106 lines
5.5 KiB
Markdown
106 lines
5.5 KiB
Markdown
---
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title: "Ansible KVM Router Lab Part 2"
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date: 2021-10-16
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draft: false
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tags: ["linux", "kvm", "libvirt", "virsh", "ansible", "bash"]
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authors: ["trent"]
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post: 27
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---
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date: 2021-10-16
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## Introduction
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This is Part 2 of a multi-part series of blog posts for building a
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[router lab](https://github.com/TrentSPalmer/router-lab){target="_blank"}
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automatically using a series of bash scripts and ansible.
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[Ansible KVM Router Lab Part 1](/posts/ansible-kvm-router-lab-part-1/){target="_blank"}
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is an overview.
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In this post I begin breaking down the bash scripts which build the router
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lab, beginning with
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[build_vms.bash](https://github.com/TrentSPalmer/router-lab/blob/master/build_vms.bash){target="_blank"}.
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In [Ansible KVM Router Lab Part 3](/posts/ansible-kvm-router-lab-part-3/){target="_blank"},
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I explain
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[define_bridge_networks.bash](https://github.com/TrentSPalmer/router-lab/blob/master/define_bridge_networks.bash){target="_blank"}
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and [shutdown_vms.bash](https://github.com/TrentSPalmer/router-lab/blob/master/shutdown_vms.bash){target="_blank"}
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scripts which are used to construct the lab.
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In [Ansible KVM Router Lab Part 4](/posts/ansible-kvm-router-lab-part-4/){target="_blank"},
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I explain
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[connect_vms_to_bridges.bash](https://github.com/TrentSPalmer/router-lab/blob/master/connect_vms_to_bridges.bash){target="_blank"},
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[start_vms.bash](https://github.com/TrentSPalmer/router-lab/blob/master/start_vms.bash){target="_blank"},
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and [rebuild_known_hosts.bash](https://github.com/TrentSPalmer/router-lab/blob/master/rebuild_known_hosts.bash){target="_blank"}
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scripts which are used to construct the lab.
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In [Ansible KVM Router Lab Part 5](/posts/ansible-kvm-router-lab-part-5/){target="_blank"},
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I explain the ansible playbook tasks used to finish building the lab.
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In [Ansible KVM Router Lab Part 6](/posts/ansible-kvm-router-lab-part-6/){target="_blank"},
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I explain
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[disconnect_vms_from_bridges.bash](https://github.com/TrentSPalmer/router-lab/blob/master/disconnect_vms_from_bridges.bash){target="_blank"},
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[undefine_and_remove_vms.bash](https://github.com/TrentSPalmer/router-lab/blob/master/undefine_and_remove_vms.bash){target="_blank"},
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and [remove_bridge_networks](https://github.com/TrentSPalmer/router-lab/blob/master/remove_bridge_networks.bash){target="_blank"}
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which are used to destroy the lab.
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## `build_vms.bash`
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### `check_uid "0"`
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[build_vms.bash](https://github.com/TrentSPalmer/router-lab/blob/master/build_vms.bash)
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begins by making sure that it is run as the _root_ user. This is because root is required to
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ssh into the clones to change their hostnames, machine-ids, and host-ssh-keys. You can call
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with `sudo bash build_vms.bash`.
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For this same reason, `~/.ssh/known_hosts` is useless so it is deleted (and then rebuilt).
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### `function build_vms()`
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Next,
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[build_vms.bash](https://github.com/TrentSPalmer/router-lab/blob/master/build_vms.bash){target="_blank"}
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calls `build_vms`, which loops over the array of MACHINES, which is an
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array that holds that names of the lab clients, passing each name in turn
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to `create_vm`.
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`create_vm` creates the virtual machine if it does not already exist, using `virt-clone`, and
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then calls `start_vm` to start it.
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`start_vm` is exported from
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[env.bash](https://github.com/TrentSPalmer/router-lab/blob/master/env.bash.example){target="_blank"},
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and per parsing the output of `virsh list --inactive`, starts the virtual machine if it is not running.
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### `function set_hostnames()`
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Next,
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[build_vms.bash](https://github.com/TrentSPalmer/router-lab/blob/master/build_vms.bash){target="_blank"}
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calls `set_hostnames`, which simultaneously calls `set_hostname` on the entire MACHINES array. `set_hostname`
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in turn waits for the virtual machine to be fully booted, then updates the files `/etc/hostname` and
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`/etc/hosts`, and then reboots the virtual machine to apply the new hostname.
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### `function confirm_hostnames()`
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`confirm_hostnames` simultaneously calls `confirm_hostname` against the entire MACHINES array.
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`confirm_hostname` waits for the virtual machine to be fully booted, then confirms the correct
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_hostname_ in `/etc/hostname`.
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### `function confirm_hostnames_in_hosts()`
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`confirm_hostnames_in_hosts` works almost exactly the same as `confirm_hostnames`, but this time
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the file `/etc/hosts` on the virtual machine is grepped for the proper _hostname_, and corrected
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if necessary.
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### `function reset_hosts_ssh_keys()`
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`reset_hosts_ssh_keys` simultaneously calls `reset_host_ssh_keys` against the MACHINES array,
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which in turn compares the host_ssh_key of the virtual machine against the _bas3_ virtual
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machine, and if necessary deletes `/etc/ssh/ssh_host_*`, generates new host_ssh_keys, restarts
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`sshd` on the virtual machine, removes `~/.ssh/known_hosts`, and then reruns itself in
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order to confirm the new host_ssh_keys.
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### `function reset_machine_ids()`
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`reset_machine_ids` simultaneously calls `reset_machine_id` against the entire MACHINES array,
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which in turn checks the _machine-id_ of the virtual machine to make sure that it is different
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than the _machine-id_ of the _base_ virtual machine, and if necessary deletes
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`/etc/machine-id` and `/var/lib/dbus/machine-id` and recreates them.
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## To Be Continued
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In [Ansible KVM Router Lab Part 3](/posts/ansible-kvm-router-lab-part-3/){target="_blank"},
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I explain
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[define_bridge_networks.bash](https://github.com/TrentSPalmer/router-lab/blob/master/define_bridge_networks.bash){target="_blank"}
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and
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[shutdown_vms.bash](https://github.com/TrentSPalmer/router-lab/blob/master/shutdown_vms.bash){target="_blank"}
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scripts which are used to construct the lab.
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