Installing Linux in a Virtual Machine

1. Why a virtual machine is the primary lab

A VM virtualizes enough hardware to boot a complete guest operating system. Unlike a container shell, it has its own kernel, PID 1, virtual disks, network devices, bootloader, and service lifecycle. That fidelity is required for later lessons on systemd, storage, boot recovery, firewalls, and kernel interfaces.

2. Understand the virtualization layers

flowchart TB
  H["Physical host hardware"] --> HV["Hypervisor or virtualization platform"]
  HV --> VM["Virtual CPU, memory, disk, firmware, and network"]
  VM --> K["Guest Linux kernel"]
  K --> US["Guest user space and services"]
  US --> LAB["DevOps Academy labs"]
  SNAP["Snapshot or clone"] -. captures .-> VM

VirtualBox, VMware Workstation/Fusion, Hyper-V, KVM/QEMU, and other platforms expose different interfaces, but the design choices are similar. Use a platform supported by your host and avoid running multiple competing hypervisors unless you understand their compatibility constraints.

3. Host preflight and resource sizing

4. Download and verify installation media

Use the distribution’s official download page and retrieve its published checksum. Verifying the ISO detects corruption and helps confirm that the file matches the release publisher’s manifest.

# Run on a Linux or WSL host after downloading the ISO and checksum file.
cd "$HOME/Downloads"

# Replace these example names with the actual downloaded files.
iso="linux-server.iso"
checksums="SHA256SUMS"

sha256sum "$iso"
grep "$(basename "$iso")" "$checksums"

# When the checksum file uses sha256sum-compatible lines:
sha256sum --check --ignore-missing "$checksums"

A checksum alone does not establish publisher identity if an attacker can replace both the ISO and checksum file. For higher assurance, follow the distribution’s documented signature-verification procedure using its official signing key.

5. Select the network mode deliberately

For the first installation, use NAT. Later, add a host-only adapter when you need stable host-to-guest SSH without exposing the VM to the entire LAN.

6. Installation plan

7. First boot: update, identify, and validate

Run the appropriate update commands for the chosen family. Read the package transaction before confirming it.

# Identify the distribution first.
cat /etc/os-release

# Debian/Ubuntu family
if command -v apt-get >/dev/null 2>&1; then
  sudo apt-get update
  sudo apt-get upgrade
fi

# Fedora/Rocky/AlmaLinux family
if command -v dnf >/dev/null 2>&1; then
  sudo dnf upgrade --refresh
fi

# Validate the complete guest.
printf '\n=== boot and init ===\n'
who -b
ps -p 1 -o pid,comm,args
systemctl is-system-running || true

printf '\n=== identity and network ===\n'
hostnamectl 2>/dev/null || hostname
ip -brief address
ip route

printf '\n=== storage ===\n'
lsblk -o NAME,SIZE,TYPE,FSTYPE,MOUNTPOINTS
findmnt -D

timedatectl status 2>/dev/null || date

If the upgrade installs a new kernel, reboot before creating the baseline snapshot, then confirm the running kernel with uname -r.

8. Optional host-to-guest SSH access

SSH makes copy-and-paste, file transfer, and automation easier. Confirm the server is installed and running inside the guest, then connect through a host-only address or a NAT port-forward configured in the hypervisor.

# Inside the guest
systemctl status ssh 2>/dev/null || systemctl status sshd
ss -lnt | grep ':22 '

# From another machine after confirming the guest address and firewall policy
ssh your_user@guest_address

# Record the host key fingerprint after first connection
ssh-keygen -F guest_address

9. Hands-on lab: create a machine baseline report

Capture the exact VM state that will define the clean checkpoint for Chapter 2.

lab="$HOME/devops-academy/linux/chapter02/lesson02"
mkdir -p "$lab"
cd "$lab"

{
  printf '=== distribution ===\n'
  cat /etc/os-release

  printf '\n=== kernel and architecture ===\n'
  uname -a

  printf '\n=== virtualization ===\n'
  systemd-detect-virt 2>/dev/null || true

  printf '\n=== boot and services ===\n'
  who -b
  ps -p 1 -o pid,comm,args
  systemctl --failed --no-pager 2>/dev/null || true

  printf '\n=== network ===\n'
  ip -brief address
  ip route

  printf '\n=== storage ===\n'
  lsblk -o NAME,SIZE,TYPE,FSTYPE,MOUNTPOINTS
  df -hT

  printf '\n=== updates ===\n'
  if command -v apt >/dev/null 2>&1; then
    apt list --upgradable 2>/dev/null || true
  elif command -v dnf >/dev/null 2>&1; then
    dnf check-update 2>/dev/null || true
  fi
} > vm-baseline-report.txt

less vm-baseline-report.txt

10. Common installation mistakes

11. Knowledge check

12. Summary

A useful VM lab is verified, deliberately sized, minimally exposed, fully updated, and documented. NAT is the safest initial network mode; a normal sudo-capable user is preferable to routine root login; and the first snapshot should represent a tested baseline rather than an unfinished installation.

13. Further reading

• Your selected distribution’s official installation guide and release notes.
• The hypervisor vendor’s documentation for virtual networking, snapshots, and guest integration.
• Linux manual pages for lsblk, findmnt, ip, ssh, and systemd-detect-virt.
• Distribution security documentation for update channels and installation-media verification.
• OpenSSH documentation — host keys, client trust, and secure remote administration.