Kubernetes Part III - The etcd package

On this post, I wanted to remark about a package called etcd.

In most installation documents for Kubernetes, these documents tend to abstract out the underlying dependency packages and components.

When I installed the Flannel network, I noticed that it used a package called etcd. I had no clue what this package was. I decided to look into it.

Etcd is a package that essentially allows you to store json parameters in a database, as opposed to storing them on the file system. Flannel uses the package because you need to store the networking parameters in /etcd.

This is GOOD TO KNOW, if you happen to make a typo, or enter incomplete or incorrect network configuration parameters.


The link I found useful for this package is located here:

https://coreos.com/etcd/docs/latest/getting-started-with-etcd.html

In Yogesh Mehta's video, he is using a painful approach to entering his etcd parameters:

# etcdctl mkdir /kube-centos/network
# etcdctl mk /kube-centos/network/config "{ \"Network\": \"172.30.0.0/16\", \"SubnetLen\":24, \"Backend\": ( \"Type\": \"vxlan\" ) }"

This 2nd command did not work for me. I kept getting an error on the Backend portion of the JSON.

I found another post that made a lot more sense, where they crafted the json into an actual json file, and then sourced that file into etcdctl by using the following approach instead:
# etcdctl mk /kube-centos/network/config < networkparms.json

Another tip is that if you screw up the entry, you can simply remove the old entry by typing:
# etcdctl rm /kube-centos/network/config
At this point you can re-enter a new corrective entry.