linuxPackages: 6.12 -> 6.18

<!-- To avoid merge conflicts, consider adding your item at an arbitrary place in the list instead. -->

- Create the first release note entry in this section!

- The default kernel package has been updated from 6.12 to 6.18. All supported kernels remain available.

## New Modules {#sec-release-26.05-new-modules}

          }

        ];

        # Use LTS that bcachefs is compatible with.

        boot.kernelPackages = lib.mkDefault pkgs.linuxPackages_6_18;

        # needed for systemd-remount-fs

        system.fsPackages = [ cfg.package ];

        services.udev.packages = [ cfg.package ];

  );

  packageAliases = {

    linux_default = packages.linux_6_12;

    linux_default = packages.linux_6_18;

    # Update this when adding the newest kernel major version!

    linux_latest = packages.linux_6_19;

    linux_rt_default = packages.linux_rt_5_15;