KVM / libvirt

Idealistically, the introduction declared a “No Sworkstations” rule (No Server-Workstations). Pragmatically, you can bend this rule a bit, by hosting some development servers inside of virtual machines (VM). Hosting VMs on your workstation is convenient for having a portable lab environment. By using virtual machines for all services, we get to maintain our core distinction between the roles of workstation and server.

This paradigm is considerably more adhoc than a proper hypervisor operating system like Proxmox. For pure server installs, Proxmox should be preferred. But if you want to have a mixed-mode native workstation, with extra server VMs, in the same portable platform, this setup works really well.

nixos-vm-template

nixos-vm-template is a tool for building and managing NixOS virtual machines with an immutable (read-only) root filesystem design. If you installed Home Manager earlier, the vm alias is already configured for you.

Read these extra pages about nixos-vm-template:

• https://github.com/EnigmaCurry/nixos-vm-template
• https://blog.rymcg.tech/blog/linux/code-agent-vm/
• https://blog.rymcg.tech/blog/linux/nixos-proxmox-vm/

The vm alias

The vm alias is configured via Home Manager and points to the nixos-vm-template Justfile. Configuration is stored in ~/.config/nixos-vm-template/env, which sets writable paths for VM output and machine configs.

The vm alias has full tab completion for all commands, VM names, profiles, and other arguments. Press Tab to see available options at any point.

To see all available commands:

vm

Available VM profiles

List the available VM profiles (base images):

vm list-profiles

Creating a VM

Create a new VM with a given name and profile:

vm create myvm dev

This will:

• Build the profile’s base image (if not already built)
• Create machine identity files (hostname, SSH keys, etc.)
• Prompt for SSH public keys for admin and user accounts
• Create the boot and /var disks
• Define the VM in libvirt

Starting and stopping VMs

vm start myvm
vm stop myvm
vm force-stop myvm

Connecting to a VM

SSH into the VM (defaults to the user account):

vm ssh myvm
vm ssh admin@myvm

Open the VM console:

vm console myvm

Listing VMs

List all defined VMs:

vm list

List all machine configs:

vm list-machines

Managing VMs

Destroy a VM (removes disks but keeps machine config):

vm destroy myvm

Completely remove a VM including its machine config:

vm purge myvm

Recreate a VM from its existing machine config:

vm recreate myvm

Upgrade a VM to a new base image (preserves /var data):

vm upgrade myvm

Snapshots and backups

Create a snapshot:

vm snapshot myvm snapshot-name

List snapshots:

vm snapshots myvm

Restore a snapshot:

vm restore-snapshot myvm snapshot-name

Backup a VM:

vm backup myvm

List backups:

vm backups

Restore from backup:

vm restore-backup myvm