[Nix-dev] Unstable Nixpkgs on stable NixOS (was: Automatically locking the screen with xautolock)

[Wout Mertens]

Your setting NIX_PATH to `nixpkgs=~/.nix-defexpr/channels/nixpkgs` makes a
lot of sense to me and I wouldn't mind it being the default for users...

In general though the whole home dir setup could use some love. There's
.nix-defexpr/, .nix-channels, .nix-profile@ and .nixpkgs/config.nix, where
it would be a lot cleaner to have everything under ~/.nix/ and on OS X
those should really be under ~/Library/Nix/.

Even nicer would be if everything (except the profile) defaulted to the
system-wide versions until the user takes an action like choosing a channel
or running nix-env. Then the user should get some warnings about getting
user-stored versions and everything gets set up automatically. Basically
making
https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/programs/shell.nix#L23-L62
lazy.

Wout.

On Tue Feb 10 2015 at 4:18:06 AM Michael Alyn Miller <malyn at strangegizmo.com>
wrote:

> The 02/08/2015 12:21, Jeffrey David Johnson wrote:
> > Nice! I'm currently binding "gksu 'i3lock -c000000 &
> > pm-suspend'" to a hotkey using i3, but this is better.  Is
> > there a standard way to get it in my fork of nixpkgs, which is
> > tracking the release-14.12 branch?  (I could just copy and
> > paste but if there's a better way now would be a good time to
> > learn.)
>
> I certainly don't have an authoritative answer to this question,
> but I'll tell you what I am doing and then maybe someone with
> much more NixOS/Nixpkgs experience will chime in with
> tweaks/guidance.
>
> In general I have the following goals for my NixOS system:
>
> 1. I want everything to be reproducible, which of course means that my
>    system is configured in /etc/nixos/configuration.nix, but also that
>    any packages that I install as an individual user are reproducible as
>    well.
> 2. Related to the above, I only want to put "system" packages into
>    configuration.nix.  My theory here is that most of my package
>    management is going to be done as a regular user, by creating
>    project-specific nix-shell environments, etc.  Also, `nix-env -q` is
>    a nice way to see everything that is installed and it doesn't appear
>    that similar tools exist at the NixOS level.
>
> Goal #1 means that configuration.nix is pretty basic -- the bare minimum
> number of packages to get my system working and launch an X environment
> (the window manager, for example, but no apps).
>
> Goal #2 was more complex.  I found the following two references on this
> topic:
>
> - <https://nixos.org/wiki/FAQ#How_can_I_manage_software_
> with_nix-env_like_with_configuration.nix.3F>
> - <https://nixos.org/wiki/Howto_keep_multiple_packages_up_to_date_at_once>
>
> I went with the first option because I wanted to be able to use `nix-env
> -q` to see what I had installed, regardless of how I did the install
> (manually or through the "myPackageSelections.nix" file).  I can provide
> more details here if you like.
>
> With that choice out of the way, the next problem that I ran into was
> getting access to newer packages.  I have contributed a couple of
> packages to Nixpkgs, fixed some others, etc. and so far I had just been
> manually installing them out of my nixpkgs checkout.  This was not
> entirely compatible with my first goal, because now I had installed
> packages that were not listed in my configuration.
>
> Enter the nixpkgs-unstable channel!  That channel seems to be updated
> pretty frequently and means that changes are available in binary form
> within a few days.  Thankfully my second goal meant that I already had a
> perfect split between stable and unstable: my NixOS configuration could
> stay on 14.12 and my user-level Nixpkgs was free to go unstable.
>
> Getting this working was relatively straightforward, although I had to
> modify my environment in a couple of unexpected ways (more on this
> later).
>
> The simple part is the `nix-channel --add https://nixos.org/channels/
> nixpkgs-unstable` <https://nixos.org/channels/nixpkgs-unstable>
> and `nix-channel --update` as a normal user.  Some things worked after
> that, but not everything.  `nix-env -i whatever` will happily use the
> nixpkgs-unstable channel because it finds that channel in ~/.nix-defexpr.
> Adding in the -f flag to specify your own expression means that nix-env
> no longer knows about the channel though.  Instead, nix-env falls back
> to NIX_PATH, which by default points at the stable NixOS channel and
> therefore has no idea that you want to use nixpkgs-unstable.
>
> I found that very confusing, although that's probably because of the
> subtlety that is the myPackageSelections.nix-based way of managing my
> package list.  In any event, I had to dig through the docs to understand
> the situation.
>
> I fixed this problem by setting NIX_PATH to `nixpkgs=~/.nix-defexpr/
> channels/nixpkgs`
> and removing the channels_root symlink from ~/nix-defexpr.  That last
> step probably isn't necessary, but every now and then nix-env would
> complain about duplicate packages and besides that I don't want to get
> (user) packages out of the stable NixOS channel anyway.
>
> This all seems to work pretty well and lets me have fast access to
> new/changed packages without compiling everything myself.  I am a bit
> worried that changing NIX_PATH and removing channels_root is going to
> cause me trouble one day, but so far everything seems fine.  As I said,
> I would welcome input here from the NixOS/Nixpkgs experts.
>
> I am curious to see what folks think about my installation approach as
> well.  I feel like this split between stable OS and unstable packages is
> a good one and that declarative user-level package management is also
> valuable.  That said, NixOS doesn't support either one "out of the box"
> so I am wondering if there is a better approach that I should be using.
>
> Hope that helps!
>
> Thanks,
> Michael Alyn Miller
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