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troubleshooting

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Troubleshooting Ubuntu in GNOME Boxes

Common Issues and Solutions

VM Won’t Start

Black Screen on Boot

# On the host, check if KVM is loaded
lsmod | grep kvm
 
# If not loaded, load KVM modules
sudo modprobe kvm
sudo modprobe kvm_intel  # For Intel CPUs
# OR
sudo modprobe kvm_amd    # For AMD CPUs

”Virtualization not enabled” Error

  • Reboot your host system and enter BIOS/UEFI
  • Look for: Virtualization Technology, VT-x (Intel), AMD-V (AMD), or SVM
  • Enable the virtualization option
  • Save and exit BIOS

VM Crashes During Boot

  1. In GNOME Boxes, right-click VM → Properties
  2. Reduce RAM allocation (might be over-allocated)
  3. Disable 3D acceleration temporarily
  4. Try booting with 1 CPU core first

Display Issues

Resolution Won’t Change / Stuck at Low Resolution

# In the VM, reinstall SPICE agent
sudo apt install --reinstall spice-vdagent
 
# Restart the service
sudo systemctl restart spice-vdagentd
 
# Force reload the kernel module
sudo modprobe -r vboxvideo  # Remove if exists
sudo modprobe virtio-gpu
 
# Manually set resolution
xrandr --output Virtual-1 --mode 1920x1080

No 3D Acceleration

# Check if 3D is working
glxinfo | grep "direct rendering"
 
# If it shows "No", install drivers
sudo apt install mesa-utils libgl1-mesa-glx libgl1-mesa-dri
 
# Check renderer
glxinfo | grep "OpenGL renderer"
# Should show "llvmpipe" or "virgl" for virtual GPU

Screen Tearing or Flickering

# Disable compositor effects
gsettings set org.gnome.desktop.interface enable-animations false
 
# Or try a different compositor
sudo apt install compton
compton --backend glx --vsync opengl-swc &

Performance Issues

VM Running Very Slowly

# Check if KVM acceleration is being used
grep -E 'vmx|svm' /proc/cpuinfo  # On host
# If no output, virtualization isn't enabled in BIOS
PP
# In the VM, verify KVM is being used
sudo apt install cpu-checker
kvm-ok
# Should report "KVM acceleration can be used"
 
# Check CPU governor
cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
# Set to performance if needed
echo performance | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor

High CPU Usage

# Find what's using CPU
top
# Or for better interface
htop
 
# Common culprits:
# - gnome-shell (try disabling extensions)
# - tracker-miner (disable file indexing)
sudo systemctl mask tracker-store.service tracker-miner-fs.service

Memory Issues

# Check memory usage
free -h
 
# Clear caches
sudo sync && echo 3 | sudo tee /proc/sys/vm/drop_caches
 
# Check for memory leaks
ps aux --sort=-%mem | head -10

Clipboard Not Working

Clipboard Sharing Broken

# Check if spice-vdagent is installed
dpkg -l | grep spice-vdagent
 
# Reinstall if needed
sudo apt install --reinstall spice-vdagent
 
# Check if service is running
systemctl status spice-vdagentd
 
# Start manually if needed
sudo systemctl start spice-vdagentd
 
# Check for running agent processes
ps aux | grep vdagent
# Should see both spice-vdagentd and spice-vdagent

Copy/Paste Only Works One Direction

# Kill and restart agents
sudo killall spice-vdagent
sudo systemctl restart spice-vdagentd
 
# Check logs for errors
journalctl -u spice-vdagentd -f

Network Problems

No Internet Connection

# Check network interfaces
ip addr show
 
# Restart network
sudo systemctl restart NetworkManager
 
# Check DNS
cat /etc/resolv.conf
# Should have nameserver entries
 
# Set DNS manually if needed
echo "nameserver 8.8.8.8" | sudo tee /etc/resolv.conf

Slow Network Speed

# Check current network driver
lspci -k | grep -A 3 -i network
 
# Should be using virtio driver
# If not, the VM might be using e1000 (slower)
 
# Test network speed
sudo apt install speedtest-cli
speedtest-cli

Shared Folders Not Working

Folder Not Appearing

# Check if spice-webdavd is installed and running
systemctl status spice-webdavd
 
# Install if missing
sudo apt install spice-webdavd
 
# Enable and start
sudo systemctl enable spice-webdavd
sudo systemctl start spice-webdavd
 
# Check for mounts
mount | grep webdav

Permission Denied on Shared Folder

# Check ownership
ls -la /media/
 
# Add user to necessary group
sudo usermod -aG fuse $USER
 
# Logout and login again
 
# If still not working, try manual mount
sudo mkdir /mnt/shared
sudo chmod 777 /mnt/shared

Audio Issues

No Sound in VM

# Check audio devices
pactl list short sinks
 
# Install PulseAudio volume control
sudo apt install pavucontrol
pavucontrol
 
# Check if output device is correct
 
# Restart PulseAudio
pulseaudio -k
pulseaudio --start

Crackling or Distorted Audio

# Edit PulseAudio config
sudo nano /etc/pulse/daemon.conf
 
# Add or modify:
default-sample-rate = 48000
default-fragments = 4
default-fragment-size-msec = 5
 
# Restart PulseAudio
pulseaudio -k

Boot Problems

VM Boots to GRUB Prompt

# At grub prompt, manually boot:
grub> set root=(hd0,1)
grub> linux /boot/vmlinuz root=/dev/sda1
grub> initrd /boot/initrd.img
grub> boot
 
# Once booted, repair GRUB:
sudo update-grub
sudo grub-install /dev/sda

Very Slow Boot Time

# Analyze boot
systemd-analyze blame
 
# Disable unnecessary services
sudo systemctl disable snapd.service
sudo systemctl disable ModemManager.service
 
# Remove quiet and splash for verbose boot (helps diagnose)
sudo nano /etc/default/grub
# Remove "quiet splash" from GRUB_CMDLINE_LINUX_DEFAULT
sudo update-grub

VM Management Issues

Can’t Delete VM

  1. Make sure VM is stopped
  2. Try from command line:
# List VMs
virsh list --all
 
# Force destroy if running
virsh destroy "Ubuntu-VM-Name"
 
# Undefine VM
virsh undefine "Ubuntu-VM-Name" --remove-all-storage

Snapshots Not Working

# Check disk space on host
df -h
 
# Clean up old snapshots in GNOME Boxes
# Right-click VM → Properties → Snapshots
# Delete old snapshots
 
# From command line
virsh snapshot-list "Ubuntu-VM-Name"
virsh snapshot-delete "Ubuntu-VM-Name" "snapshot-name"

Getting Help

Diagnostic Commands

# Comprehensive system info
sudo apt install inxi
inxi -Fxz
 
# VM-specific info
virsh dumpxml "VM-Name" | grep -E 'type|machine|os'
 
# Check GNOME Boxes logs
journalctl -u libvirtd -f

Log Files to Check

  • /var/log/syslog - General system logs
  • ~/.cache/gnome-boxes/logs/ - GNOME Boxes specific logs
  • /var/log/libvirt/qemu/ - QEMU/KVM logs

Most issues can be resolved by ensuring the SPICE tools are properly installed and running. When in doubt, a restart of both the VM and the SPICE services often helps!

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