Please visit this page for more details on how to install Docker Engine - Community for Ubuntu: https://docs.docker.com/install/linux/docker-ce/ubuntu/

• Check if Docker was already installed:
  $ sudo apt list --installed | grep docker docker-ce/bionic,now 5:19.03.12~3-0~ubuntu-bionic amd64 [installed] docker-ce-cli/bionic,now 5:19.03.12~3-0~ubuntu-bionic amd64 [installed]
  $ sudo apt list --installed | grep containerd containerd.io/bionic,now 1.2.13-2 amd64 [installed]
  You might have Docker installed with different package names: docker, docker.io , or docker-engine
  
  
• To uninstall an existing installation of Docker:
  $ sudo apt remove docker* containerd*
  [Optional] Delete Docker data folder:
  $ sudo rm -rf /var/lib/docker
  [Optional] Delete Docker custom configuration folder:
  $ sudo rm -rf /etc/docker/
  [Optional] Delete docker command configuration folder:
  $ rm -rf ~/.docker/

• Update the apt package index:
  $ sudo apt update
  
• [Optional] Install packages to allow apt to use a repository over HTTPS:
  $ sudo apt install \ apt-transport-https \ ca-certificates \ curl \ gnupg-agent \ software-properties-common
  
• Add Docker’s official GPG key:
  $ curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
  
• Set up the repository:
  $ sudo add-apt-repository \ "deb [arch=amd64] https://download.docker.com/linux/ubuntu \ $(lsb_release -cs) \ stable"
  
• Update the apt package index:
  $ sudo apt update
  
• Install the latest version of Docker Engine - Community and containerd:
  $ sudo apt install docker-ce docker-ce-cli containerd.io The following NEW packages will be installed: aufs-tools cgroupfs-mount containerd.io docker-ce docker-ce-cli pigz Get:1 https://download.docker.com/linux/ubuntu bionic/stable amd64 containerd.io amd64 1.2.10-3 [20.0 MB] Get:2 http://ca.archive.ubuntu.com/ubuntu bionic/universe amd64 pigz amd64 2.4-1 [57.4 kB] Get:3 http://ca.archive.ubuntu.com/ubuntu bionic/universe amd64 aufs-tools amd64 1:4.9+20170918-1ubuntu1 [104 kB] Get:4 http://ca.archive.ubuntu.com/ubuntu bionic/universe amd64 cgroupfs-mount all 1.4 [6,320 B] Get:5 https://download.docker.com/linux/ubuntu bionic/stable amd64 docker-ce-cli amd64 5:19.03.12~3-0~ubuntu-bionic [42.5 MB] Get:6 https://download.docker.com/linux/ubuntu bionic/stable amd64 docker-ce amd64 5:19.03.12~3-0~ubuntu-bionic [22.8 MB] Created symlink /etc/systemd/system/multi-user.target.wants/containerd.service → /lib/systemd/system/containerd.service. Created symlink /etc/systemd/system/multi-user.target.wants/docker.service → /lib/systemd/system/docker.service. Created symlink /etc/systemd/system/sockets.target.wants/docker.socket → /lib/systemd/system/docker.socket.

• Check installed packages:
  $ sudo apt list --installed | grep docker docker-ce/bionic,now 5:19.03.12~3-0~ubuntu-bionic amd64 [installed] docker-ce-cli/bionic,now 5:19.03.12~3-0~ubuntu-bionic amd64 [installed]
  $ sudo apt list --installed | grep containerd containerd.io/bionic,now 1.2.10-3 amd64 [installed]
  
• Check Docker daemon (dockerd server):
  $ ps -ef | grep docker root 12269 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock
  
• Check Docker service:
  $ sudo systemctl status docker ● docker.service - Docker Application Container Engine Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled) Active: active (running) Docs: https://docs.docker.com Main PID: 12269 (dockerd) Tasks: 17 CGroup: /system.slice/docker.service └─12269 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock dockerd[12269]: level=warning msg="Your kernel does not support swap memory limit" dockerd[12269]: level=warning msg="Your kernel does not support cgroup rt period" dockerd[12269]: level=warning msg="Your kernel does not support cgroup rt runtime" dockerd[12269]: level=info msg="Default bridge (docker0) is assigned with an IP address 172.17.0.0/16. Daemon option dockerd[12269]: level=info msg="Docker daemon" commit=633a0ea838 graphdriver(s)=overlay2 version=19.03.12 dockerd[12269]: level=info msg="API listen on /var/run/docker.sock"
  
• Check containerd Service:
  $ sudo systemctl status containerd ● containerd.service - containerd container runtime Loaded: loaded (/lib/systemd/system/containerd.service; enabled; vendor preset: enabled) Active: active (running) Docs: https://containerd.io Main PID: 11992 (containerd) Tasks: 19 CGroup: /system.slice/containerd.service └─11992 /usr/bin/containerd containerd[11992]: level=info msg=serving... address="/run/containerd/containerd.sock"

• Check Docker Version:
  $ sudo docker version Client: Docker Engine - Community Version: 19.03.12 API version: 1.40 Go version: go1.13.10 Git commit: 48a66213fe Built: Mon Jun 22 15:45:36 2020 OS/Arch: linux/amd64 Experimental: false Server: Docker Engine - Community Engine: Version: 19.03.12 API version: 1.40 (minimum version 1.12) Go version: go1.13.10 Git commit: 48a66213fe Built: Mon Jun 22 15:44:07 2020 OS/Arch: linux/amd64 Experimental: false containerd: Version: 1.2.13 GitCommit: 7ad184331fa3e55e52b890ea95e65ba581ae3429 runc: Version: 1.0.0-rc10 GitCommit: dc9208a3303feef5b3839f4323d9beb36df0a9dd docker-init: Version: 0.18.0 GitCommit: fec3683
  
• Print Docker Information:
  $ sudo docker info Client: Debug Mode: false Server: Containers: 0 Running: 0 Paused: 0 Stopped: 0 Images: 0 Server Version: 19.03.12 Storage Driver: overlay2 Backing Filesystem: extfs Supports d_type: true Native Overlay Diff: true Logging Driver: json-file Cgroup Driver: cgroupfs 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 Default Runtime: runc Init Binary: docker-init containerd version: 7ad184331fa3e55e52b890ea95e65ba581ae3429 runc version: dc9208a3303feef5b3839f4323d9beb36df0a9dd init version: fec3683 Security Options: apparmor seccomp Profile: default Kernel Version: 4.15.0-112-generic Operating System: Ubuntu 18.04.4 LTS OSType: linux Architecture: x86_64 CPUs: 8 Total Memory: 31.14GiB Name: nhabti ID: QZBD:C5WE:BJUA:6OFE:3SQF:NOW4:CL3Q:R5C5:LDLY:OVWC:GMA7:VXV3 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
  
• Verify that Docker Engine - Community is installed correctly by running the hello-world image:
  
  The command "docker run hello-world" downloads the hello-world image and runs it in a container.
  When the container runs, it prints a "Hello from Docker!" message and exits.
  
  $ sudo docker run hello-world Unable to find image 'hello-world:latest' locally latest: Pulling from library/hello-world 1b930d010525: Pull complete Digest: sha256:4fe721ccc2e8dc7362278a29dc660d833570ec2682f4e4194f4ee23e415e1064 Status: Downloaded newer image for hello-world:latest Hello from Docker! This message shows that your installation appears to be working correctly. To generate this message, Docker took the following steps: 1. The Docker client contacted the Docker daemon. 2. The Docker daemon pulled the "hello-world" image from the Docker Hub. (amd64) 3. The Docker daemon created a new container from that image which runs the executable that produces the output you are currently reading. 4. The Docker daemon streamed that output to the Docker client, which sent it to your terminal. To try something more ambitious, you can run an Ubuntu container with: $ docker run -it ubuntu bash Share images, automate workflows, and more with a free Docker ID: https://hub.docker.com/ For more examples and ideas, visit: https://docs.docker.com/get-started/

• To Enable/Disable Docker service (start on boot):
  $ sudo systemctl enable docker $ sudo systemctl disable docker
  
• To Start/Stop Docker service:
  $ sudo systemctl start docker $ sudo systemctl stop docker

• Important folders/files:
  /var/lib/docker/
  /etc/docker/key.json
  /lib/systemd/system/docker.service
  /lib/systemd/system/docker.socket
  /lib/systemd/system/containerd.service
  
  $ sudo ls -1 /var/lib/docker/ builder buildkit containers image network overlay2 plugins runtimes swarm tmp trust volumes
  $ cat /lib/systemd/system/docker.service [Unit] Description=Docker Application Container Engine BindsTo=containerd.service After=network-online.target firewalld.service containerd.service Wants=network-online.target Requires=docker.socket [Service] Type=notify # the default is not to use systemd for cgroups because the delegate issues still exists # and systemd currently does not support the cgroup feature set required for containers run by docker ExecStart=/usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock ExecReload=/bin/kill -s HUP $MAINPID TimeoutSec=0 RestartSec=2 Restart=always
  $ cat /lib/systemd/system/docker.socket [Unit] Description=Docker Socket for the API PartOf=docker.service [Socket] ListenStream=/var/run/docker.sock SocketMode=0660 SocketUser=root SocketGroup=docker [Install] WantedBy=sockets.target
  $ cat /lib/systemd/system/containerd.service [Unit] Description=containerd container runtime Documentation=https://containerd.io After=network.target [Service] ExecStartPre=-/sbin/modprobe overlay ExecStart=/usr/bin/containerd KillMode=process Delegate=yes LimitNOFILE=1048576 # Having non-zero Limit*s causes performance problems due to accounting overhead in the kernel. # We recommend using cgroups to do container-local accounting. LimitNPROC=infinity LimitCORE=infinity TasksMax=infinity [Install] WantedBy=multi-user.targe