[Installing Canal](https://projectcalico.docs.tigera.io/getting-started/kubernetes/flannel/flannel) requires updating a `CALICO_IPV4POOL_CIDR` environment variable in the installation manifest for use with K3s, which has a default Pod CIDR of "10.44.0.0/24"-- this will modify the manifest to reflect the current Pod CIDR.

canal-k3s-auto.sh

## Applies the modified manifest to K3s, which automatically applies the contents of /var/lib/rancher/k3s/server/manifests
curl -s https://docs.projectcalico.org/manifests/canal.yaml | sed -e 's|            # - name: CALICO_IPV4POOL_CIDR|            - name: CALICO_IPV4POOL_CIDR|g' -e "s|            #   value: \"192.168.0.0/16\"|              value: \"$(kubectl get nodes -o jsonpath='{.items[*].spec.podCIDR}')\"|g" | \
tee -a /var/lib/rancher/k3s/server/manifests/canal.yaml

install-canal.sh

curl -s https://docs.projectcalico.org/manifests/canal.yaml | \
sed \
-e 's|            # - name: CALICO_IPV4POOL_CIDR|            - name: CALICO_IPV4POOL_CIDR|g' \
-e "s|            #   value: \"192.168.0.0/16\"|              value: \"$(kubectl get nodes -o jsonpath='{.items[*].spec.podCIDR}')\"|g"