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elasticluster / elasticluster

Create clusters of VMs on the cloud and configure them with Ansible.
http://elasticluster.readthedocs.io/
GNU General Public License v3.0
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stateless nodes? #646

Open loveshack opened 5 years ago

loveshack commented 5 years ago

I wonder if it's a reasonable feature request to be able to use stateless nodes, with root provisioned on NFS, a network block device, or perhaps memory. That would finesse at least speed issues with ansible provisioning, and is generally the best way to manage at least less ephemeral clusters in my experience. I assume you can't PXE boot a suitable initramfs with most providers, so you'd presumably need to boot a minimal stateful system and trigger a pivot_root into the appropriate filesystem from that.

riccardomurri commented 5 years ago

Definitely something worth exploring!

I wonder how much "stateless" the nodes can be, though: each one would still need its own copy of the network config, and what else?

loveshack commented 5 years ago

I wonder how much "stateless" the nodes can be, though: each one would still need its own copy of the network config, and what else?

That depends on the distribution somewhat. For EL7, I think you can look in /etc/rwtab{,.d} and /run/initramfs/rwtab, plus systemd (ugh!) rhel-readonly service for what you might need in the ramfs. I assume it will be similar for Debian 9, but that doesn't have the systemd service. You don't need anything node-specific if you have dhcp and homogeneous nodes.