The use of Nix 2.0 significantly simplifies the installer, since we
can just pass a different store URI (--store /mnt) - it's no longer
needed to set up a chroot environment for the build, and to bootstrap
Nix into the chroot.
Also, commands that need to run in the installation (namely boot
loader installation and setting a root password) are now executed
using nixos-enter.
This also removes the need for nixos-prepare-root since any required
initialisation is done by Nix or by the activation script.
* The environment variables NIX_CONF_DIR, NIX_BUILD_HOOK and
NIX_REMOTE are no longer needed.
* A /bin/sh (from busybox) is provided by default in sandboxes.
* Various options were renamed.
Among other things, this will allow *2nix tools to output plain data
while still being composable with the traditional
callPackage/.override interfaces.
This can be disabled with the `withKerberos` flag if desired.
Make the relevant assertions lazy,
so that if an overlay is used to set kerberos to null,
a later override can explicitly set `withKerberos` to false.
Don't build with GSSAPI by default;
the patchset is large and a bit hairy,
and it is reasonable to follow upstream who has not merged it
in not enabling it by default.
This can be disabled with the `withKerberos` flag if desired.
Make the relevant assertions lazy,
so that if an overlay is used to set kerberos to null,
a later override can explicitly set `withKerberos` to false.
Don't build with GSSAPI by default;
the patchset is large and a bit hairy,
and it is reasonable to follow upstream who has not merged it
in not enabling it by default.
`nixos-generate-config` detects the `cpuFreqGovernor` suited best for my
machine, e.g. `powerManagement.cpuFreqGovernor = lib.mkDefault "powersave";`.
However the `powerManagement` module sets a sensitive default for
`cpuFreqGovernor` using `mkDefault` to avoid breackage with older
setups. Since 140ac2f1 the `hardware-configuration.nix` sets the
gorvernor with `mkDefault` as well which causes evaluation errors if the
powermanagement module is enabled:
```
error: The unique option `powerManagement.cpuFreqGovernor' is defined multiple times, in `/home/ma27/Projects/nixos-config/hardware-configuration.nix' and `/nix/var/nix/profiles/per-user/root/channels/nixos/nixpkgs/nixos/modules/config/power-management.nix'.
```
Using `mkOptionDefault` rather than `mkDefault` in the powermanagement
module fixes this issue as it decreases the priority of the module and
prefers the value set in `hardware-configuration.nix`.
I have confirmed the change using the following VM declaration:
```
{
cpuFreq = { lib, ... }: {
powerManagement.cpuFreqGovernor = lib.mkDefault "powersave";
powerManagement.enable = true;
};
}
```
