Add support for NixOS + Fedora, Arch, RH minor changes (#195)

* Add support for NixOS

Signed-off-by: Maurice Zhou <jasper@apvc.uk>

* updated files for immutable root fs

Signed-off-by: Maurice Zhou <jasper@apvc.uk>

* update ssh key location

Signed-off-by: Maurice Zhou <jasper@apvc.uk>

* change initrd host key name

Signed-off-by: Maurice Zhou <jasper@apvc.uk>

* add missing -p switch

Signed-off-by: Maurice Zhou <jasper@apvc.uk>

* comments about SSH and encrypted bpool

Signed-off-by: Maurice Zhou <jasper@apvc.uk>

* backup hardware-configuration.nix file

Signed-off-by: Maurice Zhou <jasper@apvc.uk>

* clearer wording for backup

Signed-off-by: Maurice Zhou <jasper@apvc.uk>

* global useDHCP flag is deprecated

Signed-off-by: Maurice Zhou <jasper@apvc.uk>

* point user to configuration.nix

Signed-off-by: Maurice Zhou <jasper@apvc.uk>

* fixes for systemd-autofs; network; typo

Signed-off-by: Maurice Zhou <jasper@apvc.uk>

* force command to return 0

Signed-off-by: Maurice Zhou <jasper@apvc.uk>

* fix command to postMount

Signed-off-by: Maurice Zhou <jasper@apvc.uk>

* fix mount command

Signed-off-by: Maurice Zhou <jasper@apvc.uk>

* escape $i

Signed-off-by: Maurice Zhou <jasper@apvc.uk>

* create mountpoints before booting

Signed-off-by: Maurice Zhou <jasper@apvc.uk>

* replace postDevice,preMount command

Signed-off-by: Maurice Zhou <jasper@apvc.uk>

* disable zfs-mount

Signed-off-by: Maurice Zhou <jasper@apvc.uk>

* generate machine-id

Signed-off-by: Maurice Zhou <jasper@apvc.uk>

docs/Getting Started/index.rst

@@ -16,7 +16,7 @@ documentation <https://pthree.org/2012/04/17/install-zfs-on-debian-gnulinux/>`__
    Fedora/index
    FreeBSD
    Gentoo <https://wiki.gentoo.org/wiki/ZFS>
-   NixOS <https://nixos.wiki/wiki/NixOS_on_ZFS>
+   NixOS/index
    openSUSE/index
    RHEL-based distro/index
    Ubuntu/index