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GNOME Boxes: Create and Manage Linux VMs Quickly Without Complex Configuration

Virtualization tutorial - IT technology blog
Virtualization tutorial - IT technology blog

When Does Boxes Beat virt-manager?

2am, the staging server throws an error with a newly installed package. I need to quickly test on a clean environment, but the homelab Proxmox is running a backup — 12 VMs and containers are eating all the I/O. Open virt-manager: configure the network bridge, storage pool, firmware… 15 minutes just to create a VM. Not now.

GNOME Boxes solves exactly that problem: a VM running in 3 clicks, no need to know what libvirt or QEMU even are.

Three Tools, Three Different Problems

All three — Boxes, virt-manager, VirtualBox — can create VMs. But their target users are completely different, and picking the wrong tool isn’t because the tool is bad — it’s because it wasn’t designed for your use case:

GNOME Boxes

  • Target users: Developers, desktop users who need VMs quickly
  • Actual backend: QEMU/KVM (running under the hood)
  • UI: 3-step wizard, zero configuration
  • Advanced config: None — this is both a strength and a limitation

virt-manager

  • Target users: Sysadmins, users familiar with KVM/libvirt
  • Backend: libvirt (manages QEMU/KVM)
  • UI: Full options — network, storage pool, CPU topology, PCI passthrough
  • Advanced config: Yes — bridge networking, multiple disks, snapshots

VirtualBox

  • Target users: Cross-platform users (need to run on Windows/Mac too)
  • Backend: Proprietary hypervisor, doesn’t use KVM
  • UI: Familiar interface, many options
  • Advanced config: Yes, but performance is typically 20–30% worse than QEMU/KVM

Pros and Cons of Each Tool

GNOME Boxes — So Simple It Can Be… Frustrating

The main strength is zero configuration. Install it, drop in an ISO, wait a few minutes, and the VM is running. Boxes automatically creates the disk image, allocates RAM (defaults to about 1/4 of host RAM, minimum 1GB), and never asks what a bridge network is.

But that same simplicity is also a hard limit. I’ve often wanted to:

  • Attach a second disk to a VM — no UI to do it
  • Configure bridged networking so the VM gets its own IP on the LAN — not directly supported
  • Snapshot a VM before testing — Boxes doesn’t have this feature
  • USB passthrough for physical devices — have to switch to virt-manager or QEMU CLI

Bottom line: Boxes is suited for quick testing, not for managing VMs long-term.

virt-manager — Powerful but High Entry Barrier

virt-manager exposes the full power of KVM/QEMU through a graphical interface. Snapshots, bridge networking, PCI passthrough — all doable. But to create your first VM, you need to understand what a storage pool is, how NAT differs from bridged networking, where libvirtd runs. For newcomers, that’s too many concepts just to spin up Ubuntu.

VirtualBox — Familiar but Slower on Linux

VirtualBox has one genuine advantage: the same VM files run on Windows, Mac, and Linux. That’s the only reason to choose it. Because it doesn’t use KVM, performance is noticeably worse than QEMU — I/O benchmarks typically show a 20–30% gap, and CPU-intensive workloads are even worse. On pure Linux, there’s no good reason to pick VirtualBox.

Rule of Thumb: Which Tool to Choose?

After a few years using all three, here’s the pattern I follow:

  • Quick testing of a new OS, temporary isolated environment → Boxes (5 minutes from zero to a running VM)
  • Dev environment needing specific networking, snapshots, multiple disks → virt-manager
  • Production VMs, clusters, automated backups → Proxmox or libvirt/virsh
  • Cross-platform — need to run the same VM on Windows → VirtualBox

Installing GNOME Boxes

Ubuntu / Debian

sudo apt update
sudo apt install gnome-boxes

Fedora (usually pre-installed with GNOME Workstation)

sudo dnf install gnome-boxes

Arch Linux

sudo pacman -S gnome-boxes

After installing, verify KVM is loaded by the kernel:

lsmod | grep kvm
# Expected output:
# kvm_intel    xxx   0       (Intel)
# kvm          xxx   1 kvm_intel
# Or kvm_amd for AMD CPUs

No output? Go into your BIOS and enable Intel VT-x or AMD-V. Boxes will still run without KVM, but it’ll be painfully slow — software emulation can be 5–10× slower than KVM, depending on the workload.

Creating Your First VM with GNOME Boxes

Auto-Download an OS (Fastest Method)

Open Boxes → Click the + button in the top-left corner → select “Download an OS”. Boxes has a built-in list of Ubuntu, Fedora, Debian, openSUSE… Pick one, click Download, and the VM is automatically created and starts up.

Using an Existing ISO

  1. Click + → select “Use a file”
  2. Select the ISO file from your machine
  3. Boxes auto-detects the OS and fills in the VM name
  4. Review the RAM and disk configuration — adjustable at this step
  5. Click “Create” — the VM boots straight into the installer

Adjusting VM Configuration After Creation

Hover over the VM → click the ⋮ menu → “Properties”. Here you can adjust RAM, disk size, and 3D acceleration.

Practical Tips for Long-Term Use

Finding VM Disk Files

Boxes stores all VMs as qcow2 files:

ls -lh ~/.local/share/gnome-boxes/images/
# ubuntu-24.04.qcow2    8.5G
# fedora-40.qcow2       12G

These qcow2 files can be imported into virt-manager or used directly with QEMU when you need more advanced features. VMs aren’t locked into Boxes — that’s a plus that not many people notice.

Increasing Disk Size After VM Creation (Boxes Has No UI for This)

# 1. Shut down the VM first
# 2. Resize the qcow2 file
qemu-img resize ~/.local/share/gnome-boxes/images/ubuntu-24.04.qcow2 +20G

# Verify
qemu-img info ~/.local/share/gnome-boxes/images/ubuntu-24.04.qcow2

# 3. Inside the VM, extend the partition
sudo growpart /dev/vda 1
sudo resize2fs /dev/vda1

Manual Snapshots (Boxes Has No UI Support)

# Create a snapshot before testing
qemu-img snapshot -c "before-update" \
  ~/.local/share/gnome-boxes/images/ubuntu-24.04.qcow2

# List snapshots
qemu-img snapshot -l ~/.local/share/gnome-boxes/images/ubuntu-24.04.qcow2

# Rollback
qemu-img snapshot -a "before-update" \
  ~/.local/share/gnome-boxes/images/ubuntu-24.04.qcow2

Quick VM Cloning

cp ~/.local/share/gnome-boxes/images/ubuntu-24.04.qcow2 \
   ~/.local/share/gnome-boxes/images/ubuntu-24.04-clone.qcow2

Boxes auto-detects the new file when you restart the application.

Limitations to Know Before Committing Long-Term

My homelab runs Proxmox VE with 12 VMs and containers. Boxes still has its place in that workflow — for when I need to spin up a test VM in 3 minutes without logging into the Proxmox web UI. But make no mistake: Boxes and Proxmox solve completely different problems.

But let’s be realistic about what Boxes cannot do:

  • No snapshot UI: Must use qemu-img snapshot from the terminal
  • No bridged networking: VMs are NAT-only, no dedicated IP on your LAN
  • No USB passthrough: Requires virt-manager or QEMU CLI
  • No multiple NICs: Only 1 network card by default
  • No performance tuning: Can’t configure CPU pinning, hugepages, or NUMA

Need anything from that list? Switch to virt-manager. Don’t try to hack Boxes into doing something it was never designed for.

Conclusion

GNOME Boxes is the right choice when you need a “VM that just works” — no reading libvirt documentation at 2am, no need to understand what a storage pool is. Three clicks, VM running. Perfect for trying a new OS, testing packages in a clean environment, or giving a quick demo to a colleague.

When your workload gets more complex — dedicated networking, multiple disks, frequent snapshots — that’s when to migrate to virt-manager. Boxes does its job well as the first step into the world of virtualization on the Linux desktop, and that’s enough.

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