I found a major communication problem with public perception of Lemmy. they seem to think a community is tied to a particular instance

Lemmy@lemmy.ml – 123 points – 1 years ago

This is a big problem. It creates the illusion that /c/cats on one particular instance is the real /c/cats.

This is the root of re-centralization and it must be pulled out.

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This is not a communication problem. Communities are indeed centralized and if an instance is shut down permanently or loses its data all the communities are gone. This is a big design problem of Lemmy.

Edit: it's sometimes possible to rebuild new communities on another instance and recover past messages that have been replicated on other instances (if there were full replicas) but this requires all users and moderators to agree on where to migrate and avoid splits and so on.

Not 100%-

If, I subscribe to !lemmy@lemmy.ml on my instance, it replicates a copy of everything to me.

When lemmy.ml goes down, I can indeed still see and browse the content here. I can even comment/interact with it, (and, when lemmy.ml goes up- the changes should sync back to it)

What you are describing is just a local cache of !lemmy@lemmy.ml on your instance and it works only if it has been populated before the downtime of lemmy.ml. If lemmy.ml never comes back to life nobody can post to !lemmy@lemmy.ml proper. All the communities on in would be dead.

Its actually possible to take the local copy, and set it as a local community...

With a few database commands.

So, migrating communities from offline servers is possible as long as it was federated and synced beforehand

That's besides the point. Of course it's always possible to create new communities on new instances, and import posts from various sources, but the original community would be still gone.

If an instance is shut down or becomes unusable for a long time there is no way to automatically migrate users to a new instance. Additionally, there is also no guarantee that all users will move to the same alternative instance. This can also cause unnecessary conflict around which alternative instance becomes the "legitimate" successor.

Looking at it that way- you are correct, and there really isn't a way to fix that.

I am just providing an alternative. That being, if you were subscribed to say, lemmy.ml/c/mycommunity, and lemmy.ml went down-

You CAN run a few commands, and convert lemmy.ml/c/mycommunity to a locally hosted community on your instance, without too much effort.