conf

Alternate solution:

version: "3.9"
services:
  redis:
    ...
    volumes:
      - type: bind
      source: ./conf/redis.conf
      target: /etc/redis/redis.conf

docker cli

Using --mount option:

docker run -it -d --mount type=bind,source=$(pwd)/conf/redis.conf,target=/etc/redis/redis.conf redis:latest

Using --volumes (-v) option:

docker run -it -d -v $(pwd)/conf/redis.conf:/etc/redis/redis.conf redis:latest

Note(s):

  • Remember that host_path is the source, container_path is the destination (host_path/:container_path/).
  • Use "%cd%"if running on Windows.
  • Always use absolute path when specifying the host path. If not, Docker will throw an error.
  • The main difference between --mount and --volume is that when dealing with volumes, if the host’s file or directory doesn’t exist yet, Docker will create as a directory whether it is a directory or not. However, that’s not the case with -mount as it will throw an error each time, unless the file / directory exists on the host.

Conclusion

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