Things I learned in Docker... The hard way!

docker-lessons-learnt.md

Things that I learned in Docker

The hard way!

There is no specific order to these learnings. They're just the random learnings of a madman, trying to learn and use docker for the first time... So, I'm just throwing them out there as I recall them. I said "madman," right? Of course these aren't in any order...

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Setting up Docker

- the issues I faced -

First, the backstory

I'm running Windows Home on the insider program. So, naturally, I decided to go with WSL 2, running Ubuntu-18.04, and the Docker edge build for the insider release. Unfortunately, this was riddled with issues, and it only worked for a couple of days, before I started having problems getting it to connect to the docker daemon in Windows. I troubleshot this for a couple of days, and each time I was close toa fix, something in Docker or WSL would blow up, and I'd have to start all over again. I finally decided to uninstall docker, kill WSL, and go back to the old ways... Run an Ubuntu VM and run docker from within there.

Some of the key issues that I ran into are:

• Installation - by default, no one wants you to do it this way anymore.
• Sharing folders between the host and the VM.
• Connecting to the docker daemon friggin again
• Permissions issues.

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Install docker

# install docker  
  sudo apt install apt-transport-https ca-certificates curl software-properties-common
  curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
  sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu bionic stable"
  sudo apt update
  apt-cache policy docker-ce
  sudo apt install docker-ce
  sudo systemctl status docker
  # Run docker without sudo  
    sudo usermod -aG docker ${USER}

Install docker-compose

# install docker-compose  
  sudo curl -L https://github.com/docker/compose/releases/download/1.21.2/docker-compose-`uname -s`-`uname -m` -o /usr/local/bin/docker-compose
  # set permissions  
    sudo chmod +x /usr/local/bin/docker-compose
  # validate success by checking version  
    docker-compose --version

verify docker works docker run hello-world

permissions

sudo groupadd docker
sudo usermod -aG docker $USER
sudo chmod 755 -R 
newgrp docker 
Restart your computer

validate that dockerd is running

who owns the docker sock? ls -l /var/run/docker.sock

take ownership - sudo chown *your-username* /var/run/docker.sock

Note: Ubuntu doesn't support docker-compose file of version 3.7 yet, so I had to revert back to ver 3.3

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Password issues in a Docker container

if you keep trying to update your password, and it's just not working
Validate your vars...
and remember that an environment variable defined in the docker-compose file takes precedence

  grafana:
    image: grafana/grafana
    container_name: grafana  # simplify your container names...  
    ports:  # used to connect host:comtainer ports  
      - 3000:3000
    expose: # used to expose a port outside the network  
      - 3000
    volumes:
      - grafana_data:/var/lib/grafana
      - ./grafana/provisioning:/etc/grafana/provisioning/
    environment:  # declared vars take precedence over env_file  
      - GF_SECURITY_ADMIN_PASSWORD=${GF_SECURITY_ADMIN_PASSWORD}
      - GF_AUTH_ANONYMOUS_ENABLED=${GF_AUTH_ANONYMOUS_ENABLED}
      - GF_USERS_ALLOW_SIGN_UP=${GF_USERS_ALLOW_SIGN_UP}
      - GF_INSTALL_PLUGINS=${GF_INSTALL_PLUGINS}
    env_file: 
      - ./.env
    networks:
      - private
      - public
    restart: always

Did you accidentally use " or ' on your vars, and you weren't supposed to?

GF_SECURITY_ADMIN_PASSWORD="abc123"
passes "abc123"

GF_SECURITY_ADMIN_PASSWORD=abc123
passes abc123

If your vars are good, then wipe your browser cache and kill your persistent storage volume, if you created one...

version: '3.3'
# changed from 3.7 to accommodate running from ubuntu  

volumes:
    prometheus_data: {}
    grafana_data: {}

docker-compose down
docker volume prune
docker-compose up -d

99% of the time, that did the trick for me...

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Building from Dockerfile vs Pulling from Hub

I've noticed that a lot of Dockerfiles are poorly constructed (and I'm a novice). I suggest running with build, to test how solid the images are that you plan to incorporate...

One such painful image was...

FROM node:13-alpine

WORKDIR /app

COPY package.json yarn.lock /app/

RUN \
  apk add --no-cache tini && \
  yarn --silent --no-progress --frozen-lockfile

COPY . /app/

EXPOSE 3000
ENTRYPOINT ["yarn"]
CMD ["start"]
# ENTRYPOINT ["tini"]
# CMD ["yarn", "start"]

I couldn't get it to build until I changed COPY package.json yarn.lock /app/ to COPY . /app/
and even then, it was a crap image that continuously restarted, because I could never get it to properly take the supplied package.json...

Don't waste your time with images that can't build from their published Dockerfile... My 2 cents

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Networking

TL;DR
more to come

connection refused issues

For some reason, prometheus doesn't work well with exporters inside a docker built network. I tried to make it work for 2 days, to no avail, and all of the prometheus group resolutions include having the user change to host network, versus bridge, or overlay

So, update your damn sources to use: network_mode: host

example:

  blackbox:
    image: prom/blackbox-exporter
    container_name: blackbox
    volumes:
      - ./blackbox/config:/config
    command:
      - '--config.file=/config/blackbox.yml'
    network_mode: host

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Accessing containers and running commands

docker exec -it <container name> <command>

as an example:

docker exec -it prometheus sh

You can also remotely run commands in this manner.

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Links

• docker-compose cheat sheet
• docker cheat sheet
• https://stackoverflow.com/questions/33562109/docker-command-cant-connect-to-docker-daemon

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