Troubleshooting KVM Issues

🧱 1️⃣ Initial Symptom ❌ “Booting from hard disk…” (hangs) What This Means Technically Firmware attempted to boot from the virtual disk but: Could not find a valid bootloader Or could not understand the partition scheme Or firmware mode didn’t match OS install mode This message comes from firmware (not Linux). In KVM environments, firmware is provided by: Legacy BIOS (SeaBIOS) UEFI (OVMF from TianoCore) 🔎 2️⃣ First Investigation: Is the Disk Corrupted? We checked: qemu-img info virt-filesystems What We Found qcow2 format valid Not corrupted GPT layout /dev/sda1 → vfat (511M) /dev/sda2 → ext4 /dev/sda3 → swap Critical Clue vfat EFI partition = UEFI installation That immediately ruled out: Disk corruption Missing root filesystem Missing GRUB files 💡 Lesson: Always inspect disk structure before guessing. ⚡ 3️⃣ Root Cause #1 — Firmware Mismatch Your VM XML showed: <os> <type arch= 'x86_64' machine= 'pc-q35-9.2' > hvm </type> <boot dev= 'hd' /> </os> No <loader> entry → That means legacy BIO