{"id":5437,"date":"2022-10-03T14:26:43","date_gmt":"2022-10-03T14:26:43","guid":{"rendered":"https:\/\/www.devopsschool.com\/blog\/?p=5437"},"modified":"2025-07-12T05:40:15","modified_gmt":"2025-07-12T05:40:15","slug":"understand-docker-volume-from-beginner-to-deep-dive-level","status":"publish","type":"post","link":"https:\/\/www.devopsschool.com\/blog\/understand-docker-volume-from-beginner-to-deep-dive-level\/","title":{"rendered":"Docker Tutorials: Volume – Deep Dive"},"content":{"rendered":"

In order to understand what a Docker volume is, we first need to be clear about how the filesystem normally works in Docker. Docker images are stored as series of read-only layers<\/strong>. When we start a container, Docker takes the read-only image and adds a read-write layer<\/strong> on top. If the running container modifies an existing file, the file is copied out of the underlying read-only layer and into the top-most read-write layer where the changes are applied. The version in the read-write layer hides the underlying file, but does not destroy it \u2014 it still exists in the underlying layer.<\/p>\n

When a Docker container is deleted, relaunching the image will start a fresh container without any of the changes made in the previously running container \u2014 those changes are lost. Docker calls this combination of read-only layers with a read-write layer on top a Union File System<\/strong>.<\/p>\n

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Docker has two options for containers to store files in the host machine<\/strong>, so that the files are persisted even after the container stops: volumes, and bind mounts. If you\u2019re running Docker on Linux you can also use a tmpfs mount.<\/p>\n

An easy way to visualize the difference among volumes, bind mounts, and tmpfs mounts is to think about where the data lives on the Docker host.<\/p>\n

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  1. Volumes<\/strong> – Volumes are stored in a part of the host filesystem which is managed by Docker (\/var\/lib\/docker\/volumes\/ on Linux). Volumes are the best way to persist data in Docker.<\/li>\n
  2. Bind mounts<\/strong> – Bind mounts may be stored anywhere on the host system. They may even be important system files or directories. Non-Docker processes on the Docker host or a Docker container can modify them at any time.<\/li>\n
  3. tmpfs<\/strong> – tmpfs mounts are stored in the host system\u2019s memory only, and are never written to the host system\u2019s filesystem.<\/li>\n<\/ol>\n

    What are docker volumes?<\/strong>
    Docker volumes are the preferred mechanism for persisting data generated by and used by Docker Containers. These are use of Volume…<\/p>\n

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    1. Decoupling container from storage<\/li>\n
    2. Share volume (storage\/data) among different containers<\/li>\n
    3. Attach Volume to a container<\/li>\n
    4. On Deleting container volume does not delete<\/li>\n<\/ol>\n\n\n

      Commands Collection<\/strong><\/p>\n\n\n

      # How to create docker volume?<\/span>\n$ docker volume create myvol1\n\n# How to list the docker volume?<\/span>\n$ docker volume ls\n\n# How to inspect docker volume?<\/span>\n$ docker volume inspect vol-name\n\n# How to delete docker volume?<\/span>\n$ docker volume rm vol-name\n\n# How to attach Volume to a containers? or<\/span>\n# How to share volume among containers?<\/span>\n$ docker run --name jenkins1 -v myvol1:\/var<\/span>\/jenkins_home -p 8080<\/span>:8080<\/span> -p 50000<\/span>:50000<\/span> jenkins\n$ docker run --name jenkins2 -v myvol1:\/var<\/span>\/jenkins_home -p 8085<\/span>:8080<\/span> -p 50005<\/span>:50000<\/span> jenkins[\n\n# How to use Bind mounts storage in Docker Volume?<\/span>\n$ docker run --name jenkins2 -v \/opt\/jenkins:\/var<\/span>\/jenkins_home -p 8090<\/span>:8080<\/span> -p 50010<\/span>:50000<\/span> jenkins\n$ docker run --name jenkins2 -v \/opt\/jenkins:\/var<\/span>\/jenkins_home -p 8095<\/span>:8080<\/span> -p 50015<\/span>:50000<\/span> jenkins\n\n# Difference between the -v or --mount flag in Docker?<\/span>\nOriginally, the -v or<\/span> --volume flag was used for<\/span> standalone containers and<\/span> the --mount flag was used for<\/span> swarm services. However, starting with Docker 17.06<\/span>, you can also use<\/span> --mount<\/span> with<\/span> standalone<\/span> containers<\/span>. In<\/span> general<\/span>, --mount<\/span> is<\/span> more<\/span> explicit<\/span> and<\/span> verbose<\/span>.\n\n# The<\/span> biggest<\/span> difference<\/span> is<\/span> that<\/span> the<\/span> -v<\/span> syntax<\/span> combines<\/span> all<\/span> the<\/span> options<\/span> together<\/span> in<\/span> one<\/span> field<\/span>, while<\/span> the<\/span> --mount<\/span> syntax<\/span> separates<\/span> them<\/span>.\n$ docker<\/span> run<\/span> -d<\/span> --name<\/span> devtest<\/span> --mount<\/span> source<\/span>=myvol2<\/span>,target<\/span>=\/app<\/span> nginx<\/span>:latest<\/span>\n$ docker<\/span> run<\/span> -d<\/span> --name<\/span> devtest<\/span> -v<\/span> myvol2<\/span>:\/app<\/span> nginx<\/span>:latest<\/span>\n\n# This<\/span> commands<\/span> will<\/span> not<\/span> work<\/span> as<\/span> its<\/span> --mount<\/span> require<\/span> only<\/span> volume<\/span> type<\/span>. but<\/span> not<\/span> the<\/span> mounts<\/span>.\ndocker<\/span> run<\/span> -d<\/span> --name<\/span> devtest<\/span> --mount<\/span> source<\/span>=\/opt<\/span>\/backup1<\/span>,target<\/span>=\/var<\/span>\/jenkins_home<\/span> jenkins<\/span>\n<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n