[rootless Podman - default for most users]
$ mkdir -p ~/.config/containers
$ echo "unqualified-search-registries = ['docker.io']" >> ~/.config/containers/registries.conf

[rootful Podman - running as sudo]
$ sudo sed -i "s/^#unqualified-search-registries.*/unqualified-search-registries = ['docker.io']/" /etc/containers/registries.conf
