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# Technical Specification: Automated KVM Provisioning for Hoods Gate Testing
This document outlines the architecture and implementation of a shell-based
automation utility for deploying Kernel-based Virtual Machines (KVM) on Ubuntu
Server using virt-install. This approach is designed for rapid iteration in
kernel development and network stack testing where total environment isolation
is required.
## Overview
The goal of this implementation is to provide a reproducible, command-line
driven interface for deploying headless virtual machines. By utilizing a Linux
Bridge and Serial Console redirection, developers can perform destructive
kernel operations while maintaining persistent access to the debug output,
bypassing the overhead of a graphical user interface.
## System Requirements & Prerequisites
The host system must support hardware virtualization (Intel VT-x or AMD-V) and
have the following packages installed:
- qemu-kvm: Backend emulator
- libvirt-daemon-system: Management system
- virinst: CLI Utility for provisioning
- bridge-utils: Necessary for L2 network bridging
### Storage Persistence
Virtual disk images created by this script are stored in
/var/lib/libvirt/images/. During kernel testing, if the filesystem becomes
corrupted due to experimental kernel modules, the storage must be manually
purged or overwritten.
### Network Configuration
The host must have a bridge interface (e.g., br0) configured via Netplan.
This allows the Guest VM to obtain its own IP address and provides a
transparent environment for testing custom networking protocols or firewall
rules.
## Implementation
The script, [provision-lab.sh](./provision-vm.sh), automates the
virt-install process for isolated kernel and network testing. It utilizes local
ISO media and libosinfo detection to ensure hardware-optimized environments
while configuring the serial console for direct TTY access.
## Operational Procedures
### VM Creation
Execute the script with optional parameters for resource allocation:
```shell
sudo ./provision-vm.sh <name> <vcpus> <ram_in_mb>
```
### Interacting with the Guest Kernel
Since the VM is configured without a graphics card, the standard virsh console
command is used to attach to the guest's serial port. This is essential for
capturing Kernel Panics or Early Printk output that would otherwise be lost.
Attach to Console:
```shell
virsh console <vm-name>
```
Detach from Console (Press):
```
CTRL + ]
```
### Modifying Kernel Parameters
To test specific kernel options (e.g., disabling KASLR or isolating CPUs),
edit the VM configuration directly via the XML descriptor:
```shell
virsh edit <vm-name>
```
Locate the <cmdline> tag within the <os> section to append your required flags.
### Network Analysis
Use tcpdump -i br0 on the host to monitor raw packet traffic moving through the
VM's virtual interface.
```shell
tcpdump -i br0
```
## Lifecycle Management
Operation|Command|Description
Start|virsh start <name>|Powers on the virtual machine
Stop|virsh shutdown <name>|Sends an ACPI power signal for a graceful exit
Destroy|virsh destroy <name>|Equivalent to pulling the power plug (immediate stop)
Undefine|virsh undefine <name> --remove-all-storage|Completely removes the VM and its disk images
## Technical Considerations
When performing kernel modifications, the following behaviors should be expected:
- _Storage Persistence_: Changes made to the filesystem persist unless the --remove-all-storage flag is used during deletion.
- _Network Isolation_: By using a bridge, the VM possesses its own MAC address. Ensure the host firewall (ufw/iptables) is configured to allow traffic across the bridge.
- _Instruction Set Passthrough_: If the kernel testing requires specific CPU instructions (e.g., AES-NI), append --cpu host-passthrough to the virt-install command.
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