open-vault/website/content/docs/agent/template.mdx

---
layout: docs
page_title: Vault Agent Template
sidebar_title: Templates
description: >-
  Vault Agent's Template functionality allows Vault secrets to be rendered to
  files 

  using Consul Template markup.
---

# Vault Agent Templates

Vault Agent's Template functionality allows Vault secrets to be rendered to files
using [Consul Template markup](https://github.com/hashicorp/consul-template#templating-language).

## Functionality

The `template` stanza configures the templating engine in the Vault agent for rendering
secrets to files using Consul Template markup language. Multiple `template` stanzas
can be defined to render multiple files.

When the agent is started with templating enabled, it will attempt to acquire a
Vault token using the configured Method. On failure, it will back off for a short
while (including some randomness to help prevent thundering herd scenarios) and
retry. On success, secrets defined in the templates will be retrieved from Vault and
rendered locally.

## Configuration

The top level `template` block has multiple configurations entries:

- `source` `(object: optional)` - Path on disk to use as the input template. This
  option is required if not using the `contents` option.
- `destination` `(object: required)` - Path on disk where the rendered secrets should
  be created. If the parent directories If the parent directories do not exist, Vault
  Agent will attempt to create them, unless `create_dest_dirs` is false.
- `create_dest_dirs` `(object: required)` - This option tells Vault Agent to create
  the parent directories of the destination path if they do not exist. The default
  value is true.
- `contents` `(object: optional)` - This option allows embedding the contents of
  a template in the configuration file rather then supplying the `source` path to
  the template file. This is useful for short templates. This option is mutually
  exclusive with the `source` option.
- `command` `(object: optional)` - This is the optional command to run when the
  template is rendered. The command will only run if the resulting template changes.
  The command must return within 30s (configurable), and it must have a successful
  exit code. Vault Agent is not a replacement for a process monitor or init system.
- `command_timeout` `(object: optional)` - This is the maximum amount of time to
  wait for the optional command to return. Default is 30s.
- `error_on_missing_key` `(object: optional)` - Exit with an error when accessing
  a struct or map field/key that does notexist. The default behavior will print `<no value>`
  when accessing a field that does not exist. It is highly recommended you set this
  to "true".
- `perms` `(object: optional)` - This is the permission to render the file. If
  this option is left unspecified, Vault Agent will attempt to match the permissions
  of the file that already exists at the destination path. If no file exists at that
  path, the permissions are 0644.
- `backup` `(object: optional)` - This option backs up the previously rendered template
  at the destination path before writing a new one. It keeps exactly one backup.
  This option is useful for preventing accidental changes to the data without having
  a rollback strategy.
- `left_delimiter` `(object: optional)` - Delimiter to use in the template. The
  default is "{{" but for some templates, it may be easier to use a different
  delimiter that does not conflict with the output file itself.
- `right_delimiter` `(object: optional)` - Delimiter to use in the template. The
  default is "}}" but for some templates, it may be easier to use a different
  delimiter that does not conflict with the output file itself.
- `sandbox_path` `(object: optional)` - If a sandbox path is provided, any path
  provided to the `file` function is checked that it falls within the sandbox path.
  Relative paths that try to traverse outside the sandbox path will exit with an error.
- `wait` `(object: required)` - This is the `minimum(:maximum)` to wait before rendering
  a new template to disk and triggering a command, separated by a colon (`:`).

## Example Template

Template with Vault Agent requires the use of the `secret` [function from Consul Template](https://github.com/hashicorp/consul-template#secret).  
The following is an example of a template that retrieves a generic secret from Vault's
KV store:

```
{{ with secret "secret/my-secret" }}
{{ .Data.data.foo }}
{{ end }}
```

## Example Configuration

The following demonstrates configuring Vault Agent to template secrets using the
AppRole Auth method:

```python
pid_file = "./pidfile"

vault {
  address = "https://127.0.0.1:8200"
}

auto_auth {
  method {
    type      = "approle"

    config = {
      role_id_file_path = "/etc/vault/roleid"
      secret_id_file_path = "/etc/vault/secretid"
    }
  }

  sink {
    type = "file"

    config = {
      path = "/tmp/file-foo"
    }
  }
}

template {
  source      = "/tmp/agent/template.ctmpl"
  destination = "/tmp/agent/render.txt"
}
```

If you only want to use the Vault agent to render one or more templates and do
not need to sink the acquired credentials, you can omit the `sink` stanza from
the `auto_auth` stanza in the agent configuration.

## Renewals and Updating Secrets

The Vault Agent templating automatically renews and fetches secrets/tokens.
Unlike [Vault Agent caching](/docs/agent/caching), the behavior of how Vault Agent
templating does this depends on the type of secret or token. The following is a
high level overview of different behaviors.

### Renewable Secrets

If a secret or token is renewable, Vault Agent will renew the secret at 1/3
of the secret's lease.

### Non-Renewable Secrets

If a secret or token isn't renewable or leased, Vault Agent will fetch the secret every 5 minutes. This is not
configurable. Non-renewable secrets include (but not limited to) [KV Version 2](/docs/secrets/kv/kv-v2).

### Non-Renewable Leased Secrets

If a secret or token is non-renewable but leased, Vault Agent will fetch the secret when 85% of the
secrets time-to-live (TTL) is reached. Leased, non-renewable secrets include (but not limited
to) dynamic secrets such as [database credentials](/docs/secrets/databases) and [KV Version 1](/docs/secrets/kv/kv-v1).

### Static Roles

If a secret has a `rotation_period`, such as a [database static role](/docs/secrets/databases#static-roles),
Vault Agent template will fetch the new secret as it changes in Vault. It does
this by inspecting the secret's time-to-live (TTL).

### Certificates

If a secret is a [certificate](/docs/secrets/pki), Vault Agent template will fetch the new certificate
using the certificates `validTo` field.

This does not apply to certificates generated with `generate_lease: true`. If set
Vault Agent template will apply the non-renewable, leased secret rules.