Docker Engine and Architecture FAQ’s

Components of the Docker Engine – Docker Daemon, Rest API and Docker Cli

Component that manages Images, Containers, Volumes and Network – Docker Daemon

Component that manages containers in Docker Engine – LibContainer

Container can run with Docker – Yes

Component keeps alive container even if Docker Daemon is not working – Containerd-Shim

Docker engine objects- Images, Container, Volume and Network

In Container data is writable but not persistable – Yes

Dcoker looks for images in docker hub by default- Yes

Readonly component in Docker engine – Docker Images

Default directory where Docker data is stored (Ubuntu) – /var/lib/docker

Directory where the Docker config is stored(Ubuntu)- /etc/docker

OCI stands for – Open Container Initiative

OCI specification – runtime-spec and image-spec

View version of Docker engine – docker version

Stop the Docker service – systemctl stop docker or/and systemctl stop docker.socket

Start the Docker service – systemctl start docker.socket or/and systemctl start docker

Check Status of Docker service – systemctl status docker

Debug docker whilst starting the service – dockerd –debug

Where is the Daemon file located (Ubuntu) – /etc/docker/daemon.json

Where is the daemon socket located (Ubuntu) – /var/run/docker.sock

Port to connect the docker externaly with encrypted trafic – 2376

Port to connect the docker externaly with unencrypted trafic – 2375

Start the docker daemon manually – dockerd

Default docker daemon interface – Unix Socket

Default network driver – bridge

Stop Command signals running container on STOP command – SIGTERM followed by SIGKILL

Restart policies – no, on-failure, always and unless-stopped

Reduce container downtime due to daemon failure or restart- Enable Live Restore

Docker Images FAQ’s

Default Docker Image Registry – Docker Hub

Various Image Registry –

  • Docker Trusted Registry
  • Google Container Registry
  • Amazon Container Registry
  • Azure Container Registry

Types of Images in Docker Hub

  • Official Images
  • Verified Images
  • User Images

Base vs Parent Image –

Base Image are creatged from scratch, which means its empty. You cannot create a scratch image as it is always to be used. Any other images created from Base Image but used as parent to custom images are Parent Image. e.g. Ubuntu which is made from debian image. Here debian image is a Parent Image

Docker Swarm

What is the maximum and recommended number of mananger a swarm cluste can have? There is no max limit but recommended is 7 managers in swarm cluster