# Nix-darwin: why isn't my \`packageOverrides\` working?
**URL:** https://discourse.nixos.org/t/nix-darwin-why-isnt-my-packageoverrides-working/23075
**Category:** Help
**Created:** [November 7, 2022, 11:36pm UTC](https://discourse.nixos.org/t/nix-darwin-why-isnt-my-packageoverrides-working/23075 "2022-11-07T23:36:37Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@n8henrie](https://discourse.nixos.org/u/n8henrie)
#### Post date: [November 7, 2022, 11:36pm UTC](https://discourse.nixos.org/t/nix-darwin-why-isnt-my-packageoverrides-working/23075/1 "2022-11-07T23:36:37Z")
Hello all,
I just made [my first PR to nixpkgs](https://github.com/NixOS/nixpkgs/issues/200104) ([issue](https://github.com/NixOS/nixpkgs/issues/200104) update: now merged)! It’s patching libvirt to be able to use EFI VM images on aarch64-darwin machines.
I’m confused as to why this patch doesn’t do anything when I place it in my `nix-darwin` config under `nixpkgs.config.packageOverrides`:
```nix
nixpkgs = {
config = {
packageOverrides = pkgs: {
libvirt = unstable.libvirt.overrideAttrs (old: {
mesonFlags = old.mesonFlags ++ ["-Dqemu_datadir=${unstable.qemu}/share/qemu"];
postPatch = old.postPatch + ''
sed -i '/domaincapstest/d' tests/meson.build
sed -i '/qemufirmwaretest/d' tests/meson.build
sed -i '/qemuvhostusertest/d' tests/meson.build
'';
});
};
};
};
...
environment.systemPackages = with unstable; [pkgs.libvirt];
```
Other package overrides have seemed work when placed there, but with this setup the extra build flag isn’t set:
```auto
$ nix show-derivation $(which virsh) | grep qemu_datadir
$ echo $?
1
```
However, if I put the override into `environment.systemPackages` directly, it works as expected:
```nix
environment.systemPackages = with unstable; [
(libvirt.overrideAttrs
(old: {
mesonFlags = old.mesonFlags ++ ["-Dqemu_datadir=${unstable.qemu}/share/qemu"];
postPatch = old.postPatch + ''
sed -i '/domaincapstest/d' tests/meson.build
sed -i '/qemufirmwaretest/d' tests/meson.build
sed -i '/qemuvhostusertest/d' tests/meson.build
'';
}))
];
```
```plaintext
$ nix show-derivation $(which virsh) | grep qemu_datadir
"mesonFlags": "--sysconfdir=/var/lib -Dinstall_prefix=/1rz4g4znpzjwh1xymhjpm42vipw92pr73vdgl6xs1hycac8kf2n9 -Dlocalstatedir=/var -Drunstatedir=/run -Dinit_script=none -Dapparmor=disabled -Dattr=disabled -Daudit=disabled -Dbash_completion=enabled -Dblkid=disabled -Dcapng=disabled -Dcurl=enabled -Ddocs=enabled -Dexpensive_tests=enabled -Dfirewalld=disabled -Dfirewalld_zone=disabled -Dfuse=disabled -Dglusterfs=disabled -Dhost_validate=enabled -Dlibiscsi=disabled -Dlibnl=disabled -Dlibpcap=enabled -Dlibssh2=enabled -Dlogin_shell=disabled -Dnss=disabled -Dnumactl=disabled -Dnumad=disabled -Dpciaccess=disabled -Dpolkit=disabled -Dreadline=enabled -Dsecdriver_apparmor=disabled -Dtests=enabled -Dudev=disabled -Dyajl=enabled -Ddriver_ch=disabled -Ddriver_esx=enabled -Ddriver_interface=disabled -Ddriver_libvirtd=enabled -Ddriver_libxl=disabled -Ddriver_lxc=disabled -Ddriver_network=enabled -Ddriver_openvz=disabled -Ddriver_qemu=enabled -Ddriver_remote=enabled -Ddriver_secrets=enabled -Ddriver_test=enabled -Ddriver_vbox=enabled -Ddriver_vmware=enabled -Dstorage_dir=enabled -Dstorage_disk=disabled -Dstorage_fs=disabled -Dstorage_gluster=disabled -Dstorage_iscsi=disabled -Dstorage_iscsi_direct=disabled -Dstorage_lvm=disabled -Dstorage_mpath=disabled -Dstorage_rbd=disabled -Dstorage_scsi=enabled -Dstorage_vstorage=disabled -Dstorage_zfs=disabled -Dqemu_datadir=/nix/store/dyzfcnf6r3zh5qhbx1blf2vw2r301cjb-qemu-7.1.0/share/qemu",
```
Reading other issues, is my override being applied early but then overridden somewhere else? If so, how might I have figured that out on my own?
Thanks as always for all the help!
---
### Author:  [@ElvishJerricco](https://discourse.nixos.org/u/ElvishJerricco)
#### Post date: [November 8, 2022, 1:54am UTC](https://discourse.nixos.org/t/nix-darwin-why-isnt-my-packageoverrides-working/23075/2 "2022-11-08T01:54:58Z")
```auto
environment.systemPackages = with unstable; [pkgs.libvirt];
```
You used `with`. That `pkgs` doesn’t refer to your regular `pkgs` variable; it refers to `unstable.pkgs`. This is why friends don’t let friends use `with`; not even once.
---
### Author:  [@n8henrie](https://discourse.nixos.org/u/n8henrie)
#### Post date: [November 8, 2022, 2:48am UTC](https://discourse.nixos.org/t/nix-darwin-why-isnt-my-packageoverrides-working/23075/3 "2022-11-08T02:48:12Z")
Really? I assumed that everything else (e.g. bare `foo`) in that block referred to `unstable.foo`, but that explicitly using `pkgs.libvirt` would ensure that I was referring to the “global” `pkgs`.
EDIT: So within that block, how do I refer to the “global” / outer scope `pkgs`?
---
### Author:  [@ElvishJerricco](https://discourse.nixos.org/u/ElvishJerricco)
#### Post date: [November 8, 2022, 3:00am UTC](https://discourse.nixos.org/t/nix-darwin-why-isnt-my-packageoverrides-working/23075/4 "2022-11-08T03:00:53Z")
Actually, I forgot one quirk about Nix syntax, and you might be right (depending on what your file looks like). Local variable names always take priority over “environmental” variable names that come from things like `with` or `scopedImport`. This is regardless of which type comes closer in scope. e.g. to mimic the way `pkgs` works:
```nix
let
x = { x = x; y = "foo"; };
z = { x = z; y = "bar"; };
in with z; x.y
```
This evaluates to `"foo"`, even though `z.x.y` would be `"bar"`. So I guess if `pkgs` is a local variable and not an environmental one (if it’s at the top of your file like `{ pkgs, ... }:` then it is local), then it _should_ work as you expected. If you don’t have any local `pkgs` binding though, then the _only_ one there is `unstable.pkgs`
Still, `with` makes things like this very confusing so I still recommend avoiding it.
---
### Author:  [@n8henrie](https://discourse.nixos.org/u/n8henrie)
#### Post date: [November 13, 2022, 8:10pm UTC](https://discourse.nixos.org/t/nix-darwin-why-isnt-my-packageoverrides-working/23075/5 "2022-11-13T20:10:02Z")
> [@ElvishJerricco](#):
>
> That `pkgs` doesn’t refer to your regular `pkgs` variable; it refers to `unstable.pkgs` . This is why friends don’t let friends use `with` ; not even once.
Removing `with` and manually specifying `unstable.foo` for everything else didn’t change anything.
---
### Author:  [@n8henrie](https://discourse.nixos.org/u/n8henrie)
#### Post date: [November 13, 2022, 8:11pm UTC](https://discourse.nixos.org/t/nix-darwin-why-isnt-my-packageoverrides-working/23075/6 "2022-11-13T20:11:43Z")
Adding `abort` to my `packageOverrides` doesn’t change anything, so it seems like it’s not even being evaluated.
---
### Author:  [@n8henrie](https://discourse.nixos.org/u/n8henrie)
#### Post date: [November 13, 2022, 8:14pm UTC](https://discourse.nixos.org/t/nix-darwin-why-isnt-my-packageoverrides-working/23075/7 "2022-11-13T20:14:01Z")
As additional context, the above is from my `darwin-configuration.nix`, which starts by accepting `pkgs` and is being called from a flake that calls it with `specialArgs = { pkgs = unstable; }`.
I wonder if that’s the problem? It’s being overridden?
---
### Author:  [@n8henrie](https://discourse.nixos.org/u/n8henrie)
#### Post date: [November 18, 2022, 11:55pm UTC](https://discourse.nixos.org/t/nix-darwin-why-isnt-my-packageoverrides-working/23075/8 "2022-11-18T23:55:44Z")
It ended up being more a pain to sort out than I expected.
@ElvishJerricco ended up being on the right track for part of the issue; apparently `unstable` has a `pkgs` attribute. I couldn’t figure out why _completely removing `pkgs`_ from the configuration arguments didn’t result in an error here:
```auto
{ config
, lib
, specialArgs
, options
, modulesPath
, stable
, darwinPkgs
, unstable
}:
{
...
with unstable; [pkgs.libvirt];
...
}
```
`pkgs` _should_ have been undefined! Ends up it was picking up `unstable.pkgs` 🤦♂️
Temporarily removing the `with unstable` helped reveal this issue, and appropriately gave me an error about missing `pkgs` as expected.
I eventually figured out that I could inspect the derivation like so, and it properly showed my override:
```auto
$ nix show-derivation ~/.dotfiles/?submodules=1#darwinConfigurations.$(hostname -s).pkgs.libvirt | less
```
Realizing that I could do inspect `pkgs` _even though_
- I hadn’t defined `pkgs` anywhere
- I wasn’t passing `pkgs` as an argument into the config
- and I wasn’t accepting `...` in my arguments (so there shouldn’t be anything “hiding”)
suggested that `pkgs` was magically being passed in somehow, somewhere. I still haven’t figured out where or how – maybe something [here](https://github.com/LnL7/nix-darwin/blob/088c98a584a38b5f844bb9e9cd32eb28479ca6d7/eval-config.nix#L26)?
Anyway, all I had to do was to accept `pkgs` as an argument, no other changes to my flake (and not passing it in explicitly from the flake anywhere), and my overrides started working. The diff is pretty uninspiring:
```auto
diff --git a/darwin-configuration.nix b/darwin-configuration.nix
index 4f7319c..e63a689 100644
--- a/darwin-configuration.nix
+++ b/darwin-configuration.nix
@@ -1,4 +1,5 @@
-{ config
+{ pkgs
+, config
, lib
, specialArgs
, options
```
¯\_(ツ)\_/¯
---
### Author:  [@n8henrie](https://discourse.nixos.org/u/n8henrie)
#### Post date: [December 5, 2022, 9:37pm UTC](https://discourse.nixos.org/t/nix-darwin-why-isnt-my-packageoverrides-working/23075/9 "2022-12-05T21:37:22Z")
Related:
- [AllowUnfree doesn't work with Flake managed system - #13 by Misterio](https://discourse.nixos.org/t/allowunfree-doesnt-work-with-flake-managed-system/21798/13)
- [Nixpkgs module should not allow setting both pkgs and other options · Issue #191910 · NixOS/nixpkgs · GitHub](https://github.com/NixOS/nixpkgs/issues/191910)