First of all, a quick overview of Docker.

The definition of Docker from Wikipedia:

Docker is a set of platform as a service (PaaS) products that use OS-level virtualization to deliver software in packages called containers. Containers are isolated from one another and bundle their own software, libraries and configuration files; they can communicate with each other through well-defined channels. Because all of the containers share the services of a single operating system kernel, they use fewer resources than virtual machines.

Docker is a container virtualization system used to separate processes and applications from other processes running on the same physical machine.

A container is simply another process on a machine that has been isolated from all other processes on the host machine. This isolation methodology utilizes kernel namespaces and cgroups, features that have been present in Linux for a long time.

What is a container image?

When running a container, it uses an isolated filesystem. This custom filesystem is provided by a container image. Since the image contains the container’s filesystem, it must contain everything needed to run an application – all dependencies, configuration, scripts, binaries, etc.

The image also contains other configuration for the container, such as environment variables, a default command to run, and other metadata.

Docker uses a client-server architecture. The Docker client talks to the Docker daemon, which builds, runs, and distributes your Docker containers.

The Docker client and daemon can run on the same system, or you can connect a Docker client to a remote Docker daemon running on anóther server.

The Docker client and daemon can communicate using a REST API, via UNIX sockets, or via a network interface.

Docker Compose is a special type of Docker client that lets you work with applications consisting of a set of containers.

The Docker daemon

The Docker daemon (dockerd) listens for Docker API requests and manages the Docker objects such as images, containers, networks, and volumes.

The dockerd daemon can also communicate with other daemons to manage Docker services.

root@asus:~# ps -ef | grep dockerd
root 877 1 0 13:01 ? 00:00:00 /usr/bin/dockerd -H fd:// –containerd=/run/containerd/containerd.sock
root 3196 2308 0 13:05 pts/0 00:00:00 grep –color=auto dockerd
root@asus:~#

The Docker client

The Docker client (docker) is the main way Docker users interact with Docker.

Docker commands such as docker run are sent by the docker client to dockerd, which executes them. The docker command uses the Docker API. The Docker client can communicate with more than one daemon.

Docker Hub Registry

The Docker Hub registry is a public registry which stores Docker images that anyone can use.

Docker is configured to search for and pull images from Docker Hub by default.

However, you can also run your own private Docker registry.

When you use the docker pull or docker run commands, the required images are pulled from the registry you have specified in your configuration.

And when you use the docker push command, your image is pushed to your configured registry.

Docker objects

When you use Docker, you are creating and using images, containers, networks, volumes, plugins, and other objects.

Images

An image is a read-only template with instructions for creating a Docker container.

An image can also be based on another image, with additional customization. For example, you may build an image based on the ubuntu image, but which installs the Apache web server and also your own web application, as well as the configuration details needed to make your application run correctly.

You might create your own images or you might only use those created by others and published in a registry.

To build your own image, you create a Dockerfile which defines the steps needed to create the image and run it.

Each instruction in a Dockerfile creates a layer in the image.

When you change the Dockerfile and rebuild the image, only those layers which have changed are rebuilt.

This methodology enables Docker images to be lightweight, small, and fast, compared to other virtualization technologies.

Containers

A container is a runnable instance of an image.

You can create, start, stop, move, or delete a container using the Docker API or CLI.

You can connect a container to one or more networks, attach it to storage, or even create a new image based on its current state.

By default, a container is isolated from other containers and from its host machine.

You can specify the level of isolation from a container’s network, storage, or other underlying subsystems, from other containers or from the host machine.

A container is defined by its image as well as any configuration options you specify when you create or start it.

Note that when a container is removed, any changes to its state that are not stored in persistent storage will disappear.

Example docker run command

The following command runs a Linux Ubuntu container, then attaches interactively to your local command-line session, and then runs a /bin/bash shell.

$ docker run -i -t ubuntu /bin/bash

When you run this command, this is what happens:

If the ubuntu image is not already locally present, Docker pulls it from your configured registry, as though you had run docker pull ubuntu manually.

Docker then creates a new container, as though you had run a manual docker container create command.

Docker allocates a read-write filesystem to the container, as its final layer.

This allows a running container to create or modify files and directories in its local filesystem.

Docker then creates a network interface to connect the container to the default network, since you did not specify any networking options. This includes assigning an IP address to the container.

By default, containers can connect to external networks using the host machine’s network connection.

Next, Docker starts the container and executes /bin/bash.

Because the container is running interactively and attached to your terminal (due to the -i and -t flags), you can provide input using your keyboard while the output is logged to your terminal.

When you type exit to terminate the /bin/bash command, the container stops but is not removed. You can start it again or remove it.

You can obtain Docker from the standard Ubuntu 20.04 repositories, but the version may not always be the latest or the one you want.

The procedure for installing Docker

The steps are:

update the system packages index
enable the Docker repository
import the repository GPG key
then install the package.

sudo apt update
sudo apt install apt-transport-https ca-certificates curl gnupg-agent software-properties-common

root@asus:/# apt install apt-transport-https ca-certificates curl gnupg-agent software-properties-common
Reading package lists… Done
Building dependency tree
Reading state information… Done
ca-certificates is already the newest version (20210119~20.10.1).
ca-certificates set to manually installed.
curl is already the newest version (7.68.0-1ubuntu4.3).
software-properties-common is already the newest version (0.99.3.1).
apt-transport-https is already the newest version (2.1.10ubuntu0.3).
The following NEW packages will be installed:
gnupg-agent
0 upgraded, 1 newly installed, 0 to remove and 5 not upgraded.
Need to get 5.232 B of archives.
After this operation, 46,1 kB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 http://de.archive.ubuntu.com/ubuntu groovy-updates/universe amd64 gnupg-agent all 2.2.20-1ubuntu1.1 [5.232 B]
Fetched 5.232 B in 0s (32,6 kB/s)
Selecting previously unselected package gnupg-agent.
(Reading database … 214639 files and directories currently installed.)
Preparing to unpack …/gnupg-agent_2.2.20-1ubuntu1.1_all.deb …
Unpacking gnupg-agent (2.2.20-1ubuntu1.1) …
Setting up gnupg-agent (2.2.20-1ubuntu1.1) …
root@asus:/#

Import the repository’s GPG key using the curl command:

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | apt-key add –

root@asus:~# curl -fsSL https://download.docker.com/linux/ubuntu/gpg | apt-key add –
Warning: apt-key is deprecated. Manage keyring files in trusted.gpg.d instead (see apt-key(8)).
OK
root@asus:~#

Add the Docker APT repository to the system:

add-apt-repository “deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable”

root@asus:~# add-apt-repository “deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable”
Repository: ‘deb [arch=amd64] https://download.docker.com/linux/ubuntu groovy stable’
Description:
Archive for codename: groovy components: stable
More info: https://download.docker.com/linux/ubuntu
Adding repository.
Press [ENTER] to continue or Ctrl-c to cancel.
Adding deb entry to /etc/apt/sources.list.d/archive_uri-https_download_docker_com_linux_ubuntu-groovy.list
Adding disabled deb-src entry to /etc/apt/sources.list.d/archive_uri-https_download_docker_com_linux_ubuntu-groovy.list
Hit:1 http://de.archive.ubuntu.com/ubuntu groovy InRelease
Get:2 http://de.archive.ubuntu.com/ubuntu groovy-updates InRelease [115 kB]
Ign:3 htt
… … …

security.ubuntu.com/ubuntu groovy-security/main amd64 DEP-11 Metadata [18,9 kB]
Get:24 http://security.ubuntu.com/ubuntu groovy-security/universe amd64 DEP-11 Metadata [4.628 B]
Reading package lists… Done
E: The repository ‘http://ppa.launchpad.net/alexlarsson/flatpak/ubuntu groovy Release’ does not have a Release file.
N: Updating from such a repository can’t be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
root@asus:~#

Now the Docker repository is enabled, you can install any Docker version available in the repositories.

To install the latest version of Docker, run the commands below. If you want to install a specific Docker version, skip this step and go to the next one.

sudo apt update
sudo apt install docker-ce docker-ce-cli containerd.io

root@asus:~# apt install docker-ce docker-ce-cli containerd.io
Reading package lists… Done
Building dependency tree
Reading state information… Done
The following additional packages will be installed:
docker-ce-rootless-extras docker-scan-plugin git git-man liberror-perl pigz slirp4netns
Suggested packages:
aufs-tools cgroupfs-mount | cgroup-lite git-daemon-run | git-daemon-sysvinit git-doc git-el git-email git-gui gitk gitweb git-cvs
git-mediawiki git-svn
The following NEW packages will be installed:
containerd.io docker-ce docker-ce-cli docker-ce-rootless-extras docker-scan-plugin git git-man liberror-perl pigz slirp4netns
0 upgraded, 10 newly installed, 0 to remove and 6 not upgraded.
Need to get 113 MB of archives.
After this operation, 508 MB of additional disk space will be used.
Do you want to continue? [Y/n] y

… … ..

Selecting previously unselected package git.
Preparing to unpack …/8-git_1%3a2.27.0-1ubuntu1.1_amd64.deb …
Unpacking git (1:2.27.0-1ubuntu1.1) …
Selecting previously unselected package slirp4netns.
Preparing to unpack …/9-slirp4netns_1.0.1-1_amd64.deb …
Unpacking slirp4netns (1.0.1-1) …
Setting up slirp4netns (1.0.1-1) …
Setting up docker-scan-plugin (0.8.0~ubuntu-groovy) …
Setting up liberror-perl (0.17029-1) …
Setting up containerd.io (1.4.6-1) …
Created symlink /etc/systemd/system/multi-user.target.wants/containerd.service → /lib/systemd/system/containerd.service.
Setting up docker-ce-cli (5:20.10.7~3-0~ubuntu-groovy) …
Setting up pigz (2.4-1) …
Setting up git-man (1:2.27.0-1ubuntu1.1) …
Setting up docker-ce-rootless-extras (5:20.10.7~3-0~ubuntu-groovy) …
Setting up docker-ce (5:20.10.7~3-0~ubuntu-groovy) …
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.
Setting up git (1:2.27.0-1ubuntu1.1) …
Processing triggers for man-db (2.9.3-2) …
Processing triggers for systemd (246.6-1ubuntu1.4) …
root@asus:~#

Once the installation is completed, the Docker service will start automatically.

Verify:

systemctl status docker

root@asus:~# systemctl status docker
● docker.service – Docker Application Container Engine
Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
Active: active (running) since Wed 2021-06-30 22:58:36 CEST; 9min ago
TriggeredBy: ● docker.socket
Docs: https://docs.docker.com
Main PID: 1718018 (dockerd)
Tasks: 16
Memory: 44.9M
CGroup: /system.slice/docker.service
└─1718018 /usr/bin/dockerd -H fd:// –containerd=/run/containerd/containerd.sock

Jun 30 22:58:36 asus dockerd[1718018]: time=”2021-06-30T22:58:36.752582946+02:00″ level=warning msg=”Your kernel does not support CPU realtime sc>
Jun 30 22:58:36 asus dockerd[1718018]: time=”2021-06-30T22:58:36.752632979+02:00″ level=warning msg=”Your kernel does not support cgroup blkio we>
Jun 30 22:58:36 asus dockerd[1718018]: time=”2021-06-30T22:58:36.752640243+02:00″ level=warning msg=”Your kernel does not support cgroup blkio we>
Jun 30 22:58:36 asus dockerd[1718018]: time=”2021-06-30T22:58:36.752809760+02:00″ level=info msg=”Loading containers: start.”
Jun 30 22:58:36 asus dockerd[1718018]: time=”2021-06-30T22:58:36.856955079+02:00″ level=info msg=”Default bridge (docker0) is assigned with an IP>
Jun 30 22:58:36 asus dockerd[1718018]: time=”2021-06-30T22:58:36.918027046+02:00″ level=info msg=”Loading containers: done.”
Jun 30 22:58:36 asus dockerd[1718018]: time=”2021-06-30T22:58:36.940673725+02:00″ level=info msg=”Docker daemon” commit=b0f5bc3 graphdriver(s)=ov>
Jun 30 22:58:36 asus dockerd[1718018]: time=”2021-06-30T22:58:36.940830529+02:00″ level=info msg=”Daemon has completed initialization”
Jun 30 22:58:36 asus systemd[1]: Started Docker Application Container Engine.
Jun 30 22:58:36 asus dockerd[1718018]: time=”2021-06-30T22:58:36.973960760+02:00″ level=info msg=”API listen on /run/docker.sock”
root@asus:~#

To prevent the Docker package from being updated, mark it as held back:

sudo apt-mark hold docker-ce

To execute Docker Commands as a Non-Root User:

By default, only root and user with sudo privileges can execute Docker commands.

To execute Docker commands as non-root user, add the user to the docker group that was created during the installation of the Docker CE package:

sudo usermod -aG docker $USER

root@asus:~#
root@asus:~# usermod -aG docker kevin
root@asus:~#
root@asus:~#
root@asus:~# usermod -aG docker root
root@asus:~#

Log out and log back in to refresh the group membership.

To verify Docker is successfully installed and that you can execute docker commands, run a test container:

docker container run hello-world

This command downloads the test image, if it is not found locally, then runs it in a container, which prints a “Hello from Docker” message, and then exits:

root@asus:/home/kevin# docker container run hello-world
Unable to find image ‘hello-world:latest’ locally
latest: Pulling from library/hello-world
b8dfde127a29: Pulling fs layer
b8dfde127a29: Pull complete
Digest: sha256:9f6ad537c5132bcce57f7a0a20e317228d382c3cd61edae14650eec68b2b345c
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/

root@asus:/home/kevin#

Note the container will stop after printing the message because it does not contain a long-running process.

By default, Docker always pulls images from the Docker Hub. This is a cloud-based registry which stores Docker images in public or private repositories.

root@asus:/home/kevin# docker run -it ubuntu bash
Unable to find image ‘ubuntu:latest’ locally
latest: Pulling from library/ubuntu
c549ccf8d472: Pull complete
Digest: sha256:aba80b77e27148d99c034a987e7da3a287ed455390352663418c0f2ed40417fe
Status: Downloaded newer image for ubuntu:latest
root@f152766a2e6d:/#
root@f152766a2e6d:/#
root@f152766a2e6d:/#
root@f152766a2e6d:/#
root@f152766a2e6d:/# whoami
root
root@f152766a2e6d:/# ls
bin boot dev etc home lib lib32 lib64 libx32 media mnt opt proc root run sbin srv sys tmp usr var
root@f152766a2e6d:/#
root@f152766a2e6d:/# df -h
Filesystem Size Used Avail Use% Mounted on
overlay 395G 152G 224G 41% /
tmpfs 64M 0 64M 0% /dev
tmpfs 8.8G 0 8.8G 0% /sys/fs/cgroup
shm 64M 0 64M 0% /dev/shm
/dev/nvme0n1p4 395G 152G 224G 41% /etc/hosts
tmpfs 8.8G 0 8.8G 0% /proc/asound
tmpfs 8.8G 0 8.8G 0% /proc/acpi
tmpfs 8.8G 0 8.8G 0% /proc/scsi
tmpfs 8.8G 0 8.8G 0% /sys/firmware
root@f152766a2e6d:/#

you are now inside a docker container!

Uninstalling Docker

Before uninstalling Docker you should first remove all containers, images, volumes, and docker networks.

Run the following commands to stop all running containers and remove all docker objects:

docker container stop $(docker container ls -aq)

docker system prune -a –volumes

You can now uninstall Docker as any other package installed with apt:

sudo apt purge docker-ce
sudo apt autoremove

Using Docker Images to Deploy Containers

Docker images are templates containing instructions and specifications for creating a container.

To use Docker, you need to obtain an image or else create your own by building a dockerfile.

Listing Images

To list all the docker images on your system, use:

docker images

root@asus:~# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
ubuntu latest 9873176a8ff5 12 days ago 72.7MB
hello-world latest d1165f221234 3 months ago 13.3kB
root@asus:~#

Finding an Image

Images are stored on Docker registries, such as Docker Hub (Docker’s official registry).

You can browse the images on the registry or use the following command to search the Docker registry.

Replace [keyword] with the keyword you are searching for, such as nginx or apache.

docker search [keyword]

root@asus:~# docker search apache
NAME DESCRIPTION STARS OFFICIAL AUTOMATED
httpd The Apache HTTP Server Project 3566 [OK]
tomcat Apache Tomcat is an open source implementati… 3060 [OK]
maven Apache Maven is a software project managemen… 1221 [OK]
apache/airflow Apache Airflow 260
apache/nifi Unofficial convenience binaries and Docker i… 218 [OK]
apache/zeppelin Apache Zeppelin 147 [OK]
eboraas/apache-php PHP on Apache (with SSL/TLS support), built … 144 [OK]
eboraas/apache Apache (with SSL/TLS support), built on Debi… 92 [OK]
apacheignite/ignite Apache Ignite – Distributed Database 78 [OK]
nimmis/apache-php5 This is docker images of Ubuntu 14.04 LTS wi… 69 [OK]
apache/skywalking-oap-server Apache SkyWalking OAP Server 68
bitnami/apache Bitnami Apache Docker Image 67 [OK]
apache/superset Apache Superset 50
apachepulsar/pulsar Apache Pulsar – Distributed pub/sub messagin… 42
linuxserver/apache An Apache container, brought to you by Linux… 28
antage/apache2-php5 Docker image for running Apache 2.x with PHP… 24 [OK]
apache/nutch Apache Nutch 23 [OK]
webdevops/apache Apache container 15 [OK]
apache/tika Apache Tika Server – the content analysis to… 8
newdeveloper/apache-php apache-php7.2 8
newdeveloper/apache-php-composer apache-php-composer 7
lephare/apache Apache container 6 [OK]
apache/fineract Apache Fineract 3
secoresearch/apache-varnish Apache+PHP+Varnish5.0 2 [OK]
apache/arrow-dev Apache Arrow convenience images for developm… 1
root@asus:~#

root@asus:~# docker search ubuntu
NAME DESCRIPTION STARS OFFICIAL AUTOMATED
ubuntu Ubuntu is a Debian-based Linux operating sys… 12453 [OK]
dorowu/ubuntu-desktop-lxde-vnc Docker image to provide HTML5 VNC interface … 544 [OK]
websphere-liberty WebSphere Liberty multi-architecture images … 274 [OK]
rastasheep/ubuntu-sshd Dockerized SSH service, built on top of offi… 254 [OK]
consol/ubuntu-xfce-vnc Ubuntu container with “headless” VNC session… 241 [OK]
ubuntu-upstart Upstart is an event-based replacement for th… 111 [OK]
ansible/ubuntu14.04-ansible Ubuntu 14.04 LTS with ansible 98 [OK]
1and1internet/ubuntu-16-nginx-php-phpmyadmin-mysql-5 ubuntu-16-nginx-php-phpmyadmin-mysql-5 50 [OK]
ubuntu-debootstrap debootstrap –variant=minbase –components=m… 44 [OK]
i386/ubuntu Ubuntu is a Debian-based Linux operating sys… 25
nuagebec/ubuntu Simple always updated Ubuntu docker images w… 24 [OK]
1and1internet/ubuntu-16-apache-php-5.6 ubuntu-16-apache-php-5.6 14 [OK]
1and1internet/ubuntu-16-apache-php-7.0 ubuntu-16-apache-php-7.0 13 [OK]
eclipse/ubuntu_jdk8 Ubuntu, JDK8, Maven 3, git, curl, nmap, mc, … 13 [OK]
1and1internet/ubuntu-16-nginx-php-phpmyadmin-mariadb-10 ubuntu-16-nginx-php-phpmyadmin-mariadb-10 11 [OK]
1and1internet/ubuntu-16-nginx-php-5.6-wordpress-4 ubuntu-16-nginx-php-5.6-wordpress-4 9 [OK]
1and1internet/ubuntu-16-apache-php-7.1 ubuntu-16-apache-php-7.1 7 [OK]
darksheer/ubuntu Base Ubuntu Image — Updated hourly 5 [OK]
1and1internet/ubuntu-16-nginx-php-7.0 ubuntu-16-nginx-php-7.0 4 [OK]
owncloud/ubuntu ownCloud Ubuntu base image 3
1and1internet/ubuntu-16-nginx-php-7.1-wordpress-4 ubuntu-16-nginx-php-7.1-wordpress-4 3 [OK]
smartentry/ubuntu ubuntu with smartentry 1 [OK]
1and1internet/ubuntu-16-php-7.1 ubuntu-16-php-7.1 1 [OK]
1and1internet/ubuntu-16-sshd ubuntu-16-sshd 1 [OK]
1and1internet/ubuntu-16-rspec ubuntu-16-rspec 0 [OK]
root@asus:~#

Starting a Container

To start a Docker container use:

docker start [ID]

replacing [ID] with the container ID corresponding with the container you want to start.

Stopping a Container

To stop a Docker container, replace [ID] with the container ID corresponding with the container you wish to stop:

docker stop [ID]

Removing a Container

To remove a Docker container, replace [ID] with the container ID corresponding with the container you wish to remove:

docker rm [ID]

Obtaining an Image

Once you find an image, you can download it to your server using the “docker pull” command. Replace [image] with the name of the image you’d like to use:

docker pull [image]

For instance, to pull the official nginx image:

docker pull nginx

Running an Image

To create a container based on an image, use the “docker run” command. Replace [image] with the name of the image you’d like to use.

docker run [image]

If the image hasn’t yet been downloaded and is available in the Docker registry, then the image will automatically be pulled to your server.

Managing Docker Containers

Listing Containers

To list all active (and inactive) Docker containers running on your system, run the following command:

docker ps -a

You should see something like the following:

root@asus:~# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
b5d96e61c851 ubuntu “bash” 5 minutes ago Up 5 minutes interesting_rhodes
f152766a2e6d ubuntu “bash” 25 minutes ago Exited (0) 16 minutes ago vigorous_hypatia
64b484e8e343 hello-world “/hello” 28 minutes ago Exited (0) 28 minutes ago infallible_gagarin
root@asus:~#

kevin@asus:~$ sudo su
root@asus:/home/kevin# docker version
Client: Docker Engine – Community
Version: 20.10.7
API version: 1.41
Go version: go1.13.15
Git commit: f0df350
Built: Wed Jun 2 11:56:41 2021
OS/Arch: linux/amd64
Context: default
Experimental: true

Server: Docker Engine – Community
Engine:
Version: 20.10.7
API version: 1.41 (minimum version 1.12)
Go version: go1.13.15
Git commit: b0f5bc3
Built: Wed Jun 2 11:54:53 2021
OS/Arch: linux/amd64
Experimental: false
containerd:
Version: 1.4.6
GitCommit: d71fcd7d8303cbf684402823e425e9dd2e99285d
runc:
Version: 1.0.0-rc95
GitCommit: b9ee9c6314599f1b4a7f497e1f1f856fe433d3b7
docker-init:
Version: 0.19.0
GitCommit: de40ad0
root@asus:/home/kevin#

The official Docker Hub registry is at:

https://hub.docker.com/_/node

and download the node image:

docker pull node

root@asus:/home/kevin# docker pull node
Using default tag: latest
latest: Pulling from library/node
0bc3020d05f1: Pull complete
a110e5871660: Pull complete
83d3c0fa203a: Pull complete
a8fd09c11b02: Pull complete
14feb89c4a52: Pull complete
612a5de913f3: Pull complete
b86d81a99d41: Pull complete
5dd61d4ad9e8: Pull complete
7aae82345965: Pull complete
Digest: sha256:ca6daf1543242acb0ca59ff425509eab7defb9452f6ae07c156893db06c7a9a4
Status: Downloaded newer image for node:latest
docker.io/library/node:latest
root@asus:/home/kevin#

root@asus:~# docker image ls
REPOSITORY TAG IMAGE ID CREATED SIZE
node latest 7105279fa2ab 8 days ago 908MB
ubuntu latest 9873176a8ff5 13 days ago 72.7MB
docker/getting-started latest 083d7564d904 2 weeks ago 28MB
hello-world latest d1165f221234 3 months ago 13.3kB
root@asus:~#

docker run node

root@asus:/home/kevin# docker info
Client:
Context: default
Debug Mode: false
Plugins:
app: Docker App (Docker Inc., v0.9.1-beta3)
buildx: Build with BuildKit (Docker Inc., v0.5.1-docker)
scan: Docker Scan (Docker Inc., v0.8.0)

Server:
Containers: 9
Running: 1
Paused: 0
Stopped: 8
Images: 4
Server Version: 20.10.7
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: io.containerd.runc.v2 io.containerd.runtime.v1.linux runc
Default Runtime: runc
Init Binary: docker-init
containerd version: d71fcd7d8303cbf684402823e425e9dd2e99285d
runc version: b9ee9c6314599f1b4a7f497e1f1f856fe433d3b7
init version: de40ad0
Security Options:
apparmor
seccomp
Profile: default
Kernel Version: 5.8.0-59-generic
Operating System: Ubuntu 20.10
OSType: linux
Architecture: x86_64
CPUs: 8
Total Memory: 17.59GiB
Name: asus
ID: WFX5:GZ5T:UHPK:VCR6:EHQU:DCCE:JTHA:U5SD:GWFE:XJJ5:QVJ6:RMXA
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

root@asus:/home/kevin#

To install a Jenkins container:

root@asus:~#
root@asus:~# docker pull jenkins/jenkins
Using default tag: latest
latest: Pulling from jenkins/jenkins
0bc3020d05f1: Already exists
ee3587ec32c3: Pull complete
0bd0b3e8a1ee: Pull complete
7b5615a9059c: Pull complete
62980ab719b4: Pull complete
ee9399291836: Pull complete
1a40e67771e3: Pull complete
ee53ed120856: Pull complete
34f2dd2cbb3e: Pull complete
70625628bb19: Pull complete
52967d83ef48: Pull complete
488b4fe169de: Pull complete
bd260a926aeb: Pull complete
32d7feae958e: Pull complete
a8fd2466ac4c: Pull complete
c7bfa4fe9cd5: Pull complete
Digest: sha256:443a28765cdd2133c0e816ef8d9f25c4c1e32b79b5aa1b9d2002a2f815a122bd
Status: Downloaded newer image for jenkins/jenkins:latest
docker.io/jenkins/jenkins:latest
root@asus:~# docker run -p 8080:8080 -p 50000:50000 jenkins
Unable to find image ‘jenkins:latest’ locally
docker: Error response from daemon: manifest for jenkins:latest not found: manifest unknown: manifest unknown.
See ‘docker run –help’.
root@asus:~# docker run -p 8080:8080 -p 50000:50000 jenkins/jenkins
Running from: /usr/share/jenkins/jenkins.war
webroot: EnvVars.masterEnvVars.get(“JENKINS_HOME”)
2021-07-01 17:06:24.542+0000 [id=1] INFO org.eclipse.jetty.util.log.Log#initialized: Logging initialized @308ms to org.eclipse.jetty.util.log.JavaUtilLog
2021-07-01 17:06:24.668+0000 [id=1] INFO winstone.Logger#logInternal: Beginning extraction from war file
2021-07-01 17:06:25.742+0000 [id=1] WARNING o.e.j.s.handler.ContextHandler#setContextPath: Empty contextPath
2021-07-01 17:06:25.802+0000 [id=1] INFO org.eclipse.jetty.server.Server#doStart: jetty-9.4.41.v20210516; built: 2021-05-16T23:56:28.993Z; git: 98607f93c7833e7dc59489b13f3cb0a114fb9f4c; jvm 1.8.0_292-b10
2021-07-01 17:06:26.053+0000 [id=1] INFO o.e.j.w.StandardDescriptorProcessor#visitServlet: NO JSP Support for /, did not find org.eclipse.jetty.jsp.JettyJspServlet
2021-07-01 17:06:26.118+0000 [id=1] INFO o.e.j.s.s.DefaultSessionIdManager#doStart: DefaultSessionIdManager workerName=node0
2021-07-01 17:06:26.118+0000 [id=1] INFO o.e.j.s.s.DefaultSessionIdManager#doStart: No SessionScavenger set, using defaults
2021-07-01 17:06:26.120+0000 [id=1] INFO o.e.j.server.session.HouseKeeper#startScavenging: node0 Scavenging every 600000ms
2021-07-01 17:06:26.496+0000 [id=1] INFO hudson.WebAppMain#contextInitialized: Jenkins home directory: /var/jenkins_home found at: EnvVars.masterEnvVars.get(“JENKINS_HOME”)
2021-07-01 17:06:26.605+0000 [id=1] INFO o.e.j.s.handler.ContextHandler#doStart: Started w.@677dbd89{Jenkins v2.300,/,file:///var/jenkins_home/war/,AVAILABLE}{/var/jenkins_home/war}
2021-07-01 17:06:26.621+0000 [id=1] INFO o.e.j.server.AbstractConnector#doStart: Started ServerConnector@624ea235{HTTP/1.1, (http/1.1)}{0.0.0.0:8080}
2021-07-01 17:06:26.622+0000 [id=1] INFO org.eclipse.jetty.server.Server#doStart: Started @2388ms
2021-07-01 17:06:26.623+0000 [id=23] INFO winstone.Logger#logInternal: Winstone Servlet Engine running: controlPort=disabled
2021-07-01 17:06:27.860+0000 [id=30] INFO jenkins.InitReactorRunner$1#onAttained: Started initialization
2021-07-01 17:06:27.884+0000 [id=29] INFO jenkins.InitReactorRunner$1#onAttained: Listed all plugins
2021-07-01 17:06:29.130+0000 [id=32] INFO jenkins.InitReactorRunner$1#onAttained: Prepared all plugins
2021-07-01 17:06:29.135+0000 [id=32] INFO jenkins.InitReactorRunner$1#onAttained: Started all plugins
2021-07-01 17:06:29.143+0000 [id=32] INFO jenkins.InitReactorRunner$1#onAttained: Augmented all extensions
2021-07-01 17:06:29.911+0000 [id=34] INFO jenkins.InitReactorRunner$1#onAttained: System config loaded
2021-07-01 17:06:29.912+0000 [id=30] INFO jenkins.InitReactorRunner$1#onAttained: System config adapted
2021-07-01 17:06:29.912+0000 [id=41] INFO jenkins.InitReactorRunner$1#onAttained: Loaded all jobs
2021-07-01 17:06:29.913+0000 [id=37] INFO jenkins.InitReactorRunner$1#onAttained: Configuration for all jobs updated
2021-07-01 17:06:30.027+0000 [id=56] INFO hudson.model.AsyncPeriodicWork#lambda$doRun$0: Started Download metadata
2021-07-01 17:06:30.036+0000 [id=56] INFO hudson.util.Retrier#start: Attempt #1 to do the action check updates server
2021-07-01 17:06:30.384+0000 [id=43] INFO jenkins.install.SetupWizard#init:

*************************************************************
*************************************************************
*************************************************************

Jenkins initial setup is required. An admin user has been created and a password generated.
Please use the following password to proceed to installation:

735f090fba884ee780f97e67ff2ad0bd

This may also be found at: /var/jenkins_home/secrets/initialAdminPassword

*************************************************************
*************************************************************
*************************************************************

2021-07-01 17:06:45.324+0000 [id=28] INFO jenkins.InitReactorRunner$1#onAttained: Completed initialization
2021-07-01 17:06:45.337+0000 [id=22] INFO hudson.WebAppMain$3#run: Jenkins is fully up and running
2021-07-01 17:06:45.634+0000 [id=56] INFO h.m.DownloadService$Downloadable#load: Obtained the updated data file for hudson.tasks.Maven.MavenInstaller
2021-07-01 17:06:45.634+0000 [id=56] INFO hudson.util.Retrier#start: Performed the action check updates server successfully at the attempt #1
2021-07-01 17:06:45.637+0000 [id=56] INFO hudson.model.AsyncPeriodicWork#lambda$doRun$0: Finished Download metadata. 15,609 ms

The official site for Docker hub is https://www.docker.com/community-edition#/add_ons

browse and find the Jenkins image.

then on your host machine enter:

docker pull jenkins/jenkins

(this is the copypasted command from the hub jenkins page)

To run Jenkins, you need to run the following command −

sudo docker run -p 8080:8080 -p 50000:50000 jenkins/jenkins

Note the following points about the above sudo command −

We are using the sudo command to ensure it runs with root access.

Here, jenkins/jenkins is the name of the image we want to download from Docker hub and install on our Ubuntu machine.

-p is used to map the port number of the internal Docker image to our main Ubuntu server so that we can access the container accordingly.

You will then have Jenkins successfully running as a container on the Ubuntu machine.