mkosi: make image failing with "experimental Nix feature 'nix-command' is disabled" error

[wainersm]

Describe the bug

I got the error on $SUBJECT when tried to build the mkosi-based podvm image.

I'm running Fedora 40 x86_64. Got nix 2.25.3 installed via installation script from https://nixos.org

How to reproduce

1. Install nix

$  sh <(curl -L https://nixos.org/nix/install) --no-daemon

2. Build binaries

$ cd src/cloud-api-adaptor/podvm-mkosi
$ make binaries

3. Build image

$ make image

CoCo version information

latest

What TEE are you seeing the problem on

None

Failing command and relevant log output

$ make image
Enabling production preset...
rm -rf resources/build*Image
rm -rf ./build
Building image...
touch resources/buildBootableImage
nix develop ..#podvm-mkosi --command mkosi --environment=VARIANT_ID=production
error: experimental Nix feature 'nix-command' is disabled; add '--extra-experimental-features nix-command' to enable it
make: *** [Makefile:68: image] Error 1

[wainersm]

Then I realized https://github.com/confidential-containers/cloud-api-adaptor/tree/main/src/cloud-api-adaptor/podvm-mkosi#prerequisites gave me some hints that could have saved me some time. However, as I'm not versed on nix I couldn't understand Nix needs to be configured to enable flakes and nix command nor t is recommended to install Nix with the DeterminateSystems nix-installer.

We could improve the README for nix dummies. Or, explicitly passing the magic --extra-experimental-features "flakes nix-command" option to every evocation of nix like:

diff --git a/src/cloud-api-adaptor/podvm-mkosi/Makefile b/src/cloud-api-adaptor/podvm-mkosi/Makefile
index a5761f92..d112272b 100644
--- a/src/cloud-api-adaptor/podvm-mkosi/Makefile
+++ b/src/cloud-api-adaptor/podvm-mkosi/Makefile
@@ -74,7 +74,7 @@ else ifeq ($(ARCH),s390x)
        sudo -E ../hack/build-s390x-image.sh
 else
        touch resources/buildBootableImage
-       nix develop ..#podvm-mkosi --command mkosi --environment=VARIANT_ID=production
+       nix --extra-experimental-features "flakes nix-command" develop ..#podvm-mkosi --command mkosi --environment=VARIANT_ID=production
        qemu-img convert -f raw -O qcow2 build/system.raw build/podvm-$(PODVM_DISTRO)-$(ARCH).qcow2
 endif
 
@@ -95,7 +95,7 @@ else ifeq ($(ARCH),s390x)
        sudo -E ../hack/build-s390x-image.sh
 else
        touch resources/buildBootableImage
-       nix develop ..#podvm-mkosi --command mkosi --environment=VARIANT_ID=debug
+       nix --extra-experimental-features "flakes nix-command"  develop ..#podvm-mkosi --command mkosi --environment=VARIANT_ID=debug
        qemu-img convert -f raw -O qcow2 build/system.raw build/podvm-$(PODVM_DISTRO)-$(ARCH).qcow2
 endif

[wainersm]

Then I'm hit by another problem:

$ make image
Enabling production preset...
rm -rf resources/build*Image
rm -rf ./build
Building image...
touch resources/buildBootableImage
nix --extra-experimental-features "flakes nix-command" develop ..#podvm-mkosi --command mkosi --environment=VARIANT_ID=production
Traceback (most recent call last):
  File "/nix/store/z5f0iv1pzn2vb5nl82mhj80z5gxfy6mk-mkosi-17.1/bin/..mkosi-wrapped-wrapped", line 9, in <module>
    sys.exit(main())
  File "/nix/store/pzf6dnxg8gf04xazzjdwarm7s03cbrgz-python3-3.10.12/lib/python3.10/contextlib.py", line 79, in inner
    return func(*args, **kwds)
  File "/nix/store/z5f0iv1pzn2vb5nl82mhj80z5gxfy6mk-mkosi-17.1/lib/python3.10/site-packages/mkosi/__main__.py", line 48, in main
    run_verb(args, presets)
  File "/nix/store/z5f0iv1pzn2vb5nl82mhj80z5gxfy6mk-mkosi-17.1/lib/python3.10/site-packages/mkosi/__init__.py", line 2316, in run_verb
    name = InvokingUser.name()
  File "/nix/store/z5f0iv1pzn2vb5nl82mhj80z5gxfy6mk-mkosi-17.1/lib/python3.10/site-packages/mkosi/util.py", line 98, in name
    return pwd.getpwuid(cls.uid()).pw_name
KeyError: 'getpwuid(): uid not found: 102187'
make: *** [Makefile:68: image] Error 1

102187 is my regular user ID:

$ echo $UID
102187

[stevenhorsman]

I think I ended up using curl --proto '=https' --tlsv1.2 -sSf -L https://install.determinate.systems/nix | sh -s -- install to install nix when I built is locally based on the

It is recommended to install Nix with the DeterminateSystems nix-installer.

comment

[mkulke]

Isn't a reasonably recent version of mkosi packaged on the github runner OS these days?

[beraldoleal]

I just experienced this issue today. I was not aware of this issue, so I created the PR:

#2229

IIUC, even the latest nix version still has those features as experimental. But I agree with @wainersm that if we could update the Makefile targets, it would be easier for non-nix users like me.

[wainersm]

Hi @beraldoleal ! Thanks for the fix proposal! As explained in #2233 by @mkulke, we gonna get rid of nix to build mkosi, so I will close this issue.