Readonly mode

[ghost]

Sometimes it'd be useful to temporarily put a daemon into readonly mode. It'd continue working normally, except that it won't accept writes of any kind. Ideally, there'd be no disk writes at all in this mode.

Use cases include updates and fs-repo-migrations, but also fire fighting of all kinds.

[jbenet]

@lgierth great idea

[RubenKelevra]

@Stebalien I think this can be closed. You can just read a repo without running a daemon.

[Stebalien]

That's not quite the same thing:

1. ipfs add still works, even when offline.
2. A "readonly" node should still be able to serve files over the network.

I believe the goal here is to make it possible to run a daemon from a read-only medium/snapshot.

[i-norden]

Curious if this can be closed since --writable bool - Enable writing objects (with POST, PUT and DELETE). flag exists or if the desired behavior is to create a mode where even "background" writes are not possible such as updating the local DHT.