[Nix-dev] In multi-user Nix, let the daemon handle creation of GC roots

[Wout Mertens]

Note, sharing /nix is already not really possible because the metadata is
stored in sqlite and its locking does not play nice with nfs. (*)
Another issue is that right now, nix does not /require/ the daemon to work,
and this proposal would change that.

However, you can totally share /nix between multiple hosts, you just have
to pinkie-promise not to write to it from multiple hosts at the same time.

Wout.

(*): the reason is that fnctl() locking is broken on many implementations.
If this testing project
https://sourceforge.net/projects/locktests/files/?source=navbar says it's
not broken, you can totally use nix on nfs.

On Sun, 18 Jun 2017, 5:10 AM , <sbaugh at catern.com> wrote:

>
> My understanding is that currently GC roots (symlinks in
> profiles/gcroots) are created and deleted directly by the various Nix
> tools, even in multi-user configurations. (whether on NixOS or on
> another Linux distribution)
>
> It seems to me that it would be useful for the daemon to handle making
> GC roots, and forbid users to directly create GC roots.
>
> The features that come to mind:
> - Allows later implementing policy about GC roots/space consumption
> - Allows avoiding complicated locking around doing GC
> - Allows /nix to be put on network storage transparently
> - Allows /nix to be shared between containers transparently
>
> The network-storage-/nix use case may be the most important, since there
> seems to be a lot of people who want to put /nix on NFS.
>
> Thoughts? Has this been considered?
>
> Thanks for Nix!
>
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