Debian 12: KVM Virtualization - creating guest (part 3)

To show available os for guest

$ virt-install --osinfo list | grep arch
archlinux

To use bridge add /etc/qemu/bridge.conf if not available and chmod file /usr/lib/qemu/qemu-bridge-helper

# mkdir /etc/qemu
# touch /etc/qemu/bridge.conf
# echo "allow br0" >> /etc/qemu/bridge.conf
# chmod u+s /usr/lib/qemu/qemu-bridge-helper


To create guest with name=guest01, disk size 10GB, Ram 2Gb (2048), virtual processor 2, os variant debian 12 (not available, we use debian11), boot from iso file: 

$ virt-install \
  --name guest01 \
  --memory 2048 \
  --vcpus 2 \
  --disk path=/home/dedetok/guests/guest01.qcoe2,size=10,bus=virtio \
  --cdrom /home/dedetok/Downloads/debian-12.11.0-amd64-netinst.iso \
  --nonetworks \
  --os-variant debian11 \
  --virt-type kvm

Parameters:

• --name: name to identify guest
• --ram: guest memory in megabytes
• --vcpus: number of cpu for guest
• --disk: path=<path_to_disk_image>,size=<disk_size_in_gb>,bus=virtio
  virtio is standard interface for virtual machines, it improve vm network performance
  
• --cdrom: install from iso file or CD/DVD/USB
• --nonetworks: no update or install from internet 
  or
  --network bridge=br0,model=virtio to use bridge network, see part 2
  For bridge see Network Bridge section
  

Options:

1. Graphics option
   • --graphics vnc: Enables VNC for graphical access. If virt-viewer is installed, it will automatically launch. If not, you'll need to manually connect using a VNC client like vinagre or remmina.
   • --graphics spice: Enables SPICE for graphical access. SPICE is generally considered more modern and efficient than VNC.
   • --graphics none: Disables graphical access and forces a text-mode installation using the serial console.
2. Disk option
   • Default folder for virtual disk /var/lib/libvirt/images/
     qcow2 offers features that raw (or img) doesn't:
   1. Snapshots: qcow2 allows you to create snapshots of your virtual machine's disk, enabling easy rollback to previous states.
   2. Compression: It can compress the disk image, potentially saving storage space.
   3. Sparse files: qcow2 supports sparse files, meaning it only allocates disk space for used portions of the image, which can be more efficient.
   • raw format (or just img when using virt-install) has no special features:
     It simply represents the raw data of the disk, which can be less flexible and potentially wasteful of disk space.

To show version

$ virsh version
Compiled against library: libvirt 9.0.0
Using library: libvirt 9.0.0
Using API: QEMU 9.0.0
Running hypervisor: QEMU 7.2.17

Managing VM

To List guest cm

$ virsh list --all


Connect to vm

$ virsh console [vm_name] 

or using virt-viewer 

$ virt-viewer [vm_name]

To edit vm 

$ virsh edit [vm_name]


To start vm

$ virsh start [vm_name]

to restart vm 

$ virsh reboot [vm_name] --mode initctl

to force stoping vm 

$ virsh destroy [vm_name]

to force shutdown vm 

$ virsh shutdown [vm_name] --mode acpi

to suspend vm 

$ virsh suspend [vm_name]

to resume vm after suspend 

$ virsh resume [vm_name]

to reset vm (similiar to pressing reset button on physical PC) 

$ virsh reset [vm_name]

Restarting KVM Daemon 

# systemctl restart libvirtd

to remove vm and its storage permanently  

$ virsh undefine --managed-save --remove-all-storage [vm_name]

To make vm auto run after host restart (run once) 

$ virsh autostart [vm_name]

Network bridge

Network configuration file:

1. /etc/libvirt/qemu/networks/default.xmlfir active configuration
   
2. /usr/share/libvirt/networks/default.xml for template

To enable network bridge for guest:

1. turn up bridge interface
   
2. list all network using virsh net-list
   
3. if list is empty, define default network and edit default network to use existing bridge
4. start network bridge

To turn up bridge interface 

# ifup br0

To show bridge interface  

# brctl show
bridge name    bridge id        STP enabled    interfaces
br0        8000.9aa237b1bcc8    no        enp2s0


To show network bridge (if list empty, see define default network) 

$ virsh net-list --all

To define default network 

$ virsh net-define /usr/share/libvirt/networks/default.xml


To undefined default network 

$ virsh net-undefine default

To edit default network 

$ virsh net-edit default

Change default network using edit default netowrk  

<network>
  <name>default</name>
  <uuid>84b29e1f-b2c3-4230-bc21-fba0143c026c</uuid>
  <forward mode='bridge'/>
  <bridge name='br0'/>
</network>

To start network bridge 

$ virsh net-start default


To auto start network bridge 

$ virsh net-autostart default

To add manually bridge network into vm edit vm and add 

<domain type='kvm'>
...
 <devices>
    <interface type='bridge'>
      <mac address='52:54:00:87:65:f6'/>
      <source bridge='br0'/>
      <model type='virtio'/>
      <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
...

References:

• wiki.debian.org/KVM
• wiki.debian.org/DebianInstaller/Preseed
• wiki.debian.org/BridgeNetworkConnections