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/Arch Linux/Root on ZFS/3-system-configuration.rst

@@ -110,7 +110,7 @@ System Configuration
     INST_UUID=$INST_UUID
     INST_ID=$INST_ID
     INST_VDEV=$INST_VDEV
-    DISK=$DISK" > /mnt/root/chroot
+    DISK=\"$DISK\"" > /mnt/root/chroot
     arch-chroot /mnt bash --login
 
 #. Source variables::

docs/Getting Started/Arch Linux/Root on ZFS/4-optional-configuration.rst

@@ -33,6 +33,9 @@ for pacman integration::
   exit
   rm /etc/sudoers.d/00_nobody
 
+If multi-disk setup is used, enable multi-disk
+support inside ``/etc/bieaz.cfg``.
+
 Supply password with SSH
 ~~~~~~~~~~~~~~~~~~~~~~~~