# Persistent Storage > [!IMPORTANT] > New as of 0.5.0 The preferred method to mount external containers to a Dokku managed container, is to use the Dokku storage plugin. ``` storage:ensure-directory [--chown option] # Creates a persistent storage directory in the recommended storage path storage:list [--format text|json] # List bind mounts for app's container(s) (host:container) storage:mount # Create a new bind mount storage:report [] [] # Displays a checks report for one or more apps storage:unmount # Remove an existing bind mount ``` > The storage plugin is compatible with storage mounts created with the docker-options. The storage plugin will only list mounts from the deploy/run phase. The storage plugin supports the following mount points: - explicit paths that exist on the host - docker volumes ## Usage ### Listing persistent storage Persistent storage bind mounts are specified on a per-app basis, and can be listed with the `storage:list` command: ```shell dokku storage:list node-js-app ``` ``` -----> node-js-app volume bind-mounts: /var/lib/dokku/data/storage/node-js-app:/app/storage ``` The output format can also be set to `json` for programmatic access: ```shell dokku storage:list node-js-app --format json ``` ``` [ { "host_path": "/var/lib/dokku/data/storage/node-js-app", "container_path": "/app/storage", "volume_options": "" } ] ``` ### Creating storage directories > [!IMPORTANT] > New as of 0.25.5 A storage directory can be created with the `storage:ensure-directory` command. This command will create a subdirectory in the recommended `/var/lib/dokku/data/storage` path - created during Dokku installation - and prepare it for use with an app. ```shell dokku storage:ensure-directory node-js-app ``` ``` -----> Ensuring /var/lib/dokku/data/storage/node-js-app exists Setting directory ownership to 32767:32767 Directory ready for mounting ``` By default, permissions are set for usage with Herokuish buildpacks. These permissions can be changed via the `--chown` option according to the following table: - `--chown herokuish` (default): Use `32767:32767` as the folder permissions. - This is used for apps deployed with Buildpacks via Herokuish. - `--chown heroku`: Use `1000:1000` as the folder permissions. - This is used for apps deployed with Cloud Native Buildpacks using the `heroku/builder` builder. - `--chown paketo`: Use `2000:2000` as the folder permissions. - This is used for apps deployed with Cloud Native Buildpacks using the `cloudfoundry/cnb` or `paketo` builders. - `--chown root`: Use `0:0` as the folder permissions. - This is used for containers that run their processes as root, as is typical for most Dockerfile or Docker image deploys. - `--chown false`: Skips the `chown` call. Users deploying via Dockerfile will want to specify `--chown false` and manually `chown` the created directory if the user and/or group id of the runnning process in the deployed container do not correspond to any of the above options. > [!WARNING] > Failing to set the correct directory ownership may result in issues in persisting files written to the mounted storage directory. ### Mounting storage into apps Dokku supports mounting both explicit host paths as well as docker volumes via the `storage:mount` command. This takes two arguments, an app name and a `host-path:container-path` or `docker-volume:container-path` combination. ```shell # mount the directory into your container's /app/storage directory, relative to the container root (/) # explicit host paths _must_ exist prior to usage. dokku storage:mount node-js-app /var/lib/dokku/data/storage/node-js-app:/app/storage # mount the docker volume into your container's /app/storage directory, relative to the container root (/) # docker volumes _must_ exist prior to usage. dokku storage:mount node-js-app some-docker-volume:/app/storage ``` In the first example, Dokku will then mount the shared contents of `/var/lib/dokku/data/storage/node-js-app` to `/app/storage` inside the container. The mount point is *not* relative to your app's working directory, and is instead relative to the root (`/`) of the container. Mounts are only available for containers created via `run` and by the deploy process, and not during the build process. In addition, the host path is never auto-created by either Dokku or Docker, and should be an explicit path, not one relative to the current working directory. > If the `/storage` path within the container had pre-existing content, the container files will be over-written. This may be an issue for users that create assets at build time but then mount a directory at the same place during runtime. Files are not merged. Once persistent storage is mounted, the app requires a restart. See the [process scaling documentation](/docs/processes/process-management.md) for more information. ```shell dokku ps:restart app-name ``` ### Unmounting storage If an app no longer requires a mounted volume or directory, the `storage:unmount` command can be called. This takes the same arguments as the `storage:mount` command, an app name and a `host-path:container-path` or `docker-volume:container-path` combination. ```shell # unmount the directory from your container's /app/storage directory, relative to the container root (/) dokku storage:unmount node-js-app /var/lib/dokku/data/storage/node-js-app:/app/storage # unmount the docker volume from your container's /app/storage directory, relative to the container root (/) dokku storage:unmount node-js-app some-docker-volume:/app/storage ``` Once persistent storage is unmounted, the app requires a restart. See the [process scaling documentation](/docs/processes/process-management.md) for more information. ```shell dokku ps:restart app-name ``` ### Displaying storage reports for an app > [!IMPORTANT] > New as of 0.8.1 You can get a report about the app's storage status using the `storage:report` command: ```shell dokku storage:report ``` ``` =====> node-js-app storage information Storage build mounts: Storage deploy mounts: -v /var/lib/dokku/data/storage/node-js-app:/app/storage Storage run mounts: -v /var/lib/dokku/data/storage/node-js-app:/app/storage =====> python-sample storage information Storage build mounts: Storage deploy mounts: Storage run mounts: =====> ruby-sample storage information Storage build mounts: Storage deploy mounts: Storage run mounts: ``` You can run the command for a specific app also. ```shell dokku storage:report node-js-app ``` ``` =====> node-js-app storage information Storage build mounts: Storage deploy mounts: -v /var/lib/dokku/data/storage/node-js-app:/app/storage Storage run mounts: -v /var/lib/dokku/data/storage/node-js-app:/app/storage ``` You can pass flags which will output only the value of the specific information you want. For example: ```shell dokku storage:report node-js-app --storage-deploy-mounts ``` ## Use Cases ### Sharing storage across deploys Dokku is powered by Docker containers, which recommends in their [best practices](https://docs.docker.com/engine/userguide/eng-image/dockerfile_best-practices/#containers-should-be-ephemeral) that containers be treated as ephemeral. In order to manage persistent storage for web apps, like user uploads or large binary assets like images, a directory outside the container should be mounted. ### Shared storage between containers When scaling your app, you may require a common location to access shared assets between containers, a storage mount can be used in this situation. ### Shared storage across environments Your app may be used in a cluster that requires containers or resources not running on the same host access your data. Mounting a shared file service (like S3FS or EFS) inside your container will give you great flexibility. ### Backing up Your app may have services that are running in memory and need to be backed up locally (like a key store). Mount a non ephemeral storage mount will allow backups that are not lost when the app is shut down. ### Build phase By default, Dokku will only bind storage mounts during the deploy and run phases. Under certain conditions, one might want to bind a storage mount during the build phase. This can be accomplished by using the `docker-options` plugin directly. ```shell dokku docker-options:add node-js-app build "-v /tmp/python-test:/opt/test" ``` You cannot use mounted volumes during the build phase of a Dockerfile deploy. This is because Docker does not support volumes when executing `docker build`. > [!WARNING] > **This can cause data loss** if you bind a mount under `/app` in buildpack apps as herokuish will attempt to remove the original app path during the build phase. ## App User and Persistent Storage file ownership (buildpack apps only) > [!IMPORTANT] > New as of 0.7.1 By default, Dokku will execute your buildpack app processes as the `herokuishuser` user. You may override this by setting the `DOKKU_APP_USER` config variable. > [!NOTE] > this user must exist in your herokuish image. Additionally, the default `docker-local` scheduler that comes with Dokku will ensure your storage mounts are owned by either `herokuishuser` or the overridden value you have set in `DOKKU_APP_USER`. See the [docker-local scheduler documentation](/docs/deployment/schedulers/docker-local.md#disabling-chown-of-persistent-storage) docs for more information.