app-containers/containerd: use default config

[tormath1]

This enable the configuration override from '/etc' drop-ins.

Testing done

variant: flatcar
version: 1.0.0
storage:
  files:
    - path: /etc/containerd/conf.d/oom.toml
      contents:
        inline: |
          oom_score = -12

Gives:

core@localhost ~ $ cat /proc/$(pidof containerd)/oom_score_adj
-12

[Describe the testing you have done before submitting this PR. Please include both the commands you issued as well as the output you got.]

• Changelog entries added in the respective changelog/ directory (user-facing change, bug fix, security fix, update)
• Inspected CI output for image differences: /boot and /usr size, packages, list files for any missing binaries, kernel modules, config files, kernel modules, etc.
• CI: https://jenkins.flatcar.org/job/container/job/packages_all_arches/816/cldsv/

[Copilot]

🟡 Changes recommended

The Flatcar drop-in is stripped from sysext images, and the configuration hard-codes amd64 on arm64 builds.

2 open findings

• Install containerd vendor drop-in under /usr · New
• Remove hard-coded amd64 platform default · New

What changed in this PR

Enables containerd configuration through /etc drop-ins while adopting the v3 default configuration.

Changes:

• Adds the generated containerd v3 configuration.
• Moves Flatcar-specific settings into a drop-in.

File	Description
config.toml	Adds defaults and drop-in imports.
containerd	Installs Flatcar-specific overrides.

🧠 Review effort: Balanced

---

Give feedback about Copilot approvals in this survey to enter a drawing for a $150 gift card.

[Copilot]

🟡 Changes recommended

The Flatcar overrides are discarded during migration, and the generated configuration hard-codes the amd64 platform.

3 open findings

• v2 CRI overrides are discarded during v3 migration · New
• Remove hard-coded amd64 platform default
• Install containerd vendor drop-in under /usr

🧠 Review effort: Balanced

---

Give feedback about Copilot approvals in this survey to enter a drawing for a $150 gift card.

[Copilot]

🔵 Needs a closer look

The configuration incorrectly pins arm64 builds to amd64 and lacks the required user-facing changelog entry.

2 open findings

• Remove hard-coded amd64 platform default
• Install containerd vendor drop-in under /usr

1 resolved since last review

• v2 CRI overrides are discarded during v3 migration

Previously missed (1)

In code that hasn't changed since last review

Add changelog entry for new containerd configuration interface

sdk_container/​src/​third_party/​coreos-overlay/​coreos/​sysext/​containerd/​usr/​share/​containerd/​config.toml:5

This enables a user-facing containerd configuration interface, but the PR has no changelog entry. Add one under changelog/changes; the comparable default-configuration change is documented in sdk_container/src/third_party/coreos-overlay/changelog/changes/2022-03-08-containerd-selinux.md:1.

🧠 Review effort: Balanced

---

Give feedback about Copilot approvals in this survey to enter a drawing for a $150 gift card.

[Copilot]

🟡 Changes recommended

The generated configuration pins upstream defaults, and the user-facing change lacks a changelog entry.

3 open findings

• Install containerd vendor drop-in under /usr
• Avoid pinning containerd defaults in the main configuration · New
• Document the new containerd drop-in override mechanism · New

1 resolved since last review

• Remove hard-coded amd64 platform default

🧠 Review effort: Balanced

---

Give feedback about Copilot approvals in this survey to enter a drawing for a $150 gift card.

[tormath1]

Closing in favor of: #4150