Quickly Setup KVM/QEMU libvert VM - Great for Testing

create-vm.bash

#!/usr/bin/env bash
#
#
# (C)2026 Henri Shustak, All Rights Reserved 
# Licence : GNU GPLv3 or later
#
#
# new-vm.bash
# Interactively creates a KVM/QEMU libvirt VM with a configurable
# boot mode (BIOS or UEFI), generic "linux2022" OS variant, a
# configurable virtio disk size, and an install ISO of your choosing.
#
#
# Usage: 
# 
#   ~/bin/create-vm.bash [path-to-iso]
#   If the ISO path is omitted, you'll be prompted for it.
#
#
# Installation / Update : 
#
#   # download
#   curl -o ~/bin/create-vm.bash https://gist.githubusercontent.com/henri/9f5fde073bf25af1bbdd22cae389f7b9/raw/create-vm.bash
#
#   # set execute bit
#   chmod +x ~/bin/create-vm.bash
# 
#
# Purpose: 
#
#   Quickly setup new VM's with basic settings for testing things
# 
#
# Version History:
#
#   1.0 : intial release
#
#

set -euo pipefail

# --- Prompt for inputs -------------------------------------------------

read -rp "Enter VM name: " VM_NAME
if [[ -z "$VM_NAME" ]]; then
    echo "Error: VM name cannot be empty." >&2
    exit 1
fi

ISO_PATH="${1:-}"
if [[ -z "$ISO_PATH" ]]; then
    read -rp "Enter path to ISO file: " ISO_PATH
fi
if [[ ! -f "$ISO_PATH" ]]; then
    echo "Error: ISO file not found at '$ISO_PATH'." >&2
    exit 1
fi

# --- Optional overrides (press Enter to accept defaults) ---------------

read -rp "Memory in MB [4096]: " VM_MEMORY
VM_MEMORY="${VM_MEMORY:-4096}"

read -rp "Number of vCPUs [2]: " VM_VCPUS
VM_VCPUS="${VM_VCPUS:-2}"

read -rp "Disk size in GB [30]: " DISK_SIZE
DISK_SIZE="${DISK_SIZE:-30}"
if ! [[ "$DISK_SIZE" =~ ^[0-9]+$ ]]; then
    echo "Error: Disk size must be a whole number of GB." >&2
    exit 1
fi

read -rp "Boot mode - bios or uefi [uefi]: " BOOT_MODE
BOOT_MODE="${BOOT_MODE:-uefi}"
BOOT_MODE="$(echo "$BOOT_MODE" | tr '[:upper:]' '[:lower:]')"

case "$BOOT_MODE" in
    uefi)
        BOOT_ARGS=(--boot uefi)
        ;;
    bios)
        # There's no dedicated "--boot bios" flag in virt-install;
        # BIOS (SeaBIOS) is simply the default when --boot uefi is omitted.
        BOOT_ARGS=()
        ;;
    *)
        echo "Error: Boot mode must be 'bios' or 'uefi'." >&2
        exit 1
        ;;
esac

# --- Create the VM -------------------------------------------------------

echo
echo "Creating VM '$VM_NAME' with:"
echo "  ISO:      $ISO_PATH"
echo "  Memory:   ${VM_MEMORY}MB"
echo "  vCPUs:    $VM_VCPUS"
echo "  Disk:     ${DISK_SIZE}GB (qcow2, virtio)"
echo "  Boot:     ${BOOT_MODE^^}"
echo "  OS type:  linux2022 (generic modern Linux)"
echo

virt-install \
  --name "$VM_NAME" \
  --memory "$VM_MEMORY" \
  --vcpus "$VM_VCPUS" \
  --disk size="$DISK_SIZE",format=qcow2,bus=virtio \
  --network network=default,model=virtio \
  --cdrom "$ISO_PATH" \
  --os-variant linux2022 \
  "${BOOT_ARGS[@]}" \
  --graphics spice

echo
echo "VM '$VM_NAME' created. Manage it with:"
echo "  virsh list --all"
echo "  virsh start $VM_NAME"
echo "  virsh console $VM_NAME"