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

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