I'm trying to learn to write Nix expressions, and I thought about doing my own very simple "Hello World!" (as is tradition).
So I have my dir with only this default.nix file :
{pkgs ? import <nixpkgs> {}}:
derivation {
system = "x86_64-linux";
name = "simple-bash-derivation-helloworld";
builder = pkgs.bash;
args = [ "-c" "echo 'Hello World' > $out" ];
}
Here is what I get when I try to build it:
nix-build
these derivations will be built:
/nix/store/3grmahx3ih4c50asj84p7xnpqpj32n5s-simple-bash-derivation-helloworld.drv
building path(s) ‘/nix/store/6psl3rc92311w37c1n6nj0a6jac16hv1-simple-bash-derivation-helloworld’
while setting up the build environment: executing ‘/nix/store/wb34dgkpmnssjkq7yj4qbjqxpnapq0lw-bash-4.4-p12’: Permission denied
builder for ‘/nix/store/3grmahx3ih4c50asj84p7xnpqpj32n5s-simple-bash-derivation-helloworld.drv’ failed with exit code 1
error: build of ‘/nix/store/3grmahx3ih4c50asj84p7xnpqpj32n5s-simple-bash-derivation-helloworld.drv’ failed
Removing the args line yields the same issue.
Why do I get a permission issue?
What would be the correct way to make a simple derivation just doing a bash echo?
Please note that this is a learning exercise: I do not want to use stdenv.mkDerivation here for example.
I am running nix-env (Nix) 1.11.9 on an Ubuntu 16.04 system.
Thanks in advance.
Try running ls command on /nix/store/wb34dgkpmnssjkq7yj4qbjqxpnapq0lw-bash-4.4-p12 and you will see it's a directory rather than an executable file (pointing to $out of the pkgs.bash derivation). If you wanted to refer to bash binary you would use:
builder = "${pkgs.bash}/bin/bash";
Related
On nixos, I am trying to compile the hello world example listed in the agda documentation.
In my working directory, I have the following:
The hello-world agda program, hello-world.agda:
module hello-world where
open import IO
main = run (putStrLn "Hello, World!")
A nix shell file, shell.nix:
{ pkgs ? import <nixpkgs> { } }:
with pkgs;
mkShell {
buildInputs = [
(agda.withPackages (ps: [
ps.standard-library
]))
];
}
To enter a shell with the standard-library dependency available, I ran $ nix-shell shell.nix.
Then, trying to compile the program, I ran $ agda --compile hello-world.agda, as advised by the linked agda hello world documentation.
But that gave me the following error:
$ agda --compile hello-world.agda
Checking hello-world (/home/matthew/backup/projects/agda-math/hello-world.agda).
/home/matthew/backup/projects/agda-math/hello-world.agda:3,1-15
Failed to find source of module IO in any of the following
locations:
/home/matthew/backup/projects/agda-math/IO.agda
/home/matthew/backup/projects/agda-math/IO.lagda
/nix/store/7pg293b76ppv2rw2saf5lcbckn6kdy7z-Agda-2.6.2.2-data/share/ghc-9.0.2/x86_64-linux-ghc-9.0.2/Agda-2.6.2.2/lib/prim/IO.agda
/nix/store/7pg293b76ppv2rw2saf5lcbckn6kdy7z-Agda-2.6.2.2-data/share/ghc-9.0.2/x86_64-linux-ghc-9.0.2/Agda-2.6.2.2/lib/prim/IO.lagda
when scope checking the declaration
open import IO
It seems it should be finding the standard library, since I'm running from the nix-shell with agda's standard-library specified, but that error on open import IO looks like the standard library is somehow still not found.
Any idea what the problem is likely to be?
Or what else I can do to get agda working on nixos?
You might need to create a defaults file in AGDA_DIR (which typically refers to ~/.agda/ unless overwritten through environment variable) with the libraries you want to make available to your program:
echo standard-library >> ~/.agda/defaults
which should make the compiler automatically load the standard library.
Alternatively, you can pass them in on the command-line:
agda -l standard-library
or use a project-local .agda-lib file as follows:
name: my-libary
depend: standard-library
include: -- Optionally specify include paths
You should not need to specify the include paths with Nix, but in case you do, you can use the -i command line flag or add the path to the standard-library.agda-lib file in ~/.agda/libraries.
I'm very new to Nix. I'd like to refer to project scripts in my shell.nix file, so that when I cd into my project directory I can refer to them by name, and I can keep them up-to-date whenever the sources change.
To learn how to do this, I created a very simple derivation for a shell script. Eventually I'd like to use other languages, but I'm starting simple. It looks like this:
project
nix
myScript
default.nix
builder.sh
shell.nix
# default.nix
{ pkgs ? import <nixpkgs> {} }:
pkgs.stdenv.mkDerivation rec {
name = "myScript";
echo = pkgs.coreutils + "/bin/echo";
builder = "${pkgs.coreutils}/bin/bash";
args = [ ./builder.sh ];
}
# builder.sh
$echo "$echo Hello world" > $out
When I run nix-build myScript.nix it creates a symlinked result file that looks like this:
/nix/store/3mfkgajns47hfv0diihzi2scwl4hm2fl-coreutils-9.1/bin/echo Hello world
I tried referencing this in my shell.nix file like this:
{ pkgs ? import (fetchTarball "https://github.com/NixOS/nixpkgs/archive/bf972dc380f36a3bf83db052380e55f0eaa7dcb6.tar.gz") {} }:
let
myScript = import ./myScript {};
in
pkgs.mkShell {
buildInputs = [
myScript
];
shellHook = ''
echo Loading shell.nix
'';
}
But whenever I enter the projects directory and run the command `myScript, I get an error:
zsh: command not found: myScript
I already have direnv configured correctly, which I can confirm by adding other shell tools and checking their versions. So it's something wrong with my nix files.
I'm almost certainly doing something wrong here. I know I can simplify this with pkgs.writeShellScriptBin, but the shell script is more a minimal example of what I want to get working. Eventually I'd use more complex derivations.
What I think is wrong
I think the myScript derivation or builder is doing something wrong. It does create the expected output file (i.e. I can chmod +x and run it, and it works) but I suspect I need to tell nix how to run it? I'm not sure. And also I might be importing the derivation incorrectly.
This is a problem with your default.nix, not your shell.nix.
For mkShell to work with buildInputs as you intend, you need $out to be a directory with an $out/bin/myScript, not a file on its own. nixpkgs has a helper that will do this for you, in https://github.com/NixOS/nixpkgs/blob/master/pkgs/build-support/trivial-builders.nix --
# default.nix; no builder.sh needed
{ pkgs ? import <nixpkgs> {} }:
pkgs.writeShellScript "myScript" ''
echo "Hello world" # use the bash-builtin echo, not the external coreutils one
'';
I would like to test (from xonsh) if a command is available or not. If I try this from the xonsh command prompt:
which bash
Then it works:
user#server ~ $ which bash
/usr/bin/bash
But it does not work from xonsh script:
#!/usr/bin/env xonsh
$RAISE_SUBPROC_ERROR = True
try:
which bash
print("bash is available")
except:
print("bash is not available")
Because it results in this error:
NameError: name 'which' is not defined
I understand that which is a shell builtin. E.g. it is not an executable file. But it is available at the xnosh command prompt. Then why it is not available inside an xonsh script? The ultimate question is this: how can I test (from an xonsh script) if a (subprocess mode) command is available or not?
import shutil
print(shutil.which('bash'))
While nagylzs' answer led me to the right solution, I found it inadequate.
shutil.which defaults to os.environ['PATH']. On my machine, the default os.environ['PATH'] doesn't contain the active PATH recognized by xonsh.
~ $ os.environ['PATH']
'/usr/bin:/bin:/usr/sbin:/sbin'
I found I needed to pass $PATH to reliably resolve 'which' in the xonsh environment.
~ $ $PATH[:2]
['/opt/google-cloud-sdk/bin', '/Users/jaraco/.local/bin']
~ $ import shutil
~ $ shutil.which('brew', path=os.pathsep.join($PATH))
'/opt/homebrew/bin/brew'
The latest version of xonsh includes a built-in which command. Unfortunately, the version included will emit an error on stdout if the target isn't found, a behavior that is not great for non-interactive use.
As mentioned in another answer, which exists in the current version of xonsh (0.13.4 as of 15/12/2022) so your script would work. However, it outputs its own error message so it's necessary to redirect stderr to get rid of it.
Also, unless you redirect its stdout as well (using all>), it migh be a good idea to capture its output so the final version would look like this:
#!/usr/bin/env xonsh
$RAISE_SUBPROC_ERROR = True
try:
bash = $(which bash err> /dev/null)
print(f"bash is available: {bash}")
except:
print("bash is not available")
So, finally starting to get a stable nix environment that I can basically do all of my development in. Hooray!
Now I want to make it reproducible, as in yarn.lock (for those familiar with npm/yarn in javascript land) or Pipfile.lock (very similar for Python).
Basically the idea is that I would have a way to generate a similar lock file whenever I run nix-env -if my-env.nix, or after running this command, if that is how it would work. From this lock file, I could then exactly restore my nix profile, down to the exact versions of dependencies and sub-dependencies of the installed profile. This could be checked into git or whatever after testing out new improvements, and so a record of the environment would be maintained.
It seems to me this would be one of the most obvious use cases for Nix, and one of the major advantages over just using Docker (though the two aren't mutually exclusive), so I apologize if I've missed some relevant documentation.
What you're probably looking for is a shell.nix file like this:
let
pkgs = import (fetchTarball {
url = "https://github.com/NixOS/nixpkgs/archive/696c6bed4e8e2d9fd9b956dea7e5d49531e9d13f.tar.gz";
sha256 = "1v3yrpj542niyxp0h3kffsdjwlrkvj0mg4ljb85d142gyn3sdzd4";
}) {};
in pkgs.mkShell {
buildInputs = with pkgs; [
git
hello
];
}
Upon calling nix-shell (which by default uses the shell.nix file in the current directory), you'll be in an environment with git and hello from the specific given nixpkgs revision. This can be reproduced among all nix users (okay almost*). I can really recommend using shell.nix files for all development.
Alternatively, there's also the lesser known -r flag to nix-env, which states that
--remove-all, -r
Remove all previously installed packages first. This is equivalent to running nix-env -e '.*' first, except that everything happens in a single transaction.
You can effectively use it to replace the stateful ~/.nix-profile/manifest.nix. Create a file env.nix containing:
let
pkgs = import <nixpkgs> {};
in {
inherit (pkgs) git hello;
}
Now running nix-env -ir env.nix will install exactly git and hello and remove everything else, so you can reproduce your nix-env installations with this single file. To install additional things: Add it to the file and run the command again. You can also pin nixpkgs to a specific version as in the file above to not care about your nix-channel setup (which is also stateful).
Edit: It's also possible to get some packages from your channel and some of a specific nixpkgs revision:
let
pkgs = import <nixpkgs> {};
fixed = import (fetchTarball {
url = "https://github.com/NixOS/nixpkgs/archive/696c6bed4e8e2d9fd9b956dea7e5d49531e9d13f.tar.gz";
sha256 = "1v3yrpj542niyxp0h3kffsdjwlrkvj0mg4ljb85d142gyn3sdzd4";
}) {};
in {
inherit (pkgs) git;
inherit (fixed) hello;
}
*: The nix config, overlays and your system (Linux/Mac) can still influence this. It's a good idea to use import <nixpkgs> { config = {}; overlays = []; } for development to avoid this.
After many suggestions from folks on IRC, I was able to put together the following script, which takes a nix expression as its only argument, and copies the derivation file and records the nixpkgs versions locally while installing the specified environment:
#!/bin/bash
if [ -z "$1" ] || [ "${1: -4}" != ".nix" ] || [ ! -f "$1" ]
then
echo "No .nix file supplied"
exit -1
fi
ENV_DRV=$(nix-instantiate "$1")
cp "$ENV_DRV" ./env_backup.drv
chmod u+rw ./env_backup.drv
nix-env --set "$ENV_DRV"
NIXPKGS_VERSION=$(nix-instantiate --eval '<nixpkgs/lib>' -A version)
NIXOS_VERSION=$(nix-instantiate --eval '<nixos/lib>' -A version)
printf "nixpkgs: %s\\nnixos: %s" "$NIXPKGS_VERSION" "${NIXOS_VERSION}" > .nix_versions
Caveat: your nix expression should have the nix package in it, since we are using nix-env --set.
I haven't tried using a copied .drv file yet, but it somehow needs to be restored into the nix store; I've mainly included it as a last resort and for debugging. The output into .nix_versions should be more helpful, as these contain git commit hashes (after the last ".") that can be used to employ the correct revision of nixpkgs (thanks to infinisil on IRC):
pkgs = import "${(import <nixpkgs> {}).fetchFromGitHub { owner = "NixOS"; repo = "nixpkgs"; rev = "<your revision hash>"; sha256 = "<the hash of the output>"; }}" {}
To fill in the hash, either supply an incorrect hash to get the correct hash back, or just use the following: nix-prefetch-url --unpack github.com/nixos/nixpkgs/archive/<revision>.tar.gz.
Or, if manually checking out nixpkgs, you can just do e.g.:
with import ((builtins.getEnv "HOME") + "/workspace/nixpkgs") { }; # or:
with import "../nixpkgs" { }; # or similar
I haven't tested this sort of thing with nix-shell yet, but hope to do so soon.
I've just started using the Nix package manager on OSX and I'm attempting to create my first package for the pass binary (https://www.passwordstore.org) - which is not available in the Nixpkgs repository.
I'm attempting to specify a runtime dependency (getopt), however this doesn't appear to be available when the binary is used.
This is my packages's default.nix:
{ pkgs ? import <nixpkgs> {} }:
with pkgs;
let
version = "1.7.1";
in {
pass = stdenv.mkDerivation rec {
name = "pass-${version}";
src = fetchurl {
url = "https://git.zx2c4.com/password-store/snapshot/password-store-1.7.1.tar.xz";
sha256 = "0scqkpll2q8jhzcgcsh9kqz0gwdpvynivqjmmbzax2irjfaiklpn";
};
buildInputs = [ stdenv makeWrapper];
installPhase = ''
make install PREFIX=$out/artifact
makeWrapper $out/artifact/bin/pass $out/bin/pass \
--set PATH ${stdenv.lib.makeBinPath [ getopt ]}
'';
meta = {
homepage = "https://www.passwordstore.org";
description = "The standard unix password manager";
license = stdenv.lib.licenses.gpl2Plus;
};
};
}
I can successfully build this package (nix-build --show-trace) and install it (nix-env -i ./result).
Listing the runtime dependencies for my package shows getopt listed:
nix-store -qR $(which pass)
...
/nix/store/c5swmygzc0kmvpq6cfkvwm2yz1k57kqy-getopt-1.1.4
However when I come to use the binary (pass init my-key) I get the following error:
/nix/store/...-pass-1.7.1/artifact/bin/pass: line 302:
/usr/local/bin/getopt: No such file or directory
Can anyone advise what I'm doing wrong?
Thanks
It looks like getopt gets a special treatment. The darwin.sh script looks for it using brew and port and falls back to /usr/local. That's why the (correct) wrapper has no effect.
So the solution seems to be, to make it look for getopt in PATH, which is provided by the wrapper script. You can probably make it as simple as GETOPT=getopt (which is similar to openbsd.sh)
For patching source code, see the NixPkgs documentation
After running nix-build, you should run cat result/bin/pass to look at your wrapper script and make sure it looks OK. It should be a shell script that sets the PATH to include getopt and then calls result/artifact/bin/pass.
Then try running the wrapper script. Note that the wrapper should be in result/bin, not result/artifact/bin.