os31 distribution directory files

[Mikus Grinbergs]

http://dev.laptop.org/~cjb/f11-1.5/os31/ contains five large files. 
    I have trouble figuring out the WHY of providing all these files:

  *  os31.zd is input to 'fs-update' when using the XO OFW to install
     the build to an SD card that will reside in the XO-1.5.
     Clear enough.

  *  os31.img.gz is input to 'zcat' when using a Linux system to
     install the build to an SD card that will reside in the XO-1.5.
     Clear enough.

  *  os31.iso is input to 'livecd-iso-to-disk' when using a Fedora
     system to install the build to a removable device.
     The intent is clear, though I haven't tried with this file.

  *  os31.bootable.gz is input to 'zcat' when using a Linux system to
     install the ("live") build to a removable device.
     I think the intent is to save running the 'livecd-iso-to-disk'.

  *  os31.tree.tar.lzma is input to 'tar' when using a Linux system
     to install the ("permanent"?)build to a removable device.
     I hoped this method would let me keep the build on an USB stick.

     But I did not understand why the content of this tarfile omitted
     a 'vmlinuz' (in fact, the whole of '/boot' was omitted).  Is
     that a bug -- or can the XO-1.5 boot without needing 'vmlinuz' ?


mikus