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128 lines
3.6 KiB
Plaintext
---
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title: Understanding Docker in 10 Minutes
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description: "Docker explained for self-hosters. No CS degree required. Containers, images, volumes, and Docker Compose — the only concepts you actually need."
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---
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# Understanding Docker in 10 Minutes
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Docker is the reason self-hosting went from "sysadmin hobby" to "anyone can do it." It packages software into neat, isolated containers that run the same everywhere.
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You don't need to become a Docker expert. You need to understand **four concepts**.
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## Concept 1: Images
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An **image** is a snapshot of software — pre-built, pre-configured, ready to run. Think of it like an `.iso` file, but for apps.
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```bash
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# Download the Plausible Analytics image
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docker pull plausible/analytics:latest
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```
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Images live on [Docker Hub](https://hub.docker.com) — a public registry of 100,000+ images. When our deploy guides say `image: plausible/analytics:latest`, they're pulling from here.
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## Concept 2: Containers
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A **container** is a running instance of an image. Image = blueprint. Container = the actual building.
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```bash
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# Start a container from an image
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docker run -d --name my-plausible plausible/analytics:latest
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# See running containers
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docker ps
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# Stop a container
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docker stop my-plausible
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# Remove a container (data in volumes is safe)
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docker rm my-plausible
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```
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> 💡 **Why?** Containers are isolated from each other and from your host system. Breaking one container doesn't break anything else.
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## Concept 3: Volumes
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**Volumes** store your data *outside* the container. This is critical because containers are disposable — when you update an image, you destroy the old container and create a new one. Volumes survive this process.
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```bash
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# Mount a volume called "plausible-data"
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docker run -v plausible-data:/var/lib/clickhouse plausible/analytics
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```
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Without volumes, your data dies when the container dies. **Always use volumes.**
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```bash
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# List all volumes
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docker volume ls
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# Backup a volume (copy to local tar)
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docker run --rm -v plausible-data:/data -v $(pwd):/backup alpine \
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tar czf /backup/plausible-backup.tar.gz /data
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```
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## Concept 4: Docker Compose
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This is the big one. **Docker Compose** lets you define multi-container setups in a single YAML file. Most real-world tools need multiple containers (app + database + cache), and Docker Compose handles that.
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```yaml
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# docker-compose.yml
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version: '3.8'
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services:
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app:
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image: plausible/analytics:latest
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ports:
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- "8000:8000"
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depends_on:
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- db
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db:
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image: postgres:14-alpine
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volumes:
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- db_data:/var/lib/postgresql/data
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environment:
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POSTGRES_PASSWORD: supersecret
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volumes:
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db_data:
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```
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Then run it:
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```bash
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# Start everything
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docker compose up -d
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# See logs
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docker compose logs -f
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# Stop everything
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docker compose down
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# Update to latest images
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docker compose pull && docker compose up -d
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```
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That's the pattern for **every single deploy guide** in these docs:
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1. Copy the `docker-compose.yml`
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2. Tweak the environment variables
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3. Run `docker compose up -d`
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4. Done.
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## The 5 Commands You'll Actually Use
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| Command | What it does |
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|---|---|
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| `docker compose up -d` | Start all services in the background |
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| `docker compose down` | Stop all services |
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| `docker compose logs -f` | Watch live logs (Ctrl+C to exit) |
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| `docker compose pull` | Download latest images |
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| `docker ps` | List running containers |
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That's it. That's Docker for self-hosters.
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## Next Steps
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→ [Reverse Proxies Explained](/concepts/reverse-proxies) — How to access your tools via `app.yourdomain.com`
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→ [Your First Deployment](/quick-start/first-deployment) — Put this knowledge to use
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