trents_blog/docs/posts/ansible-kvm-router-lab-part-3.md

title	date	draft	tags	authors	post
Ansible KVM Router Lab Part 3	2021-10-16	false	linux kvm libvirt virsh ansible bash	trent	28

date: 2021-10-16

Introduction

This is Part 3 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 this post 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 Ansible KVM Router Lab Part 6{target="_blank"}, I explain disconnect_vms_from_bridges.bash{target="_blank"}, undefine_and_remove_vms.bash{target="_blank"}, and remove_bridge_networks{target="_blank"} which are used to destroy the lab.

define_bridge_networks.bash

The router-lab has two bridge networks, in addition to the initial out-of-band network which is used to contact the virtual machines directly.

check_uid "${USER_UID}"

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

function define_bridge_networks()

define_bridge_networks calls define_bridge_network twice, once for each of the upper bridge and the lower bridge. define_bridge_network parses the output of virsh net-list --all to determine if the network is defined yet. If not, virsh net-define vm_router_lab_lower_bridge.xml or virsh net-define vm_router_lab_upper_bridge.xml are invoked as necessary. define_bridge_network then recursively calls itself for confirmation.

Links for vm_router_lab_upper_bridge.xml{target="_blank"} and vm_router_lab_lower_bridge.xml{target="_blank"}.

function start_bridge_networks()

start_bridge_networks calls start_bridge_network twice, once for each of the upper and the lower bridge. start_bridge_network in turn parses the output of virsh net-info vm_router_lab_upper_bridge and/or virsh net-info vm_router_lab_lower_bridge to determine if the cooresponding network is running, and if not invokes virsh net-start vm_router_lab_upper_bridge or virsh net-start vm_router_lab_lower_bridge, and then recursively calls itself again for confirmation.

function autostart_bridge_networks()

autostart_bridge_networks is nearly identical to start_bridge_networks, but virsh net-autostart vm_router_lab_upper_bridge or virsh net-autostart vm_router_lab_lower_bridge, are invoked in order to mark the cooresponding network to autostart.

shutdown_vms.bash

After creating the upper and lower bridge networks, it is necessary to shut down the lab clients before connecting the lab clients to the bridge networks. This is because network interfaces must be permanently added to the lab client definitions.

check_uid "${USER_UID}"

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

function shutdown_vms()

shutdown_vms simultaneously calls shutdown_vm on the entire MACHINES array. shutdown_vm in turn parses the output of virsh list --state-running to determine if the virtual machine is running, and if so invokes virsh shutdown <vm>. shutdown_vm then recursively calls itself to confirm that the virtual machine is indeed shut down.

To Be Continued

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.