Samir Mewada – Best DevOps

What is POD? define in 15 bullets points

Samir Mewada — Wed, 18 Aug 2021 11:32:31 +0000

Pods are the smallest, most basic deployable object
State of the pod is pending, running, succeeded / failed
Pods are instantiated
Pods contains one or more containers
pods are part of nodes
each pod has unique IP address
pod is created in node
typically, same service / app containers are not deployed in same pod (port has to be unique)
Pods are like minions.
Pods is virtual or logical concept… pods cannot be accessed directly.
network parameters within a pod are shared across all containers
pods can communicate across nodes directly

What is the architecture and components of Kubernetes?

Samir Mewada — Wed, 18 Aug 2021 11:14:43 +0000

master / Control plane

Master
	– Api server -> POD -> Container -> Docker image –> Google Registry
	– Etcd -> POD -> Container -> Docker image –> Google Registry
	– Controller mgmr -> POD -> Container -> Docker image –> Google Registry
	– Schedular -> POD -> Container -> Docker image –> Google Registry
	– kubelet
	– docker
	– kube proxy -> POD -> Container -> Docker image –> Google Registry
	– kubectl
	– kubeadm

Worker
	– kubelet
	– docker
	– kube proxy -> POD -> Container -> Docker image –> Google Registry
	– kubectl
	– kubeadm

Workstation
	– kubectl

Define a docker image in 10 bullets points.

Samir Mewada — Tue, 17 Aug 2021 07:27:43 +0000

Docker image contains collection of file systems (root,user,application)
Docker image can contain one or many layers. rootfs layer is always present.
In case of file system conflict, the top layer takes precedence.
The layered file systems are identified using UUID which are created using SHA256 algorithm.
tagging is used to identify specific UUID with user friendly name
docker inspect command can show the UUID of various layers used in the image.
docker inspect command can be used to view docker image metadata
docker info command will show Docker Root Dir, where all the docker images are stored.
Docker merged directory is created when docker container process is started and it is removed when the container is stopped.
file changes made in docker container are persisted in “diff” directory which is used to re-create the merged directory when docker container is started next time.
docker rmi command can be used to remove docker image

Assignment Day2

Samir Mewada — Tue, 17 Aug 2021 05:18:47 +0000

update

docker update command allows to update the allocation of computing units and scheduling algorithm based on the actual hardware resources available.

docker update –cpus 0.5 –memory-swap 1073741824 –memory 1073741824 52659b1482a1 624ce71391eb

wait

docker wait command waits for one or more container to exit and provides the return status of the docker exit

[root@ip-172-31-15-56 centos]# docker wait 4638992d8355
0
[root@ip-172-31-15-56 centos]#

[root@ip-172-31-15-56 centos]# docker wait 1852fb6244e3
137
[root@ip-172-31-15-56 centos]#

Assignment questions (Docker training)

Samir Mewada — Mon, 16 Aug 2021 09:59:51 +0000

What is the diff between docker pause and docker unpause?

docker pause and unpause allows to temporarily stop and resume the docker container process.

What is the diff between docker stop and docker kill?

docker stop may allow system to gracefully exist before stopping the docker (by signalling) whereas docker kill could forcefully terminate the docker container process. kill can be used in the event of system hang or similar situation.