trents_blog/docs/posts/ansible-kvm-router-lab-part-6.md

title	date	draft	tags	authors	post
Ansible KVM Router Lab Part 6	2021-10-17	false	linux kvm libvirt virsh ansible bash	trent	31

date: 2021-10-17

Introduction

This is Part 6 of a multi-part series of blog posts for building a router lab{target="_blank"} automatically using a series of bash scripts and ansible.

Ansible KVM Router Lab Part 1{target="_blank"} is an overview.

In Ansible KVM Router Lab Part 2{target="_blank"}, I break down the script build_vms.bash{target="_blank"}.

In Ansible KVM Router Lab Part 3{target="_blank"}, I explain define_bridge_networks.bash{target="_blank"} and shutdown_vms.bash{target="_blank"} scripts which are used to construct the lab.

In Ansible KVM Router Lab Part 4{target="_blank"}, I explain connect_vms_to_bridges.bash{target="_blank"}, start_vms.bash{target="_blank"}, and rebuild_known_hosts.bash{target="_blank"} scripts which are used to construct the lab.

In Ansible KVM Router Lab Part 5{target="_blank"}, I explain the ansible playbook tasks used to finish building the lab.

In this post I explain how I use disconnect_vms_from_bridges.bash{target="_blank"}, undefine_and_remove_vms.bash{target="_blank"}, and remove_bridge_networks.bash{target="_blank"}, to destroy the lab.

shutdown_vms.bash

I explain shutdown_vms.bash in Ansible KVM Router Lab Part 3{target="_blank"}.

disconnect_vms_from_bridges.bash

check_uid "${USER_UID}"

disconnect_vms_from_bridges.bash begins by making sure that it is run as a non-privileged user. You can call the script with bash disconnect_vms_from_bridges.bash.

function detach_vms()

detach_vms loops over the MACHINES array, passing each name twice to detach_vm, once for the upper bridge network, and again for the lower bridge network.

function detach_vm()

detach_vm invokes virsh dominfo against the given virtual machine, and parses the output to decide if the machine is running or not. If the given virtual machine is running, detach_vm calls detach_running_vm against the given virtual machine and the given network. If the given virtual machine is not running, detach_vm calls detach_shut_off_vm against the given virtual machine and against the given network.

function detach_running_vm()

detach_running_vm invokes virsh domiflist against the given virtual machine and greps that for the given network to decide whether or not the given virtual machine is attached to the given network. If the given virtual machine is attached to the given network, detach_running_vm once again similarly invokes virsh domiflist, but this time parsing the mac of the attached interface. detach_running_vm then invokes virsh detach-interface against parsed mac, and then recursively calls itself for the purpose of verification.

function detach_shut_off_vm()

detach_shut_off_vm is almost identical to detach_running_vm, but the options for the invocation of virsh detach-interface are adjusted to be appropriate for a virtual machine which is not running.

undefine_and_remove_vms.bash

check_uid "${USER_UID}"

undefine_and_remove_vms.bash begins by making sure that it is run as a non-privileged user. You can call the script with bash undefine_and_remove_vms.bash.

function destroy_vms()

destroy_vms simultaneously passes the entire MACHINES array to destroy_vm, which parses the output of virsh list --all to find out if the virtual machine exists, and if it does invokes the command virsh undefine with the --remove-all-storage option, against the virtual machine.

remove_bridge_networks.bash

check_uid "${USER_UID}"

remove_bridge_networks.bash begins by making sure that it is run as a non-privileged user. You can call the script with bash remove_bridge_networks.bash.

function disable_autostart_bridge_networks()

disable_autostart_bridge_networks passes each of the upper and lower bridge network names to disable_autostart_bridge_network, which parses the output of virsh net-info to find out if the network has autostart enabled, and if it is, invokes virsh net-autostart with the --disable option to disable autostart for the given network, and then recursively calls itself for the purpose of verification.

function stop_bridge_networks()

stop_bridge_networks passes each of the upper and lower bridge network names to stop_bridge_network, which parses the output of virsh net-info in order to find out if the given network is running, and it if is, invokes virsh net-destroy against the given network to stop it, and then recursively calls itself for the purpose of verification.

function undefine_bridge_networks()

undefine_bridge_networks passes each of the upper and lower bridge network names to undefine_bridge_network, which parses the output of virsh net-list --all in order to find out if the given network is defined, and if it is, invokes virsh net-undefine against the given network to undefine it, and then recursively calls itself for the purpose of verification.