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7. Virtual machines

Install Virtual Machines from the App Catalog. It runs virtual machines with KVM, the hypervisor built into Linux. To run them at full speed, the processor needs VT-x or AMD-V, turned on in the computer's firmware (Hardware). Without it, virtual machines still run, but very slowly.

Creating a virtual machine

Virtual Machines > Create... offers three ways:

  • A ready-made system: Debian, Ubuntu or AlmaLinux, ready in one click, with no installer to go through and an account made for you. The image comes from its publisher, checked against the publisher's own checksums, and is kept for the next virtual machine, which can then be made without the internet. Its disk is at least as large as the publisher's image (OSM says so if the size chosen is smaller). OSM makes the account's password: it is shown when the virtual machine is made, and again with Account... in its More menu.
  • A virtual machine: Windows, Linux or anything else, from its installer ISO. Upload the ISO file with Files first (for example to an iso folder on a volume), then choose it here.
  • OSM: to try OSM in OSM, started from OSM's installer. Put OSM's USB image or ISO in a shared folder with Files first.

Then choose:

  • the processors, memory and disk size (the disk is a file on a volume, which grows as it is used);
  • the network: on the server's bridge, the virtual machine gets its own address from your router, like any computer; on NAT, it reaches the network through the server and is hidden behind it;
  • UEFI with Secure Boot, and a TPM 2.0 (needed by Windows 11).

Using a virtual machine

  • Connect opens the screen of a running virtual machine in a window of the desktop, with its keyboard and mouse.
  • Shut down asks the system inside to shut down; Force stop is like pulling the plug; Pause and Resume freeze and continue it.
  • Settings... changes its priority, whether it starts with the server, the ISO in its CD drive and, while it is shut down, its processors and memory. Its disks and network stay as they were made.
  • To take the ISO out once the system is installed, choose (empty) for CD / ISO in Settings.... An OSM virtual machine started from OSM's USB image has Remove the installer... in its More menu instead.
  • Delete... removes the virtual machine and its disk files, unless you tick Keep its disk files.

Priority and start order

Like apps, each virtual machine has a Priority: Critical, High, Normal or Low, for the processor and the disks when the server is busy. When the server starts, the virtual machines that start with it come up in order of priority, Critical first. One that cannot start then (not enough memory, for example) is a notification that says why.

Devices

PCI and USB devices... gives a device of the server to one virtual machine: a USB stick or dongle, a graphics card, a network card, a disk controller.

  • PCI devices need the IOMMU (VT-d or AMD-Vi) turned on in the firmware; OSM then turns it on in Linux with one switch, which takes a restart. A device is given with the other devices of its IOMMU group, which Settings > System Info > Hardware lists; the group of the chipset itself cannot be given away.
  • PCI devices are added and removed only while the virtual machine is shut down; USB devices also while it runs.
  • A device the server uses itself is marked The server uses it. To give it away anyway, you tick I understand, and want it anyway: the server can lose its disks, its network or its screen.
  • While the virtual machine runs, the device belongs to it alone; it comes back to the server afterwards.

Protecting a virtual machine's data

A virtual machine's disks are files in a system folder of a volume, so the volume's RAID protects them from a failed disk. Snapshots and backup tasks cover shared folders, not those files: back up what matters from inside the virtual machine (to a shared folder of the server, for example), or keep its data in a shared folder it reaches over the network.