CoreOS for hosts machines

I read some people using Core OS as host machines to run containers with Rancher. I would probably stick to RancherOS but its not supported in Xenserver and I know the Xentools are still worked on to run on a container for RancherOS, so that leaves me currently with CentOS/RHEL 7 or Core OS but since Core OS with fleet and flannel is a cluster OS, I’m not sure why people would do this.

It seems to me that Rancher does all the network, clustering and management assuming you stick to Cattle, so what is the benefit of launching the containers in Core OS?

Should I just stick to CentOS 7 for master/slaves or go with Core OS for slaves? Assuming here master are running Rancher and slaves are just dumb systems running containers.

Yeah, unfortunately no official service for Xen guest utilities yet (

fleet and flannel are optional when using CoreOS. I don’t think they’d provide any value if you were using Rancher so you could just ignore them.

Rancher doesn’t care about the host operating system very much, so whether you use CentOS or CoreOS is largely a matter of preference.

Yes, that is my point, so what are the benefits then? Thin OS and updated automatically?

I guess it would make more sense just to go with RancherOS which is even smaller and lighter if you are looking the slimmest and most secure base OS.

The nice thing about CentOS 7 and CoreOS with XenServer is that you can actually manage the individual containers inside a host VM. The hypervisor is aware of the containers insides the guests.