KVM

Open VM ports to others

ssh -L 0.0.0.0:3000:localhost:4000 vmguest -p 5000 -l crz

3000: local port to open
4000: remote port to forward
5000: remote ssh port

DCHP

Release IP

sudo dhclient -r

ask DHCP

sudo dhclient

Manual IP config

ifconfig eth0 192.168.1.5 netmask 255.255.255.0 up
route add default gw 192.168.1.1
echo "nameserver 1.1.1.1" > /etc/resolv.conf
  

GPU Passthrough

intel_iommu=on iommu=pt to /etc/sysconfig/grub
Rebuild grub grub2-mkconfig -o /etc/grub2-efi.cfg
Check dmesg | grep -i -e DMAR -e IOMMU | grep enabled
Add pci-stub.ids=10de:11fa to /etc/sysconfig/grub
Rebuild grub grub2-mkconfig -o /etc/grub2-efi.cfg
Check lspci -nnk -d 10de:13c2 | grep stub

Trim qcow2

This is preferrable.

Cloud init

virt-install --name garlic \
	--memory 4096 --noreboot \
	--os-variant detect=on,name=ubuntu22.04 \
	--cloud-init user-data="/home/superman/cloudinit-user-data.yaml" \
	--disk=size=30,backing_store="/srv/images/jammy-server-cloudimg-amd64-disk-kvm.img"
  

Port forward

On /etc/libvirt/hooks/qemu:

#!/bin/bash

# IMPORTANT: Change the "VM NAME" string to match your actual VM Name.
# In order to create rules to other VMs, just duplicate the below block and configure
# it accordingly.
if [ "${1}" = "VM NAME" ]; then

   # Update the following variables to fit your setup
   GUEST_IP=
   GUEST_PORT=
   HOST_PORT=

   if [ "${2}" = "stopped" ] || [ "${2}" = "reconnect" ]; then
    /sbin/iptables -D FORWARD -o virbr0 -p tcp -d $GUEST_IP --dport $GUEST_PORT -j ACCEPT
    /sbin/iptables -t nat -D PREROUTING -p tcp --dport $HOST_PORT -j DNAT --to $GUEST_IP:$GUEST_PORT
   fi
   if [ "${2}" = "start" ] || [ "${2}" = "reconnect" ]; then
    /sbin/iptables -I FORWARD -o virbr0 -p tcp -d $GUEST_IP --dport $GUEST_PORT -j ACCEPT
    /sbin/iptables -t nat -I PREROUTING -p tcp --dport $HOST_PORT -j DNAT --to $GUEST_IP:$GUEST_PORT
   fi
fi
  

Resize not working

Things to try:

apt install spice-vdagent
Agent has 2 parts: spice-vdagentd running as root and spice-vdagent. The root service is started by spice-vdagent.socket but on Debian it does not activate it for some reason. Starting the user process seems to trigger the socket to active the service:

/usr/bin/spice-vdagent

Non-KDE/GNOME desktops may not resize automatically, for those: xrandr --output Virtual-0 --auto. Also a daemon that checks automatically can be used:

#!/bin/sh

set -eu

sleep_time=2

while true; do
  cmd="$(
    xrandr | awk '
      NR == 1 {
        gsub(/,/, "", $10)
        res_a = sprintf("%ix%i", $8, $10)
      }

            NR == 2 { display = $1 }
      
      NR == 3 { res_b = $1 }
      
      END {
        if (res_a != res_b) {
          printf("xrandr --output %s --auto\n", display)
        }
      }
      '
  )"

  if [ -n "$cmd" ]; then
    eval "$cmd"
  fi

  sleep "$sleep_time"
done

  