Use RHEL/CentOS 8 specific repository for docker-ce

[alexsuppanz]

Hi,

since Docker already provides Builds for CentOS/RHEL 8 this PR changes the Repository URL to the EL 8 repo. During my tests I also discovered two additional things:

• containerd.io is a dependency of docker-ce (verified on RHEL 8 system)
• The installation of EL 7 docker-ce version on EL 8 fails due to unresolved dependencies -> "msg": "Depsolve Error occured: \n Problem: package docker-ce-3:19.03.13-3.el7.x86_64 requires containerd.io >= 1.2.2-3, but none of the providers can be installed...

So I also removed the step do install containerd.io separately

Regards,
Alex

[alpar-t]

Thanks for your contribution! I'm not sure we can switch to the latest version of of containerd but we could probably move up to 1.4.3-1. We found that newer versions have a bug that causes containers to be stuck in ECE. I'd like @obierlaire to take a look at this PR too, I know he won't be able to do so soon, please expect a delay.

[alexsuppanz]

Hi @alpar-t
I know about the problem with current containerd versions (can't verify it, since we are running RHEL 7 with Docker 1.13).
But anyway, installing containerd for centos 7 repo would fail on RHEL 8 (and I guess also on CentOS 8, since they are binary twins). Elastic docs for installing ECE on RHEL / CentOS 8 mention to install containerd.io-1.3.* and docker-ce-19.03.* . So maybe we should stick to this version also in the playbook?
What would happen in case of we install ECE with the versions mentioned in the docs, but perform an update afterwards. Would we also see the issue? Then docs should definitely mention that...

I saw, that a new version of containerd has been released ( containerd.io-1.4.6-3.1.el8.x86_64.rpm ). Can someone check if the bug persists?