Glossary
Short definitions for terms that come up across multiple tiers but don't warrant their own deep-dive page.
Terms defined once here and linked to from wherever they come up, rather than re-explained on every page that uses them.
Hypervisor
Software that creates and runs virtual machines by sharing a physical machine's CPU, RAM, and storage between them. Proxmox VE is a "type 1" (bare-metal) hypervisor - it runs directly on hardware rather than on top of another OS. See Why Virtualize?.
Virtual machine (VM)
A fully emulated computer - its own kernel, its own virtual hardware - running as a guest on a hypervisor. Heavier than a container but fully isolated, which matters for things like running a different OS or untrusted workloads. See Proxmox VMs and Containers.
LXC container
A Linux container that virtualizes at the OS level rather than the hardware level - it shares the host's kernel but has its own filesystem and process namespace. Lighter than a VM, used heavily inside Proxmox for services that don't need full isolation. See Proxmox VMs and Containers.
VLAN
A virtual LAN - a way of splitting one physical network into multiple isolated logical networks using a managed switch, so (for example) IoT devices can't talk to your NAS even though everything shares the same cabling. See Network Segmentation.
Reverse proxy
A service that sits in front of your other services, routing incoming requests to the right one based on hostname, and usually handling TLS termination so individual services don't each need their own certificate. See Reverse Proxy and TLS.
DHCP reservation
A rule on your router that always hands the same IP address to a specific device's MAC address, without hardcoding a static IP on the device itself. Keeps addresses predictable without giving up centralized control. See Networking Basics.
ZFS
A filesystem and volume manager combined, with built-in checksumming, snapshots, and pooled storage across multiple disks. Popular in homelabs for its data-integrity guarantees and cheap, instant snapshots. See Storage and ZFS.
NAS
Network-Attached Storage - a device or VM dedicated to serving files over the network (via NFS or SMB) rather than storage living locally on whichever machine needs it. See Centralized Storage.
Quorum
The minimum number of nodes in a cluster that must agree before the cluster takes action, used to prevent a "split-brain" situation where two halves of a broken cluster both think they're in charge. See Proxmox Clustering and HA.
High availability (HA)
An architecture where a service keeps running (or restarts elsewhere automatically) if the hardware under it fails, rather than staying down until a human intervenes. See Proxmox Clustering and HA.
Infrastructure as code (IaC)
Defining your infrastructure - VMs, networks, storage - as version- controlled configuration files instead of clicking through a UI, so it can be reviewed, repeated, and rebuilt exactly. See Infrastructure as Code.
GitOps
A workflow where a Git repository is the source of truth for what should be running, and changes deploy automatically when you push to it, rather than deploying by manually running commands. See GitOps for Homelab.
ACME / Let's Encrypt
ACME is the protocol used to automatically request and renew TLS certificates from a supporting certificate authority - it isn't inherently tied to free certificates, though that's the common case for a homelab. Let's Encrypt is the free certificate authority most homelab tools use by default. See Reverse Proxy and TLS.
WireGuard
A modern, fast VPN protocol built into the Linux kernel, used by tools like Tailscale to give you secure remote access to your homelab without forwarding ports on your router. See Remote Access.
3-2-1 backup rule
A backup guideline: keep at least 3 copies of your data, on 2 different types of media, with 1 copy off-site. A baseline to aim for, not a strict law. See Backups 101.
UPS / NUT
A UPS (Uninterruptible Power Supply) is a battery that keeps a machine running briefly after a power loss; NUT (Network UPS Tools) is the software that lets other machines on the network find out the UPS is on battery and shut themselves down gracefully before it runs out. See UPS and Graceful Shutdown.
Split-horizon DNS
A DNS setup where the same hostname resolves to a different answer
depending on whether the query comes from inside or outside your own
network - e.g. jellyfin.yourdomain.com resolving to a local IP on
your LAN, with no public record at all otherwise. See
Local DNS for Your Homelab.
SPF, DKIM, and DMARC
Three DNS-based email authentication mechanisms that let a receiving mail server verify a message claiming to be from your domain actually came from a server you authorized to send it, and what to do if it didn't. Getting all three right is a large part of why self-hosting outbound email is harder than it looks. See Should You Self-Host Email?.
Internal CA
A certificate authority you run yourself, issuing TLS certificates that only your own devices trust (because you've installed its root certificate on them), as an alternative to certificates from a public authority like Let's Encrypt. See Certificate Management at Scale.