> ## Documentation Index
> Fetch the complete documentation index at: https://3to1go.docs.thesteau.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Central configuration

> Environment variables for deployment, and settings you change from Central's UI.

Central is configured in two places:

* **Environment variables** in `.env` for deployment details: database, ports, and folders. Apply changes with `docker compose up -d` to recreate the affected containers; `docker compose restart` alone does not reload `.env`.
* **Edit Central Settings** in the UI for day-to-day behavior. These are saved in PostgreSQL.

## Environment variables

### Compose and database

| Variable | Default | Description |
| - | - | - |
| `BACKUP_DIR` | `./data/backups` | Host folder mounted at `/backups`. Used by the example Compose file. |
| `POSTGRES_DB` | `three_to_one_go` | Database name, shared by Central and the Postgres container. |
| `POSTGRES_USER` | none | Database user. **Required** unless `INDEX_DATABASE_URL` is set. |
| `POSTGRES_PASSWORD` | none | Database password. **Required** unless `INDEX_DATABASE_URL` is set. |
| `INITIAL_ADMIN_PASSWORD` | `admin` | Password for the first `admin` user. Only used when no user accounts exist. A password change is required on first sign-in, even with a custom value. |

### Using an external PostgreSQL

By default Central connects to the `postgres` service on port `5432`. To use another server, either set a full URL:

| Variable | Description |
| - | - |
| `INDEX_DATABASE_URL` | Full connection URL, such as `postgresql://user:pass@db.example.lan:5432/three_to_one_go`. Overrides everything below. |

or set the parts individually:

| Variable | Default |
| - | - |
| `INDEX_DATABASE_HOST` | `postgres` |
| `INDEX_DATABASE_PORT` | `5432` |
| `INDEX_DATABASE_NAME` | `POSTGRES_DB`, then `three_to_one_go` |
| `INDEX_DATABASE_USER` | `POSTGRES_USER` |
| `INDEX_DATABASE_PASSWORD` | `POSTGRES_PASSWORD` |

When using an external database, also remove the bundled `postgres` service and Central's `depends_on: postgres` entry from the Compose file if you no longer want to run that database container.

### Server and paths

| Variable | Default | Description |
| - | - | - |
| `HTTP_HOST` | `0.0.0.0` | Address Central listens on. |
| `HTTP_PORT` | `6555` | Port Central listens on. If you change it, update the Compose `ports` mapping too. |
| `BACKUP_ROOT` | `/backups` | Snapshot folder inside the container. |
| `STAGING_DIR` | `/staging` | Folder for uploads in progress. |
| `ISSUER_KEY_FILE` | `/config/issuer.key` | Key used to sign Edge credentials. Created on first start if missing. |
| `SESSION_COOKIE_SECURE` | off | Set to `true` when serving Central over HTTPS. See [Sign-in](/shared/sign-in#session-cookies-over-https). |

## Settings in the UI

Open **Edit Central Settings**.

| Setting | Default | Description |
| - | - | - |
| Dark Mode | on | UI theme. |
| Pause incoming uploads | off | Reject new upload sessions. Uploads already in progress can continue. |
| Keep Last Snapshots | `3` | How many snapshots to keep per job and Edge instance. Older ones are pruned after each upload. |
| Log Level | `INFO` | Container log verbosity. |
| Max Upload Size MB | `2048` | Largest archive Central will accept. |
| Upload Chunk Size MB | `8` | Chunk size Central asks Edges to use. |
| Upload Session TTL Hours | `24` | Upload session lifetime, refreshed as upload activity continues. Expired sessions are removed by cleanup. |
| Cleanup Interval Seconds | `300` | How often expired upload sessions are cleaned up. Minimum `10`. |
| Snapshot Integrity Check Interval | `0` (off) | Hours between automatic integrity checks. See [Integrity checks](/central/snapshots#integrity-checks). |

**Trusted Certificates** are also managed here. See [Trusted certificates](/shared/trusted-certificates).

Restart Central after changing **Log Level** or **Snapshot Integrity Check Interval** so the running logger or verification schedule uses the new value.

<Note>
  Raise **Max Upload Size MB** if a job's archive is larger than 2 GB. Otherwise Central rejects its upload.
</Note>