I’m interested in setting up my own instances for Lemmy, Mastodon, and Matrix.

Can I use the same https://domain.tld for all of them without any subdomains?

For example:
lemmyuser@mydomain.tld
mastodonuser@mydomain.tld
matrixuser@mydomain.tld

Will this work across all of my self-hosted instances, or do I need to append a subdomain for each, e.g., lemmyuser@lemmy.mydomain.tld?

  • You are able to host all these services and more on the same domain. I do a similar thing with different services at different subdomains. I don’t believe the username@ portion can help point to different services, that syntax is usually associated with email addresses.

    I think the best way to go about it would be having different subdomains such as lemmy.domain.tld, matrix.domain.tld, etc.
    To accomplish that, I have a wildcard subdomain point to my server, my reverse proxy (Caddy) handles figuring out which subdomain maps to which service on top of handling TLS certificates for me.

      • All of my services are in containers, I use Docker usually via Docker Compose. That gives me one file to establish all of my services, update/start/stop/check logs with consistent command formats for all services, and keeps the data separate from the application. If I need to rebuild, put a backup of my data in the right spot and change names in filepaths as needed, run a backup of the Docker Compose file and I’m up and running again.

        The only things I don’t have in a container is Fail2Ban on my rented, public facing server to minimize noise of bots trying to login.

  • Ultimately, you need some way of routing the traffic to the correct place. Having all 3 services on the same domain, listening on the same ports is going to be a nightmare to manage because something needs to be clever enough to route the traffic to the right service without any information to go off of, other than maybe headers. Expensive firewalls can technically do this but it’s not fun to configure and is really brittle.

    As inferred, you could use the same domain but you’d have to configure your services to listen on a different port so you’ll end up with something like https://domain.tld:8443 for Mastodon and https://domain.tld:8444 for lemmy.

    You can technically use subfolders, i.e. domain.tld/mastodon and domain.tld/lemmy but you’re not going to get the results you want and I can’t say for sure that the software will deal with it nicely.

    This is why we tend to use reverse proxies and configure them to route all traffic from subdomaina.domain.tld to one service and subdomainb.domain.tld to another service. It’s just easier.