sqsh_layers_with_ram_upper_why_it_is_awesome.txt

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So, why is using a non-retentive layered rootfs so awesome?  Good question.
The more I use it, the more I like it.  You might find you like it, too.
Especially if you're constantly compiling things and messing up your nice clean
installation.

 1. It's a magic undo button.  First and foremost, it gives you the ability
    to just go ahead and install whatever you want w/out any fear of
    breaking your system.  So, you just installed a new version of some
    package and it completely broke the universe?  No biggee, just reboot
    and you'll have the system back up and running in no time.  Oh, the new
    version works greate and you want it to be a permanent change?  Just
    make a new sqsh_layer out of /mnt/root-true/upper/upper and add it to
    your bootloader config.

 2. Quickly see what you've changed since the last time you baselined your
    rootfs.  This makes keeping track of changes very easy.

 3. Installing rapidly.  You can build up multiple machines using the same
    sqsh_layers very rapidly and just tweak a few things (e.g., hostname)
    via upper layer.

 4. Super easy upgrades.  Just stick new sqsh_layers on your boot device,
    maybe clean things out of your upper layer, and reboot.

 5. Just go ahead and kill power w/out doing a safe reboot.  I dare you.  As
    long as your sqsh_layerdev is mounted read-only (the default) (or not
    even mounted if you loaded the layers into RAM), you don't ever have to
    wory about power outage (and an itchy power button finger) corrupting
    your root filesystem.  Yup, "safe shutdown" just got reduced to "remove
    power".

 6. Shared rootfs images accross multiple virtual machines.  This advanced
    technique involves using the same device containing a colloction of
    sqsh_layers as the sqsh_layerdev for multiple virtual machines
    (read-only!) that each have their own independent root devices (i.e.,
    for upper layer).  This makes it incredibly easy to quickly go from
    having no virtual machines to having a whole fleet of them.  And you can
    upgrade the sqsh_layers once and upgrade all of the virtual machines at
    once.