Docker Installation

https://docs.docker.com/engine/install/

If you follow Docker's official documentation, you'll see that there are installation instructions per Linux distribution, with step-by-step instructions for each one.

Let's be clear about one thing: there's a very easy installation script, but it should only be used in test or development environments; it's not recommended to use this script in production. It downloads the script and runs it directly in the specified shell, in this case bash.

Test the installation with the convenience script on the master machine, for example.

vagrant ssh master to enter the master machine and execute the command below

# Convenience script (development/test only)
curl -fsSL https://get.docker.com | sh
sudo curl -fsSL https://get.docker.com | bash
sudo systemctl start docker
sudo systemctl enable docker
sudo usermod -aG docker vagrant

Check the output with the command

vagrant@worker1:~$ docker system info
Client:
 Context:    default
 Debug Mode: false
 Plugins:
  app: Docker App (Docker Inc., v0.9.1-beta3)
  buildx: Docker Buildx (Docker Inc., v0.8.2-docker)
  compose: Docker Compose (Docker Inc., v2.6.0)
  scan: Docker Scan (Docker Inc., v0.17.0)

Server:
 Containers: 0
  Running: 0
  Paused: 0
  Stopped: 0
 Images: 0
 Server Version: 20.10.17
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Native Overlay Diff: true
  userxattr: false
 Logging Driver: json-file
 Cgroup Driver: cgroupfs
 Cgroup Version: 1
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
 Swarm: inactive
 Runtimes: runc io.containerd.runc.v2 io.containerd.runtime.v1.linux
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 10c12954828e7c7c9b6e0ea9b0c02b01407d3ae1
 runc version: v1.1.2-0-ga916309
 init version: de40ad0
 Security Options:
  apparmor
  seccomp
   Profile: default
 Kernel Version: 5.4.0-120-generic
 Operating System: Ubuntu 20.04.4 LTS
 OSType: linux
 Architecture: x86_64
 CPUs: 2
 Total Memory: 976.6MiB
 Name: worker1.docker-dca.example
 ID: 5ACX:CQ4L:GD3H:LRFV:NM2J:FVJQ:RA2C:NA3W:WWZE:NSXI:TTTZ:VJ53
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 Registry: https://index.docker.io/v1/
 Labels:
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false

WARNING: No swap limit support
vagrant@worker1:~$

On Ubuntu

https://docs.docker.com/engine/install/ubuntu/

Test the installation on the Ubuntu machine as it should be done in a production environment

vagrant ssh worker1 to enter the worker1 machine and execute the command below

 sudo apt-get update
 sudo apt-get install \
    ca-certificates \
    curl \
    gnupg \
    lsb-release

Let's add the Docker repository key to download packages directly from there and then add the repository

 sudo mkdir -p /etc/apt/keyrings
 curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg

 echo \
  "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu \
  $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

After that, it's necessary to update the repository and install Docker, Docker CLI, and containerd.

What is containerd? Containerd is a graduated project at CNCF. It's a container runtime used by Docker itself to create its containers. It's one of the mandatory installation packages for Docker as well as for several others.

What we can understand here is that Docker is a container manager, not an orchestrator, and needs a runtime.

Would it be possible to install only containerd and have container support? Yes. If we install Kubernetes, we don't need to install Docker completely, only the runtime.

# Official Docker package installation
sudo apt-get update
sudo apt-get install docker-ce docker-ce-cli containerd.io docker-compose-plugin

Could we install directly via apt-get install docker from Ubuntu's repository? Yes, you can, but is it correct? NO. So if they ask on the exam, you already know... it shouldn't be done that way.

On Red Hat and CentOS

https://docs.docker.com/engine/install/centos/

epel-release is not necessary, but it's good, as they are essential OS packages.

sudo yum install yum-utils epel-release  -y

If it's CentOS

 sudo yum-config-manager \
    --add-repo \
    https://download.docker.com/linux/centos/docker-ce.repo

If it's Red Hat

sudo yum-config-manager \
    --add-repo \
    https://download.docker.com/linux/rhel/docker-ce.repo

# Docker installation on CentOS/Red Hat
sudo yum install docker-ce docker-ce-cli containerd.io docker-compose-plugin -y

# Start Docker service
sudo systemctl start docker

... notice that it's not very different, only the process of adding repositories and the installation command

Continuation

It's necessary for the user to have permission to run Docker commands without using sudo.

# Add user to docker group
sudo usermod -aG docker $USER

# Enable and start Docker service
sudo systemctl enable docker
sudo systemctl start docker

Parameterization

https://docs.docker.com/config/daemon/ https://docs.docker.com/engine/reference/commandline/dockerd/

Docker daemon parameterization should be done in the file

• Linux: /etc/docker/daemon.json
• Windows: C:\ProgramData\docker\config\daemon.json

These files are not created by default, you need to create them.

All parameterization requires the daemon to be reloaded

# Reload daemon after changes
sudo systemctl daemon-reload

The Docker daemon persists all its data inside

• Linux: /var/lib/docker
• Windows: C:\ProgramData\docker

Below is a configuration showing everything that can be changed. It's just an example.

{
  "allow-nondistributable-artifacts": [],
  "api-cors-header": "",
  "authorization-plugins": [],
  "bip": "",
  "bridge": "",
  "cgroup-parent": "",
  "cluster-advertise": "",
  "cluster-store": "",
  "cluster-store-opts": {},
  "containerd": "/run/containerd/containerd.sock",
  "containerd-namespace": "docker",
  "containerd-plugin-namespace": "docker-plugins",
  "data-root": "",
  "debug": true,
  "default-address-pools": [
    {
      "base": "172.30.0.0/16",
      "size": 24
    },
    {
      "base": "172.31.0.0/16",
      "size": 24
    }
  ],
  "default-cgroupns-mode": "private",
  "default-gateway": "",
  "default-gateway-v6": "",
  "default-runtime": "runc",
  "default-shm-size": "64M",
  "default-ulimits": {
    "nofile": {
      "Hard": 64000,
      "Name": "nofile",
      "Soft": 64000
    }
  },
  "dns": [],
  "dns-opts": [],
  "dns-search": [],
  "exec-opts": [],
  "exec-root": "",
  "experimental": false,
  "features": {},
  "fixed-cidr": "",
  "fixed-cidr-v6": "",
  "group": "",
  "hosts": [],
  "icc": false,
  "init": false,
  "init-path": "/usr/libexec/docker-init",
  "insecure-registries": [],
  "ip": "0.0.0.0",
  "ip-forward": false,
  "ip-masq": false,
  "iptables": false,
  "ip6tables": false,
  "ipv6": false,
  "labels": [],
  "live-restore": true,
  "log-driver": "json-file",
  "log-level": "",
  "log-opts": {
    "cache-disabled": "false",
    "cache-max-file": "5",
    "cache-max-size": "20m",
    "cache-compress": "true",
    "env": "os,customer",
    "labels": "somelabel",
    "max-file": "5",
    "max-size": "10m"
  },
  "max-concurrent-downloads": 3,
  "max-concurrent-uploads": 5,
  "max-download-attempts": 5,
  "mtu": 0,
  "no-new-privileges": false,
  "node-generic-resources": [
    "NVIDIA-GPU=UUID1",
    "NVIDIA-GPU=UUID2"
  ],
  "oom-score-adjust": -500,
  "pidfile": "",
  "raw-logs": false,
  "registry-mirrors": [],
  "runtimes": {
    "cc-runtime": {
      "path": "/usr/bin/cc-runtime"
    },
    "custom": {
      "path": "/usr/local/bin/my-runc-replacement",
      "runtimeArgs": [
        "--debug"
      ]
    }
  },
  "seccomp-profile": "",
  "selinux-enabled": false,
  "shutdown-timeout": 15,
  "storage-driver": "",
  "storage-opts": [],
  "swarm-default-advertise-addr": "",
  "tls": true,
  "tlscacert": "",
  "tlscert": "",
  "tlskey": "",
  "tlsverify": true,
  "userland-proxy": false,
  "userland-proxy-path": "/usr/libexec/docker-proxy",
  "userns-remap": ""
}