Add vmedia boot support in ramdisk element

[Ramakrishnan G (rameshg87)]

Currently the ramdisk element assumes that the parameters for the deploy are passed through kernel command-line.

But when the kernel/ramdisk is booted over virtual cdrom media (using isolinux instead of pxelinux), the parameters to deploy are passed inside a text file (like parameters.txt) inside the virtual floppy media by the IloDriver. By doing so, saves the creation/modification of the ISO everytime required.

When the parameters is passed through virtual floppy media, there will be a new kernel command line argument added (boot_method=vmedia), from which the ramdisk element can decide to mount the virtual floppy media and read the parameters.

[Ramakrishnan G (rameshg87) (rameshg87)]

UseCase:

Currently the main user of this change will be the proposed IloDriver in Ironic Project
(See design spec: https://review.openstack.org/97744)

The admin will package the deploy kernel and ramdisk into a bootable iso image. A new kernel argument boot_method=vmedia will be added in the ISO as kernel command-line argument. During deploy, IloDriver will attach this bootable iso image as virtual media on the HP Proliant machine. The arguments to be passed to the ramdisk are passed through virtual media floppy. This is where this change comes in. If the baremetal node booted via virtual media, then the arguments are read from the virtual media floppy.

[Ramakrishnan G (rameshg87) (rameshg87)]

Testing Details:

1. Simulated the flow of IloDeploy.
     A. Created kernel/ramdisk with ramdisk-image-create from diskimage-builder with deploy-ironic element.
     B. Bundled the kernel/ramdisk into a bootable iso using isolinux. Added a kernel parameter boot_method=vmedia in isolinux.cfg
     C. Create a small vfat image of 100KB and added a file parameters.txt in it. Added the parameters DISK,
          DEPLOYMENT_ID, DEPLOYMENT_KEY, ISCSI_TARGET_IQN and some values on it.
     D. Attached the iso image as virtual media cdrom on a HP Proliant Gen 8 server and attached the vfat image as virtual media
          floppy (files accessible over http)
     E. Booted the proliant box and made the sure the booted ramdisk recognises the arguments DISK,
          DEPLOYMENT_ID, DEPLOYMENT_KEY, ISCSI_TARGET_IQN.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/97143
Committed: https://git.openstack.org/cgit/openstack/diskimage-builder/commit/?id=5e18777691c6224ef66d2d4843c3735eb33b407c
Submitter: Jenkins
Branch: master

commit 5e18777691c6224ef66d2d4843c3735eb33b407c
Author: Ramakrishnan G <email address hidden>
Date: Tue Jul 15 21:36:11 2014 +0530

    Add virtual media boot support in ramdisk element.

    This change adds support in ramdisk element for recognising
    boot from virtual media cdrom and read the parameters from
    the configuration file in virtual media floppy.
    Change-Id: I28ca888b4ead4905f7141b38ed4b9a3614d00d26
    Closes-Bug: #1321564