[atomic] Expansion of host/docker storage in new Atomic with direct LVM

[Colin Walters <walters verbum org>]

I know some of you may have seen discussion around "docker-storage-setup" go by; it's a new component, and only available in the most recent cloud images.

We're going to need more docs, in particular man pages around this.  I wanted to provide a quick demo example of how it can be used.

The high level background is that Atomic uses a 3GB partition for the host (at present, I may reduce this to 2GB as we slim down, but it needs to be enough for two trees plus user data).

The rest is by default allocated on boot for Docker LVM storage.  In a cloud scenario such as OpenStack or EC2, it's normal for the cloud provider to assign a larger disk.  docker-storage-setup by default allocates *all* of the additional free space for Docker, but in some scenarios you might want to give some to the host.

Here's a demo user-data file that gives the host / 6GB, with the rest for Docker:

#cloud-config
users:
  - name: walters
    gecos: Colin Walters
    sudo: ALL=(ALL) NOPASSWD:ALL
    ssh-authorized-keys:
     - ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDhNhbnKX9mNKsOWTloW/e4XlWBzctBkIDPp8/rV7Ff+S09ykp0k6CG+sWBbh7sipkR//qavRSO+iE1bVBxS1CtV1zMz5sN9n8HUna+sAJB7V34gXCa3Fk3uPgm6OMuNn+wgIVdJH2MUXB0OLHX3onoM3w3f2e0r7zz9aBTJcXIVlkSTEfaivrSkKydzf88tRt3nOG+xGWXKWRDniSOODVI65CY+NIYXz1o2s8CS+CKrezUT6sj2nmkXKtQr7dQ97X7zDXYkhrtVpoVBEhkcc1Rhz6vjrhw9Rh6k7/t/GA3bm6GAxzLX5ZiI6OLWazm3MPTcBGgVd7JNh8A3lh1mwlH walters lenny

write_files:
  - path: /etc/sysconfig/docker-storage-setup
    permissions: 0644
    owner: root
    content: |
      ROOT_SIZE=6G