为什么 nixos-rebuild 开关会为未使用的东西创建一个商店？

Question

我在将频道从 nixos-18.09 切换到 nixos-unstable 并返回时对我的系统做了一些事情，现在运行出现了一个问题，导致 $ nixos-rebuild switch 无法从运行宁成功。

当我尝试这样做时，出现以下错误：

writing manifest file 'singledispatch.egg-info/SOURCES.txt'
Copying singledispatch.egg-info to build/bdist.linux-x86_64/wheel/singledispatch-3.4.0.3-py3.6.egg-info
running install_scripts
Traceback (most recent call last):
  File "nix_run_setup", line 8, in <module>
    exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))
  File "setup.py", line 20, in <module>
    long_description = f.read()
  File "/nix/store/qbyckcddc74s2fi060n8xqcn8gygrhjl-python3-3.6.8/lib/python3.6/encodings/ascii.py", line 26, in decode
    return codecs.ascii_decode(input, self.errors)[0]
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 898: ordinal not in range(128)
builder for '/nix/store/mcncvdwadrq1335bwy279dg7q0sxhvhp-python3.6-rsa-4.0.drv' failed with exit code 1
cannot build derivation '/nix/store/pifmbmqallj7jkl3ar1wv8nqyfzq08hr-python3.6-python-jose-3.0.1.drv': 1 dependencies couldn't be built
building '/nix/store/1qy7ka8c0s3mjv51pdiyyp103d11awkb-python3.6-termstyle-0.1.11.drv'...
building '/nix/store/8zvlx7367p21vj0iccsvhpz1jv3wx0b6-python3.6-websocket_client-0.54.0.drv'...
cannot build derivation '/nix/store/3w08jzilgvddzx728nnkpaadc7sd9p2v-python3.6-moto-1.3.7.drv': 1 dependencies couldn't be built
building '/nix/store/qfkfr913dx4ssp1qahfd9wcj6csf6yxm-python3.6-xlrd-1.1.0.drv'...
building '/nix/store/dvi6y2zlc4gwli0qqhxhr6cbvfs5qwhx-python3.6-xlwt-1.3.0.drv'...
building '/nix/store/p38p279r5y8bh7n9pvw8194k9zvnybic-reload-container.drv'...
cannot build derivation '/nix/store/sf4d3zrds99sq22s096f4pdwb2602mf2-python3.6-pandas-0.23.4.drv': 1 dependencies couldn't be built
building '/nix/store/hy1197qj5ivb54wicyn0ljdbv8qxp0zc-remove-references-to.drv'...
building '/nix/store/6cqp8vf151gvxbnz03qp4sj9awd8lnfc-smb-dummy.conf.drv'...
building '/nix/store/cb5r8y9llx4yw64kyg2hhwds4g123h29-stage-1-init.sh.drv'...
building '/nix/store/4ps1704mhdqj5bp1ck7sa2x67l7h08x4-su.pam.drv'...
cannot build derivation '/nix/store/hx05mqxryfl1aqvc5lqf0q05n230qnz3-system-path.drv': 1 dependencies couldn't be built
building '/nix/store/zrrbcfif92d7yz1d4vlcnva3gx8npc2k-systemd-boot-builder.py.drv'...
building '/nix/store/z8mld3scs2hzb6k3hffjqvfyrg9qnlg7-systemd-user.pam.drv'...
building '/nix/store/0gixkqfsr3plwcyf72izycpkr5rf1r6k-udev-rules.drv'...
cannot build derivation '/nix/store/19sp5z5i8kg7x0inyrb1kzm1n6g6rzcc-nixos-system-nixos-19.03pre164715.201d739b0ff.drv': 1 dependencies couldn't be built
error: build of '/nix/store/19sp5z5i8kg7x0inyrb1kzm1n6g6rzcc-nixos-system-nixos-19.03pre164715.201d739b0ff.drv' failed

我已经尝试通过运行ning

删除有问题的路径

$ nix-store --delete /nix/store/19sp5z5i8kg7x0inyrb1kzm1n6g6rzcc-nixos-system-nixos-19.03pre164715.201d739b0ff.drv

根据

，该路径没有'referrers'

$ nix-store -q --referrers /nix/store/19sp5z5i8kg7x0inyrb1kzm1n6g6rzcc-nixos-system-nixos-19.03pre164715.201d739b0ff.drv`)

我还使用 $ nix-store --gc 进行了垃圾收集。然而，运行ning $ nixos-rebuild switch 仍然重新创建此路径并再次给出相同的错误。

为什么 $ nixos-rebuild switch 创建这条路径，我怎样才能再次成功地获得该命令运行ning？

我完全不确定为什么 nixos-system-nixos-19.03 会出现在我的系统上；此时我只跟踪 nixos-18.09 频道：

$ nixos-channel --list
nixos-18.09 https://nixos.org/channels/nixos-18.09

Answer 1

如果您过滤错误消息，事件链就很清楚了：

builder for '/nix/store/mcncvdwadrq1335bwy279dg7q0sxhvhp-python3.6-rsa-4.0.drv' failed with exit code 1
cannot build derivation '/nix/store/pifmbmqallj7jkl3ar1wv8nqyfzq08hr-python3.6-python-jose-3.0.1.drv': 1 dependencies couldn't be built
cannot build derivation '/nix/store/3w08jzilgvddzx728nnkpaadc7sd9p2v-python3.6-moto-1.3.7.drv': 1 dependencies couldn't be built
cannot build derivation '/nix/store/sf4d3zrds99sq22s096f4pdwb2602mf2-python3.6-pandas-0.23.4.drv': 1 dependencies couldn't be built
cannot build derivation '/nix/store/hx05mqxryfl1aqvc5lqf0q05n230qnz3-system-path.drv': 1 dependencies couldn't be built
cannot build derivation '/nix/store/19sp5z5i8kg7x0inyrb1kzm1n6g6rzcc-nixos-system-nixos-19.03pre164715.201d739b0ff.drv': 1 dependencies couldn't be built
error: build of '/nix/store/19sp5z5i8kg7x0inyrb1kzm1n6g6rzcc-nixos-system-nixos-19.03pre164715.201d739b0ff.drv' failed

因此，Python rsa 模块的构建失败，因为该包存在错误。

我们为什么依赖rsa？因为...

您的系统配置为在其默认 PATH 中安装 Python 3.6 pandas。
pandas 依赖包 moto 到运行其测试 (pkgs/development/python-modules/pandas/default.nix:38).
moto 包依赖于 python-jose (pkgs/development/python-modules/moto/default.nix:44)。
python-jose 包依赖于 rsa 包 (pkgs/development/python-modules/python-jose/default.nix:33)。

顺便说一句，虽然在 nixpkgs-unstable 上是这种情况，但 18.09 版本（截至此答案的最新发布）没有 python-jose 对 rsa 的这种依赖性，因此也没有'展示手头的问题。我可以建议改用它吗？

为什么 nixos-rebuild 开关会为未使用的东西创建一个商店？

Why is nixos-rebuild switch creating a store for something that is not used?

nixos