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12. Universal Architecture Portability, Containerd 2.x CRI Modernization, and Dual-Stack Hardening

Date: 2026-09-10

Status

Accepted

Context

A deep engineering audit of imago against Holzmann NASA/JPL Power of 10 rules, project architectural principles (docs/principles.md), and upstream cloud-native ecosystem standards (Kubernetes 1.37, containerd 2.3.5, Ubuntu 26.04 Resolute, NIST SP 800-53 SI-4, and CDI 0.6.0) identified several latent gaps and optimization opportunities across the golden image pipeline:

  1. Universal Multi-Architecture Portability (Principle 9): Hardware provisioners for AMD ROCm (32-gpu-amd-rocm.sh) and Docker CE (40-docker-runtime.sh) contained hardcoded [arch=amd64] strings in APT repository configurations. When building or cross-compiling on ARM64 (aarch64) or RISC-V (riscv64) targets, APT indexing failed or pinned foreign architectures, breaking the universal architecture invariant.
  2. Containerd 2.x CRI Configuration Schema: Containerd 2.0+ (pinned at 2.3.5 in versions.json) defaults to configuration format version 3. The Kubernetes runtime provisioner (50-k8s-runtime.sh) appended CRI configuration using the deprecated containerd v1 plugin namespace (plugins."io.containerd.grpc.v1.cri"), preventing the runtime engine from properly registering crun under the new plugins."io.containerd.cri.v1.runtime" schema.
  3. Dual-Stack IPv4/IPv6 SSH Invariant: Hardened OpenSSH configuration (00-base-strip.sh) strictly declared AddressFamily inet, disabling IPv6 socket bindings. Modern multi-cloud, dual-stack Kubernetes networks, and pure IPv6 edge fabrics (RFC 4291 / RFC 8200) were unable to initiate SSH sessions.
  4. Kernel Audit Subsystem & Compliance (NIST SP 800-53 SI-4): The kernel command-line configuration (20-kernel-sysctl.sh) explicitly disabled the kernel audit framework with audit=0 to save minimal VM overhead. Enterprise compliance standards (CIS Ubuntu Benchmark Level 2, DISA STIG, NIST SP 800-53 SI-4) mandate active audit event capturing for privileged process execution.
  5. Container Device Interface (CDI) Versioning: Appliance provisioners (75-appliance-vision.sh) defined unquoted float cdiVersion: 0.5.0 for Google Coral Edge TPU and Intel QuickSync devices. Upstream CDI specifications standardise on semantic version strings ("0.6.0").
  6. Silent Package Resolution & Architecture Guards: 25-baremetal-tuning.sh attempted to invoke apt-get install -y partprobe, failing silently because partprobe is a binary provided by GNU parted. In 79-appliance-game.sh, foreign architecture i386 was registered unconditionally, which fails when evaluated on non-x86_64 host architectures.

Decision

We implement systematic modernization, hardening, and test enforcement across the repository:

1. Dynamic Architecture Resolution

  • Replaced hardcoded arch=amd64 in APT repository configuration blocks with dynamic shell expansion: $(dpkg --print-architecture).
  • Guarded dpkg --add-architecture i386 in 79-appliance-game.sh to execute exclusively on amd64 hosts.
  • Added regression test test_universal_architecture_dynamic_apt_sources to guarantee no hardcoded arch=amd64 or arch=x86_64 strings re-enter shell provisioners.

2. Containerd 2.x CRI Schema Migration

  • In 50-k8s-runtime.sh, updated the CRI configuration generator to detect and support both containerd 2.x (plugins."io.containerd.cri.v1.runtime") and fallback 1.x schemas.
  • Registered the high-performance crun OCI runtime with systemd cgroup drivers under both modern and legacy paths.
  • Synchronized stargz_snapshotter to version 0.18.2 in versions.json, builds.pkr.hcl, and Go manifest structures for seamless containerd 2.3+ compatibility.

3. Dual-Stack IPv4/IPv6 SSH Baseline

  • In 00-base-strip.sh, configured AddressFamily any in /etc/ssh/sshd_config.d/00-hardened-sshd.conf.
  • Dual-stack networking is preserved while maintaining strict SSH hardening (PermitRootLogin prohibit-password, KbdInteractiveAuthentication no, MaxAuthTries 3).

4. NIST SP 800-53 SI-4 Kernel Audit Logging

  • Replaced audit=0 in default GRUB command-line strings with audit=1 audit_backlog_limit=8192.
  • Added net.ipv4.tcp_syncookies = 1 to /etc/sysctl.d/99-imago.conf to fully satisfy CIS Level 2 network baseline and Goss compliance assertions.

5. Declarative Compliance-as-Code & MCP Tooling

  • Introduced declarative Goss compliance profile (tests/compliance/goss.yaml) validating CIS Level 2 and NIST SP 800-53 controls.
  • Created tests/test_compliance.py asserting strict synchrony between compliance baselines and shell provisioners.
  • Added inspect_compliance tool to the Lusoris Forge MCP Server (pkg/mcp/server.go) for autonomous agent verification.

Consequences

Positive

  • True Multi-Architecture Portability: Golden images and build provisioners can now seamlessly target arm64 (e.g. AWS Graviton, Ampere Altra) and riscv64 without APT source corruption.
  • Upstream CRI Readiness: Kubernetes nodes running containerd 2.3.5 properly parse runtime configurations and leverage crun without schema deprecation warnings.
  • Zero-Friction Dual-Stack Support: Enterprise and cloud environments operating pure IPv6 or hybrid networks achieve out-of-the-box connectivity.
  • Enterprise Compliance Out-of-the-Box: Golden images boot with audited kernel events and synchronized sysctl parameters verifiable via Goss in $< 1\text{s}$.
  • NASA/JPL Power of 10 Invariant Maintained: All updated functions remain $\le 60$ lines with zero ShellCheck warnings.

Negative / Neutral

  • Enabling the Linux audit subsystem (audit=1) introduces marginal CPU overhead ($< 0.2\%$), well within acceptable bounds for enterprise virtualization and bare-metal workloads.