Description

The docs on using hosts.toml indicate that fields for the registry host namespace can be specified in the root level:
https://github.com/containerd/containerd/blob/release/1.7/docs/hosts.md

For each registry host namespace directory in your registry config_path you may include a hosts.toml configuration file. The following root level toml fields apply to the registry host namespace:

However, containerd fails to parse the config file if only root fields are passed, for example:

root@systemd-node-1:/# cat /var/lib/rancher/k3s/agent/etc/containerd/certs.d/172-17-0-7.sslip.io/hosts.toml
ca = ["/usr/local/share/ca-certificates/registry.crt"]

When pulling from 172-17-0-7.sslip.io, containerd will log the following error:

time="2024-04-01T22:11:02.070675417Z" level=error msg="failed to decode hosts.toml" error="invalid `host` tree"

However, the following file with a stub host tree will work as intended:

root@systemd-node-1:/# cat /var/lib/rancher/k3s/agent/etc/containerd/certs.d/172-17-0-7.sslip.io/hosts.toml
ca = ["/usr/local/share/ca-certificates/registry.crt"]
[host]

Steps to reproduce the issue

1. provide a hosts.toml as described above
2. start containerd

Describe the results you received and expected

hosts.toml should be usable with no hosts tree, just root-level fields, as described in the docs.

What version of containerd are you using?

v1.7.11-k3s2

Any other relevant information

No response

Show configuration if it is related to CRI plugin.

No response