Install docker swarm with existing containers

Hello,

I’m relatively new to Docker and I’m still learning how it works.

At work, the dev team uses a physical hosted server with multiple docker containers (jenkins, nginx, etc).

These are just standalone containers, using volumes.

I was tasked to install Docker Swarm, not for the load balancing or scaling but mostly for the rolling update feature. We only have 1 server.

I did some research and I could only find info on services. Basically, you create a service, specify the number replicas and Docker Swarm automatically creates containers on the worker nodes.

What do I do if already have existing containers? I found no info on this so I’m wondering if I need to create new services for these containers and then just delete the existing ones.

Anyone of you have experience with this?

Thank you.
Steve