Oops, at some point I missed that this is all about nix-shell.
So, by looking into nix-shell, we see that packages names are evaluated
here https://github.com/NixOS/nix/blob/master/scripts/nix-build.in#L226.
This means that the package names used with "-p" must exist within
"<nixpkgs>", which you just shown do not...
This is all a misunderstanding. When trying to resolve <nixpkgs>,
nix-shell looks at yout NIX_PATH.
Your nix-path contains something like this :
/nix/var/nix/profiles/per-user/root/channels/nixos:nixos-config=/etc/nixos/configuration.nix:/nix/var/nix/profiles/per-user/root/channels
So, the first place where nixpkgs is looked for is
/nix/var/nix/profiles/per-user/root/channels/nixos, and as the nixos
channel comes with a folder named nixpkgs, this is the one selected.
To work around this, you have one solution: override nixpkgs location.
You can either use
NIX_PATH=nixpkgs=/nix/var/nix/profiles/per-user/root/channels/nixpkgs
nix-shell -p letsencrypt, or
nix-shell -p letsencrypt -I
nixpkgs=/nix/var/nix/profiles/per-user/root/channels/nixpkgs
Other variations may also work, like
NIX_PATH=/nix/var/nix/profiles/per-user/root/channels/ nix-shell -p
letsencrypt, or
nix-shell -p letsencrypt -I /nix/var/nix/profiles/per-user/root/channels/
Now, this happens because nixos defines NIX_PATH to be the nixos pkgs
tree, and therefore <nixpkgs> always resolves to nixos packages.
As to why this package is listed in nix-env, this is because nix-env
gets its default expression from ~/.nix-defexpr, which behaves more
sanely, not looking at NIX_PATH.
If you want to know more about the future unification of nix-*commands,
https://github.com/NixOS/nix/issues/779 (and referenced pages) are a
good start.
It appears that the nice channel.package is very specific to nix-env,
and not used by the other tools.
In particular, nix-shell provides no way to use packages from different
channels at the same time.
Regards,
-- Layus.
On 31/03/16 15:30, Dmitry Malikov wrote:
> What's the output of (normal user)
> $ nix-channel --list
Well, it's empty.
>To inspect your system state, try to run
>> nix-instantiate --eval --expr --strict "<nixpkgs>"
/nix/store/bc71r4k7bms0ykfl5zxgww1fi3kb0jdw-nixos-15.09.1180.e8e1cb8/nixos/nixpkgs
>> nix-instantiate --eval --expr --strict "<nixos>"
/nix/store/bc71r4k7bms0ykfl5zxgww1fi3kb0jdw-nixos-15.09.1180.e8e1cb8/nixos/nixos
>> sudo nix-instantiate --eval --expr --strict "<nixpkgs>"
/nix/store/bc71r4k7bms0ykfl5zxgww1fi3kb0jdw-nixos-15.09.1180.e8e1cb8/nixos/nixpkgs
>> sudo nix-instantiate --eval --expr --strict "<nixos>"
/nix/store/bc71r4k7bms0ykfl5zxgww1fi3kb0jdw-nixos-15.09.1180.e8e1cb8/nixos/nixos
><nixpkgs> gets evaluated in the context of the current user, so you
will get very different results when using sudo.
Nah, they look pretty much the same.
>Now, there is no reason for the attribute returned by `nix-env -f
"<nixpkgs>" -qaP` to be missing when calling `nix-shell "<nixpkgs>"
-p` because the nixpkgs are exactly the same.
Yep, probably this explains something.
>> nix-env -qaP -f "<nixpkgs>" | grep letsencrypt
>>
So, what are the best practices of having nixos and nixpkgs-unstable
channels? Should root user be subscribed to nixos and the normal user
to nixpkgs one?
On 31 March 2016 at 11:46, Guillaume Maudoux (Layus)
<[email protected] <mailto:[email protected]>> wrote:
Hmm.. could it be that your system is confused by multiple channels ?
What's the output of (normal user)
$ nix-channel --list
I think your best bet is `nix-shell "<nixpkgs>" -p letsencrypt`
where nixpkgs is your channel name.
You can even go further and set the nixpkgs path directly using
nix-shell
/nix/store/7kxsv9svwcaxzkxxjg0zxcb151mic8vw-nixos-16.03pre76756.885acea/nixos/nixpkgs
-p letsencrypt
nix-env can also take such a path
To inspect your system state, try to run
$ nix-instantiate --eval --expr --strict "<nixpkgs>"
$ nix-instantiate --eval --expr --strict "<nixos>"
$ sudo nix-instantiate --eval --expr --strict "<nixpkgs>"
$ sudo nix-instantiate --eval --expr --strict "<nixos>"
<nixpkgs> gets evaluated in the context of the current user, so
you will get very different results when using sudo.
To ensure a consistent result, you can also pass the nixpkg tree
to nix-env with option -f.
$ nix-env -qaP -f "<nixpkgs>"
Now, there is no reason for the attribute returned by `nix-env -f
"<nixpkgs>" -qaP` to be missing when calling `nix-shell
"<nixpkgs>" -p` because the nixpkgs are exactly the same.
All this highlights the inconsistency between (and within) the tools.
But that's another story :-).
Layus.
Le 31/03/16 11:25, Dmitry Malikov a écrit :
>> nix-shell -p nixpkgs.pkgs.letsencrypt
error: undefined variable ‘nixpkgs’ at (string):1:66
(use ‘--show-trace’ to show detailed location information)
Any other ideas?
On 31 March 2016 at 10:37, Arseniy Seroka <[email protected]
<mailto:[email protected]>> wrote:
nix-shell -p nixpkgs.pkgs.letsencrypt
--
Sincerely,
Arseniy Seroka
On 31 March 2016 02:21:40 Dmitry Malikov
<[email protected] <mailto:[email protected]>> wrote:
>> sudo nix-channel --list
nixpkgs https://nixos.org/channels/nixpkgs-unstable
nixos https://nixos.org/channels/nixos-15.09
>> nixos-version
15.09.1180.e8e1cb8 (Dingo)
>> nix-env --version
nix-env (Nix) 1.10
Anything else?
On 31 Mar 2016, at 00:45, Jonn Mostovoy <[email protected]
<mailto:[email protected]>> wrote:
Just worked for me, exactly the same command.
My version of nixpkgs is way older though.
On Mar 31, 2016 12:40 AM, "Dmitry Malikov"
<[email protected] <mailto:[email protected]>> wrote:
>>
nix-env -qaP '*' | grep letsencrypt
nixpkgs.letsencrypt
letsencrypt-0.4.0
>> nix-shell -p letsencrypt
error: undefined variable ‘letsencrypt’ at (string):1:66
(use ‘--show-trace’ to show detailed location information)
What am I missing here?
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