2025-06-15 18:49:18 +02:00

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Ubuntu VM Management with Cloud Hypervisor

This directory contains scripts for creating and managing Ubuntu VMs using Cloud Hypervisor with btrfs thin provisioning.

Scripts Overview

ubuntu_vm_start.sh - Creates and starts new VMs
ubuntu_vm_manage.sh - Manages existing VMs (list, status, console, stop, etc.)
setup_vm_network.sh - Sets up networking for SSH access to VMs

Prerequisites

Root access
Btrfs filesystem (script will detect and guide setup)
Cloud Hypervisor installed
Basic networking tools

Quick Start

1. Set up networking (one-time setup)

sudo ./setup_vm_network.sh

2. Create and start a VM

sudo ./ubuntu_vm_start.sh my-vm 2048 2

This creates a VM named "my-vm" with 2GB RAM and 2 CPU cores.

3. List all VMs

sudo ./ubuntu_vm_manage.sh list

4. Connect to VM console

sudo ./ubuntu_vm_manage.sh console my-vm

Detailed Usage

Creating VMs

sudo ./ubuntu_vm_start.sh <vm_name> <memory_mb> <cpu_cores>

Examples:

# Create a small VM
sudo ./ubuntu_vm_start.sh test-vm 1024 1

# Create a larger VM
sudo ./ubuntu_vm_start.sh dev-vm 4096 4

What happens:

Downloads Ubuntu 24.04 cloud image (first time only)
Creates btrfs subvolumes for thin provisioning
Sets up cloud-init with default user
Creates network interfaces
Starts the VM with Cloud Hypervisor

Managing VMs

sudo ./ubuntu_vm_manage.sh <command> [vm_name]

Available commands:

Command	Description	Example
`list`	Show all VMs and their status	`./ubuntu_vm_manage.sh list`
`status <vm>`	Detailed status of specific VM	`./ubuntu_vm_manage.sh status my-vm`
`console <vm>`	Connect to VM console	`./ubuntu_vm_manage.sh console my-vm`
`stop <vm>`	Stop a running VM	`./ubuntu_vm_manage.sh stop my-vm`
`delete <vm>`	Delete VM completely	`./ubuntu_vm_manage.sh delete my-vm`
`ssh <vm>`	Show SSH connection info	`./ubuntu_vm_manage.sh ssh my-vm`

Accessing VMs

Method 1: Console Access (Always Available)

sudo ./ubuntu_vm_manage.sh console my-vm

Direct serial console access
No network required
Press Ctrl+A then X to exit
Default login: ubuntu / ubuntu

Method 2: SSH Access (Requires Network Setup)

Set up networking first:
```
sudo ./setup_vm_network.sh
```
Find VM IP address:
```
vm-ips
# or
arp -a | grep 192.168.100
```
SSH to the VM:
```
ssh ubuntu@192.168.100.X
```
Default password: ubuntu

Network Configuration

The setup_vm_network.sh script configures:

Bridge interface: br0 with IP 192.168.100.1/24
DHCP server: Assigns IPs 192.168.100.10-100 to VMs
NAT: Enables internet access for VMs
DNS: Uses Google DNS (8.8.8.8, 8.8.4.4)

Network Troubleshooting

Check bridge status:
```
ip addr show br0
```
Check VM IP assignments:
```
vm-ips
```
Check DHCP leases:
```
cat /var/lib/dhcp/dhcpd.leases
```
Restart networking:
```
systemctl restart dnsmasq
```

Storage (Btrfs)

VMs use btrfs subvolumes for efficient storage:

Base image: Shared read-only Ubuntu image
VM snapshots: Copy-on-write clones for each VM
Thin provisioning: Only changed blocks use disk space

Storage locations:

Base images: /var/lib/vms/base/
VM instances: /var/lib/vms/vms/<vm-name>/

Storage commands:

# List subvolumes
btrfs subvolume list /var/lib/vms

# Show space usage
btrfs filesystem usage /var/lib/vms

# Show individual VM sizes
du -sh /var/lib/vms/vms/*

VM Configuration

Default VM Setup:

OS: Ubuntu 24.04 LTS
User: ubuntu (password: ubuntu)
Sudo: Passwordless sudo enabled
SSH: Enabled with password authentication
Packages: curl, wget, git, htop, vim pre-installed

Customizing VMs:

Edit the cloud-init configuration in ubuntu_vm_start.sh to:

Add SSH keys
Install additional packages
Set custom passwords
Configure services

Troubleshooting

VM won't start:

Check if Cloud Hypervisor is installed:
```
which cloud-hypervisor
```
Check btrfs filesystem:
```
btrfs filesystem show /var/lib/vms
```
Check available resources:
```
free -h
nproc
```

Can't connect to VM:

Verify VM is running:
```
./ubuntu_vm_manage.sh status my-vm
```
Try console access first:
```
./ubuntu_vm_manage.sh console my-vm
```
Check network setup:
```
ip addr show br0
vm-ips
```

VM is slow or unresponsive:

Check host resources:
```
top
iostat
```
Adjust VM resources:
- Stop VM: ./ubuntu_vm_manage.sh stop my-vm
- Delete and recreate with different specs

Security Notes

Default password is ubuntu - change after first login
Consider adding SSH keys instead of password auth
VMs have internet access through NAT
Console access requires root privileges on host

Examples

Create a development environment:

# Set up networking
sudo ./setup_vm_network.sh

# Create VM
sudo ./ubuntu_vm_start.sh dev-env 4096 4

# Wait for boot, then connect
sudo ./ubuntu_vm_manage.sh console dev-env

# Inside VM, change password and install tools
passwd
sudo apt update && sudo apt install -y build-essential nodejs npm

Create multiple VMs:

# Create web server
sudo ./ubuntu_vm_start.sh web-server 2048 2

# Create database server
sudo ./ubuntu_vm_start.sh db-server 4096 2

# Create load balancer
sudo ./ubuntu_vm_start.sh lb 1024 1

# List all VMs
sudo ./ubuntu_vm_manage.sh list

Performance Tips

Use appropriate VM sizing - Don't over-allocate resources
Monitor host resources - Ensure sufficient RAM/CPU
Use btrfs compression - Add compress=zstd mount option
Regular cleanup - Delete unused VMs to free space
SSD storage - Use SSD for better I/O performance

Backup and Recovery

Backup a VM:

# Stop VM first
sudo ./ubuntu_vm_manage.sh stop my-vm

# Create snapshot
sudo btrfs subvolume snapshot /var/lib/vms/vms/my-vm /var/lib/vms/backups/my-vm-$(date +%Y%m%d)

Restore from backup:

# Delete current VM
sudo ./ubuntu_vm_manage.sh delete my-vm

# Restore from snapshot
sudo btrfs subvolume snapshot /var/lib/vms/backups/my-vm-20231215 /var/lib/vms/vms/my-vm

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