Add tool to generate iso images for kvm based tests

tests/kvm_tests/linux_iso_image_generator/.gitignore

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+/cache/
+/output/
+/__pycache__/

tests/kvm_tests/linux_iso_image_generator/README.md

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+# Rocky Linux 8.10 Unattended ISO Builder
+
+This workspace creates a repeatable Rocky Linux 8.10 installer ISO using:
+
+- a JSON config file (`build-config.json`)
+- a Kickstart template (`templates/rocky8.ks.tmpl`)
+- a non-interactive build script (`build_rockylinux_8_10_iso.py`)
+
+## What this produces
+
+An output ISO that boots the Rocky installer and uses embedded Kickstart values for unattended installation.
+
+Configured defaults include:
+
+- user `therock`
+- `therock` account created locked (no password login)
+- user in `wheel`
+- passwordless sudo for `therock`
+- `sshd` enabled
+- ping (ICMP echo) allowed
+- generated passwordless SSH keypair for `therock`
+- key-only SSH login policy for `therock` (password auth disabled)
+
+## Prerequisites (on the build host)
+
+Install required tools:
+
+```bash
+sudo apt-get update
+sudo apt-get install -y genisoimage xorriso isolinux syslinux-utils openssh-client python3
+```
+
+The build script prefers `mkisofs` (from `genisoimage`) and falls back to `xorrisofs`/`xorriso`.
+On Rocky/RHEL build hosts, install equivalent packages that provide either `mkisofs` or `xorrisofs`.
+
+## Configure
+
+Edit `build-config.json`:
+
+- all keys are required; the build script does not apply defaults
+- optionally set `source_iso_sha256` for checksum verification
+- customize hostname/timezone/lang/paths as needed
+- SSH behavior:
+  - leave `ssh_authorized_public_key` empty to auto-generate keypair
+  - generated keys default to `./output/ssh/therock_ed25519` and `.pub`
+  - set `ssh_authorized_public_key` if you want to inject an existing public key
+  - keep `disable_user_password_auth: true` to enforce key-only login for `therock`
+
+## Build
+
+From this directory:
+
+```bash
+python3 ./build_rockylinux_8_10_iso.py ./build-config.json
+```
+
+By default, the builder now does both steps:
+
+1) builds the unattended ISO, and
+2) launches a QEMU/KVM VM from that ISO (same behavior as `testing/qemu_iso_launch.sh`).
+
+In default mode, the script waits until guest customization is reachable/validated over SSH
+(`id`, `sudo -n true`, `systemctl is-active sshd`), then it powers off the guest automatically.
+This prevents leaving QEMU running unintentionally and leaves a finalized installed qcow2 image.
+
+If you want only the ISO build (no VM run), use:
+
+```bash
+python3 ./build_rockylinux_8_10_iso.py --bare-image ./build-config.json
+```
+
+If you want QEMU to keep running (disable auto-shutdown mode), use:
+
+```bash
+python3 ./build_rockylinux_8_10_iso.py --run ./build-config.json
+```
+
+Output ISO path (default):
+
+`./output/Rocky-8.10-x86_64-autoinstall.iso`
+
+Installed qcow2 image path (default):
+
+`./output/Rocky-8.10-x86_64-autoinstall.qcow2`
+
+Optional config override in `build-config.json`:
+
+```json
+"output_installed_image_path": "./output/my-rocky-final.qcow2"
+```
+
+Generated SSH keys (default):
+
+- private key: `./output/ssh/therock_ed25519`
+- public key: `./output/ssh/therock_ed25519.pub`
+
+Example login after install:
+
+```bash
+ssh -i ./output/ssh/therock_ed25519 therock@<installed-host-ip>
+```
+
+## Launch with QEMU/KVM (No GPU passthrough)
+
+Use the helper script:
+
+```bash
+./testing/qemu_iso_launch.sh
+```
+
+This launch path uses virtual display devices only and does not use GPU PCI passthrough (`vfio-pci`).
+It forwards host `127.0.0.1:2222` to guest `:22` by default.
+The helper script defaults to a `60G` disk to satisfy current partitioning requirements.
+If you override disk size manually, keep it at least about `40G` (recommended `60G`).
+
+The same QEMU launch behavior is now integrated into `build_rockylinux_8_10_iso.py`.
+Use `--run` to keep the VM running, or `--bare-image` to skip VM launch.
+
+After installer completes and the VM boots into the installed OS, connect with:
+
+```bash
+ssh -i ./output/ssh/therock_ed25519 \
+  -o StrictHostKeyChecking=no \
+  -o UserKnownHostsFile=/dev/null \
+  -p 2222 therock@127.0.0.1
+```
+
+If SSH is not ready yet, poll until it becomes available:
+
+```bash
+for i in $(seq 1 120); do
+  ssh -i ./output/ssh/therock_ed25519 \
+    -o BatchMode=yes \
+    -o StrictHostKeyChecking=no \
+    -o UserKnownHostsFile=/dev/null \
+    -o ConnectTimeout=5 \
+    -p 2222 therock@127.0.0.1 "echo SSH_OK && id" && break
+  sleep 10
+done
+```
+
+## Launch with QEMU/KVM (PCI passthrough)
+
+1) Set PCI IDs in `build-config.json`:
+
+```json
+"pci_passthrough_device_ids": ["0000:01:00.0", "0000:01:00.1"]
+```
+
+2) Make sure those devices are bound to `vfio-pci` on the host.
+
+3) Launch with passthrough script:
+
+```bash
+./testing/qemu_iso_launch_pci_passthrough.sh
+```
+
+This script reads PCI IDs from `build-config.json` and fails early if IDs are missing,
+not present on host, or not bound to `vfio-pci`.
+It also defaults to a `60G` disk to satisfy current partitioning requirements.
+
+## Notes
+
+- The Kickstart template uses `clearpart --all --initlabel` with explicit partition rules, which wipes target disks during install.
+- `/boot` is explicitly set to `1536 MiB` (1.5 GiB).
+- `/` has minimum size `30720 MiB` (30 GiB) and then grows to fill remaining space.
+- `/home` is not created as a separate filesystem; user homes live under `/`.
+- SSH key authorization for `therock` is configured by Kickstart `sshkey` during install.
+- Boot configs are patched to default to direct install (skip media-check default) and include serial console args for headless VM troubleshooting.