Update daemonset manifest to mount /etc/machine-id

[avestuk]

Mounted as ReadOnly in order to minimize attack surface as in #3880

This fixes an issue I had running weave in a Kind cluster where getOldStyleSystemUUID() did not return any uuid as those files were not present inside the weave container. Because /host/etc/machine-id did not exist an attempt to read /host/var/lib/dbus/machine-id would be made but the host machine did not have a /var/lib/dbus/machine-id file. This would result in both uuid and machineid being "" and causing the container to exit.

func getSystemUUID(hostRoot string) ([]byte, error) {
	uuid, err := getOldStyleSystemUUID()
	if err != nil && !os.IsNotExist(err) {
		return nil, err
	}
	machineid, err := ioutil.ReadFile(hostRoot + "/etc/machine-id")
	if os.IsNotExist(err) {
		machineid, err = ioutil.ReadFile(hostRoot + "/var/lib/dbus/machine-id")
	}
	if err != nil && !os.IsNotExist(err) {
		return nil, err
	}
	if len(uuid) == 0 && len(machineid) == 0 {
		return nil, errors.New("All system IDs are blank")
	}
	return append(machineid, uuid...), nil
}

My change attempts to maintain the spirit of #3880 by using a new hostPath volume to only mount /etc/machine-id from the host into the weave container.

[avestuk]

Appears to have some overlap with #3877

[bboreham]

Excellent, many thanks.

[bboreham]

Released in v2.8.1