Linux Virtual Machines

This document will explore creating and managing virtual machines on Linux with the following VM stack:

Resources

Installation on OpenSUSE 15.5

Use zypper to install libvirt, qemu, and virt-manager:

Note: This may install ~145 packages and may take a few minutes.

zypper install libvirt qemu virt-manager

Next, enable the libvirtd service:

mawenzi-06:~/ccarlson # systemctl enable --now libvirtd
Created symlink /etc/systemd/system/multi-user.target.wants/libvirtd.service → /usr/lib/systemd/system/libvirtd.service.
Created symlink /etc/systemd/system/sockets.target.wants/virtlockd.socket → /usr/lib/systemd/system/virtlockd.socket.
Created symlink /etc/systemd/system/sockets.target.wants/virtlogd.socket → /usr/lib/systemd/system/virtlogd.socket.
Created symlink /etc/systemd/system/sockets.target.wants/libvirtd.socket → /usr/lib/systemd/system/libvirtd.socket.
Created symlink /etc/systemd/system/sockets.target.wants/libvirtd-ro.socket → /usr/lib/systemd/system/libvirtd-ro.socket.

Start the libvirtd service:

mawenzi-06:~/ccarlson/vms # systemctl start libvirtd
mawenzi-06:~/ccarlson/vms # systemctl status libvirtd
● libvirtd.service - Virtualization daemon
     Loaded: loaded (/usr/lib/systemd/system/libvirtd.service; enabled; vendor preset: disabled)
     Active: active (running) since Thu 2025-08-21 14:48:14 MDT; 29s ago
TriggeredBy: ● libvirtd.socket
             ● libvirtd-admin.socket
             ● libvirtd-ro.socket
       Docs: man:libvirtd(8)
             https://libvirt.org
   Main PID: 28603 (libvirtd)
      Tasks: 19 (limit: 32768)
     CGroup: /system.slice/libvirtd.service
             └─ 28603 /usr/sbin/libvirtd --timeout 120

Aug 21 14:48:14 mawenzi-06 systemd[1]: Starting Virtualization daemon...
Aug 21 14:48:14 mawenzi-06 systemd[1]: Started Virtualization daemon.

virt-install

https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/7/html/virtualization_deployment_and_administration_guide/sect-guest_virtual_machine_installation_overview-creating_guests_with_virt_install

CLI for creating Guest domains (guest VMs).

virsh

https://www.libvirt.org/manpages/virsh.html

Virsh is a management CLI that interfaces with the libvirt API and is used to manage VMs.

Terminology:

  • Node: the baremetal host we’re running on

  • Domain: A virtual machine

List networks

Lists all networks.

virsh net-list

Example
mawenzi-06:~ # virsh net-list
 Name   State   Autostart   Persistent
----------------------------------------

List all domains

Lists all domains, even ones that are shut off.

virsh list --all

Example
sp08:~ # virsh list --all
 Id   Name          State
------------------------------
 1    cm_1_admin    running
 2    cm_1_n1       running
 3    cm_1_n2       running
 4    cm_2_admin    running
 5    cm_2_n1       running
 6    cm_2_n2       running
 7    cm_3_admin    running
 8    cm_3_n1       running
 9    cm_3_n2       running
 -    cm_cc_admin   shut off
 -    daos_1_n1     shut off
 -    daos_1_n2     shut off
 -    daos_1_n3     shut off
 -    daos_1_n4     shut off
 -    daos_1_n5     shut off

Get summary information about domain

Shows information about a domain.

virsh dominfo <domain>

Example
sp08:~ # virsh dominfo cm_1_admin
Id:             1
Name:           cm_1_admin
UUID:           0b44a7e9-b0ee-430b-9a3d-a2bbdd9eeb8c
OS Type:        hvm
State:          running
CPU(s):         6
CPU time:       2940.9s
Max memory:     12582912 KiB
Used memory:    12582912 KiB
Persistent:     yes
Autostart:      disable
Managed save:   no
Security model: apparmor
Security DOI:   0

Get information about host

virsh nodeinfo

Shows information about our KVM host.

Example
sp08:~ # virsh nodeinfo
CPU model:           x86_64
CPU(s):              24
CPU frequency:       2510 MHz
CPU socket(s):       1
Core(s) per socket:  6
Thread(s) per core:  2
NUMA cell(s):        2
Memory size:         98783136 KiB

Start a domain

virsh start <domain>

Starts up a domain. Akin to booting up a node.

Autostart a domain

virsh autostart <domain>

Mark domain to automatically start when the host starts.

libvirt

https://www.libvirt.org/