Docker

Question 1

How to login?

Answer 1

docker login harbor.fleetcomplete.dev -u username -p password

Question 2

How to fetch an image?

Answer 2

docker pull registry.aquasec.com/console:6.2.21171

Question 3

How to tag?

Answer 3

docker tag 12345 my.registry/my.image:1

Question 4

Check logs?

Answer 4

docker logs 12345 –follow

Question 5

Delete image?

Answer 5

docker rmi gitlab/gitlab-ce:13.12.5-ce.0

Question 6

Delete container?

Answer 6

docker stop gitlab # first stop the container though
docker rm gitlab # removes the container already running.
.

Question 7

Running containers shared the kernel with the underlying host OS?

Answer 7

True

Question 8

Kubernetes vs Docker

Answer 8

K8S is the orchestrator of containerized apps. By default uses Docker as container runtime.

Question 9

ContainerD

Answer 9

A specialized part of docker that takes care of low level tasks like stopping and starting contianers.

Question 10

Docker as a technology

Answer 10

= RUNTIME + DAEMON/Engine + Orchestrator/Swarm

Orchestrator.

Daemon(dockerd) = RemoteAPI + Networking + Volumes + Image mgt .. etc

Runtime = containerd(higher level maintains the complete lifecycle of an image) + runc(lower level interfaces with underlying OS)
Responsibel for OS constructs, cgroups and namespaces.

dockerd communicates with containerd over grpc

Question 11

OCI

Answer 11

Open Cotainer Initiative

Question 12

Docker Installation

Answer 12

Docker Client
Docker Daemon/Engine

The client talks to daemon via local Unix socket

/var/run/docker.sock
docker client can execute commands through docker.sock on daemon.

Question 13

Check docker images

Answer 13

docker image ls

Question 14

Run an image

Answer 14

docker container run -it ubuntu:latest /bin/bash

Question 15

List containers running

Answer 15

docker container ls

docker container ls -a # list all containers

Question 16

Attach to a running container

Answer 16

docker container exec gitlab -it /bin/bash

Question 17

Build a docker image

Answer 17

docker image build -t myimage:123 .

Question 18

Run an image as a container

Answer 18

docker container run -d –name myweb –publish 8080:8080 myimage:123

-d run in the background

Question 19

What is runc?

Answer 19

runc is a CLI wrapper for libcotainer that was originally designed to replace the LXC.

Question 20

What is a dangling image?

Answer 20

Image without any tag.

docker image ls –filter dangling=true

Question 21

How to check manifest of an image

Answer 21

docker image manifest ubuntu:latest

Question 22

How to make a container restart automaticaller

Answer 22

docker container run –name neversaydie -it –restart always alpine:latest sh
–restart unless-stopped

Question 23

Example gitlab volume mount

Answer 23

docker run –detach \
–hostname gitlab.fleetcomplete.com \
–publish 443:443 –publish 23:22 –publish 80:80 \
–name gitlab \
–restart always \
–volume /src/gitlab/config:/etc/gitlab \
–volume /src/gitlab/logs:/var/log/gitlab \
–volume /src/gitlab/data:/var/opt/gitlab \
gitlab/gitlab-ce:fc-latest

Question 24

docker-compose yaml example

Answer 24

version: "3.8"
services:
  web-frontend:
    build: .
    command: python app.py
    ports:
      - target: 5000
        published: 5000
    networks:
      - counter-net
    volumes:
      - type: volume
        source: counter-volume
        target: code
  redis:
    image: redis:alpine
    network:
      - counter-net
networks:
  counter-net:
volumes:
  counter-volume:

Question 25

List network

Answer 25

docker network ls

Question 26

List volumes

Answer 26

docker volume ls

Question 27

Start an app using docker compose

Answer 27

docker-compose -f myapp.yaml up -d

docker-compose -f myapp.yaml down # stops and deletes the containers.

docker-compose restart
docker-compose ps