Kernel errors like:
kubernetes cgroup: fork rejected by pids controller in /kubepods/burstable/...
accompainied by errors creating threads or starting processes on base OS can be caused by the kubepods cgroup pids.max
being to low
cat /sys/fs/cgroup/pids/kubepods/pids.max
If this is low, it can be reset by setting kernel.pid_max to a large number (kernel.pid_max=4194304) then restart kubelet. After a bit, kubepods/pids.max should be bumped up to the same number (can take a few minutes)