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

[Jörg Thalheim]

On 2017-06-18 06:43, Wout Mertens wrote:
>
> 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.

I used this in a single-user setup:

https://github.com/nixos-users/wiki/wiki/NFS#nix-store-on-nfs

I did not experienced problems so far

>
> (*): 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 <mailto: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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