open-vault/website/source/intro/getting-started/secret-backends.html.md

layout	page_title	sidebar_current	description
intro	Secret Backends	gettingstarted-secretbackends	Secret backends are what create, read, update, and delete secrets.

Secret Backends

Previously, we saw how to read and write arbitrary secrets to Vault. To do this, we used the secret/ prefix. This prefix specifies the secret backend to use, and Vault defaults to mounting the generic backend to secret/. The generic backend reads and writes raw data to the backend storage.

Vault supports other backends in addition to "generic", and this feature in particular is what makes Vault unique. For example, the "aws" backend generates AWS access keys dynamically, on demand. Another example -- this time of a backend that doesn't yet exist -- is a backend that reads and writes data directly to an HSM. As Vault matures, more and more backends will be added.

To represent backends, Vault behaves much like a filesystem: backends are mounted at specific paths. For example, the "generic" backend is mounted at the secret/ prefix.

On this page, we'll learn about the mount system and the operations that can be performed with them. We do this as prerequisite knowledge to the next page, where we'll create dynamic secrets.

Mount a Backend

To start, let's mount another "generic" backend. Just like a normal filesystem, Vault can mount a backend multiple times at different mount points. This is useful if you want different access control policies (covered later) or configurations for different paths.

To mount the backend:

$ vault mount generic
Successfully mounted 'generic' at 'generic'!

By default, the mount point will be the same name as the backend. This is because 99% of the time, you don't want to customize this mount point. In this example, we mounted the "generic" backend at generic/.

You can inspect mounts using vault mounts:

$ vault mounts
Path      Type     Description
generic/  generic
secret/   generic  generic secret storage
sys/      system   system endpoints used for control, policy and debugging

You can see the generic/ path we just mounted, as well as the built-in secret path. You can also see the sys/ path. We won't cover this in the getting started guide, but this mount point is used to interact with the Vault core system.

Spend some time reading and writing secrets to the new mount point to convince yourself it works. As a bonus, write to the secret/ endpoint and observe that those values unavailable via generic/: they share the same backend, but do not share any data. In addition to this, backends (of the same type or otherwise) cannot access the data of other backends; they can only access data within their mount point.

Unmount a Backend

Once you're sufficiently convinced mounts behave as you expect, you can unmount it. When a backend is unmounted, all of its secrets are revoked and its data is deleted. If either of these operations fail, the backend remains mounted.

$ vault unmount generic/
Successfully unmounted 'generic/'!

In addition to unmounting, you can remount a backend. Remounting a backend changes its mount point. This is still a disruptive command: the stored data is retained, but all secrets are revoked since secrets are closely tied to their mount paths.

What is a Secret Backend?

Now that you've mounted and unmounted a backend, you might wonder: "what is a secret backend? what is the point of this mounting system?"

Vault behaves a lot like a virtual filesystem. The read/write/delete operations are forwarded to the backend, and the backend can choose to react to these operations however it wishes. For example, the "generic" backend simply passes this through to the storage backend (after encrypting data first).

However, the "aws" backend (which you'll see soon), will read/write IAM policies and access tokens. So, while you might do a vault read aws/deploy, this isn't readnig from any physical path "aws/deploy". Instead, the AWS backend is dynamically generating an access key based on the "deploy" policy.

This abstraction is incredibly powerful. It lets Vault interface directly with physical systems such as the backend as well as things such as SQL databases, HSMs, etc. But in addition to these physical systems, Vault can interact with more unique environments: AWS IAM, dynamic SQL user creation, etc. all using the same read/write interface.

Next

You now know about secret backends and how to operate on the mount table. This is important knowledge to move forward and learn about other secret backends.

Next, we'll use the AWS backend to generate dynamic secrets.