The official RHEL LVM images in Azure have a quite peculiar partitioning: The disk contains one volume group with multiple logical volumes. The quirk is that the sum of the sizes of the logical volumes is actually smaller than the size of the volume group. In other words, the volume group contains empty space.

As we want to build these images via the service, we have to add such a possibility to the API.

Goal:

• Implement a new total size customization in the service API (Weldr already has it).
  • The resulting image is always at least total size big.
  • If the partitions cannot fit, the total size is ignored.
    • This is true for both the default partitions and custom ones.
  • If the sum of partition sizes is smaller than the total size:
    • for LVM, the physical partition underneath the volume group is grown. The size of logical volumes is unchanged, thus the volume group has some empty space.
    • for raw, the root partition is grown to fill in the missing space

Acceptance Criteria:

• All goals are met.
• The feature is demoed.

Open questions:

• Growing the root partition in the case of raw images is slightly weird, but that's how weldr currently behaves, so I didn't want to change the semantics.