Change VM disk format from raw to qcow2 with 100GB virtual size

[Arden97]

Description

Changed VM disk creation from 20GB raw format to 100GB qcow2 format with metadata preallocation

Rationale:

• GUI installations require more disk space
• virt-install cannot pass preallocation options to qemu-img
• preallocation=metadata provides near-raw performance with minimal overhead
• /var/log/audit size reduction hack in translate_ssg_kickstart() is no longer needed with 100GB virtual space
• Fix Always create VMs with qcow2 disks #559

Review hints

• /hardening/oscap/stig check was successfully run on the remote TF machine, disk pre-creation with appropriate 100 GB size was verified

[comps]

I left a few small comments.

Also, @matusmarhefka recently made #586 which introduces 30GB images and some hacks to make large partitions work. Should they also be increased to 100 GB, for consistency? Can any of the hacks be now removed, or are we waiting for OpenSCAP blueprint adjustments (#587)?

[matusmarhefka]

I left a few small comments.

Also, @matusmarhefka recently made #586 which introduces 30GB images and some hacks to make large partitions work. Should they also be increased to 100 GB, for consistency? Can any of the hacks be now removed, or are we waiting for OpenSCAP blueprint adjustments (#587)?

Actually yes, the disk image file generated by composer-cli is sparse so we can update

contest/lib/osbuild.py

Lines 41 to 44 in 183e64c

	# composer-cli compose start --size: disk image size in MiB.
	# 30 GiB should be enough for all profiles, e.g. STIG which uses 10 GiB
	# /var/log/audit partition because of DISA requirements.
	QCOW2_IMAGE_SIZE_MIB = 30 * 1024

to allocate even 100 GB:

QCOW2_IMAGE_SIZE_MIB = 100 * 1024

But the partitioning_mode = "raw" still needs to be set (until OpenSCAP/openscap#2334 is resolved), otherwise the / partition won't be able to grow when IB composes an image and we might encounter No space left on device issues with some profiles like STIG.

[Arden97]

PR was verified by custom productization pipeline

[matusmarhefka]

LGTM