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Debian bullseye Unattended VM Guest Installer

Updated for Debian 11.x support.

This is an automated script that will make use of virt-install to configure and deploy a Debian system without any user interaction. Just set it and let it go. Utilizes the preseed config to run unattended.

This script is based off one written by Dmitri Popov located here: debian-vm-install. Dmitri's intent was for the script he wrote to be used by someone to write their own, and this is the result spending a morning working on it.

Usage: ./install.sh -n <Name> -r <RAM> -c <CPU> -d <DISK> -mac <MAC>
  -n       Sets the guest, VM, and disk name. Required.
  -r       Sets the amount of memory to allocate in MB
  -c       Sets the number of vCPUs to assign
  -d       Sets the size of the disk in GB
  -t       Sets the type of server this will be. Uses default-postinst.sh
  -mac     Sets the MAC address. Leave blank for random.

Examples:
  This will create a guest named "webserver" with 512mb
  RAM, 2 vCPUs, 25GB disk, and an assigned MAC address.

  ./install.sh webserver -r 512 -c 2 -d 25 -mac 52:54:00:bf:b3:80

  This will create a guest using the defaults inherited from
  config.sh named "vmtest" with a random MAC.

  ./install.sh vmtest

Guest OS out of the box is minimal with no GUI and serial console support so you can Guest OS is minimal no-GUI Debian installation configured with serial console for ability to virsh console <GUEST_NAME>, and OpenSSH server with your SSH key or/and password pre-configured.

Prerequisites

I was able to run this out of the box after installing the following on a fresh Debian 11.x host.

  • apt install qemu-kvm libvirt-clients libvirt-daemon-system virtinst

These additional packages are required for bridged networking and VLANs.

  • apt install bridge-utils vlan

Things to do before you run

Update config.sh with the following values:

  • DOMAIN: Sets the domain. You can also use /bin/hostname -d to use what DHCP assigned the host.
  • DIST_URL: Sets the URL for your distribution. By default this is using the CDN mirror by Debian, but depending on your country you may want to change this to reflect somewhere closer/faster. netselect is a utility that can help with selecting a good low latency mirror, along with a wget or curl throughput test.
  • VM_MEM: Default memory (in MB) to assign.
  • VM_CPU: Default number of vCPUs to assign.
  • VM_DISK: Default size (in GB) to allocate.
  • VM_TYPE: The type of default VM. You will need to update default-postinst.sh to contain the type you specify if it does not already exist.
  • VM_DISKLOC: Location to create the disk image.
  • PS_USER_FULLNAME: Your full name.
  • PS_USERNAME: The user name to set the default user to.
  • PS_LOCALE: The system locale.
  • PS_KEYBOARD: The type of keyboard.
  • PS_DEB_MIRROR: The mirror to use for downloading packages. See DIST_URL for more selection information.
  • PS_TZ: The timezone to use. Take care to escape the forward slash. Example: America\/New_York.
  • PS_SSHKEY_SOURCE: The source of the SSH key. Options: github, config, user.
  • PS_SSHKEY_GITHUB: The URL to your public key on your git profile. Example: https://github.com/TaylorBurnham.keys.
  • PS_SSHKEY_SET: If you set config for the PS_SSHKEY_SOURCE you will need to paste the full contents of the ssh-rsa string in this variable. This is handy if you use different keys for your lab vs. production.

Some considerations from Dmitri's original README:

  • It's worth considering to enable password authentication in preseed.cfg at least during first run so you could virsh console <GUEST_NAME> in case network connection in guest does not comes up with DHCP or IP of the guest is unclear.

Network configuration

The script works best with a bridged network where guests are able to use the local DHCP server. There's other more advanced options you can work with if you are using completely private networking, but that is not part of my needed use case.

You may update VM_INTERFACE in the config.sh to specify a different interface.

Below is an example of my network configuration from my test system.

Location: /etc/network/interfaces

# Loopback
auto lo
iface lo inet loopback

# Primary interface
auto enp6s0
iface enp6s0 inet manual
iface enp6s0 inet6 manual

# br0 for guests
auto br0
iface br0 inet dhcp
  bridge_ports enp6s0 # bridge_ports must point to your primary interface
  bridge_stp off
  bridge_fd 0
  bridge_maxwait 0

More Info and References