Introduced in 0.5.0
The preferred method to mount external containers to a Dokku managed container, is to use the Dokku storage plugin.
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
There are a few caveats to using the persistent storage plugin:
- Using implicit paths that do not exist are no longer supported, and actually deprecated in Docker 1.9.0. When you specify a persistent storage mount, the host directory is not autocreated by either Dokku or Docker.
- We recommend using the directory
/var/lib/dokku/data/storagedirectory as the root host path for mounts, and we create this on Dokku installation.
- Mounts are only available at run and deploy times, and you must redeploy (restart) an app to mount or unmount to an existing app's container.
- When a directory is mounted, any existing files within the container will be overwritten. If you are writing assets during the build process and then replace the directory with a mount, those files will no longer exist. This is a Docker limitation.
- Paths are mounted within the container at the root of the disk -
/- and are not relative to
/app(for buildpacks deploys) or the
WORKDIR(for Dockerfile/Docker images).
- For applications using buildpack deploys, the host directory should be owned by the user and group id
32767. This is due to how permissions within Herokuish - which builds the Docker images - works. For Dockerfile or Docker image deployments, please use the user and group id which corresponds to the one running the process within the container.
This example demonstrates how to mount the recommended directory to
/storage inside an application called
Dokku will then mount the shared contents of
/storage inside the container.
Once you have mounted persistent storage, you will also need to restart the application. See the process scaling documentation for more information.
A more complete workflow may require making a custom directory for your application and mounting it within your
/app/storage directory instead. The mount point is not relative to your application's working directory, and is instead relative to the root of the container.
# creating storage for the app 'node-js-app' mkdir -p /var/lib/dokku/data/storage/node-js-app # ensure the proper user has access to this directory chown -R dokku:dokku /var/lib/dokku/data/storage/node-js-app # as of 0.7.x, you should chown using the `32767` user and group id for buildpack deploys # For dockerfile deploys, substitute the user and group id in use within the image chown -R 32767:32767 /var/lib/dokku/data/storage/node-js-app # mount the directory into your container's /app/storage directory, relative to root dokku storage:mount app-name /var/lib/dokku/data/storage/node-js-app:/app/storage
You can mount one or more directories as desired by following the above pattern.
Displaying storage reports for an app
Introduced in 0.8.1
You can get a report about the app's storage status using the
=====> 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.
You can pass flags which will output only the value of the specific information you want. For example:
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 applications, 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.
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.
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.
You cannot use mounted volumes during the build phase of a Dockerfile deploy. This is because Docker does not support volumes when executing
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.
Application User and Persistent Storage file ownership (buildpack apps only)
Introduced in 0.7.1
By default, Dokku will execute your buildpack application 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 scheduler-docker-local documentation docs for more information.