OpenStack Overview

1. Architecture

2. Commands

• In compute node, run `virsh capabilities`, you can see the capability of that node.
• `virsh dumpxml instance-id`
• Describe the vm

3. Reboot

• Soft reboot
• It relies completely on the guest OS and ACPI passed through QEMU
• Hard reboot
• Just make it work. 
• It resolves most issue
• It is at the hypervisor and Nova level 
• It makes zero assumptions about the state of the hypervisor
• Notable effort has been placed to make internal operations idempotent, and call them here.
• Steps
• Destroy the domain
• Equivalent of `virsh destroy`
• Does not destroy data, only the QEMU process
• Effectively a `kill -9` of the QEMU process
• Re-establish any and all volume connections.
• Regenerate the Libvirt XML
• Check for and re-download any missing backing files (instance_dir/_base)
• Plug VIFs (re-create bridges, VLAN interfaces, etc.)
• Regenerate and apply iptables rules