[mount] Ignore unformatted filesystems only

Mount guesses the filesystem if it is unset or if it is set to auto,
thanks to blkid. That is the case for the bind mountpoints like /dev or
/run/udev in mount.conf. See `mount(8)` for more details.

src/modules/mount/main.py

@@ -56,7 +56,7 @@ def mount_partition(root_mount_point, partition, partitions):
         raise
 
     fstype = partition.get("fs", "").lower()
-    if not fstype or fstype == "unformatted":
+    if fstype == "unformatted":
         return
 
     if fstype == "fat16" or fstype == "fat32":

src/modules/mount/mount.conf

@@ -12,10 +12,13 @@
 # Extra filesystems to mount. The key's value is a list of entries; each
 # entry has four keys:
 #   - device    The device node to mount
-#   - fs        The filesystem type to use
+#   - fs (optional) The filesystem type to use
 #   - mountPoint Where to mount the filesystem
 #   - options (optional) Extra options to pass to mount(8)
 #
+# The device is not mounted if the mountPoint is unset or if the fs is
+# set to unformatted.
+#
 extraMounts:
     - device: proc
       fs: proc