How do I modify a derivation for a service locally?

dstcruz · October 8, 2019, 7:03pm

I’m trying to modify this locally:

NixOS/nixpkgs/blob/21597ed69e6d776810fc57161e446d3314229e74/nixos/modules/services/networking/xrdp.nix

{ config, lib, pkgs, ... }:

with lib;

let
  cfg = config.services.xrdp;
  confDir = pkgs.runCommand "xrdp.conf" { preferLocalBuild = true; } ''
    mkdir $out

    cp ${cfg.package}/etc/xrdp/{km-*,xrdp,sesman,xrdp_keyboard}.ini $out

    cat > $out/startwm.sh <<EOF
    #!/bin/sh
    . /etc/profile
    ${cfg.defaultWindowManager}
    EOF
    chmod +x $out/startwm.sh

    substituteInPlace $out/xrdp.ini \
      --replace "#rsakeys_ini=" "rsakeys_ini=/run/xrdp/rsakeys.ini" \

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Namely, I’m trying to add the changes suggested by Microsoft for xrdp use in a hyper-v linux guess found here:

github.com

microsoft/linux-vm-tools/blob/4dcc278f842ef1de4cc2c7b24ecb1c048415ff07/arch/install-config.sh

#!/bin/bash

#
# This script is for Arch Linux to configure XRDP for enhanced session mode
#
# The configuration is adapted from the Ubuntu 16.04 script.
#

if [ "$(id -u)" -ne 0 ]; then
    echo 'This script must be run with root privileges' >&2
    exit 1
fi

# Use Qi to check for exact package name
if ! pacman -Qi xrdp > /dev/null ; then
    echo 'xrdp not installed. Run makepkg.sh first to install xrdp.' >&2
    exit 1
fi

# Use Qs to allow xorgxrdp-devel-git

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I’m not sure what is the best way to make these modifications locally. I’m not sure if I’m supposed to be looking at making an overlay like this:

As is probably obvious already, I’m a bit confused by the above, given that the nix derivation I’m trying to modify doesn’t seem to be a package?

jonringer · October 8, 2019, 8:10pm

I think the most proper thing would be to change the xrdp module to include hooks that you need for it to work successfully. You should be test it locally with nixos-rebuild switch -I nixpkgs=path/to/editted/default.nix. Once it works, submit a PR so that others may share

dstcruz · October 9, 2019, 2:53pm

Got any pointers as to where to start learning how to include said hooks?

jonringer · October 9, 2019, 3:05pm

Unfortunately I can’t find any good documentation on how to build NixOS modules, and I would hate to say, “look at source code” because it’s not a great way to learn. @Infinisil do you know of any resources?

dstcruz · October 9, 2019, 3:16pm

If you mean “options” I think I can figure this out. To test this out, do I need to clone the repo and make my modifications there, then use -I /my/local/repo for testing the build? Or can I just have a single file (without the full clone)?

jonringer · October 9, 2019, 3:22pm

I personally would clone the repo, that way you can iterate with doing nixos-rebuild. If you’re doing this on a local machine, it probably won’t be too bad. But if you’re doing this on an azure VM, then it will be pretty bad.

aanderse · October 10, 2019, 9:59am

You can go the single file route if you want to by utilizing disabledModules on the existing module and then import on your local coy.