Launch options
Add your own launch arguments to a CS2 or Minecraft server's start command, learn the rules and when they apply, and when to use the boot script instead.
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Launch arguments (launch args) are extra flags added to the command that starts your game server. They let you set things that can only be decided at startup. You’ll find them on the server page under Advanced → Launch & Boot. This page covers which games accept them, how to set them, the rules, and the boot script for anything more.
Which games accept launch args
The Launch args field only appears for games whose start command has room for them. Today that’s:
| Game | Where your args go | Example |
|---|---|---|
| CS2 | At the end of the server’s command line, after the game’s own settings. | +game_mode 1 -maxplayers 12 |
| Minecraft (all versions) | Into the Java command, before the server starts. They’re options for Java, not Minecraft commands. | -XX:+UseG1GC |
For other games the field isn’t shown. You can still change how they start with the boot script, described below.
For CS2 specifics, see CS2 launch options.
Set launch args
- Open the server page, then Advanced → Launch & Boot.
- Type your flags in Launch args. The placeholder shows an example:
+game_mode 1 -maxplayers 12. - Click Save. It’s only active when you’ve changed something.
- Apply them: stop the server, then start it again with Restore.
Launch args are kept across restores, like the server’s other settings. To remove them, clear the field and save. Changing them needs the Control servers permission.
Rules
Launch args are checked when you save. If something’s wrong, the reason appears under the field.
| Rule | Message you’ll see |
|---|---|
| At most 400 characters | Launch args can be at most 400 characters |
Only letters, digits, spaces and + - _ . / : = , | Launch args may only contain letters, digits, spaces and + - _ . / : = , |
No flags SlashPlay manages itself: -port, +rcon_password, +sv_password, +sv_hibernate_when_empty | … is managed by the platform and can’t be overridden |
Quotes, $, ; and similar characters aren’t allowed, so each argument must be a single word. Extra spaces are tidied up automatically.
Why those four flags? SlashPlay picks the port, sets the RCON and join passwords from the server page, and relies on the server staying awake to know when it’s ready. Use the join password setting instead of +sv_password.
Examples
CS2, competitive for 10 players:
+game_mode 1 -maxplayers 10For changing modes and maps while the server runs, the Game-specific tab is easier: see CS2 game modes and maps.
Minecraft, with the G1 garbage collector:
-XX:+UseG1GCSlashPlay already gives Java the right amount of memory for the server’s size, so you don’t need to set -Xmx. To give Minecraft more memory, pick a bigger size.
The boot script, for everything else
Every server has a start script at .slashplay/boot.sh, part of Full Box mode. SlashPlay generates it from the game’s standard start command, with your launch args included. For anything launch args can’t do, such as running a command before the game starts, or changing the start command of a game without a Launch args field, edit that script from the terminal.
- Changes to the script apply on the next Restart server.
- Reset boot script on the Launch & Boot tab (server running) restores the default if you break it.
Troubleshooting
I don’t see a Launch args field. Your game doesn’t accept launch args. Use the boot script instead.
My args don’t seem to do anything. You probably restarted instead of stopping and starting. Stop the server, then restore it. Also check the console output at startup for the game’s own errors.
The server crashes at boot after I added args. An argument the game doesn’t understand can stop it starting. Clear the field, save, and start again. A crash during boot isn’t charged.