/docker-training-fg

Docker Training FG

2019 Ondrej Sika <ondrej@ondrejsika.com>

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Usesful Docker Commands

  • docker system prune - prune unnecessary data from docker - layers, containers, volumes, ...
  • docker system df - docker disk usage
  • docker ps -s - show sizes of containers

Docker & Docker Compose Examples

Startup order

  • Docker use depends_on when resolve startup order
  • Docker doesnt wait to application is being ready - Kubernetes handles this
  • Need some workaround

Example: docker-training-examples/startup-order

Variables

Varible Substitution

Run TAG=2 PORT=80 docker-compose up -d

version: '3.7'
services:
  hello:
    image: ondrejsika/go-hello-world:${TAG:-latest}
    ports:
      - ${PORT:-80}:80

Multiple Composes

See multiple-composes example

Docker Compose CLI Variables

Reference

Docker Compose

  • COMPOSE_PROJECT_NAME - Specify prefix for compose containers (same as docker-compose -p <project name>)
  • COMPOSE_FILE - Specify one or multiple compose files separated by COMPOSE_PATH_SEPARATOR. (COMPOSE_FILE=c1.yml:c2.yml docker-compose is same as docker-compose -f c1.yml -f c2.yml)
  • COMPOSE_PATH_SEPARATOR - default : on Unix, ; on Windows

Docker Compose & Docker (cli)

DOCKER_HOST, DOCKER_TLS_VERIFY and DOCKER_CERT_PATH - configures connection to Docker daemon.

See the docs

.env file

.env file can store all environment variables (for docker containers, for docker compose substitution and docker compose cli) in one place

I recommend you put the .env into you .gitignore

Try with variable substitution example

Docker Images

Image Names

  • debian:9 - official Debian image maintained by Docker on Docker Hub - https://hub.docker.com/_/debian
  • ondrejsika/debian:9 - Debian image in user namespace on Docker Hub
  • reg.istry.cz/debian:9 - Debian image on self hosted Docker registry

Official Images

  • OS - eg.: debian, centos, ...
  • Languages - eg.: python, golang, ...
  • Technologies - nginx, postgres, ...

Building Own Images

Docker file reference - https://docs.docker.com/engine/reference/builder/

Examples in docker-training-examples

BuildKit

Docs

Use BuildKit

DOCKER_BUILDKIT=1 docker build .

Or in config /etc/docker/daemon.json:

{ "features": { "buildkit": true } }
Cache (In Docker Build)

Cache

# syntax = tonistiigi/dockerfile:runmount20180618
RUN --mount=type=cache,dst=/cache,readonly=false ...

Mount host path

# syntax = tonistiigi/dockerfile:runmount20180618
RUN --mount=src=/data,dst=/mnt/data,readonly=false ...

Docker Registry

  • Gitlab (Open Source version)
  • JFrog Artifactory

Gitlab Premium (19 USD/user/month) supports

Run registry locally (dev purposes)

Create SSL certs if needed (or provide them for example using Let's Encrypt). Then run this:

docker run -d \
  --restart=always \
  --name registry \
  -u `id -u`:`id -g` \
  -v `pwd`/certs:/certs \
  -v `pwd`/registry-data:/var/lib/registry \
  -e REGISTRY_HTTP_ADDR=0.0.0.0:443 \
  -e REGISTRY_HTTP_TLS_CERTIFICATE=/certs/fullchain.pem \
  -e REGISTRY_HTTP_TLS_KEY=/certs/privkey.pem \
  -p 443:443 \
  registry:2

Registry for Traefik

ondrejsika/docker-registry-traefik

Pruning Docker Registry

Use docker-distribution-pruner from Gitlab

Example usage for Gitlab Docker Registry

EXPERIMENTAL=true docker-distribution-pruner -config=/var/opt/gitlab/registry/config.yml

Volumes

Official Docs

Mounts (host FS into container)

Access container FS

docker run --name nginx -d -p 8000:80 nginx

docker exec

docker exec -w /usr/share/nginx/html nginx cat index.html
docker exec -ti -w /usr/share/nginx/html nginx bash
docker exec -w /usr/share/nginx/html nginx sh -c 'echo "<h1>Hello from exec</h1>" > index.html'
docker run --link nginx ondrejsika/curl -s nginx

docker cp

Docs

Copy from conteiner
docker cp nginx:/usr/share/nginx/html/index.html /tmp/index.html
cat /tmp/index.html
Copy to container
echo "<h1>Hello from cp</h1>" > /tmp/index.html
docker cp /tmp/index.html nginx:/usr/share/nginx/html/
docker run --link nginx ondrejsika/curl -s nginx

Backup & Restore

Docs

Backup Volumes

Docs

You have a Redis with some data in /data volume:

docker run --name redis -d redis
docker exec redis redis-cli set hello 'hello world'
docker stop redis

# Backup
docker run --rm --volumes-from redis -v /tmp/backup:/backup ubuntu tar cvf /backup/backup.tar /data

Restore Volumes

Docs

Run new Redis

docker create --name redis2 redis

# Restore data
docker run --rm --volumes-from redis2 -v /tmp/backup:/backup ubuntu bash -c "cd /data && tar xvf /backup/backup.tar --strip 1"

docker start redis2

# Check it
docker exec redis2 redis-cli get hello

# Clean up
docker rm -f redis redis2
docker run --rm -v /tmp/backup:/backup ubuntu rm /backup/backup.tar

Backup, Restore & Transfer

My update of "official" backup/restore info

Backup Volumes to Image

docker run --name redis -d redis
docker exec redis redis-cli set hello 'hello world'
docker stop redis

# Backup
docker run --name backup --volumes-from redis ubuntu tar cvf /backup.tar /data

# Commit
docker commit backup backup-image

# Remove container
docker rm backup

Restore Volumes form Image

docker create --name redis2 redis

# Restore data
docker run --rm --volumes-from redis2 backup-image bash -c "cd /data && tar xvf /backup.tar --strip 1"

docker start redis2

# Check it
docker exec redis2 redis-cli get hello

# Clean up
docker rm -f redis redis2

Database Images with Data

Data loaded on conteiner init

docker build -t postgres-data-init examples/postgres-data-init
docker run --name pg -d postgres-data-init
sleep 4
docker exec -u postgres pg psql -c "select hello from hello;"
docker rm -f pg

Data saved in image (data are part of image)

docker build -t postgres-data-image--base examples/postgres-data-image
docker run --name pg -d postgres-data-image--base
sleep 4
docker exec -i -u postgres pg psql < examples/postgres-data-image/init.sql
docker stop pg
docker commit pg postgres-data-image
docker rm pg
docker run --name pg -d postgres-data-image
sleep 4
docker exec -u postgres pg psql -c "select hello from hello;"
docker rm -f pg

Versioning

Image has <repository>:<tag> where repository is name of your image and tag is version

Example of tags:

Traefik

Cloud native proxy

https://traefik.io

  • SSL using Let's Encrypt
  • Hot reloads (watching Docker socket)
  • Docker / Kubernetes support

Examples:

Gitlab CI

slides, demo gitlab

Why Gitlab CI

  • Docker First - Great Docker & Kubernetes support
  • CI Jobs run in Docker
  • Environments - Manage deployments running by CI

Setup Gitlab Runner

Docker from Docker Gitlab Runner - https://github.com/ondrejsika/gitlab-ci-runner

Example Gitlab CI Project with Docker and Traefik

https://github.com/ondrejsika/gitlab-ci-example-docker-traefik

Digital Ocean

Sources

Want more

Pripravuji

  • Ansible
  • Terraform