Cilium sysext

[reavessm]

Install Cilium via sysext

This PR adds the cilium sysext which downloads the cilium binary and creates a systemd unit install it to a cluster on boot. Additional args are provided via an env var.

How to use

Run create_cilium_sysext.sh v0.16.24 cilium. This creates the binary in cilium/usr/local/bin/cilium as well as the systemd unit file to run cilium install on boot.

Testing done

I ran this against a demo cluster running on libvirt with the kubernetes sysext.

• Changelog entries added in the respective changelog/ directory (user-facing change, bug fix, security fix, update)
• Inspected CI output for image differences: /boot and /usr size, packages, list files for any missing binaries, kernel modules, config files, kernel modules, etc.

[reavessm]

At some point I'd like to update the usage docs to include an example of a drop-in to get this to run only after kubeadm.service, but I didn't want to make that a default dependency since you technically could install k8s from a couple different ways.

[t-lo]

At some point I'd like to update the usage docs to include an example of a drop-in to get this to run only after kubeadm.service, but I didn't want to make that a default dependency since you technically could install k8s from a couple different ways.

Using the bakery kubernetes sysext in a more complex configuration might be a nice and self-contained way to document this.

[reavessm]

I mean I have a full HA k8s setup using crio, cilium and HAProxy+Keepalived using a variation of this sysext in multiple butane configs. I can make another PR adding some docs on that if you think it'd be worth it

[t-lo]

I mean I have a full HA k8s setup using crio, cilium and HAProxy+Keepalived using a variation of this sysext in multiple butane configs. I can make another PR adding some docs on that if you think it'd be worth it

Yes, I think it's absolutely worth it!