nixos-rebuild failed switching to unstable-channel

[rollschild]

Issue description

Hi,

I'm very new to NixOS and have been tinkering the configuration.nix for almost a week. I am currently on 20.09. However, I would like to switch to unstable-channel, so I did the following:

$ sudo nix-channel --add https://nixos.org/channels/nixpkgs-unstable nixpkgs
$ sudo nix-channel --add https://nixos.org/channels/nixos-unstable nixos
$ sudo nixos-rebuild switch --upgrade

But the build failed with the following errors (I only pasted the logs with actual keywords like "failed" or "error"):

builder for '/nix/store/naqhj71jnyjwgzps1s5scrlpdf83jza9-gtk2-immodule.cache.drv' failed with exit code 127
builder for '/nix/store/lpsdcbn2hmrd0f04a0d7l67j1jfsmb0r-gtk3-immodule.cache.drv' failed with exit code 127
builder for '/nix/store/0d21dnxqvhchlzw07l3bymir7fasb17n-hwdb.bin.drv' failed with exit code 126
builder for '/nix/store/0pdrmsmvzlc7by52ksyhnzszbnqzljdr-neovim-0.4.4.drv' failed with exit code 1
builder for '/nix/store/dl1rzpx8sam3l37210p7854gyhgr8jz8-sway-1.6.drv' failed with exit code 126
cannot build derivation '/nix/store/0x2lcfys2ispldcki31np7zmpqqfscrm-etc.drv': 1 dependencies couldn't be built
building '/nix/store/fdhxhylf9hd4g5faw5gngchq9fl3b53g-linux-5.10.32-modules.drv'...
cannot build derivation '/nix/store/ddhb6cqwyrxs45f3kl41y8g6bdx655za-system-path.drv': 1 dependencies couldn't be built
cannot build derivation '/nix/store/j4hm78y4bz8yi65swxnzm2l5gmaxpp68-nixos-system-nixos-21.05pre287161.d3ba49889a7.drv': 1 dependencies couldn't be built
error: build of '/nix/store/j4hm78y4bz8yi65swxnzm2l5gmaxpp68-nixos-system-nixos-21.05pre287161.d3ba49889a7.drv' failed

For this error message, I don't even know where to start debugging. The build for 20.09 worked fine for me and I didn't change my configuration.nix. I did find some useful information in #35020 but nix-store --verify --repair as suggested in that issue did not work for me.

How do I solve this? Thanks in advance!

Technical details

$ nix-shell -p nix-info --run "nix-info -m"                                                      ✔ 
 - system: `"x86_64-linux"`
 - host os: `Linux 5.4.114, NixOS, 20.09.4055.eb7e1ef185f (Nightingale)`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.3.10`
 - channels(<myusername>): `""`
 - channels(root): `"nixos-21.05pre287161.d3ba49889a7, nixpkgs-21.05pre287202.123db833485"`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

[rollschild]

I solved this myself. It turned out #35020 is useful. I did a $ sudo nix-store --verify --check-contents --repair and it solved the issue.