What the startup settings on a game server do
Most game server panels have a page for startup settings: a command, a few variables and sometimes a choice of version or Java release. It is tempting to ignore it until something breaks, but this page decides how your server program is launched, and a small change can fix a crash or cause one. This guide explains what those settings generally mean, so you can change them with confidence. Exact labels vary by game and panel, so treat the names here as examples.
What the startup command is
When you press start, the panel runs a command inside your server's isolated environment. The command is the same one you would type if you ran the server program on your own computer. For a Minecraft Java server it usually looks like this:
java -Xms128M -Xmx{{SERVER_MEMORY}}M -jar server.jar nogui
Broken into parts:
javastarts the Java runtime.-Xmsand-Xmxset the minimum and maximum memory the program may use.-jar server.jarnames the file to run.noguistops the program opening a window, which makes no sense on a server.
Other games have their own forms, such as a binary file with flags for the map, port and player count.
Variables
Panels often fill parts of the command from variables, shown as editable fields. Common ones:
| Variable | Purpose |
|---|---|
| Server jar file | Which file is launched |
| Version | Which game version to download or run |
| Memory | The share of your plan the program may use |
| Port | The network port the game listens on |
| Max players | The slot limit |
| Extra flags | Additional options added to the command |
Change a variable here instead of editing the command text, so the panel keeps the structure intact.
Changing the server jar or version
If a server will not start after an upgrade, the jar name in startup settings often no longer matches the file on disk. Check that the file really exists in the file manager and that the name, including capitals and the .jar ending, matches exactly. See Change your Minecraft version for the safe order of steps, and Server crashing on startup if it still fails.
Java versions
Different game versions need different Java releases. A new Minecraft version may require a newer Java than an older one. If you pick the wrong one, the console shows a message about unsupported class file versions. Fix Java version errors explains what each message means.
Memory settings
The maximum memory flag decides how much RAM the program can use. Setting it to your entire plan leaves nothing for the operating system, the panel overhead or the JVM's own non-heap memory, which can cause the container to be killed. A common safe habit is to leave a margin below your plan's limit, and many panels do this automatically. Setting it too low causes slowdowns and out-of-memory errors. Fix Minecraft out-of-memory errors goes into this.
Extra flags
Some people add tuned garbage collection flags to improve performance. These can help large servers, but copying a long list of flags from a forum without understanding it is a common source of problems. Prefer the defaults, change one thing at a time and measure the result, using the guidance in Understanding TPS and MSPT.
Docker image or runtime choice
Some panels let you choose a runtime image, which decides what software is available in the environment, such as a specific Java release. Changing it is like changing the computer the server runs on. Match it to the game version's requirements.
Auto-start and restart behaviour
Settings such as "start on boot" or "restart on crash" control what happens without you. They are helpful for uptime, but a server stuck in a crash loop can restart endlessly and hide the real error. If your server keeps coming back up and failing, read Fix a server that keeps restarting.
Safe way to change startup settings
- Stop the server first.
- Take a backup, or at least write down the old values. See Creating and restoring backups.
- Change one setting at a time.
- Start the server and watch the console for the first error. See Use the server console.
- Revert if it fails, and compare with what you had.
What not to change
- Port settings that the panel manages. Changing them can make the server unreachable. See How game server ports work.
- Paths the panel expects, such as the working directory.
- Anything you do not understand, on a server people rely on.
When a setting is locked
Panels may restrict some fields so you cannot break the environment. If you need a change that is not available, explain the goal in a ticket rather than looking for a workaround. How to write a support request shows what to include.
Quick troubleshooting table
| Symptom | Check |
|---|---|
| "Unable to access jarfile" | The file name in startup settings |
| "Unsupported class file version" | Java version versus game version |
| Killed without an error | Memory flag too close to the plan limit |
| Wrong port in the console | Port variable |
| Won't start after adding flags | Remove the new flags |
Still stuck? Open a ticket on Discord - run /ticket in any channel, pick a department, and include your Server ID or Invoice ID so we can jump straight in.