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Installed docker on Centos (running using VirtualBox) following steps below:

sudo yum install -y yum-utils device-mapper-persistent-data lvm2

sudo yum install docker

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

And I rebooted my virtual machine, and as I type 'docker --version, I get below:

"Emulate Docker CLI using podman. Create /etc/containers/nodocker to quiet msg.  podman version 1.0.5"

Can anybody explain what is going on in my machine?

swcraft
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3 Answers3

4

@swxraft if you run the commands in the order posted in your question

sudo yum install -y yum-utils device-mapper-persistent-data lvm2

sudo yum install docker

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

you installed a docker in the REHL repo (probably an alias to podman). And then loaded the repo for the oficial docker but never installed from there.

Extra info:

A) installation docker

How to install docker: follow this link [1] instead @govinda-malavipathirana. Latest docker-ce needs a newer containerd.io but REHL is excluding the ones in the docker repo. So you need to install docker -ce with --nobest (see instructions and error in link). Also you need to disable the firewall.d to have DNS in docker.

B) why docker is not in REHL8

Docker cli and daemon are not supported by REHL8 and its derivatives and it is "blocked" in several ways. Why is not suported -> monolitic and old [2]

Docker images ARE supported using podman. The images created with docker work with podman and viceversa. Also podman commands are the same as docker client.

Podman is a substitute of docker (but it does not use a daemon). They recommend to add a symlink docker -> podman and you will not notice the difference [3]

[1]https://linuxconfig.org/how-to-install-docker-in-rhel-8

[2]http://crunchtools.com/why-no-docker/

[3]https://developers.redhat.com/blog/2019/02/21/podman-and-buildah-for-docker-users/

Radim Vansa
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Pablo Marin-Garcia
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3

Docker will not support RedHat 8, it will be installed as Podman.

So you can try it with Amazon linux2 instead of RedHat. You have to create a new instance in AWS with Amazon linux2, then it will work.

Ivan Aracki
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Varma Kucharlapati
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Since docker is not officially supported by REHL8/CentOS8. You have to install it by additional steps. This is a good article I have found in the internet, shows how to install docker in CentOS 8.

https://computingforgeeks.com/install-docker-and-docker-compose-on-rhel-8-centos-8

Govinda Malavipathirana
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  • The repo has already been added.. btw my CentOS version is 8 and I am digging what podman does to block docker from getting installed. I never installed Podman myself. – swcraft Dec 16 '19 at 15:56
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    Actually docker is not officially supported by RHEL 8 / CentOS 8, it being replaced by RedHat by their own tool called `buildah` and `podman`. – Govinda Malavipathirana Dec 16 '19 at 16:00
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    Docker has never officially supported any RHEL version from CE, part of their policy, likely related to open source build tooling for the open source version. CentOS 8 came out after the last Docker CE release, so I expect it will be supported in the next release. RH's embrace, extend, extinguish policy with Docker is concerning, they could have easily released their own tool without hijacking docker's name. – BMitch Dec 16 '19 at 16:09
  • I have updated the answer, there is some guidance for install `docker` on centOS 8. Hope it might work, but need some extra work. – Govinda Malavipathirana Dec 16 '19 at 16:10