Ytdyklly

Consider a single big server running multiple services on FreeBSD such as Plex, OpenVPN, Nextcloud, etc, with each service running in a jail.

Would Docker be appropriate as a Linux analogue to such a configuration?

I've never used Docker or other container solutions, but from what I gather from reading online, Docker containers are better suited for short term uses - being able to start a fresh server, kill it when you're done with it, and then pop up another brand new server when it's needed.

If the goal is to have an isolated service that runs continuously, changes frequently (new files uploaded to the containerized service, etc), and can be easily started and stopped as necessary in the same way as a FreeBSD jail, is Docker the right solution?

Conceptually, Docker containers use Linux namespaces, which are similar to FreeBSD jails.

In addition, Docker containers make it easy to to incrementally add "layers" with files, so you can quickly get a standardized environment to execute whatever services you need. While these layers are considered static, and you'd deploy a new container if there are changes to this environment, you can also mount different stuff into the Docker container, and change files inside that as frequently as you want.

There's no big problem with running a Docker container for a long time. However, Docker containers really shine if you need to scale your application: You can deploy as many copies of a container on different host machines machines as you want, all driven by demand, and Docker abstracts over this so the containers don't really notice on how many physical hosts they run.

So if you have multiple services, you'd typically run each inside its own container.

I'm not sure if this answers the question. Maybe the best way to learn about it is to try to make or deploy a few Docker containers of your own, and see if it suits your needs.