borgmatic/docs/how-to/provide-your-passwords.md

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How to provide your passwords	key parent order 🔒 Provide your passwords How-to guides 2

Environment variable interpolation

If you want to use a Borg repository passphrase or database passwords with borgmatic, you can set them directly in your borgmatic configuration file, treating those secrets like any other option value. But if you'd rather store them outside of borgmatic, whether for convenience or security reasons, read on.

As of version 1.6.4, borgmatic supports interpolating arbitrary environment variables directly into option values in your configuration file. That means you can instruct borgmatic to pull your repository passphrase, your database passwords, or any other option values from environment variables. For instance:

storage:
    encryption_passphrase: ${MY_PASSPHRASE}

This uses the MY_PASSPHRASE environment variable as your encryption passphrase. Note that the { } brackets are required. Just $MY_PASSPHRASE will not work.

In the case of encryption_passphrase in particular, an alternate approach is to use Borg's BORG_PASSPHRASE environment variable, which doesn't even require setting an explicit encryption_passphrase value in borgmatic's configuration file.

For database configuration, the same approach applies. For example:

hooks:
    postgresql_databases:
        - name: users
          password: ${MY_DATABASE_PASSWORD}

This uses the MY_DATABASE_PASSWORD environment variable as your database password.

Interpolation defaults

If you'd like to set a default for your environment variables, you can do so with the following syntax:

storage:
    encryption_passphrase: ${MY_PASSPHRASE:-defaultpass}

Here, "defaultpass" is the default passphrase if the MY_PASSPHRASE environment variable is not set. Without a default, if the environment variable doesn't exist, borgmatic will error.

Disabling interpolation

To disable this environment variable interpolation feature entirely, you can pass the --no-environment-interpolation flag on the command-line.

Related features

Another way to override particular options within a borgmatic configuration file is to use a configuration override on the command-line. But please be aware of the security implications of specifying secrets on the command-line.

Additionally, borgmatic action hooks support their own variable interpolation, although in that case it's for particular borgmatic runtime values rather than (only) environment variables.