The base_runtime_spec for containerd requires a complete OCI spec,
not just the rlimits section. The minimal spec was causing runc to
fail with "open /proc/self/fd: no such file or directory" because
essential mounts and namespaces were missing.
This commit uses kind's default cri-base.json as the base and adds
the rlimits configuration on top. The spec includes all necessary
mounts, namespaces, capabilities, and kind-specific hooks.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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