Once Dokku has been configured with at least one user, applications can be deployed via a `git push` command. To quickly see Dokku deployment in action, you can use the Heroku Ruby on Rails example app.
When you create a new app, Dokku by default *does not* provide any datastores such as MySQL or PostgreSQL. You will need to install plugins to handle that, but fortunately [Dokku has official plugins](/dokku/plugins/#official-plugins-beta) for common datastores. Our sample app requires a PostgreSQL service:
Now you can deploy the `ruby-rails-sample` app to your Dokku server. All you have to do is add a remote to name the app. Applications are created on-the-fly on the Dokku server.
Dokku supports deploying applications via [Heroku buildpacks](https://devcenter.heroku.com/articles/buildpacks) with [Herokuish](https://github.com/gliderlabs/herokuish#buildpacks) or using a project's [dockerfile](https://docs.docker.com/reference/builder/).
You can also remove an application from your Dokku installation. This will unlink all linked services and destroy any config related to the application. Note that linked services will retain their data for later use (or removal).
This will prompt you to verify the application's name before destroying it. You may also use the `--force` flag to circumvent this verification process:
While it is possible to use password-based authorization to push to Dokku, it is preferable to use key-based authentication for security. You can add your public key to the dokku user's `authorized_keys` file with the following command:
Dokku only supports deploying from its master branch, so if you'd like to deploy a different local branch use: ```git push dokku <local branch>:master```
You can also support pushing multiple branches using the [receive-branch](/dokku/development/plugin-triggers/#receive-branch) plugin trigger in a custom plugin.
Dokku uses git locally (i.e. not a docker image) to build its own copy of your app repo, including submodules. This is done as the `dokku` user. Therefore, in order to deploy private git submodules, you'll need to drop your deploy key in `/home/dokku/.ssh/` and potentially add github.com (or your VCS host key) into `/home/dokku/.ssh/known_hosts`. The following test should help confirm you've done it correctly.
Note that if the buildpack or dockerfile build process require ssh key access for other reasons, the above may not always apply.
### Specifying a custom buildpack
In certain cases you may want to specify a custom buildpack. While dokku uses herokuish to support all the [official heroku buildpacks](https://github.com/gliderlabs/herokuish#buildpacks), it is possible that the buildpack detection does not work well for your application. As well, you may wish to use a custom buildpack to handle specific application logic.
To use a specific buildpack, you can run the following dokku command:
```shell
# replace APP with the name of your application
# replace REPOSITORY_URL with your buildpack's url
Please check the documentation for your particular build pack as you may need to include configuration files (such as a Procfile) in your project root.
Dokku is, at its core, a docker container manager. Thus, it does not necessarily play well with other out-of-band processes interacting with the docker daemon. One thing to note as in [issue #1220](https://github.com/progrium/dokku/issues/1220), dokku executes a cleanup function prior to every deployment. This function removes all exited containers and all 'unattached' images.
