KVM Hypervisor notes

Installation

Set up a new virtual machine (VM)

Apparently, one way to test is to install and launch a copy of this OS itself which arrives from a remote location:

# virt-install --name ubuntu-guest --os-variant ubuntu20.04 --vcpus 2 --ram 2048 --location \
               --location http://ftp.ubuntu.com/ubuntu/dists/focal/main/installer-amd64/ \
               --network bridge=virbr0,model=virtio --graphics none \
               --extra-args='console=ttyS0,115200n8 serial'

When you do this, you see a TUI and things unfold pretty much as they do during a proper installation of Ubuntu 20.04. The installation complete, I looked at the network interface configuration to see if, as happens to the hosting operation system running VirtualBox, I could find the guest OS' IP address. Sure enough. Then I logged in via ssh:

$ ifconfig
        ...

virbr0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.122.1  netmask 255.255.255.0  broadcast 192.168.122.255
        ether 52:54:00:94:67:a3  txqueuelen 1000  (Ethernet)
        RX packets 36935  bytes 2061031 (2.0 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 51072  bytes 412408442 (412.4 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

        ...
$ ssh 192.168.122.1
The authenticity of host '192.168.122.1 (192.168.122.1)' can't be established.
ED25519 key fingerprint is SHA256:WNU9rI1TVlhY8cbJ24dVc0mF2KgQcsetgpRyLOnSOX8.
This key is not known by any other names
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added '192.168.122.1' (ED25519) to the list of known hosts.
[email protected]'s password:
Welcome to Ubuntu 22.04.1 LTS (GNU/Linux 5.15.0-48-generic x86_64)

 * Documentation:  https://help.ubuntu.com
 * Management:     https://landscape.canonical.com
 * Support:        https://ubuntu.com/advantage

  System information as of Thu Sep 22 10:28:49 PM UTC 2022

  System load:  0.0615234375       Users logged in:          1
  Usage of /:   2.1% of 914.78GB   IPv4 address for docker0: 172.17.0.1
  Memory usage: 3%                 IPv4 address for enp0s25: 192.168.0.108
  Swap usage:   0%                 IPv4 address for enp0s25: 192.168.0.121
  Temperature:  39.0 C             IPv4 address for virbr0:  192.168.122.1
  Processes:    220

 * Super-optimized for small spaces - read how we shrank the memory
   footprint of MicroK8s to make it the smallest full K8s around.

   https://ubuntu.com/blog/microk8s-memory-optimisation

1 update can be applied immediately.
To see these additional updates run: apt list --upgradable


Last login: Thu Sep 22 22:28:49 2022 from 192.168.0.149
$

However, I immediately (and silently) lost my ssh session; I'll have to figure out what that's all about.

KVM/s filesystem presence

/var/lib/libvirt/
├── boot
├── dnsmasq
├── images       # where the VM image storage is kept (i.e.: the VM's diskspace)
├── qemu
└── sanlock

Using virsh to manage an existing (VM)

Apparently, this is done using the virsh command. First, list the VM to get its name:

# virsh list
 Id   Name           State
------------------------------
 2    ubuntu-guest   running

Before removing this VM, let's think about what would be important were we to have a truly complex KVM set-up.

# virsh dumpxml --domain vm-name
(lots of XML describing the VM)
# virsh dumpxml --domain ubuntu-guest | grep 'source file'
      <source file='/var/lib/libvirt/images/ubuntu-guest.qcow2' index='1'/>

Other useful commands:

Tearing down and removing an existing (VM)

Start by getting the VM's name.

# virsh list
 Id   Name           State
------------------------------
 2    ubuntu-guest   running

There's no way to remove the storage associated with a VM, so be sure to find out what that is and make a note of it:

# virsh dumpxml --domain ubuntu-guest | grep 'source file'
      <source file='/var/lib/libvirt/images/ubuntu-guest.qcow2' index='1'/>

How to delete the VM:

# virsh undefine vm-name --remove-all-storage
# rm -rf filesystem-path

Following this, let's delete the VM we created (and spent the time installing—yikes!) and its filesystem storage. I don't need this VM; I only created it because the tutorial I was following did it. First, shut down the VM.

# virsh shutdown ubuntu-guest
Domain 'ubuntu-guest' is being shutdown
# virsh undefine ubuntu-guest --remove-all-storage
# virsh list
 Id   Name   State
--------------------
# rm -rf '/var/lib/libvirt/images/ubuntu-guest.qcow2'

SELinux or AppArmor issues...

Decidedly, there's more to do. I believe the problem above, if running on CentOS (Red Hat), would be an SELinux issue. On Ubuntu, the present case, it's an AppArmor issue and I have not yet found a solution (though I have tried several). The trick is mainstreaming libvirt's use by a dedicated user or group or carefully exempting it from scrutiny.

(No, I do not understand why the Ubuntu guest OS VM installed and ran without this problem.)

I'll have to get back to this. One obstacle is that the Cypress validator is no longer particularly useful (as it once was) even when it can be got to run. It's child's play to do that using VirtualBox, but then the troubles only begin. So, I lack motivation.

Install software for remote virtualization management

# kvm-ok
INFO: /dev/kvm exists
KVM acceleration can be used
# apt-get update
# apt-get install qemu-kvm libvirt-daemon-system
# adduser russ libvirt                             # adds me to this group

At this point, it's ready to get a guest OS installed. The point is to be able to do this from a remote host, ostensibly with a GUI. In particular, I have an .ova image for the Cypress 7 VM. I'm going to try that remotely.