nix-shell error:

[root@nixos:/home/zeta/example_projects/simple_examples/my_script]# ls
default.nix  my_script.hs

[root@nixos:/home/zeta/example_projects/simple_examples/my_script]# nix-shell 
building '/nix/store/qxxl4jd1q2jpljl3b8ilz4spzhp0zp7c-cabal2nix-my_script.drv'...
installing
error: creating directory '/nix/var': Permission denied
error: creating directory '/nix/var': Permission denied
** need a revision for VCS when the hash is given. skipping.
** need a revision for VCS when the hash is given. skipping.
** need a revision for VCS when the hash is given. skipping.
** need a revision for VCS when the hash is given. skipping.
cabal2nix: user error (Failed to fetch source. Does this source exist? Source {sourceUrl = "/nix/store/0c335601jszw1kwkghn7qanzlrv40mdi-my_script", sourceRevision = "", sourceHash = Guess "", sourceCabalDir = ""})
builder for '/nix/store/qxxl4jd1q2jpljl3b8ilz4spzhp0zp7c-cabal2nix-my_script.drv' failed with exit code 1
error: build of '/nix/store/qxxl4jd1q2jpljl3b8ilz4spzhp0zp7c-cabal2nix-my_script.drv' failed

[root@nixos:/home/zeta/example_projects/simple_examples/my_script]# 

[zeta@nixos:/my_script]$ ls
CHANGELOG.md Setup.hs my-script.cabal
Main.hs default.nix my_script.hs
[zeta@nixos:/my_script]$ nix-shell
building '/nix/store/qxxl4jd1q2jpljl3b8ilz4spzhp0zp7c-cabal2nix-my_script.drv'...
installing
error: creating directory '/nix/var': Permission denied
error: creating directory '/nix/var': Permission denied
** need a revision for VCS when the hash is given. skipping.
** need a revision for VCS when the hash is given. skipping.
** need a revision for VCS when the hash is given. skipping.
** need a revision for VCS when the hash is given. skipping.
cabal2nix: user error (Failed to fetch source. Does this source exist? Source {sourceUrl = "/nix/store/0c335601jszw1kwkghn7qanzlrv40mdi-my_script", sourceRevision = "", sourceHash = Guess "", sourceCabalDir = ""})
builder for '/nix/store/qxxl4jd1q2jpljl3b8ilz4spzhp0zp7c-cabal2nix-my_script.drv' failed with exit code 1
error: build of '/nix/store/qxxl4jd1q2jpljl3b8ilz4spzhp0zp7c-cabal2nix-my_script.drv' failed
[zeta@nixos:/my_script]$

let
pkgs = import { };
in
pkgs.haskellPackages.developPackage
{
root = ./.;
modifier = drv:
pkgs.haskell.lib.addBuildTools drv (with pkgs.haskellPackages;
[
cabal-install
ghcid
]);
}