Fedora & RHEL: fix slow loading mpt3sas.

Credit: @mdiepart from #282

Closes #282 #262

Fix variable export before chroot

Credit: @mdiepart from #282

remind user to enable multi-disk support

NixOS: handle installation failure wrt encrypted boot pool

Closes #279
Signed-off-by: Maurice Zhou <jasper@apvc.uk>

docs/Getting Started/RHEL-based distro/RHEL 8-based distro Root on ZFS/2-system-installation.rst

@@ -266,3 +266,6 @@ System Installation
 
     dnf --installroot=/mnt copr enable -y m0p/bieaz
     dnf --installroot=/mnt install -y bieaz python3-dnf-plugin-rozb3
+
+   If multi-disk setup is used, enable multi-disk
+   support inside ``/mnt/etc/bieaz.cfg``.

docs/Getting Started/RHEL-based distro/RHEL 8-based distro Root on ZFS/3-system-configuration.rst

@@ -31,6 +31,12 @@ System Configuration
 
     echo 'add_dracutmodules+=" zfs "' > /mnt/etc/dracut.conf.d/zfs.conf
 
+#. Force load mpt3sas module if used::
+
+     if grep -q mpt3sas /proc/modules; then
+       echo 'forced_drivers+=" mpt3sas "'  > /mnt/etc/dracut.conf.d/zfs.conf
+     fi
+
 #. Interactively set locale, keymap, timezone, hostname and root password::
 
     rm -f /mnt/etc/localtime
@@ -80,7 +86,7 @@ System Configuration
     TERM=xterm
     INST_VDEV=$INST_VDEV
     INST_VDEV=$INST_VDEV
-    DISK=$DISK" > /mnt/root/chroot
+    DISK=\"$DISK\"" > /mnt/root/chroot
     arch-chroot /mnt bash --login
 
 #. Source variables::