How to use containerd with conf_template option

install-containerd.sh

DASEL_VER="1.15.0"
CRI_VER="1.5.1"

#
# install dasel
#

curl -fsSL "https://github.com/TomWright/dasel/releases/download/v${DASEL_VER}/dasel_linux_amd64" -o /usr/local/bin/dasel
chmod +x /usr/local/bin/dasel

#
# install containerd, excluding default 10-containerd-net.conflist
#

curl -fsSL "https://github.com/containerd/containerd/releases/download/v${CRI_VER}/cri-containerd-cni-${CRI_VER}-linux-amd64.tar.gz" -o "/tmp/cri-containerd-cni-${CRI_VER}-linux-amd64.tar.gz"
curl -fsSL "https://github.com/containerd/containerd/releases/download/v${CRI_VER}/cri-containerd-cni-${CRI_VER}-linux-amd64.tar.gz.sha256sum" -o "/tmp/cri-containerd-cni-${CRI_VER}-linux-amd64.tar.gz.sha256sum"
(cd /tmp && sha256sum --check "/tmp/cri-containerd-cni-${CRI_VER}-linux-amd64.tar.gz.sha256sum")

tar --no-overwrite-dir -C / -xzf "/tmp/cri-containerd-cni-${CRI_VER}-linux-amd64.tar.gz" --exclude='etc/cni/net.d/10-containerd-net.conflist'

rm -f "/tmp/cri-containerd-cni-${CRI_VER}-linux-amd64.tar.gz" "/tmp/cri-containerd-cni-${CRI_VER}-linux-amd64.tar.gz.sha256sum"

#
# prepare configuration
#

mkdir -p /etc/containerd
containerd config default | tee /etc/containerd/config.toml
cat <<'EOF' | tee /etc/containerd/cni.template
{
  "name": "cbr0",
  "cniVersion": "0.3.1",
  "plugins": [
    {
      "type": "flannel",
      "delegate": {
        "hairpinMode": true,
        "isDefaultGateway": true
      },
      "ipam": {
        "type": "host-local",
        "ranges": [{{range $i, $range := .PodCIDRRanges}}{{if $i}}, {{end}}[{"subnet": "{{$range}}"}]{{end}}],
        "routes": [{{range $i, $route := .Routes}}{{if $i}}, {{end}}{"dst": "{{$route}}"}{{end}}]
      }
    },
    {
      "type": "portmap",
      "capabilities": {
        "portMappings": true
      }
    }
  ]
}
EOF

# change conf_template
dasel put string -f /etc/containerd/config.toml -p toml '.plugins.io\.containerd\.grpc\.v1\.cri.cni.conf_template' '/etc/containerd/cni.template'

# change SystemdCgroup
dasel put bool -f /etc/containerd/config.toml -p toml '.plugins.io\.containerd\.grpc\.v1\.cri.containerd.runtimes.runc.options.SystemdCgroup' 'true'

#
# enable containerd service
#

systemctl daemon-reload
systemctl reenable containerd.service
systemctl restart containerd.service