QEMU VM Toolkit

This project provides two helper scripts to automate the process of creating customized VM images and launching virtual machines using QEMU/KVM, cloud-init, and tmux.

Dependencies

Make sure the following tools are installed:

• QEMU/KVM
• cloud-utils (for cloud-localds)
• tmux (for session management)

On Ubuntu/Debian:

sudo apt update
sudo apt install -y qemu-kvm cloud-utils genisoimage tmux

Workflow

1. Use create_vm_image.sh to build a VM image + cloud-init ISO in ./out/.
2. Use launch_vm.sh to boot the VM inside tmux.
3. SSH into the VM using the forwarded port (user networking).

Quickstart

Ubuntu 26.04

# Step 0: Download a base cloud image into ./img
mkdir -p ./img
pushd ./img
wget https://cloud-images.ubuntu.com/resolute/current/resolute-server-cloudimg-amd64.img
popd

# Step 1: Create VM image
./create_vm_image.sh -b ./img/resolute-server-cloudimg-amd64.img -n ubuntu26_vm.img -u linux -s 64G

# Step 2: Launch VM in tmux
./launch_vm.sh -i out/ubuntu26_vm.img -p 2020 -c 4 -m 4 -t ubuntu26-vm -C out/cloud-init-ubuntu26_vm.iso

# Step 3: SSH into VM
ssh linux@localhost -p 2020

# The default login password is ubuntu

Arch Linux

# Step 0: Download a base cloud image into ./img (inside this repo)
mkdir -p ./img
pushd ./img
wget https://fastly.mirror.pkgbuild.com/images/latest/Arch-Linux-x86_64-cloudimg.qcow2  # Arch Linux
popd

# Step 1: Create VM image
./create_vm_image.sh -b img/Arch-Linux-x86_64-cloudimg.qcow2 -n arch_vm.img -u linux -s 32G

# Step 2: Launch VM in tmux
./launch_vm.sh -i out/arch_vm.img -p 2020 -c 4 -m 4 -t arch-vm -C out/cloud-init-arch_vm.iso

# Step 3: SSH into VM
ssh linux@localhost -p 2020

# The default login password is ubuntu

Batch Allocate Student VMs

Use allocate_vms.sh to create and launch multiple VMs that share the same base image. Each VM gets an SSH port of base_port + index.

./allocate_vms.sh -b ./img/resolute-server-cloudimg-amd64.img -n 20 -p 3000 -u student -h oslab -i oslab -t oslab

Example connections:

ssh student00@localhost -p 3000
ssh student01@localhost -p 3001
... ...

To stop and remove a batch of allocated VMs:

./cleanup_vms.sh -n 20 -i oslab -t oslab -o out -S 0

Scripts

1. create_vm_image.sh

Creates a new VM disk image from a base cloud image (Ubuntu or Arch), applies cloud-init configuration (hostname, username, password), and generates an ISO for bootstrapping.

Usage

./create_vm_image.sh -b <base_image> -n <new_image> -h <hostname> -u <username> -p <password> -s <disk_size> [-o <out_dir>]

Options

• -b: Path to the base image (default: ./img/jammy-server-cloudimg-amd64.img)
• -n: Name of the new VM image (default: custom_vm_image.img)
• -h: VM hostname (default: VM)
• -u: VM username (default: ubuntu)
• -p: VM password (default: ubuntu)
• -s: VM disk size (default: 10G)
• -o: Output directory for the image and cloud-init files (default: out)

Example

./create_vm_image.sh -n myvm.img -h myhost -u alice -p secret123 -s 20G

This will:

1. Create a myvm.img disk (20G).
2. Set the hostname to myhost.
3. Create a user alice with password secret123.
4. Generate cloud-init-<image>.iso for first-boot configuration in out/.

Arch Linux example

./create_vm_image.sh -b ./img/Arch-Linux-x86_64-cloudimg.qcow2 -n arch_vm.img -h archvm -u arch -p arch -s 20G
./launch_vm.sh -i out/arch_vm.img -p 2222 -c 2 -m 4 -t arch-vm -C out/cloud-init-arch_vm.iso
ssh arch@localhost -p 2222

Base image registry (optional)

You can define base image aliases in images.env and pass the alias to -b:

./create_vm_image.sh -b ARCH_LINUX -n arch_vm.img -h archvm -u arch -p arch -s 20G

2. launch_vm.sh

Launches a VM inside a tmux session for easier management. Supports both user networking (with SSH port forwarding) and tap networking (for bridged connections).

Usage

./launch_vm.sh -i <vm_image> -c <vcpu> -m <memory> -p <host_port> \
  [-C <cloud_init_image>] [-t <tmux_session_name>] \
  [-n <network_type>] [-T <tap_interface>]

Options

• -i: Path to the VM image (required)
• -c: Number of vCPUs (default: 2)
• -m: Memory size in GB (default: 2)
• -p: Host port forwarded to guest SSH port 22 (default: 2222)
• -C: Optional path to a cloud-init ISO (e.g., cloud-init.iso)
• -t: Tmux session name (default: vm-session)
• -n: Network type: user or tap (default: user)
• -T: TAP interface name if using -n tap (default: tap0)

Examples

Basic launch with user networking:

./launch_vm.sh -i myvm.img -c 2 -m 4 -p 2200 -t vm1

• Starts the VM with 2 CPUs, 4GB RAM.
• Forwards host port 2200 → guest port 22.
• Runs inside tmux session vm1.
• Connect with:

ssh alice@localhost -p 2200

Launch with tap networking:

sudo ./launch_vm.sh -i myvm.img -c 4 -m 8 -n tap -T tap0 -t vm-tap

• Starts the VM with 4 CPUs, 8GB RAM.
• Uses tap device tap0 for bridged networking.
• Runs inside tmux session vm-tap.