Docker

Common Errors

permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Get "http://%2Fvar%2Frun%2Fdocker.sock/v1.24/images/json": dial unix /var/run/docker.sock: connect: permission denied

• To rectify, do the following commands:

sudo usermod -aG docker $USER

sudo systemctl restart docker

sudo systemctl enable docker

• Note: Sometimes docker still doesn't want to play nice so a sudo reboot now or computer restart should do the trick!

Install

• Pacman

pacman -S docker docker-buildx

• Debian

apt install docker

General

• Docker uses a layered architecture.

# ----------- v1
FROM debian

RUN apt install x y z 

RUN pip install px py pz

COPY . /opt/src-code

ENTRYPOINT APP=/opt/src-code/run

# ----------- v2
FROM debian

RUN apt install x y z 

RUN pip install px py pz

COPY . /opt/diff-src-code

ENTRYPOINT APP=/opt/diff-src-code/run

• Docker will cache the same base, and then edit the diff to save time and resources.

• Image Layers: Read Only (when using docker build)

• Container Layer: Read / Write (when using docker run)

volumes

• -v is the original way, but --mount is the preferred method.

• Volumes are located in /var/lib/docker/volumes

• There are 2 types of volumes:

  • Bind Mount (external ie not volume created by docker)
  • Volume Mount (volumes created by docker via docker volume create <VOLUME_NAME>)

• Storage drivers

  • aufs
  • zfs
  • btrfs
  • device mapper
  • overlay
  • overlay2

• Volume Drivers

  • Local (/var/lib/docker/volumes)
  • Azure File Storage
  • ...

Docker Filesystem

• Located in /var/lib/docker

/var/lib/docker/
├── buildkit
├── containers      ; all files related to containers
├── image           ; files related to images
├── network
├── overlay2
├── plugins
├── runtimes
├── swarm
├── tmp
└── volumes         ; volumes created by docker