I’m sure you must have heard the word Docker being thrown about many times but somewhat got scared of the entire concept. Well, be frightened no more. In this tutorial, we’ll demystify Docker and show you how you can install Docker on Ubuntu 18.04 Bionic Beaver. Docker is a free and open source platform that enables developers to run their applications in containers. Containers are an equivalent of virtual machines only that they are lightweight, more portable and resource friendly in term of CPU and memory usage.
Installing Docker
To get the latest Docker version, it’s recommended that you install Docker from Docker’s official repository. But first, You need to add the GPG key for the official Docker repository to your Ubuntu 18.04 system.
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
Output
Ok
Next, You need to add the Docker repository to APT sources as shown
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"
Next, update your System with Docker packages from the newly added repository
sudo apt-get update
Sample Output
Hit:1 http://us-east-2.ec2.archive.ubuntu.com/ubuntu xenial InRelease Get:2 http://us-east-2.ec2.archive.ubuntu.com/ubuntu xenial-updates InRelease [1 09 kB] Get:3 http://us-east-2.ec2.archive.ubuntu.com/ubuntu xenial-backports InRelease [107 kB] Get:4 http://security.ubuntu.com/ubuntu xenial-security InRelease [107 kB] Get:5 https://download.docker.com/linux/ubuntu xenial InRelease [65.8 kB] Get:6 https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages [3,6 53 B] Fetched 392 kB in 0s (727 kB/s) Reading package lists... Done Building dependency tree Reading state information... Done All packages are up to date.
Finally, install Docker in your System as shown
sudo apt-get install -y docker-ce
At this point, Docker should now be up and running. To confirm this run
systemctl status docker
Sample Output
● docker.service - Docker Application Container Engine
Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
Active: active (running) since Sat 2018-07-14 11:58:48 UTC; 1min 28s ago
Docs: https://docs.docker.com
Main PID: 20309 (dockerd)
CGroup: /system.slice/docker.service
├─20309 /usr/bin/dockerd -H fd://
└─20315 docker-containerd --config /var/run/docker/containerd/containerd.toml
Working with Docker and Docker images
By default, containers pull images from Docker Hub which is a registry managed by Docker. practically anyone can create and host their Docker images on Docker Hub. In fact, a majority of Linux distros that require Docker containers have images that are already hosted on Docker Hub.
To verify if you can access and download images from Docker Hub, Run
docker run hello-world
You should get output similar to the one below
latest: Pulling from library/hello-world
9db2ca6ccae0: Pull complete
Digest: sha256:4b8ff392a12ed9ea17784bd3c9a8b1fa3299cac44aca35a85c90c5e3c7afacdc
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/engine/userguide/
To search for images on Docker Hub use the search sub-command. In the example below, we’ll search for Fedora
NAME DESCRIPTION STARS OFFICIAL AUTOMATED fedora Official Docker builds of Fedora 671 [OK] mattdm/fedora A basic Fedora image corresponding roughly t… 49 fedora/apache 34 [OK] mattsch/fedora-nzbhydra Fedora NZBHydra 5 [OK] vbatts/fedora-varnish https://github.com/vbatts/laughing-octo/tree… 2 [OK] darksheer/fedora22 Base Fedora 22 Image -- Updated hourly 2 [OK] darksheer/fedora25 Hourly updated Fedora 24 Docker Hub Image 1 [OK] darksheer/fedora Hourly update latest Fedora Image 1 [OK] darksheer/fedora23 Hourly updated Fedora 23 1 [OK] darksheer/fedora24 Hourly update Fedora 24 1 [OK] ovirtguestagent/fedora-atomic The oVirt Guest Agent for Fedora Atomic Host… 0 resin/artik710-fedora-golang Go (golang) is a general purpose, imperative… 0 resin/artik10-fedora Docker builds of Fedora from Resin for Samsu… 0 mattsch/fedora-sonarr Fedora Sonarr 0 [OK] smartentry/fedora fedora with smartentry 0 [OK] vergissberlin/fedora-development Docker fedora image to use for development, … 0 [OK] vcatechnology/fedora A Fedora image that is updated daily 0 [OK] rhub/fedora-gcc-devel R-devel on Fedora latest 0 buildstream/buildstream-fedora A container image that provides the BuildStr… 0 chrisshort/docker-fedora25-ansible Docker container for Ansible Role/Playbook C… 0 [OK] urbaniak/fedora fedora with additional packages for python 0
To download an image an image from Docker Hub use the pull sub-command as shown
docker pull fedora
Sample Output
Using default tag: latest Using default tag: latest latest: Pulling from library/fedora e71c36a80ba9: Pull complete Digest: sha256:7ae08e5637170eb47c01e315b6e64e0d48c6200d2942c695d0bee61b38c65b39 Status: Downloaded newer image for fedora:latest
To view the number of images that have been downloaded to your computer, run
docker images
Output
REPOSITORY TAG IMAGE ID CREATED SIZE hello-world latest 2cb0d9787c4d 3 days ago 1.85kB mysql latest 8d99edb9fd40 2 weeks ago 445MB httpd latest 2a7d646dbba8 2 weeks ago 178MB fedora latest cc510acfcd70 2 months ago 253MB daduy/cacti latest 90fd4a0f3281 3 years ago 526MB
Upon downloading the image, you can run a container using the downloaded image using the run sub-command.
docker run fedora
To have interactive shell access to the container use the -it flags
docker run -it fedora bash
Output
[root@6a0596b8fa81 /]#
Note that the 6a0596b8fa81 digit represents the container id.
To view active containers, run
docker ps
To view both active and passive containers, run
docker ps -a
Output
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 9d48f3506f78 httpd "httpd-foreground" 9 minutes ago Exited (0) 9 minutes ago objective_mcnulty 2ed1fe816a33 mysql "docker-entrypoint.s…" 11 minutes ago Exited (1) 11 minutes ago affectionate_shockley c19c66828c1d hello-world "/hello" 11 minutes ago Exited (0) 11 minutes ago elegant_northcutt c7ec951bcbf0 httpd "httpd-foreground" 12 minutes ago Exited (0) 11 minutes ago quizzical_carson 0af73fe05c6e hello-world "/hello" About an hour ago Exited (0) About an hour ago mystifying_golick
To stop a running container, run
docker stop container-id
That’s all we had for today, stay tuned for more engaging and informative articles. Your thoughts on this tutorial are welcome.
