[Nix-dev] nix-channel --update does not work

[Ambrus Kaposi]

Dear All,

I am trying to update NixOS on a computer which has not been updated
for around half a year and since then the channel mechanism has
switched from bz2 to xz compression.
This is the error I get:

root# nix-channel --update
fetching list of Nix archives at
`http://nixos.org/releases/nixos/nixos-0.2pre4454_979117b-789154b/MANIFEST.bz2'.
..
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
downloading Nix expressions from
`http://nixos.org/releases/nixos/nixos-0.2pre4454_979117b-789154b/nixexprs.tar.bz2'...
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
curl: (22) The requested URL returned error: 404 Not Found
/nix/store/lplzx6nf17hk2a9q549gm8hi7nqhx58z-nix-1.1/bin/nix-prefetch-url:
download of ‘http://nixos.org/releases/nixos/nixos-0.2pre4454_979117b-789154b/nixexprs.tar.bz2’
failed
cannot fetch `http://nixos.org/releases/nixos/nixos-0.2pre4454_979117b-789154b/nixexprs.tar.bz2'
at /run/current-system/sw/bin/nix-channel line 114.

I tried to manually prefetch the xz file, recompress it as bz2,  and
prefetch it to the nix store but nix-channel still wants to download
it again.
Using a manually modified version of nix-prefetch-url also did not help.

Do you have any ideas on how to solve this? Am I missing something?

Many thanks,
Ambrus