Ondrej Sika (sika.io) | ondrej@sika.io | go to course -> | install docker ->

Docker Training

About Course

• Docker Training in Czech Republic & Slovakia
• Docker Training in Europe

Related Courses

• Kubernetes Training in Czech Republic & Slovakia
• Kubernetes Training in Europe

Any Questions?

Write me mail to ondrej@sika.io

Course

About Me - Ondrej Sika

Freelance DevOps Engineer, Consultant & Lecturer

• Complete DevOps Pipeline
• Open Source / Linux Stack
• Cloud & On-Premise
• Technologies: Git, Gitlab, Gitlab CI, Docker, Kubernetes, Terraform, Prometheus, ELK / EFK, Rancher, Proxmox

Star, Create Issues, Fork, and Contribute

Feel free to star this repository or fork it.

If you found bug, create issue or pull request.

Also feel free to propose improvements by creating issues.

Chat

For sharing links & "secrets".

• Slack - https://sikapublic.slack.com/
• Microsoft Teams
• https://sika.link/chat (tlk.io)

DevOps Kniha (Czech only)

https://kniha.sika.io

What is Docker?

Docker is an open-source project that automates the deployment of applications inside software containers ...

Docker containers wrap up a piece of software in a complete filesystem that contains everything it needs to run: code, runtime, system tools, system libraries – anything you can install on a server.

Containers vs virtualization

Virtualization

A VM is an abstraction of physical hardware. Each VM has a full server hardware stack from virtualized BIOS to virtualized network adapters, storage, and CPU.

That stack allows run any OS on your host but it takes some power.

Containers

Containers are abstraction in linux kernel, just proces, memory, network, … namespaces.

Containers run in same kernel as host - it is not possible use different OS or kernel version, but containers are much more faster than VMs.

Usage of Docker

• Almost everywhere
• Development, Testing, Production
• Better (easier, faster) deployment process
• Separates running applications

Docker containers in cluster

• Kubernetes
• Docker Swarm

Docker Editions (CE / EE)

Docker Engine Community

Docker CE is ideal for individual developers and small teams looking to get started with Docker and experimenting with container-based apps.

Docker Engine Enterprise

Docker Engine - Enterprise is designed for enterprise development of a container runtime with security and an enterprise grade SLA in mind.

Docker Enterprise

Docker Enterprise is designed for enterprise development and IT teams who build, ship, and run business critical applications in production at scale.

Source: https://docs.docker.com/install/overview/

12 Factor Apps

12factor.net

Set of 12 rules how to write modern applications.

Install Docker

• Official installation - https://docs.docker.com/engine/installation/
• My install instructions (in Czech) - https://ondrej-sika.cz/docker/instalace/
• Bash Completion on Mac - https://blog.alexellis.io/docker-mac-bash-completion/

Test the installation

docker run hello-world

Remote Docker (over SSH)

You can use remote Docker using SSH. Just export varibale DOCKER_HOST with ssh://root@docker.sikademo.com and your local Docker clint will be executed on docker.sikademo.com server.

export DOCKER_HOST=ssh://root@docker.sikademo.com
docker version
docker info

Docker plugin for VS Code

https://marketplace.visualstudio.com/items?itemName=ms-azuretools.vscode-docker

Basic Usage

Image and Container

An image is an inert, immutable, file that's essentially a snapshot of a container. Images are created with the build command, and they'll produce a container when started with run. Images are stored in a Docker registry.

System Wide Info

• docker version - print version
• docker info - system wide information
• docker system df - docker disk usage
• docker system prune - cleanup unused data
• docker volume prune --all - cleanup unused volumes (including named volumes)

Docker Images

• docker pull <image> - download an image
• docker image ls - list all images
• docker image ls -q - quiet output, just IDs
• docker image ls <image> - list image versions
• docker image rm <image> - remove image
• docker image inspect <image> - show image properties

Update all local images

docker image ls --format="{{.Repository}}:{{.Tag}}" | xargs -I {} docker pull {}

Docker Registry

Docker image name also contains location of it source. Those names can be used:

• debian - Official images on Docker Hub
• ondrejsika/debian - User (custom) images on Docker Hub
• ghcr.io/ondrejsika/debian - Github Container Registry
• ttl.sh/debian - Image in my own registry

Own Docker Registry

Docker Registry is build in Gitlab and Github for no additional cost. You can find it in packages section.

You can run registry manually using this command:

docker run -d -p 5000:5000 --restart=always --name registry registry:2

See full deployment configuration here: https://docs.docker.com/registry/deploying/

Docker Registry in Self-Hosted Gitlab

You have to add registry_external_url to Your Gitlab config and reconfigure.

echo "registry_external_url 'registry.example.com'" >> /etc/gitlab/gitlab.rb
gitlab-ctl reconfigure

My Example Registry: simple-registry.sikademo.com

See: https://simple-registry.sikademo.com/v2/_catalog

Deployed into Kubernetes by sikalabs/simple-registry chart

sikalabs/simple-registry chart

Setup SikaLabs Charts

helm repo add sikalabs https://helm.sikalabs.io
helm repo update

Install sikalabs/simple-registry chart

helm install registry sikalabs/simple-registry --set host simple-registry.sikademo.com

ttl.sh - Anonymous & ephemeral Docker image registry

• https://ttl.sh/
• https://github.com/replicatedhq/ttl.sh

Crane

• https://github.com/google/go-containerregistry/tree/main/cmd/crane
• https://github.com/google/go-containerregistry/blob/main/cmd/crane/doc/crane.md

Install Crane

Mac

brew install crane

Linux (using slu)

slu install-bin crane

Copy Image

Copy image from one registry to another without pulling it to local machine.

crane copy <source> <destination>

example

crane copy sikalabs/dev ttl.sh/dev

List Image Tags (versions)

crane ls ghcr.io/sikalabs/slu

Docker Run

docker run [ARGS] <image> [<command>]

Examples

Basic Docker Run

docker run hello-world

With custom command

docker run debian cat /etc/os-release

docker run ubuntu cat /etc/os-release

With TTY & Standart Input

docker run -ti debian

Containers

• docker container ls - list containers
• docker ps - list containers
• docker start <container>
• docker stop <container>
• docker restart <container>
• docker rm <container> - remove container

Common Docker Run Params

• --name <name> - set container name (Wozniak easter egg)
• -d - run in detached mode
• -ti - map TTY a STDIN (for bash eg.)
• -e <variable>=<value> - set ENV variable
• --env-file=<env_file> - load all variables defined in ENV file

Restart Policy

By default, if container process stop (or fail), container will be stopped.

You can choose another behavion using argument --restart <restart policy>.

• --restart on-failure - restart only when container return non zero return code
• --restart always - always, even on Docker daemon restart (server restart also)
• --restart unless-stopped - similar to always, but keep stopped container stopped on Docker daemon restart (server restart also)

If you want to set maximum restart count for on-failure restart policy, you can use: --restart on-failure:<count>

List Containers

• docker container ls - list running containers
• docker container ls -a - list all containers
• docker container ls -a -q - list IDs of all containers

or

• docker ps - list running containers
• docker ps -a - list all containers
• docker ps -a -q - list IDs of all containers

Example of -q

docker rm -f $(docker ps -a -q)

or my dra (docker remove all) alias

alias dra='docker ps -a -q | xargs -r docker rm -f'

dra

Or using slu:

slu s dra

Docker Exec

docker exec <container> <command>

Arguments

• -d - run in detached mode
• -e <variable>=<value> - set ENV variable
• -ti - map TTY a STDIN (for bash eg.)
• -u <user> - run command by specific user

Postgres 15 example

docker run --name pg15 -e POSTGRES_PASSWORD=pg -d postgres:15

docker exec -ti pg15 bash

docker exec -ti -u postgres pg15 psql

Postgres 16 example

docker run --name pg16 -e POSTGRES_PASSWORD=pg -d postgres:16

docker exec -ti pg16 bash

docker exec -ti -u postgres pg16 psql

Docker Logs

All containers have to log into STDOUT or STDERR.

Example of logging to STDOUT from legacy application - examples/log_to_file

docker logs [-f] [-t] <container>

Args

• -f - following output (similar to tail -f ...)
• -t - show time prefix

Examples

docker run --name loggen -d sikalabs/slu:v0.60.0 slu loggen --json

docker logs loggen

docker logs -f loggen

docker logs -f loggen | jq .i

docker logs -t loggen

docker logs -ft loggen

Log Drivers

You can use native Docker logging or some log drivers.

For example, if you want to log into syslog, you can use --log-driver syslog.

You can send logs directly to ELK (EFK) or Graylog using gelf. For elk logging you have to use --log-driver gelf –-log-opt gelf-address=udp://1.2.3.4:12201.

See the logging docs: https://docs.docker.com/config/containers/logging/configure/

Json File (Default Log Driver)

Log Driver options:

• max-size - Max size of log file (default -1 - unlimited), use for example 100k for kB, 10m for MB or 1g for GB.
• max-file - Nuber of log rotated files (default 1)
• compress - Compression for rotated logs (default disabled)

Examle:

docker run --name log-rotation -d --log-opt max-size=1k --log-opt max-file=5 ondrejsika/log-rotation

Docker Inspect

Get lots of information about container in JSON.

docker inspect <container>

Inspect Format

Using Go Template Language.

Examples:

docker inspect loggen --format "{{.NetworkSettings.IPAddress}}"

docker inspect loggen --format "{{.LogPath}}"

Docker Volumes

Docs

• Volumes are persistent data storage for containers.
• Volumes can be shared between containers and data are written directly to host.

CLI

• docker volume - all volume management commands
• docker volume ls - list all volumes
• docker volume rm <volume> - remove volume
• docker volume prune - remove all not used (not bount to container) volumes

Examples

• docker run -ti -v /data debian
• docker run -ti -v my-volume:/data debian
• docker run -ti -v $(pwd)/my-data:/data debian

Get Volume Paths from Image

docker image inspect redis --format "{{.Config.Volumes|json}}"

docker image inspect postgres:11 --format "{{.Config.Volumes|json}}"

Read only volumes

If you want to mount your volumes read only, you have to add :ro to volume argument.

Examples

• docker run -ti -v my-volume:/data:ro debian
• docker run -ti -v $(pwd)/my-data:/data:ro debian

First example does't make sense read only.

Show All Volumes & Mounts for All Containers

docker ps -a --format '{{ .ID }}' | xargs -I {} docker inspect -f '{{ .Name }} ({{ .ID }}){{ printf "\n" }}{{ range .Mounts }}{{ printf "\n\t" }}{{ .Type }} {{ if eq .Type "bind" }}{{ .Source }}{{ end }}{{ .Name }} => {{ .Destination }}{{ end }}{{ printf "\n" }}' {}

Find Containers Which Use Specific Volume

docker ps -a --filter volume=<volume>

Example

docker ps -a --filter volume=my-volume

Socket forwading

If you want to forward socket into container, you can also use volume. If you work with sockets, read only parameter doesn't work.

docker run -v /var/run/docker.sock:/var/run/docker.sock docker docker ps

or

docker run -v /var/run/docker.sock:/var/run/docker.sock -ti docker

!! Possible Security Risk !!

You can mount your's host rootfs to container with root privileges. Everybody ho has access to docker or docker socket has root privileges on your host.

userns-remap can fix that

docker run -v /:/rootfs -ti debian

userns-remap

Docker can remap root user from container to hight-number user on host.

More: https://docs.docker.com/engine/security/userns-remap/

Enabble userns-remap

dockerd argument

dockerd --userns-remap="default"

Config /etc/docker/daemon.json

{
  "userns-remap": "default"
}

Examples

docker run -v /:/rootfs -ti debian cat /rootfs/etc/shadow

docker run -v /:/rootfs -ti --userns=host debian cat /rootfs/etc/shadow

Docker In Docker

Run Docker in Docker

docker run --name docker -d --privileged docker:dind

Try run any Docker command in this container:

docker exec docker docker info
docker exec docker docker image ls
docker exec docker docker run hello-world
docker exec -ti docker sh

Port Forwarding

Docker can forward specific port from container to host

docker run -p <host port>:<cont. port> <image>

You can specify an address on the host as well

docker run -p <host address>:<host port>:<cont. port> <image>

Examples

docker run -ti -p 8080:80 nginx
docker run -ti -p 127.0.0.1:8080:80 nginx

The latter will make connection possible only from localhost.

See http://127.0.0.1:8080

Own Images

Dockerfile

Dockerfile is preferred way to create images.

Dockerfile defines each layer of image by some command.

To make image use command docker build

Dockerfile Commands

• FROM <image> - define base image
• RUN <command> - run command and save as layer
• COPY <local path> <image path> - copy file or directory to image layer
• ADD <source> <image path> - instead of copy, archives added by add are extracted
• ENV <variable> <value> - set ENV variable
• USER <user> - switch user
• WORKDIR <path> - change working directory
• VOLUME <path> - define volume
• CMD <command> - command we want to run on container start up. Difference between CMD and ENTRYPOINT will be exaplain later
• EXPOSE <port> - Define on which port the conteiner will be listening

.dockerignore

• Ignore files for docker build process.
• Similar to .gitignore

Example of .dockerignore for Next.js (Node) project

Dockerfile
out
node_modules
.DS_Store

Build Image from Dockerfile

• docker build <path> -t <image> - build image
• docker build <path> -f <dockerfile> -t <image>
• docker tag <source image> <target image> - rename docker image

Cross Platform Build

Use --platform for cross platform builds

Build AMD64

docker build --platform linux/amd64 .

Build ARM64 (for Apple Silicon)

docker build --platform linux/arm64 .

Practice

Simple Image

See Simple Image example

Get Source

git clone https://github.com/ondrejsika/docker-training
cd docker-training/examples/simple-image
rm Dockerfile Dockerfile.debian

Image Size Differences

List images and see the difference in image sizes

docker image ls simple-image

Hadolint

Hadolint is Dockerfile linter.

Github: https://github.com/hadolint/hadolint

Install & Use Hadolint

Install on Mac

brew install hadolint

Use hadolint

hadolint <dockerfile>

You can ignore checks & specify trusted registries

hadolint --ignore DL3003 --ignore DL3006 <dockerfile> # exclude specific rules
hadolint --trusted-registry registry.sikademo.com <dockerfile>

Use from Docker

You can also use Hadolint from Docker

docker run --rm -i hadolint/hadolint < Dockerfile
docker run --rm -i hadolint/hadolint hadolint --ignore DL3006 - < Dockerfile

or (for PowerShell)

cat Dockerfile | docker run --rm -i hadolint/hadolint
cat Dockerfile | docker run --rm -i hadolint/hadolint hadolint --ignore DL3006 -

Build Arguments

Example in Dockerfile

ARG FROM_IMAGE=debian:9
FROM $FROM_IMAGE

FROM debian
ARG PYTHON_VERSION=3.7
RUN apt-get update && \
    apt-get install python==$PYTHON_VERSION

Build using

docker build \
  --build-arg FROM_IMAGE=python .
docker build .

docker build \
  --build-arg PYTHON_VERSION=3.6 .

See Build Args example.

Multi Stage Builds

Dockerfile for multistage builds

FROM java-jdk as build
RUN gradle assembly

FROM java-jre
COPY --from=build /build/demo.jar .

Build Multistage Images

# By default, last stage is used
docker build -t <image> <path>

# Select output stage
docker build -t <image> --target <stage> <path>

Examples

docker build -t app .
docker build -t build --target build .

Practice

Multistage Image

See Multistage Image example

Get Source

cd ../multistage-image
rm Dockerfile

Multistage image size differences

docker image ls multistage-image

ASP.NET Core Example

Source: https://github.com/dotnet/dotnet-docker/tree/master/samples/aspnetapp

git clone https://github.com/dotnet/dotnet-docker.git
cd samples/aspnetapp
docker build -t dotnet-example .
docker run -ti -p 8000:80 dotnet-example

See: http://127.0.0.1:8000

Kaniko

• Build Docker images in Conteiner / Kubernetes without Docker daemon
• https://github.com/GoogleContainerTools/kaniko

See examples/kaniko

cd example/kaniko
make build
make run

RUN --mount=type=cache

examples/build_mount_cache

Entrypoint vs Command

Entrypoint Examples

• Postgress with Default Data
• Wait for It

Docker Networks

Docker support those network drivers:

• bridge (default)
• host
• none
• custom (bridge)

Bridge (default)

docker run debian:10 ip a

Host

docker run --net host debian:10 ip a

None

docker run --net none debian:10 ip a

Network Commands

• docker network ls
• docker network create <network>
• docker network rm <network>

Create Network

Example:

docker network create -d bridge my_bridge

Run & Add Containers:

# Run on network
docker run -d --net=my_bridge --name nginx nginx
docker run -d --net=my_bridge --name apache httpd

# Connect to network
docker run -d --name nginx2 nginx
docker network connect my_bridge nginx2

Test the network

docker run -ti --net my_bridge ondrejsika/host nginx
docker run -ti --net my_bridge ondrejsika/host apache
docker run -ti --net my_bridge ondrejsika/curl nginx
docker run -ti --net my_bridge ondrejsika/curl apache

Macvlan Network

If you need assign IP addresses from your local network directly to containers, you have to use Macvlan.

https://docs.docker.com/network/macvlan/

docker network create -d macvlan \
  --subnet=192.168.101.0/24 \
  --ip-range=192.168.101.128/25 \
  --gateway=192.168.101.1\
  -o parent=eth0 macvlan

ctop

ctop is a top-like interface for container metrics.

• ctop.sh
• github.com/bcicen/ctop

Install

Mac

brew install ctop

Using slu

slu install-bin ctop

Official installation instructions: https://github.com/bcicen/ctop#install

Run

ctop

or with Docker

docker run --rm -ti \
  --name=ctop \
  --volume /var/run/docker.sock:/var/run/docker.sock \
  quay.io/vektorlab/ctop:latest

Portainer

Portainer is a web UI for Docker.

Homepage: portainer.io

Run Portainer

docker run -d --name portainer -p 8000:8000 -p 9000:9000 -v /var/run/docker.sock:/var/run/docker.sock -v portainer_data:/data portainer/portainer

See: http://127.0.0.1:9000

Run Portainer behind Traefik v1

docker run \
  -d \
  --name portainer \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -v portainer_data:/data \
  --label=traefik.enable=true \
  --label=traefik.frontend.rule=Host:portainer.lab0.sikademo.com \
  --label=traefik.port=9000 \
  --net traefik \
  portainer/portainer

See: https://portainer.lab0.sikademo.com

Run Portainer behind Traefik v2

https://github.com/ondrejsika/docker-compose-examples/tree/master/portainer

Nixery.dev

Nixery.dev provides ad-hoc container images that contain packages from the Nix package manager. Images with arbitrary packages can be requested via the image name.

More at https://nixery.dev/

Examples

docker run nixery.dev/hello hello

docker run -ti nixery.dev/htop htop

docker run -ti nixery.dev/shell/git/curl/mc bash

cAdvisor (Container Advisor)

google/cadvisor (homepage)

cAdvisor (Container Advisor) provides container users an understanding of the resource usage and performance characteristics of their running containers. It is a running daemon that collects, aggregates, processes, and exports information about running containers. Specifically, for each container it keeps resource isolation parameters, historical resource usage, histograms of complete historical resource usage and network statistics. This data is exported by container and machine-wide.

Install:

# use the latest release version from https://github.com/google/cadvisor/releases
VERSION=v0.49.1
docker run \
  --volume=/:/rootfs:ro \
  --volume=/var/run:/var/run:ro \
  --volume=/sys:/sys:ro \
  --volume=/var/lib/docker/:/var/lib/docker:ro \
  --volume=/dev/disk/:/dev/disk:ro \
  --publish=8080:8080 \
  --detach=true \
  --name=cadvisor \
  --privileged \
  --device=/dev/kmsg \
  gcr.io/cadvisor/cadvisor:$VERSION

Check out:

• Web UI - http://127.0.0.1:8080/
• /metrics (prometheus) - http://127.0.0.1:8080/metrics

Run behind Traefik v1

VERSION=v0.46.0
docker run \
  --volume=/:/rootfs:ro \
  --volume=/var/run:/var/run:ro \
  --volume=/sys:/sys:ro \
  --volume=/var/lib/docker/:/var/lib/docker:ro \
  --volume=/dev/disk/:/dev/disk:ro \
  --detach=true \
  --name=cadvisor \
  --privileged \
  --device=/dev/kmsg \
  --label=traefik.enable=true \
  --label=traefik.frontend.rule=Host:cadvisor.lab0.sikademo.com \
  --label=traefik.port=8080 \
  --net=traefik \
  gcr.io/cadvisor/cadvisor:$VERSION

See: https://cadvisor.lab0.sikademo.com

Run cAdvisor behind Traefik v2

https://github.com/ondrejsika/docker-compose-examples/tree/master/cadvisor

Distroless Images

• https://github.com/GoogleContainerTools/distroless
• examples/distroless_python
• examples/distroless_flask (multistage)
• distroless/examples/python3
• distroless/examples/python3-requirements

Thank you! & Questions?

That's it. Do you have any questions? Let's go for a beer!

Docker Compose

What is Docker Compose?

Docker Compose is a tool for defining and running multi-container Docker applications.

With Docker Compose, you use a Compose file to configure your application's services.

docker-compose vs docker compose

docker-compose is the old command. docker compose is the new command. Both commands are the same.

docker-compose.yml vs compose.yml

docker-compose.yml is the old name. compose.yml is the new name. Both names are the same.

Install Docker Compose

Docker Compose is part of Docker Desktop (Mac, Windows). Only on Linux, you have to install it:

• https://docs.docker.com/compose/install/
• https://docs.docker.com/compose/completion/

Install docker compose CLI plugin on Linux

mkdir -p ~/.docker/cli-plugins/
curl -SL https://github.com/docker/compose/releases/download/v2.7.0/docker-compose-linux-x86_64 -o ~/.docker/cli-plugins/docker-compose
chmod +x ~/.docker/cli-plugins/docker-compose

on Mac (Apple Silicon)

mkdir -p ~/.docker/cli-plugins/
curl -SL https://github.com/docker/compose/releases/download/v2.29.7/docker-compose-darwin-aarch64 -o ~/.docker/cli-plugins/docker-compose
chmod +x ~/.docker/cli-plugins/docker-compose

Or

slu install-bin docker-compose
mkdir -p ~/.docker/cli-plugins/
ln -s /usr/local/bin/docker-compose ~/.docker/cli-plugins/docker-compose

Validate

docker compose version

Example Compose File

services:
  app:
    build: .
    ports:
      - 8000:80
  redis:
    image: redis

Here is a compose file reference: https://docs.docker.com/compose/compose-file/compose-file-v3/

Here is a nice tutorial for YAML: https://learnxinyminutes.com/docs/yaml/

Service

Service is a container running and managed by Docker Compose.

Run Docker Compose

docker compose up [ARGS] [<service>, ...]

Example

docker compose up

Build Compose

Just build, don't run

docker compose build

Build without cache

docker compose build --no-cache

Build with args

docker compose build --build-arg BUILD_NO=53

Common Compose File Attributes

Image

Just pull & run image

services:
  app:
    image: redis

Build

Simple, just build path

services:
  app:
    build: .

Extended form with every build configuration

services:
  app:
    build:
      context: ./app
      dockerfile: ./app/docker/Dockerfile
      args:
        BUILD_NO: 1
    image: ttl.sh/app

Inline Dockerfile

services:
  example:
    build:
      dockerfile_inline: |
        FROM debian:12-slim
        CMD ["echo", "Hello from inline Dockerfile"]

Platoform specific build

services:
  example:
    build: .
    platform: linux/amd64

Port Forwarding

services:
  app:
    ports:
      - 8000:80
      - 127.0.0.1:80:80

Volume

Volumes are very similar but there is a little difference

services:
  app:
    volumes:
      - /data1
      - data:/data2
      - ./data:/data3

volumes:
  data:

Command

services:
  app:
    command: ["python", "app.py"]

Environment Variables

services:
  app:
    environment:
      RACK_ENV: development
      SHOW: "true"
      SESSION_SECRET:

ENV Files

services:
  app:
    env_file:
      - default.env
      - prod.env

Variable Substitution

Docker Compose uses standart bash variable substitution

Variable with Default Value

services:
  app:
    image: ${IMAGE:-ondrejsika/go-hello-world:3}

Mandatory Variable

services:
  app:
    image: ${IMAGE?Environment variable IMAGE is required}

YAML Anchors

x-base: &base
  image: debian
  command: ["env"]

services:
  en:
    <<: *base
    environment:
      HELLO: Hello
  cs:
    <<: *base
    environment:
      HELLO: Ahoj

Deploy

services:
  app:
    deploy:
      replicas: 4

Compose Project Name

name: "compose-name-example"

Create a Composite

See simple compose example

git clone https://github.com/ondrejsika/docker-training.git example--simple-compose
cd example--simple-compose/examples/simple-compose
rm Dockerfile docker-compose.yml

Try it wihout Docker Compose. Run the example:

docker build -t counter .
docker network create counter
docker run --name redis -d --net counter -v redis-data:/data redis
docker run --name counter -d --net counter -p 80:80 -e REDIS=redis counter

Stop & Remove

docker stop counter redis
docker rm counter redis
docker network rm counter

Now, we can create Docker compose and Compose File manually.

Create Dockerfile:

FROM python:3.7-slim
WORKDIR /app
COPY requirements.txt .
RUN pip install -r requirements.txt
COPY . .
CMD ["python", "app.py"]
EXPOSE 80

Try without Docker Compose

docker build -t counter .
docker network create counter
docker run --name redis -d --net counter redis
docker run --name counter -d --net counter -p 8000:80 counter
docker stop counter redis
docker rm counter redis
docker network rm counter

Create docker-compose.yml:

services:
    counter:
        build: .
        image: ttl.sh/examples/simple-compose/counter
        ports:
            - ${PORT:-80}:80
        depends_on:
            - redis
    redis:
        image: redis

Compose Commands

• docker compose config - validate & see final docker compose yaml
• docker compose ps - see all composite's containers
• docker compose exec <service> <command> - run something in container
• docker compose version - see version of docker-compose binary
• docker compose logs [-f] [<service>] - see logs

Compose Up Arguments

• -d - run in detached mode
• --force-recreate - always create new cont.
• --build - build on every run
• --no-build - don't build, even images not exist
• --remove-orphans

Manage Compose

• docker compose start [<service>]
• docker compose stop [<service>]
• docker compose restart [<service>]
• docker compose kill [<service>]

docker compose up vs docker compose run

docker compose up

• run all services (or multiple selected services)
• you can't specify command, volums, environment from cli arguments

docker compose run

• run only one service
• run dependencies on background
• you can specify command, volums, environment from cli arguments

Stop and Remove Compose

docker compose down

Scaling Compose

docker compose up --scale <service>=<n>

Traefik

• https://traefik.io/traefik/
• https://github.com/traefik/traefik
• https://github.com/ondrejsika/ondrejsika-docker-traefik
• https://doc.traefik.io/traefik/reference/dynamic-configuration/docker/

Docker Compose Override

If you want override your docker-compose.yml, you can use -f param for multiple compose files. You can also create docker-compose.override.yml which will be used automatically.

See compose-override example.

Podman

Podman shortnames.conf

Shortnames project is collecting registry alias names for shortnames to fully specified container image names.

https://github.com/containers/shortnames/blob/main/shortnames.conf

See your shortnames

cat /etc/containers/registries.conf.d/shortnames.conf

Thank you! & Questions?

That's it. Do you have any questions? Let's go for a beer!

Ondrej Sika

• email: ondrej@sika.io
• web: https://sika.io
• twitter: @ondrejsika
• linkedin: /in/ondrejsika/
• Newsletter, Slack, Facebook & Linkedin Groups: https://join.sika.io

Do you like the course? Write me recommendation on Twitter (with handle @ondrejsika) and LinkedIn (add me /in/ondrejsika and I'll send you request for recommendation). Thanks.

Wanna to go for a beer or do some work together? Just book me :)

Training Sessions

2022-09-22 TTC

• https://github.com/sika-training-examples/2022-09-22--ttc--docker-compose

Docker FAQ

DNS Troubles in Docker Build

If you see something like that, it may be caused by DNS server trouble.

You can check see your DNS server using:

docker run debian cat /etc/resolv.conf

Or check if it works:

docker run ondrejsika/host google.com

You can fix it by setting Google or Cloudflare DNS to /etc/docker/daemon.json:

{ "dns": ["1.1.1.", "8.8.8.8"] }

Lecturer Notes

Download Images before course, prevent slow connections

./pull-images.sh

If you want update list of used images in file images.txt, run ./save-image-list.sh and remove locally built images.