Custom node condition in Kubernetes
When you go through node object in k8s you can see that there is a field called
$ kubectl describe node kind-control-plane ... Conditions: Type Status LastHeartbeatTime LastTransitionTime Reason Message ---- ------ ----------------- ------------------ ------ ------- MemoryPressure False Sun, 30 Aug 2020 10:54:31 +0200 Sun, 30 Aug 2020 10:53:23 +0200 KubeletHasSufficientMemory kubelet has ...
ICMP Echo permissions
Network ping tool, one of the most widely used tool to debug network problem. It's mainly using ICMP protocol, due to specific security requirements to send/receive ICMP ECHO packets regular user is not allowed to use it. How can dealt with it on linux box ?
- the easiest way ...
gRPCurl - curl for gRPC
CNI - the Container Network Interface
CNI is simple interface based on environment variables and JSON config. Both environment variables and JSON config are processed by CNI plugin started by container management system like Kubernetes. CNI plugin is responsible for connecting container namespace into selected network, second responsibility for CNI is to provide IP address it ...read more
Docker and Kubernetes at network layer
I wrote some posts about how kubernetes is interacting with docker at CRI level, but what about networking ? Docker has developed it's own solution called CNM to maintain network, to interact with it just use commands under docker network. How it looks like in k8s multi node environment:
# docker ...
dropwatch - discover where network packets are dropped
Let's imagine situation where you experience network problem with dropping packets and you've no idea where the problem is located. So first of all prepare environment:
# iptables -A OUTPUT -p icmp -j DROP # ping -c 3 -W 1 184.108.40.206 PING 220.127.116.11 (8 ...
mkubectx - single command across all your selected kubernetes contexts
Pause - most popular container in k8s environment
Probably the most popular container in kubernetes environment. Container image is really small:
$ docker images | grep -i pause k8s.gcr.io/pause 3.2 80d28bedfe5d 2 months ago 683kB
Codebase is also small pause. According to source code it is responsible for doing pretty... nothing, except of dealing ...read more
How to change default k8s container runtime to containerd ?
Default kubelet container runtime configuration use docker as CRI. Containerd has another implementation of CRI, it should fullfill the same requirements as docker so ie. it's responsible to maintain container images. Containerd extends its functionality by using plugins, one of them is
cri. To interact with containerd we can ...
How kubernetes is interacting with docker ?
In a few words Container Runtime Interface is the answer to this questions. But we are going a little bit deeper. First of all what is CRI ? CRI is one of the most mature interface in kubernetes, it's a bridge between kubelet and container runtime. . Creating such interfaces in ...read more