【发布时间】：2019-01-03 17:38:07
【问题描述】：
在将频道从nixos-18.09 切换到nixos-unstable 并返回时，我对我的系统做了一些处理，现在遇到了一个问题，导致$ nixos-rebuild switch 无法成功运行。
当我尝试这样做时，我收到以下错误：
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
我已尝试通过运行删除违规路径
$ nix-store --delete /nix/store/19sp5z5i8kg7x0inyrb1kzm1n6g6rzcc-nixos-system-nixos-19.03pre164715.201d739b0ff.drv
根据
，该路径没有“推荐人”$ 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。但是，运行 $ nixos-rebuild switch 仍然会重新创建此路径并再次给出相同的错误。
为什么$ nixos-rebuild switch 创建此路径，我怎样才能让该命令再次成功运行？
我不知道为什么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
【问题讨论】：
-
如果没有构建成功，那么依赖它的任何东西都不会成功，因此会创建一个 gc 根，所以是的，
nix-store --gc对此一无所知。 -
nix show-derivation -r /nix/store/19sp5z5i8kg7x0inyrb1kzm1n6g6rzcc-nixos-system-nixos-19.03pre164715.201d739b0ff.drv是你的朋友 -- 它拥有追踪此事件所需的一切。 -
...或者，如果您想要图形形式的内容，
nix-store -q --graph /nix/store/19sp5z5i8kg7x0inyrb1kzm1n6g6rzcc-nixos-system-nixos-19.03pre164715.201d739b0ff.drv可能是一个不错的起点。 -
也就是说，您的错误消息也很清楚依赖链是什么。您的系统配置为在默认 PATH 中使用带有
pandas的 Python 3。pandas依赖于moto，它依赖于python-jose，它依赖于rsa，这就是失败的原因。 -
顺便说一句，
nixos-channel命令来自哪里？nix-channel --list我熟悉；nixos-channel --list，没有那么多。如果您想检查与nixos-rebuild相关的nix 频道，请确保查看为root 配置的频道，而不是您的用户帐户；因此，sudo nix-channel --list是合适的。
标签： nixos