Virtualization
Create Virtual Machines (VMs), clone, run, test, study and use them.

Oracle VirtualBox @Windows10Pro

Cloning the machines and post-install for Oracle Linux v9
At the moment of writing, on 2025-07-18, my VirtualBox is v7.1.6.
 
 Open VirtualBox, find the source machine, click once to select 
 
 It is possible to either use menu: Snapshot> Clone
 
 Or click on [Clone] icon with a sheep:
 
 Or right-click on virtual machine itself:
 
 of press C-S-c (CTRL+SHIFT+c) or, from the list: C-o (CTRL+o) 
 Give machine a new name, check location and remember to choose "Generate new MAC for adapters". Your network infra will be happy to see healthy traffic and route it properly.
 
 When machne is cloned, let's start it:
 
 Post-cloning precedures 
 All commands executed in the elevated shell 
 sudo su
 
 Change hostname 
 hostnamectl hostname lt58dox1
 
 During cloning the machines, change physical ID and MAC address in the hypervisor (sometimes, it will not do it automatically in VirtualBox, proxmox and others). 
 When machines are cloned, 'machine ID': 
 cat /etc/machine-id
rm -f /etc/machine-id
systemd-machine-id-setup
systemd-machine-id-setup --commit --print
 
 SSH server's keys need to be re-generated to be seen as different machines 
 rm -rf /etc/ssh/ssh_host_*
ssh-keygen -A
ls -la /etc/ssh/ssh_host_*
 
 And finally perform reboot 
 shutdown -r now
 
 As there will be new MAC assigned, check for new IP addresses: 
 ip -br a

Adding more space to virtual machine by adding new disk and expanding using LVM
Daily task, which comes as daily routing, to extend the disk space: 
 Switch off the machine 
 Open VM properties in Oracle VirtualBox Manager, Storage,
 
 Click [Create]
 
 Name the disk accordingly to be consistent with other drives. Ensure that disk is saved nearby the VM itself. In my case, I am extending root partition for 50 GB.
 
 After new disk is created, choose it double-clicking it.
 
 Should end by seeing new disk in the virtual machine properties under 'Storage' list, attached to proper controller, 'SATA' - in my case.
 
 Confirm with [OK] 
 Power on the machine 
 List disks with. New disk should be visible. 
 lsblk
 
 
 Follow LVM Disk Extension guide to finalize extension.

Proxmox Virtual Environment (PVE)

Enabling no-subscription repositories
On Debian v13 (trixie) 
 mv /etc/apt/sources.list.d/pve-enterprise.sources /root
 
 Create new file 
 nano /etc/apt/sources.list.d/pve-no-subscription.list 
 
 repos 
 deb http://download.proxmox.com/debian/pve trixie pve-no-subscription
 
 Adjust Debian repos 
 nano /etc/apt/sources.list.d/debian.sources 
 
 repos 
 Types: deb
URIs: http://deb.debian.org/debian
Suites: trixie trixie-updates
Components: main contrib non-free-firmware
Signed-By: /usr/share/keyrings/debian-archive-keyring.gpg

Types: deb
URIs: http://security.debian.org/debian-security
Suites: trixie-security
Components: main contrib non-free-firmware
Signed-By: /usr/share/keyrings/debian-archive-keyring.gpg
 
 Verify repositories declaration 
 apt policy
 
 
 Do APT update 
 apt update
 
 
 List packages ready for update, most important that there are new packages from PVE repo. 
 apt list --upgradable
 
 
 Perform upgrade (when needed) 
 apt upgrade