Docker and Docker Compose Explained for UGREEN NAS Users

If you own a UGREEN NAS storage— or you’re thinking about getting one — you’ve probably seen “Docker” mentioned in the App Center, setup guides, and community discussions. Many of the most popular apps UGREEN NAS users run, from Plex media servers to Home Assistant and Pi-hole, are deployed using Docker. It’s the foundation for many of the third-party services UGREEN NAS users deploy beyond the built-in apps.

What is Docker?

Docker is a platform that packages an application and everything it needs — its code, libraries, and dependencies — into a self-contained unit that runs the same way on almost any system. Instead of installing software directly onto your UGREEN NAS operating system, Docker runs each app inside its own isolated environment called a container.

Three terms are worth knowing:

• Image: A read-only template that includes the app and everything it needs to run. When you install Plex on your UGREEN NAS, you’re pulling the linuxserver/plex image from a registry.
• Container: A running instance of an image. You can start, stop, restart, or delete a container without affecting the image it came from, which means experimenting is low-risk.
• Registry: A service that stores and distributes images. Docker Hub is the largest public one, and it’s where most of the apps you’ll run on your UGREEN NAS come from.

If you deploy Plex with Docker, the image is the packaged Plex software, the container is the running Plex server, and the registry is where that image was downloaded from. The benefit on a NAS is straightforward: you can test an app, remove it later, and avoid scattering system-level changes across the operating system.

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What is Docker Compose?

Docker works well for one container. Many real NAS setups are not one container. They are several related services that need to start together, share folders, and communicate on the same network. Docker Compose exists for that case.

Instead of clicking through a GUI and recreating settings from memory, Compose stores the setup in a text file, usually called docker-compose.yml or compose.yaml. That file can define images, ports, mounted folders, environment variables, restart policies, and service relationships in one place. With it, the same setup can be recreated consistently with docker compose up -d and stopped with docker compose down.

How It Works

Take a Plex media server as an example. If you install Plex through the Docker app in your UGREEN NAS App Center, you’ll click through a series of screens to configure everything — the container image, port mappings, volume paths for your Movies and TV Shows folders, your timezone, your Plex claim token, CPU and memory limits, and whether the container should auto-restart. That works, but every setting lives inside the GUI. If you want to reinstall Plex, move it to another UGREEN NAS, or share your exact setup with someone else, you’re clicking through those same screens again from memory.

Docker Compose solves this by letting you define every one of those settings in a single text file called docker-compose.yml. The file is readable, editable, and portable — you can back it up, version it, copy it to another machine, and recreate your exact Plex setup with one command: docker compose up -d. When you need to stop the container, docker compose down shuts it down cleanly. Compose becomes even more useful when you move beyond a single app. A setup that includes Plex alongside a request manager like Overseerr, for example, is far easier to manage as a single Compose file than as separate GUI-configured containers.

Why It Matters

Compose turns a multi-step setup into a single file you can save, share, and reuse. For a UGREEN NAS user, that means less clicking through GUI screens every time you rebuild an app, and a clear record of how your setup is configured — useful when something breaks later and you can’t remember what you changed.

Docker vs. Docker Compose: Key Differences

The simplest way to think about it: Docker runs individual containers, Docker Compose coordinates groups of them. If you only need Pi-hole on your UGREEN NAS, plain Docker through the App Center GUI is enough. If you’re running Plex alongside supporting services, or any setup where multiple containers need to share folders and communicate, Docker Compose is what makes it manageable. Most UGREEN NAS users will end up using both — often starting with the GUI and moving to Compose files once they outgrow the click-through approach.

Common Mistakes to Avoid When Using Docker on a UGREEN NAS

A few pitfalls trip up almost everyone who starts using Docker on a UGREEN NAS. Knowing them in advance saves hours of troubleshooting later.

1. Confusing images with containers

Why it matters: An image is the template — the linuxserver/plex you downloaded from the App Center, for example. A container is a running instance created from that image. Deleting a container doesn’t delete the image, and deleting an image doesn’t stop a container that’s already running from it. Mixing the two up leads to “why is this still running after I deleted it?” moments and failed cleanup attempts.

Fix: Before you delete anything, check what you’re actually deleting. In the UGREEN NAS Docker app, containers and images live on separate tabs for a reason. If you want to fully remove an app, stop and delete the container first, then delete the image.

2. Ignoring persistent storage

Why it matters: By default, anything a container writes stays inside the container’s own filesystem. If you recreate that container later — after an update, a rebuild, or an accidental deletion — it starts fresh with nothing from the previous run. This is how people lose Plex watch history, Home Assistant configurations, and Nextcloud files they assumed were safe.

Fix: Map container folders to shared folders on your UGREEN NAS so the important data lives on the NAS itself, not inside a disposable container. For Plex, that means pointing the container’s config and media paths to folders you’ve created in the UGREEN File Manager. If an app’s data matters to you, map it out — every time, no exceptions.

3. Using random host ports and forgetting them

Why it matters: Every container that exposes a service needs its own host port. It’s easy to accept a default without noting it down, and easy to accidentally assign the same port to two apps — at which point one of them silently fails to start. Months later, when an app is unreachable, you’ll have no idea which port it was supposed to be on.

Fix: Keep a simple list somewhere you’ll actually find it later — app name, container name, host port. A pinned note, a text file on the NAS, or a row in a spreadsheet all work. The format doesn’t matter. Having the list does.

4. Staying in the GUI when a setup has outgrown it

Why it matters: The Docker app in UGOS is great for single containers and quick experiments. Once you’re running multiple containers that need to share folders or talk to each other, managing them as separate GUI entries becomes fragile. One missed setting during a rebuild can break the whole stack, and there’s no single place to see how everything is wired together.

Fix: When a setup involves more than two or three related containers, move it to a docker-compose.yml file. You’ll have one readable document describing the entire stack, and rebuilding becomes a single command instead of a series of clicks across multiple screens.

Getting Started with Docker on Your UGREEN NAS

Docker and Docker Compose are the foundation for running third-party apps on a UGREEN NAS, which is why they show up so often in setup guides and community discussions. Docker gives you isolation and repeatability for individual apps, and Docker Compose adds structure when you’re coordinating more than one.