OphirCloud Academy
Virtual machines · slides
15 slides · text and inline SVG only, so it is safe to publish.
01 / 15
Virtual machines
- Architecture, hypervisors, and the foundation of modern cloud computing.
- OphirCloud Academy · Road to certification
02 / 15
The apartment building
- Physical hardware: the land, plumbing and electricity.
- The hypervisor: the manager allocating space and enforcing the rules.
- Guest OS: tenants who each believe the building is theirs alone.
03 / 15
The virtualisation stack
- Physical hardware — CPU, memory, disk, network.
- Hypervisor — the abstraction layer that divides it.
- Guest OS — an isolated execution environment with its own kernel.
04 / 15
Type 1 and Type 2
- Type 1 (bare metal): runs directly on hardware — ESXi, Proxmox, Hyper-V, KVM. Maximum performance; what a data centre uses.
- Type 2 (hosted): runs as an application on your desktop — VirtualBox, VMware Workstation. One more operating system in the stack.
05 / 15
Hardware-assisted virtualisation
- Ring 3: applications. Ring 0: the guest kernel.
- Intel VT-x and AMD-V add a new privilege level — VMX root mode — for the hypervisor.
- Without it, the guest kernel had to be rewritten; with it, guests run unmodified.
06 / 15
What isolation buys you
- A compromised application is contained by a boundary the kernel enforces.
- A guest cannot read another guest's memory or files.
- The boundary is hardware-enforced, not a convention.
07 / 15
Why virtualise
- Security: strict boundaries between workloads.
- Portability: a guest is a bundle of files; move it or copy it.
- Legacy: run older software safely, next to the new stack.
- Efficiency: many workloads on one physical machine.
08 / 15
What it costs
- The guest OS tax: a full kernel is booted for every instance.
- Memory overhead: reservations are made whether or not they are used.
- Duplication: the same scheduling and drivers, repeated per guest.
- Boot times measured in minutes, not milliseconds.
09 / 15
The DevOps VM toolchain
- Packer — bake immutable golden images.
- Terraform — declare the compute resources.
- Ansible / Chef — enforce post-boot configuration.
- Vagrant — reproduce the environment locally.
10 / 15
The market
- VMware ESXi — the data centre standard.
- Microsoft Hyper-V — Windows integration first.
- KVM — the open-source powerhouse, and what most public clouds run.
11 / 15
VMs versus containers
- VMs: hardware virtualisation, heavy isolation, minutes to boot.
- Containers: OS-level virtualisation, shared kernel, milliseconds to boot.
- Both are isolation; only one ships an operating system with every instance.
12 / 15
The backbone of IaaS
- AWS EC2, Azure VMs and GCP Compute Engine are distributed hypervisors with an API.
- You never touch the hardware — you hold a policy and a record of what should exist.
13 / 15
Networking you will meet
- Bridged: the guest sits on your LAN and can be reached.
- NAT: the guest reaches out, but nobody reaches in.
- Host-only: a private link between host and guest, no internet.
- Most 'I cannot connect to my VM' is this adapter setting, not the firewall.
14 / 15
Snapshots, clones, templates
- A snapshot freezes a disk state so you can experiment and roll back.
- A clone copies a VM; a template is a clone you cannot start by accident.
- A snapshot lives with its disk — it is not a backup.
15 / 15
Where to go next
- Read: /learn/virtual-machines
- Do: the EC2 lab (aws-ec2-01) and the services lab (linux-services-01)
- Then: Containers and Kubernetes — what the guest OS tax buys you out of.
Diagrams are inline SVG drawn for this course; no stock imagery is used. Print to PDF from the browser to keep a copy.