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create-vm

Use .iso and Kickstart files to auto-generate a guest VM.

About

I was looking for a way to automate the creation of VMs for testing various distributed system / cluster software packages. I've used Vagrant in the past but I wanted something that would:

  • Allow me to use raw ISO files as the basis for guest VMs.
  • Guest VMs should be set up with bridged IPs that are routable from the host.
  • Guest VMs should be able to reach the Internet.
  • Other hosts on the local network should be able to reach guest VMs. (Setting up additional routes is OK).
  • VM creation should work with any distro that supports Kickstart files.
  • Scripts should be able to create and delete VMs in a scripted, fully-automatic manner.
  • Guest VMs should be set up to allow passwordless ssh access from the "ansible" user.

I've previously used virsh's virt-install tool to create VMs and I like how easy it is to set up things like extra network interfaces and attach existing disk images. The scripts in this repo fully automate the virsh VM creation process.

Scripts

This repo contains these scripts:

create-vm - Use .iso and kickstart files to auto-generate a VM.

delete-vm - Delete a virtual machine created with create-vm.

get-vm-ip - Get the IP address of a VM managed by virsh.

encrypt-pw - Returns a SHA512 encrypted password suitable for pasting into Kickstart files.

I've also included a sample ubuntu.ks Kickstart file for creating an Ubuntu host.

Host setup

I'm running the scripts from a host with Ubuntu Linux 18.10 installed. I added the following to the host's Ansible playbook to install the necessary virtualization packages:

  - name: Install virtualization packages
    apt:
      name: "{{item}}"
      state: latest
    with_items:
    - qemu-kvm
    - libvirt-bin
    - libvirt-clients
    - libvirt-daemon
    - libvirt-daemon-driver-storage-zfs
    - python-libvirt
    - python3-libvirt
    - system-config-kickstart
    - vagrant-libvirt
    - vagrant-sshfs
    - virt-manager
    - virtinst

If you're not using Ansible just apt-get install the above packages.

create-vm options

create-vm supports the following options:

   -h      Show this message
   -n      Host name (required)
   -i      Full path and name of the .iso file to use (required)
   -k      Full path and name of the Kickstart file to use (required)
   -r      RAM in MB (defaults to 1024)
   -c      Number of VCPUs (defaults to 2)
   -s      Amount of storage to allocate in GB (defaults to 20)
   -b      Bridge interface to use (defaults to virbr0)
   -m      MAC address to use (default is to use a randomly-generated MAC)
   -v      Verbose
   -d      Debug mode

Sample Kickstart file

There are plenty of documents on the Internet on how to set up Kickstart files.

A couple of things that are special about the included Kickstart file...

The Ansible user: Although I'd prefer to create the "ansible" user as a locked account, with no password just an ssh public key, Kickstart on Ubuntu does not allow this, so I do set up an encrypted password.

To set up your own password, use the encrypt-pw script to create a SHA512-hashed password that you can copy and paste into the Kickstart file. After a VM is created you can use this password if you need to log into the VM via the console.

To use your own ssh key, replace the ssh key in the %post section with your own public key.

The %post section at the bottom of the Kickstart file does a couple of things:

  • It updates all packages with the latest versions.
  • To configure a VM with Ansible, you just need ssh access to a VM and Python installed. on the VM. So I use %post to install an ssh-server and Python.
  • I start the serial console, so that virsh console $vmname works.
  • I add a public key for Ansible, so I can configure the servers with Ansible without entering a password.

Despite the name, the commands in the %post section are not the last commands executed by Kickstart on an Ubuntu 18.10 server. The "ansible" user is added after the %post commands are executed. This means that the Ansible ssh public key gets added before the ansible user is created. To make key-based logins work I set the UID:GID of authorized_keys to 1000:1000. The user is later created with UID=1000, GID=1000, which means that the authorized_keys file ends up being owned by the ansible user by the time the VM creation is complete.

Examples

Create an Ubuntu 18.10 server

This creates a VM using Ubuntu's text-based installer. Since the -d parameter is used, progress of the install is shown on screen.

create-vm -n node1 -i ~/isos/ubuntu-18.10-server-amd64.iso -k ~/conf/ubuntu.ks -d

Create 8 Ubuntu 18.10 servers

This starts the VM creation process and exits. Creation of the VMs continues in the background.

for n in `seq 1 8`; do
    create-vm -n node$n -i ~/isos/ubuntu-18.10-server-amd64.iso -k ~/conf/ubuntu.ks
done

Delete 8 virtual machines

for n in `seq 1 8`; do
    delete-vm node$n
done

Connect to a VM via the console

virsh console node1

Connect to a VM via ssh

ssh ansible@`get-vm-ip node1`

Generate an Ansible hosts file

(
    echo '[hosts]'
    for n in `seq 1 8`; do
        ip=`get-vm-ip node$n`
        echo "node$n ansible_host=$ip ip=$ip ansible_user=ansible"
    done
) > hosts.ini

Handy virsh commands

virsh list - List all running VMs.

virsh domifaddr node1 - Get a node's IP address. Does not work with all network setups, which is why I wrote the get-vm-ip script.

virsh net-list - Show what networks were created by virsh.

virsh net-dhcp-leases $network - Shows current DHCP leases when virsh is acting as the DHCP server. Leases may be shown for machines that no longer exist.

Known Issues

  • VMs created without the -d (debug mode) parameter may be created in "stopped" mode. To start them up, run the command virsh start $vmname.
  • Depending on how your host is set up, you may need to run these scripts as root.
  • Ubuntu text mode install messes up terminal screens. Run reset from the command line to restore a terminal's functionality.
  • I use Ansible to set a guest's hostname, not Kickstart, so all Ubuntu guests created have the host name "ubuntu".