For the second time within a week, the following happened:
When i ran sudo nixos-rebuild switch --upgrade-all the result was error: reading symbolic link '/nix/var/nix/profiles/per-user/root/channels/"': No such file or directory.
The empty entry is the reason for the failure to update. I can “solve” it by adding the unstable channel again but i would like to know what is happening, this never happened before…