How to enable KVM virsh console access

Requirements

The virtual machine must have the pty configured. From the KVM server edit the domain and make sure there is this section:

From KVM Server

sudo virsh edit virtual-machine

<serial type='pty'>
  <source path='/dev/pts/0'/>
  <target type='isa-serial' port='0'>
    <model name='isa-serial'/>
  </target>
  <alias name='serial0'/>
</serial>
<console type='pty' tty='/dev/pts/0'>
  <source path='/dev/pts/0'/>
  <target type='serial' port='0'/>
  <alias name='serial0'/>
</console>

From Debian / Ubuntu guest

You eithar have to enable the serial service or add it to grub.

Option 1: Enable Serial Service

sudo systemctl enable --now serial-getty@ttyS0.service

Option 2: Add console to grub

Search for the grub.cfg configuration file and add this to GRUB_CMDLINE_LINUX_DEFAULT:

GRUB_CMDLINE_LINUX_DEFAULT="console=tty0 console=ttyS0,115200n8"

From KVM server

virsh list
Id    Name                           State
----------------------------------------------------
1     freebsd                        running
2     ubuntu-box1                    running
3     ubuntu-box2                    running

Type the following command from KVM host to login to the guest named ubuntu-box1

virsh console ubuntu-box1

OR

virsh console 2

Use CTRL + 5 to exit the console.