When something does not work

The order is always the same: what the console says, then what the panel says, and only then the machine.

The server will not boot

Open the console and read the first ten lines after the banner. The answer is almost always there.

What you see	What it is
`UnsupportedClassVersionError`	Wrong Java. Change the image.
`-XmxM` in the command	A misspelled variable. Unknown ones render empty.
`Permission denied` on a file	Ownership. Files → Change permissions.
`Address already in use`	Something else holds the port. Allocations.
Nothing for a long time after the banner	A modpack unpacking. A minute is normal.
`EULA`	`eula.txt`, in files.

Players cannot connect, but the server is up

The panel opens a port on the machine, and there its responsibility ends. Work from the inside out:

Is the server listening? The console should say Done and a port.
Is the allocation right? Network — the first one is what fills SERVER_PORT.
The machine's firewall. The installer opened the panel's ports, not the game's.
The router. A port forward that did not come back after a reboot looks exactly like a server that is down.
DNS. A domain is not a route. If the port does not work, a domain will not fix it.

The console shows nothing

First, whether the server is actually running — the state is beside its name. Then the status at the top right of the console: connected, connecting…, disconnected.

A disconnected that does not come back is usually a reverse proxy that does not pass WebSockets. The panel pings every 25 seconds; a proxy with a shorter idle timeout will still close it.

An empty console for a running server that something other than the panel started is normal only until the next restart — the panel adopts running servers.

I type a command and nothing happens

Before 0.3.3 there was one usual cause: the panel had restarted in the meantime and that closed the server's input. Since 0.3.3 it does not happen — but a server still running from an older version is still in that state. Stop it and start it once and it moves over by itself.

When a command does not arrive, the panel says so. The > command line appears only once the server has taken it.

A panel update failed

The message is the real one. Two usual causes: nowhere to write (the directory holding the binary must belong to the user the panel runs as) and the build is gone (a channel points at a withdrawn release for a while). More under Updating.

Before you write to support

Send this straight away — it is exactly what we would ask for:

the panel's version (stygion-core --version),
what you pressed and what happened,
the first twenty lines of the console after the start,
whether the server is on the master or on a node.