Category: Tech Notes

Posted on

Checking iptables filtering for bridge networking on Ubuntu (for Kubernetes setup)

If you’re installing and configuring a Kubernetes cluster on bare metal or in a VM yourself, one of the install steps using kubeadm says to check iptables filtering for bridge networking, but it doesn’t exactly say how to do this per distro.

The setting required is:

net.bridge.bridge-nf-call-iptables=1

There are specific steps in the kubadm docs above for RHEL/CentOS to add this setting. For Ubuntu it seems this is set by default, but you can confirm by:

sysctl net.bridge.bridge-nf-call-iptables

and the expected setting is 1:

net.bridge.bridge-nf-call-iptables = 1

It seems on Ubuntu 16.04 server this is set to 1 by default, but if it’s 0, you can edit this property in /etc/sysctl.conf

Posted on

kubernetes: switching kubectl contexts

Info about your currently configured clusters and contexts referring to each of these contexts is stored in ~/.kube/config . You can browse this into with: 

kubectl config view

For contexts, scroll down to the contexts section.

For your currently configured context:

 kubectl config current-context

To switch to another context:

kubectl config use-context contextname

Related info on kubectl: https://kubernetes.io/docs/tasks/access-application-cluster/configure-access-multiple-clusters/

Posted on

Exposing a public service on Google Kubernetes Engine

To expose a service running on Google Kubernetes Engine to inbound traffic, create a LoadBalancer for the service like this:

kubectl expose deployment exampleservice --type=LoadBalancer --name=exampleservice

Once created, describe the service, and the LoadBalancer Ingress IP is your public IP for the service.

Google’s LoadBalancer service is charged per hour of usage and per GB of traffic. Check the docs for cost.

Proudly powered by WordPress