LPIC-3 304: Virtualization & High Availability — Deep Dive Study Guide

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Complete LPIC-3 certification guide: exam objectives for 300 Mixed Environment, 303 Security, and 304 Virtualization & High Availability specializations.

The LPIC-3 304: Virtualization & High Availability exam covers hardware virtualization (KVM, Xen), OS-level virtualization (LXC/LXD), high-availability clustering with Pacemaker, block-level replication with DRBD, load balancing, and cluster storage. This guide provides comprehensive coverage of each objective.

KVM Virtualization

Architecture

KVM (Kernel-based Virtual Machine) turns the Linux kernel into a type-1 hypervisor using hardware virtualization extensions (Intel VT-x / AMD-V). QEMU provides device emulation, and libvirt provides management abstraction.

libvirt and virsh

grep -E "(vmx|svm)" /proc/cpuinfo
kvm-ok

# List active VMs
virsh list

# List all VMs (including inactive)
virsh list --all

# Get VM details
virsh dominfo vm1

# Start and stop VMs
virsh start vm1
virsh shutdown vm1
virsh destroy vm1   # Force power-off

# VM lifecycle
virsh suspend vm1
virsh resume vm1
virsh reboot vm1

VM Provisioning with virt-install

# Create a new VM from ISO
virt-install \
  --name vm1 \
  --memory 4096 \
  --vcpus 2 \
  --disk size=50,format=qcow2,bus=virtio \
  --cdrom /iso/debian-12.iso \
  --network network=default,model=virtio \
  --graphics vnc,listen=0.0.0.0 \
  --os-variant debian12

# Create VM with existing disk image
virt-install \
  --name vm2 \
  --memory 8192 \
  --vcpus 4 \
  --disk /var/lib/libvirt/images/vm2.qcow2,bus=virtio \
  --import \
  --network bridge=br0,model=virtio \
  --os-variant linux

# Unattended installation with --location
virt-install \
  --name web1 \
  --memory 2048 \
  --vcpus 1 \
  --disk size=20 \
  --location http://deb.debian.org/debian/dists/stable/main/installer-amd64/ \
  --extra-args "auto preseed/url=http://web/preseed.cfg"

Network Configurations

# Create a bridge on the host
nmcli con add type bridge ifname br0
nmcli con add type ethernet ifname eno1 master br0

# Attach VM to bridge
virt-install --network bridge=br0 ...

Storage Configurations

# Create qcow2 disk
qemu-img create -f qcow2 vm1.qcow2 50G
qemu-img create -f qcow2 -b base.qcow2 -F qcow2 vm1.qcow2  # Backing file (thin provisioning)

# Resize disk
qemu-img resize vm1.qcow2 +20G

# Convert disk format
qemu-img convert -f raw -O qcow2 disk.raw disk.qcow2

# Add disk to VM
virsh attach-disk vm1 /var/lib/libvirt/images/data.qcow2 vdb --persistent
virsh detach-disk vm1 vdb --persistent

Live Migration

# Migrate running VM to another host (shared storage)
virsh migrate --live vm1 qemu+ssh://dest-host/system

# Non-shared storage migration with copying
virsh migrate --live --copy-storage-all vm1 qemu+ssh://dest-host/system

# Tunneled migration (encrypted over SSH)
virsh migrate --live --tunnelled vm1 qemu+ssh://dest-host/system

Xen Hypervisor

Xen uses a different architecture than KVM, with a privileged Domain 0 (Dom0) that manages unprivileged DomU guests.

Xen Usage

# List domains
xl list

# Create a PV (para-virtualized) guest
xl create /etc/xen/vm1.cfg

# DomU config: /etc/xen/vm1.cfg
kernel = "/boot/vmlinuz-6.1"
ramdisk = "/boot/initrd.img-6.1"
memory = 2048
name = "vm1"
vcpus = 2
disk = ["phy:/dev/vg_xen/vm1-root,xvda2,w"]
root = "/dev/xvda2"

# Migrate Xen guest
xl migrate vm1 dest-host

# Save and restore
xl save vm1 /tmp/vm1.state
xl restore /tmp/vm1.state

PV vs HVM vs PVH

• PV (Paravirtualized): Guest kernel is modified for Xen. No hardware virtualization required. Best performance but requires kernel support.
• HVM (Hardware Virtual Machine): Full hardware virtualization. Unmodified guests run with QEMU device emulation.
• PVH: Hybrid — uses PV for I/O but HVM for CPU/memory. Best of both worlds.

LXC/LXD Containers

LXC Commands

# List containers
lxc-ls -f

# Create a container
lxc-create -t download -n container1 -- --dist debian --release bookworm --arch amd64

# Start and attach
lxc-start -n container1 -d
lxc-attach -n container1

# Execute command in container
lxc-attach -n container1 -- apt update

# Snapshot
lxc-snapshot -n container1
lxc-snapshot -n container1 -L    # list snapshots
lxc-snapshot -n container1 -r snap0  # restore

LXD (Next-Gen LXC)

# Initialize LXD
lxd init

# Launch a container
lxc launch ubuntu:24.04 my-container

# List containers
lxc list

# Execute commands
lxc exec my-container -- apt upgrade

# Configure resource limits
lxc config set my-container limits.memory 2GB
lxc config set my-container limits.cpu 2

# File operations
lxc file pull my-container/etc/hosts .
lxc file push hosts my-container/etc/hosts

# Snapshot management
lxc snapshot my-container backup1
lxc restore my-container backup1

# Container images
lxc image list
lxc image copy ubuntu:24.04 local: --alias my-ubuntu

LXC vs KVM Comparison

Pacemaker/Corosync Clustering

Architecture

• Corosync: Provides messaging, membership, and quorum services
• Pacemaker: Cluster resource manager that handles failover
• Resource Agents: Scripts that manage start/stop/monitor of services

Cluster Setup

# Install on all nodes
apt-get install pacemaker corosync pcs

# Authenticate nodes (run on one node)
pcs host auth node1 node2 -u hacluster

# Create cluster
pcs cluster setup mycluster node1 node2

# Start cluster
pcs cluster start --all

# Check status
pcs status
crm_mon -1

Resource Configuration

# Disable STONITH (lab only — never in production)
pcs property set stonith-enabled=false

# Set quorum policy
pcs property set no-quorum-policy=ignore

# Create a virtual IP resource
pcs resource create virtual_ip ocf:heartbeat:IPaddr2 \
  ip=10.0.0.100 cidr_netmask=24 \
  op monitor interval=10s

# Create a webserver resource group
pcs resource create web_server systemd:nginx \
  op monitor interval=30s
pcs resource group add webservice virtual_ip web_server

# Create a filesystem resource
pcs resource create web_fs ocf:heartbeat:Filesystem \
  device=/dev/drbd0 directory=/var/www fstype=ext4

# Resource constraints
pcs constraint colocation add web_fs with drbd_master INFINITY
pcs constraint order drbd_master then web_fs

Fencing (STONITH)

# IPMI fencing
pcs stonith create ipmi-fence fence_ipmilan \
  pcmk_host_list="node1 node2" \
  ipaddr=10.0.0.201 login=admin passwd=secret \
  lanplus=1

# Check fence device
pcs stonith show ipmi-fence

# Test fencing
pcs stonith fence node1

DRBD (Distributed Replicated Block Device)

Resource Configuration

# /etc/drbd.d/web.res
resource web {
   protocol C;
   on node1 {
      device /dev/drbd0;
      disk /dev/vg_drbd/web-data;
      address 10.0.0.1:7788;
   }
   on node2 {
      device /dev/drbd0;
      disk /dev/vg_drbd/web-data;
      address 10.0.0.2:7788;
   }
}

DRBD Commands

# Create metadata
drbdadm create-md web

# Enable resource
drbdadm up web

# Set primary (initial setup — on one node only)
drbdadm primary --force web

# View status
drbdadm status
cat /proc/drbd

# Switch primary role
drbdadm primary web
drbdadm secondary web

# Resync after split-brain
drbdadm -- --discard-my-data connect web

DRBD Replication Protocols

Load Balancing

keepalived (VRRP)

# /etc/keepalived/keepalived.conf
vrrp_instance VI_1 {
   state MASTER
   interface eth0
   virtual_router_id 50
   priority 100
   advert_int 1
   authentication {
      auth_type PASS
      auth_pass secret123
   }
   virtual_ipaddress {
      10.0.0.100/24 dev eth0
   }
}

virtual_server 10.0.0.100 80 {
   delay_loop 6
   lb_algo rr
   lb_kind NAT
   protocol TCP
   real_server 10.0.0.10 80 {
      weight 1
      HTTP_GET {
         url { path /health }
      }
   }
   real_server 10.0.0.11 80 {
      weight 1
      HTTP_GET {
         url { path /health }
      }
   }
}

# Manage
systemctl restart keepalived
ip addr show   # Virtual IP should appear on master

HAProxy

# /etc/haproxy/haproxy.cfg
global
   log /dev/log local0
   chroot /var/lib/haproxy
   stats socket /run/haproxy/admin.sock mode 660 level admin

defaults
   mode http
   timeout connect 5000ms
   timeout client 50000ms
   timeout server 50000ms

frontend http-in
   bind *:80
   default_backend servers

backend servers
   balance roundrobin
   option httpchk GET /health
   server web1 10.0.0.10:80 check weight 10
   server web2 10.0.0.11:80 check weight 10
   server web3 10.0.0.12:80 check weight 5 backup

HAProxy Stats

# Enable stats interface
listen stats
   bind *:8080
   stats enable
   stats uri /
   stats auth admin:password

Cluster Storage

GFS2 (Global File System 2)

# Create GFS2 on shared storage
mkfs.gfs2 -p lock_dlm -j 2 -t mycluster:web /dev/drbd0

# Mount (on both nodes)
mount /dev/drbd0 /var/www

# GFS2 management
gfs2_tool sb /dev/drbd0 all
gfs2_edit -p journal /dev/drbd0

OCFS2 (Oracle Cluster File System 2)

# Create OCFS2
mkfs.ocfs2 --cluster-stack=o2cb --cluster-name=mycluster /dev/sdb1

# Mount
mount -t ocfs2 /dev/sdb1 /shared

# Management
o2info --fs /shared
tunefs.ocfs2 -Q "LABEL=shared_data" /dev/sdb1

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