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Persistent Storage

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] <directory>  # Creates a persistent storage directory in the recommended storage path
storage:list <app>                                     # List bind mounts for app's container(s) (host:container)
storage:mount <app> <host-dir:container-dir>           # Create a new bind mount
storage:report [<app>] [<flag>]                        # Displays a checks report for one or more apps
storage:unmount <app> <host-dir:container-dir>         # 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

Creating storage directories

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/doku/data/storage path - created during Dokku installation - and prepare it for use with an app.

dokku storage:ensure-directory lollipop
-----> Ensuring /var/lib/dokku/data/storage/lollipop 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/buildpacks builder.
  • --chown packeto: Use 2000:2000 as the folder permissions.
    • This is used for apps deployed with Cloud Native Buildpacks using the cloudfoundry/cnb or packeto builders.
  • --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.

# 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 for more information.

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.

# 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 for more information.

dokku ps:restart app-name

Displaying storage reports for an app

New as of 0.8.1

You can get a report about the app's storage status using the storage:report command:

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.

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:

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 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.

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.

Note: 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)

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 for more information.

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