Last updated on July 14th, 2022 at 10:27 pm
Welcome to our guide on how to install docker on Rocky Linux 8. Docker is a platform that enables developers and system administrators to build, run, and share applications with containers.
There exits two editions of docker available, Docker CE and Docker EE:
- Docker (Community Edition) is the open-source, community supported version of Docker and is available for free.
- Docker EE (Enterprise Edition) is a commercial/premium version of docker and is supported by Docker Inc.
We will be learning how to install and use Docker CE on Rocky Linux 8.
Install Docker on Rocky Linux 8
There are different methods in which you can install docker on Rocky Linux 8;
- Installing docker on Rocky Linux 8 from Docker Repositories
- Installing docker manually on Rocky Linux 8 using the RPM binary package
- Installing docker using Docker Installation Script (Beyond the scope of this tutorial).
Install Docker on Rocky Linux 8 from Docker Repositories
Uninstall old Docker Versions
If any of the old docker versions are installed on your system, ensure that you remove them and their dependencies before you proceed.
dnf remove docker*
Install docker Repository on Rocky Linux 8
To ensure seamless future upgrades of Docker packages, you can install it from their official repos. For this, you need to setup the Docker repositories on Rocky Linux 8 by executing the command below;
dnf config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
The command above installs and enable docker repo on Rocky Linux 8.
Install Docker Engine (docker) on Rocky Linux 8
Once the repos are in place, proceed to install docker-ce and other tools including containerd.io, an open and reliable container runtime on Rocky Linux 8 and docker CLI utility, docker-ce-cli.
dnf install docker-ce
Sample output;
Dependencies resolved. ============================================================================================================================================================================ Package Architecture Version Repository Size ============================================================================================================================================================================ Installing: docker-ce x86_64 3:20.10.7-3.el8 docker-ce-stable 27 M Installing dependencies: checkpolicy x86_64 2.9-1.el8 baseos 345 k container-selinux noarch 2:2.162.0-1.module+el8.4.0+556+40122d08 appstream 51 k containerd.io x86_64 1.4.6-3.1.el8 docker-ce-stable 34 M docker-ce-cli x86_64 1:20.10.7-3.el8 docker-ce-stable 33 M docker-ce-rootless-extras x86_64 20.10.7-3.el8 docker-ce-stable 9.2 M docker-scan-plugin x86_64 0.8.0-3.el8 docker-ce-stable 4.2 M fuse-common x86_64 3.2.1-12.el8 baseos 20 k fuse-overlayfs x86_64 1.4.0-3.module+el8.4.0+556+40122d08 appstream 71 k fuse3 x86_64 3.2.1-12.el8 baseos 49 k fuse3-libs x86_64 3.2.1-12.el8 baseos 93 k libcgroup x86_64 0.41-19.el8 baseos 69 k libslirp x86_64 4.3.1-1.module+el8.4.0+556+40122d08 appstream 68 k policycoreutils-python-utils noarch 2.9-14.el8 baseos 251 k python3-audit x86_64 3.0-0.17.20191104git1c2f876.el8.1 baseos 85 k python3-libsemanage x86_64 2.9-6.el8 baseos 126 k python3-policycoreutils noarch 2.9-14.el8 baseos 2.2 M python3-setools x86_64 4.3.0-2.el8 baseos 625 k slirp4netns x86_64 1.1.8-1.module+el8.4.0+556+40122d08 appstream 50 k Enabling module streams: container-tools rhel8 Transaction Summary ============================================================================================================================================================================ Install 19 Packages Total download size: 111 M Installed size: 449 M Is this ok [y/N]: y
Installing docker from an RPM package
You can as well install docker on Rocky Linux 8 using an RPM package.
Download the latest versions of the individual packages installed above from Docker Packages page.
Replace the version/release numbers of the packages accordingly.
dnf install https://download.docker.com/linux/centos/8/x86_64/stable/Packages/docker-ce-20.10.7-3.el8.x86_64.rpm -y
dnf install -y https://download.docker.com/linux/centos/8/x86_64/stable/Packages/docker-ce-cli-20.10.7-3.el8.x86_64.rpm
dnf install -y https://download.docker.com/linux/centos/8/x86_64/stable/Packages/containerd.io-1.4.6-3.1.el8.x86_64.rpm
Starting Docker Service
To start and enable Docker and Containerd service to run on system boot;
systemctl enable --now docker containerd
Running Docker as a non-root user
If you run Docker as standard user, you may get such an error;
[[email protected] ~]$ docker ps -a
Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Get http://%2Fvar%2Frun%2Fdocker.sock/v1.24/containers/json: dial unix /var/run/docker.sock: connect: permission deniedTherefore, if you need to run docker as non-root user, simply add the user you want to run docker as to docker group or simply, grant the user sudo rights. For example to add a user, koromicha, to docker group;
usermod -aG docker koromicha
groups koromicha
koromicha : koromicha docker
Next, log out and login again as the non root user that you added to the docker group so that your group membership can be re-evaluated.
You can then run docker as a non root user.
Verifying docker installation
Check the docker version;
docker --version
Docker version 20.10.7, build f0df350To verify that docker is running well, you can try running the hello-world container image.
[[email protected] ~]$ docker run hello-world
Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
b8dfde127a29: Pull complete
Digest: sha256:df5f5184104426b65967e016ff2ac0bfcd44ad7899ca3bbcf8e44e4461491a9e
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 list all running/stopped containers;
[[email protected] ~]$ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
4083300e3660 hello-world "/hello" 3 minutes ago Exited (0) 5 minutes ago laughing_visvesvarayaRunning Docker Images on Rocky Linux 8
While verifying docker installation above, we ran the hello-world docker container image. Building and running docker containerized applications is the next step after setting up your docker environment.
So there are two things here:
- You can either build and run your own docker container images or
- pull already created and shared images from docker hub, an image repository for Docker images.
In this demo, we will learn how to use already created docker images from docker hub. With docker command, you can easily pull docker images from docker hub, as we did with the hello-world image above.
If you want to build your own images and share on docker hub, then you need to sign up to create your own namespace for storing your images, which then can be publicly available.
Using docker command
docker command has quite a number of command line options for running various tasks.
The command line syntax is;
docker [OPTIONS] COMMAND
You can view various command options and commands by executing;
docker --help
...
Options:
--config string Location of client config files (default "/home/koromicha/.docker")
-c, --context string Name of the context to use to connect to the daemon (overrides DOCKER_HOST env var and default context set with "docker context use")
-D, --debug Enable debug mode
...
Management Commands:
builder Manage builds
config Manage Docker configs
container Manage containers
...
Commands:
attach Attach local standard input, output, and error streams to a running container
build Build an image from a Dockerfile
commit Create a new image from a container's changes
cp Copy files/folders between a container and the local filesystem
create Create a new container
...
To view help for a specific docker command;
docker COMMAND --help
For example, to find the usage of docker run command;
docker run --help
Running Docker Images from Docker Hub
Searching for Docker Images on Docker Hub
You can search for the specific publicly available Docker images on Docker Hub using docker search command. The docker search command syntax is;
docker search [OPTIONS] TERM
Use docker search --help to see more options.
For example, to search all the images containing the term hello-world;
docker search hello-world
NAME DESCRIPTION STARS OFFICIAL AUTOMATED hello-world Hello World! (an example of minimal Dockeriz… 1479 [OK] kitematic/hello-world-nginx A light-weight nginx container that demonstr… 150 tutum/hello-world Image to test docker deployments. Has Apache… 83 [OK] dockercloud/hello-world Hello World! 19 [OK] crccheck/hello-world Hello World web server in under 2.5 MB 15 [OK] vad1mo/hello-world-rest A simple REST Service that echoes back all t… 5 [OK] arm32v7/hello-world Hello World! (an example of minimal Dockeriz… 3 ppc64le/hello-world Hello World! (an example of minimal Dockeriz… 2 datawire/hello-world Hello World! Simple Hello World implementati… 1 [OK] markmnei/hello-world-java-docker Hello-World-Java-docker 1 [OK] thomaspoignant/hello-world-rest-json This project is a REST hello-world API to bu… 1 ansibleplaybookbundle/hello-world-db-apb An APB which deploys a sample Hello World! a… 1 [OK] ansibleplaybookbundle/hello-world-apb An APB which deploys a sample Hello World! a… 1 [OK]
Some column headings are self explanatory. Other columns include;
- STARS : Shows the number of likes the image has had.
- OFFICIAL : Specifies whether the image is built from a trusted source.
- AUTOMATED : Shows whether the image has been automatically build from source code in an external repository and automatically pushed to Docker repositories.
Usually, an image with no prefix is considered official docker hub image, stable and being maintained. It also contains [OK] on the Official column.
Pulling Docker Image to Local Registry
Once you have identified the image that you need to run, you can either pull it and store it on your local registry using the the docker pull command or simply run it using docker run command.
For example, to search and pull an Ubuntu system docker image;
docker search ubuntu
NAME DESCRIPTION STARS OFFICIAL AUTOMATED ubuntu Ubuntu is a Debian-based Linux operating sys… 12507 [OK] dorowu/ubuntu-desktop-lxde-vnc Docker image to provide HTML5 VNC interface … 552 [OK] websphere-liberty WebSphere Liberty multi-architecture images … 276 [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] neurodebian NeuroDebian provides neuroscience research s… 84 [OK] 1and1internet/ubuntu-16-nginx-php-phpmyadmin-mysql-5 ubuntu-16-nginx-php-phpmyadmin-mysql-5 50 [OK] open-liberty Open Liberty multi-architecture images based… 47 [OK] ubuntu-debootstrap debootstrap --variant=minbase --components=m… 44 [OK] i386/ubuntu Ubuntu is a Debian-based Linux operating sys… 25 solita/ubuntu-systemd Ubuntu + systemd 24 [OK] ...
Let us pull the official Ubuntu image.
docker pull ubuntu
This will by default pull the most recent version of Ubuntu currently available, usually the latest LTS versions.
Using default tag: latest latest: Pulling from library/ubuntu a31c7b29f4ad: Pull complete Digest: sha256:b3e2e47d016c08b3396b5ebe06ab0b711c34e7f37b98c9d37abe794b71cea0a2 Status: Downloaded newer image for ubuntu:latest docker.io/library/ubuntu:latest
You can specify other tags for specific types of Ubuntu though;
docker search ubuntu:20.04
List Available Docker Images
You can list locally available images using docker images command.
docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
ubuntu latest c29284518f49 5 days ago 72.8MB
hello-world latest d1165f221234 4 months ago 13.3kBRunning a Docker Container Image
Once you have pulled a container from Docker hub and is available locally, you can either run it with docker run or docker create command.
With docker run, you can create a container, start it and access it using a shell to run any command inside it. The docker run command line syntax is;
Usage: docker run [OPTIONS] IMAGE [COMMAND] [ARG…]
For example, to run our Ubuntu image we pulled from Docker hub above in an interactive manner (option -i) drop to the shell (option -t, to allocate pseudo-TTY);
docker run -it ubuntu
This drops to the shell;
[email protected]:/#
You are now inside an Ubuntu container, with a container ID, 9b93a21dac21, as root user. Anything that you run or execute under this shell happens within the filesystem of the container itself.
You can execute the commands directly without dropping to container shell;
docker run ubuntu cat /etc/os-release
NAME="Ubuntu" VERSION="20.04.2 LTS (Focal Fossa)" ID=ubuntu ID_LIKE=debian PRETTY_NAME="Ubuntu 20.04.2 LTS" VERSION_ID="20.04" HOME_URL="https://www.ubuntu.com/" SUPPORT_URL="https://help.ubuntu.com/" BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/" PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy" VERSION_CODENAME=focal UBUNTU_CODENAME=focal
If you run the container interactively and started a shell, you can run your commands inside it.
When you exit the shell, the shell attached to the container is detached and container stops. If you used the options, -i and -t when running docker container, you can exit the shell without stopping the container, use the keystrokes Ctrl + p then Ctrl + q.
You can as well run container in background and print container ID
docker run -dit --name ubuntudemo ubuntu
To attach it to the console;
docker attach ubuntudemo
Listing Docker Containers
You can list live (currently running) containers using docker ps command.
docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
a1a815bb0de6 ubuntu "bash" 5 seconds ago Up 2 seconds ubuntu-demoTo list all containers, those running and those exited;
docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES a1a815bb0de6 ubuntu "bash" 26 seconds ago Up 22 seconds ubuntu-demo 075d2a694b0c ubuntu "bash" About a minute ago Exited (0) About a minute ago ubuntudemo be8a66af520a ubuntu "cat /etc/os-release" 2 minutes ago Exited (0) 2 minutes ago eloquent_dirac 9b93a21dac21 ubuntu "bash" 3 minutes ago Exited (0) 2 minutes ago happy_elbakyan 61407c90dae8 hello-world "/hello" 13 minutes ago Exited (0) 13 minutes ago intelligent_gagarin
Start and Stop Docker Containers
You can start exited/stopped containers using docker start command.
For example, to start container named, happy_elbakyan, with an ID of 9b93a21dac21, run the command;
docker start happy_elbakyan
Or
docker start 9b93a21dac21
Similarly, you can stop a running docker using its name or container ID with docker stop command.
For example;
docker stop ubuntudemo
Removing Docker Containers
Once you are done with your containers, you can remove them using docker rm command.
To remove a stopped container with an ID of 9b7867c1daad, for example, in our docker ps -a output above;
docker rm 9b7867c1daad
You cannot remove a running container unless you force the removal using using -f or --force option of docker rm command.
docker rm 1c280cf21322 -f
Removing Docker Images
Docker images can as well be removed using docker rmi command. For example, you can list images and get the image ID of the specific image you want to remove;
docker images -a
You can show numeric IDS using -q option.
docker images -a -q
74435f89ab78 bf756fb1ae65
Delete an image;
docker rmi 74435f89ab78
Or use the name repo name;
docker rmi ubuntu
Use option -f or --force to force the deletion.
That concludes our guide on how to install docker on Rocky Linux 8.
Further Reading
Other Tutorials
Install ModSecurity 3 with Apache in a Docker Container
Deploy a Single Node Elastic Stack Cluster on Docker Containers
Install and Run MariaDB as a Docker Container
