En la entrada Troubleshooting Kubernetes (II) encontré restos de la instalación de Flannel en la Raspberry Pi. Eliminé los pods que hacían referencia a Flannel y conseguí que el nodo k2 no se volviera a colgar.
Sin embargo, el problema sigue dándose en el nodo k3.
Revisando el contenido de /var/lib/kubernetes/pods/ he visto que algunos pods hacían referencia, todavía, a Flannel.
...
/var/lib/kubelet/pods/3a5e2819-21e5-11e7-bcfd-b827eb650fdb/volumes/kubernetes.io~configmap/wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_flannel-cfg.deleting~470691428.deleting~439642480.deleting~747926470.deleting~067946013.deleting~791070092.deleting~964331938.deleting~717873461.deleting~755129373.deleting~499171027
/var/lib/kubelet/pods/3a5e2819-21e5-11e7-bcfd-b827eb650fdb/volumes/kubernetes.io~configmap/wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_flannel-cfg.deleting~504683568.deleting~184413472.deleting~138413964.deleting~985160408.deleting~943143520.deleting~459558341.deleting~578589077.deleting~501462031.deleting~769373718
/var/lib/kubelet/pods/3a5e2819-21e5-11e7-bcfd-b827eb650fdb/volumes/kubernetes.io~configmap/wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_flannel-cfg.deleting~613861491.deleting~841547526.deleting~012178845.deleting~177797190.deleting~192052322.deleting~958792988.deleting~338401309.deleting~623810479.deleting~369130424
/var/lib/kubelet/pods/3a5e2819-21e5-11e7-bcfd-b827eb650fdb/volumes/kubernetes.io~configmap/wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_flannel-cfg.deleting~470691428.deleting~288881360.deleting~534630955.deleting~520377076.deleting~598159984.deleting~426698803.deleting~142931759.deleting~872800923.deleting~808586860
/var/lib/kubelet/pods/3a5e2819-21e5-11e7-bcfd-b827eb650fdb/volumes/kubernetes.io~configmap/wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_flannel-cfg.deleting~470691428.deleting~439642480.deleting~747926470.deleting~067946013.deleting~791070092.deleting~622848191.deleting~646325460.deleting~868409130.deleting~824166496
/var/lib/kubelet/pods/3a5e2819-21e5-11e7-bcfd-b827eb650fdb/volumes/kubernetes.io~configmap/wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_flannel-cfg.deleting~668636622.deleting~334825066.deleting~737147422.deleting~055159245.deleting~572255670.deleting~485248219.deleting~690855316.deleting~753094008.deleting~457647557
/var/lib/kubelet/pods/3a5e2819-21e5-11e7-bcfd-b827eb650fdb/volumes/kubernetes.io~configmap/wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_flannel-cfg.deleting~756292309.deleting~273222811.deleting~039503494.deleting~182629307.deleting~984614903.deleting~081831640.deleting~628560452.deleting~303652395.deleting~450650534
/var/lib/kubelet/pods/3a5e2819-21e5-11e7-bcfd-b827eb650fdb/volumes/kubernetes.io~configmap/wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_wrapped_flannel-cfg.deleting~883601122.deleting~535739903.deleting~385002935.deleting~558075878.deleting~174007749.deleting~757820208.deleting~194356513.deleting~813327027.deleting~485662152
...
Esta vez he detectado el problema al intentar calcular el espacio usado por esta carpeta, ya que la Raspberry Pi se ha quedado como “colgada”, aunque al lanzar htop no se observaba un uso excesivo de CPU.
Finalmente, he usado el mismo sistema que la otra vez: eliminar todas las subcarpetas de cada uno de los pods (dejando únicamente los que no se pueden borrar al estar en uso).
Después de la purga masiva de rm -rf /var/lib/kubelet/pods/ sólo han quedado dos carpetas en uso; el número corresponde con el número de pods planificados sobre el nodo k3 desde kubectl:
$ kubectl get pods --all-namespaces -o wide
NAMESPACE NAME READY STATUS RESTARTS AGE IP NODE
kube-system etcd-k1 1/1 Running 4 36d 192.168.1.11 k1
kube-system kube-apiserver-k1 1/1 Running 4 36d 192.168.1.11 k1
kube-system kube-controller-manager-k1 1/1 Running 4 36d 192.168.1.11 k1
kube-system kube-dns-279829092-1b27r 3/3 Running 12 36d 10.32.0.2 k1
kube-system kube-proxy-20t3b 1/1 Running 0 25m 192.168.1.13 k3
kube-system kube-proxy-3dggd 1/1 Running 4 36d 192.168.1.11 k1
kube-system kube-proxy-5b8k3 1/1 Running 2 12d 192.168.1.12 k2
kube-system kube-scheduler-k1 1/1 Running 4 36d 192.168.1.11 k1
kube-system weave-net-6qr0l 2/2 Running 8 36d 192.168.1.11 k1
kube-system weave-net-mxp2w 2/2 Running 0 25m 192.168.1.13 k3
kube-system weave-net-tmmdj 2/2 Running 4 12d 192.168.1.12 k2
$
Un reinicio y ¡listo!, problema -espero- resuelto de forma definitiva.