---
type: operations
title: Environment Variable Setup
description: How to provide and validate the required env vars for the 10Backward container — .env, docker-compose, and the runtime check in entrypoint.sh.
tags: [env, ops, setup]
timestamp: 2026-08-04T17:51:00Z
---

# Purpose

Job 1083 promoted every previously-optional knob in `.env.example`
to required, and renamed three of them. Operators must populate the
full set before the container will boot.

# Required Variables

| Variable                 | Example value                  | Purpose                                           |
|--------------------------|--------------------------------|---------------------------------------------------|
| `MASTODON_BASE_URL`      | `https://mastodon.social`      | Mastodon instance to post against.                |
| `MASTODON_ACCESS_TOKEN`  | _(from your Mastodon account)_ | OAuth access token.                               |
| `MASTODON_VISIBILITY` | `public` | Post visibility (`public` or `unlisted`). |
| `SITE_URL` | `https://blog.example.com` | Source blog URL. |
| `HASHTAGS` | `#throwback,#10backward` | Hashtags appended to every throwback post. |
| `THROWBACK_PREFIX` | `Heute vor 10 Jahren:` | Prefix prepended to every Mastodon status. |
| `MAX_RETRIES` | `5` | Maximum number of pipeline attempts. |
| `RUN_AT` | `09:00` | Daily fire time (`HH:MM`, 24-hour). |
| `TZ` | `Europe/Berlin` | IANA timezone for cron and application. |
| `BLOG_REPO_URL` | project default | Optional source repository URL. |
| `BLOG_DIR` | `blog` | Optional clone directory, relative to `DATA_DIR` unless absolute. |

# Where Each Name Is Enforced

* `entrypoint.sh` — validates all nine required keys, validates `RUN_AT`, and installs the cron file as root. The cron-launched wrapper then drops privileges to `bot` before Python runs.
* `tenbackward.config.validate_config` — validates the merged raw required keys plus URL, visibility, timezone, and retry syntax. Defaults are applied only after required-key validation.
* `docker-compose.yml` — supplies development environment values and mounts `./data` at `/app/data`.

# Setup Steps

1. Copy the template:

    ```bash
    cp .env.example .env
    ```

2. Replace placeholder values in `.env` (the example ships with
   `MASTODON_ACCESS_TOKEN=replace-me` and `https://mastodon.example`).

3. Verify the file parses by running the validator directly:

    ```bash
    python -m tenbackward
    ```

    A successful validation run emits one `startup` JSON log line and
    exits `0`. Missing/invalid config exits `2`.

4. Bring up the container:

    ```bash
    docker compose up --build
    ```

    The required-var check in `entrypoint.sh` runs first; if any
    variable is empty, the container exits before `cron` starts.

# Renames vs. Job 1082

| Old key                | New key                  |
|------------------------|--------------------------|
| `MASTODON_VISIBILITY`  | `VISIBILITY`             |
| `THROWBACK_PREFIX`     | `THROWNBACK_PREFIX`      |
| `RETRY_COUNT`          | `MAX_RETRIES`            |

If you have an existing `.env` from the scaffold, rename these
manually. The renamed variables are **not** backwards compatible — the
container will refuse to start with both versions set.

# Defaults

`MAX_RETRIES` defaults to `5`; `BLOG_REPO_URL` and `BLOG_DIR` also have application defaults. Other application-facing required keys must be present in the raw merged dotenv/process environment. The Docker image supplies `TZ=Europe/Berlin`, and Compose supplies development fallbacks, but production deployments should set every required value explicitly.

# Related

* [Config Schema](/architecture/config-schema.md)
* [System Architecture](/architecture/system-overview.md)
* [Cron Lifecycle](/operations/cron-lifecycle.md)