---
sidebar_label: pg
description: OpenTofu can store state remotely in a Postgres database with locking.
---

# Backend Type: pg

Stores the state in a [Postgres database](https://www.postgresql.org) version 10 or newer.

This backend supports [state locking](../../../language/state/locking.mdx).

## Example Configuration

```hcl
terraform {
  backend "pg" {
    conn_str = "postgres://user:pass@db.example.com/tofu_backend"
  }
}
```

Before initializing the backend with `tofu init`, the database must already exist:

```
createdb tofu_backend
```

This `createdb` command is found in [Postgres client applications](https://www.postgresql.org/docs/10/reference-client.html) which are installed along with the database server.


### Using environment variables

We recommend using environment variables to configure the `pg` backend in order
not to have sensitive credentials written to  disk and committed to source
control.

The `pg` backend supports the standard [`libpq` environment variables](https://www.postgresql.org/docs/current/libpq-envars.html).

The backend can be configured either by giving the whole configuration as an
environment variable:

```hcl
terraform {
  backend "pg" {}
}
```

```shellsession
$ export PG_CONN_STR=postgres://user:pass@db.example.com/tofu_backend
$ tofu init
```

or just the sensitive parameters:

```hcl
terraform {
  backend "pg" {
    conn_str = "postgres://db.example.com/tofu_backend"
  }
}
```

```shellsession
$ export PGUSER=user
$ read -s PGPASSWORD
$ export PGPASSWORD
$ tofu init
```

## Data Source Configuration

To make use of the pg remote state in another configuration, use the [`terraform_remote_state` data source](../../../language/state/remote-state-data.mdx).

```hcl
data "terraform_remote_state" "network" {
  backend = "pg"
  config = {
    conn_str = "postgres://localhost/tofu_backend"
  }
}
```

## Configuration Variables

:::danger Warning
We recommend using environment variables to supply credentials and other sensitive data. If you use `-backend-config` or hardcode these values directly in your configuration, OpenTofu will include these values in both the `.terraform` subdirectory and in plan files. Refer to [Credentials and Sensitive Data](../../../language/settings/backends/configuration.mdx#credentials-and-sensitive-data) for details.
:::

The following configuration options or environment variables are supported:

- `conn_str` - Postgres connection string; a `postgres://` URL. The `PG_CONN_STR` and [standard `libpq`](https://www.postgresql.org/docs/current/libpq-envars.html) environment variables can also be used to indicate how to connect to the PostgreSQL database.
- `schema_name` - Name of the automatically-managed Postgres schema, default to `terraform_remote_state`. Can also be set using the `PG_SCHEMA_NAME` environment variable.
- `skip_schema_creation` - If set to `true`, the Postgres schema must already exist. Can also be set using the `PG_SKIP_SCHEMA_CREATION` environment variable. OpenTofu won't try to create the schema, this is useful when it has already been created by a database administrator.
- `skip_table_creation` - If set to `true`, the Postgres table must already exist. Can also be set using the `PG_SKIP_TABLE_CREATION` environment variable. OpenTofu won't try to create the table, this is useful when it has already been created by a database administrator.
- `skip_index_creation` - If set to `true`, the Postgres index must already exist. Can also be set using the `PG_SKIP_INDEX_CREATION` environment variable. OpenTofu won't try to create the index, this is useful when it has already been created by a database administrator.

## Technical Design

This backend creates one table **states** in the automatically-managed Postgres schema configured by the `schema_name` variable.

The table is keyed by the [workspace](../../../language/state/workspaces.mdx) name. If workspaces are not in use, the name `default` is used.

Locking is supported using [Postgres advisory locks](https://www.postgresql.org/docs/9.5/explicit-locking.html#ADVISORY-LOCKS). [`force-unlock`](../../../cli/commands/force-unlock.mdx) is not supported, because these database-native locks will automatically unlock when the session is aborted or the connection fails. To see outstanding locks in a Postgres server, use the [`pg_locks` system view](https://www.postgresql.org/docs/9.5/view-pg-locks.html).

The **states** table contains:

- a serial integer `id`, used as the key for advisory locks
- the workspace `name` key as _text_ with a unique index
- the OpenTofu state `data` as _text_
