Servers

A server is one itzg/minecraft-server container that CommandBlock creates, starts, and routes to.

Create a server

From Servers → Create server, fill in:

Field	Notes
Type	The loader: VANILLA, PAPER, PURPUR, FABRIC, QUILT, FORGE, NEOFORGE or SPIGOT. Maps to the itzg TYPE.
Memory	Java heap / container memory. Pick from the slider or type an exact value like 6G. The slider is bounded by the host's real memory.
Display name	Shown in the UI.
How players reach it	Through the router by hostname, or directly on a host port. One or the other - see direct access.
Hostname	The address players connect with, e.g. smp.example.com. Must be unique - it's the router's key. Only asked for when routed.
Version	Minecraft version (blank = latest release).

Only versions Mojang actually publishes a server jar for are offered. Releases before 1.2.5 are client-only, and picking one used to leave the container crash-looping on a download that doesn't exist.

Under Advanced you can also set the Java version, Aikar's JVM flags (on by default for 1.21 and newer, where they help), extra JVM args, arbitrary itzg env vars, and the any-client-version toggle below.

On create, CommandBlock pulls the image, starts the container on its Docker network with no published port, and stamps a mc.host label the router uses.

Letting any client version join

Allow any client version installs the Via stack (ViaVersion + ViaBackwards + ViaRewind) into the server, so a 1.8 client and a current one can join the same backend. It's available at create time and in the settings.

This only translates the game protocol - authentication is untouched, so the server stays in online mode and player UUIDs are unchanged.

Servers older than 1.20

The Via stack is skipped on servers older than 1.20: itzg aborts startup when there's no matching download, so enabling it there would prevent the server from booting at all.

Lifecycle

Start, stop and restart from the dashboard card, the server row, or the detail page. Delete removes the container and its world data (host folder or volume, per your storage setting).

The detail page shows live vitals - status, uptime, CPU, memory, players online, version, type and connection address - plus an embedded console wired to RCON.

Settings

Each server has a Settings modal (from the row's kebab menu or the detail header):

• General / MOTD - the most-used server.properties with a live MOTD editor, plus the server's display name.
• Runtime - memory, Java version, Aikar/JVM flags, and extra itzg env vars (applied on the next restart).
• Version - change the Minecraft version. The container is recreated in place and the world is kept.
• Wake & sleep - start on join and auto-sleep when idle, per server. See Wake & sleep.
• Network - whether the server is reached through the router by hostname or on its own host port. See direct access.
• Icon - upload a PNG; it's cropped to the 64×64 server-icon and shown in the UI and in-game.

Back up before changing version

Recreating keeps the world, but Minecraft's world format only upgrades forward - moving a world to an older version can corrupt it. Take a backup first.

Backups

Snapshot a server's world, or take a full-server backup you can restore or clone a new server from. See Backups.

Connecting

Add each server in the Minecraft client by its hostname (e.g. smp.example.com). See Hostname routing for the DNS + firewall setup.