# mapdir <optional relative path under mount>
#   <relative path under source to mount>
#   ...
mapdir
  mod1
  mod2
  mod3
  mod4

# mapdircreate <optional relative path under mount>
#   <relative path under source to mount>
#   ...
mapdircreate
  overwrite

# mapfile <optional relative path under mount>
#   <relative path under source to mount>
#   ...
mapfile root1.txt
  root1.txt
mapfile root1w.txt
  root1w.txt
mapfile root2.txt
  root2.txt
mapfile root2w.txt
  root2w.txt