Startup Parameters

Startup parameters control how your server starts and behaves. Each server has configurable variables based on its Egg configuration, allowing you to customize memory limits, game modes, world settings, and more.

Understanding Startup Variables

Startup variables are placeholders in the startup command that get replaced with actual values:

Example Startup Command

java -Xms{{SERVER_MEMORY}}M -Xmx{{SERVER_MEMORY}}M -jar {{SERVER_JARFILE}}

Variables like {{SERVER_MEMORY}} are replaced:

Actual Command

java -Xms2048M -Xmx2048M -jar server.jar

Viewing Startup Configuration

Get startup information for your server:

Get Startup Info

GET /api/client/servers/{server}/startup

Response

{
  "object": "list",
  "data": [
    {
      "object": "egg_variable",
      "attributes": {
        "name": "Server Jar File",
        "description": "The name of the server jarfile to run.",
        "env_variable": "SERVER_JARFILE",
        "default_value": "server.jar",
        "server_value": "paper.jar",
        "is_editable": true,
        "rules": "required|string|max:20"
      }
    },
    {
      "object": "egg_variable",
      "attributes": {
        "name": "Server Version",
        "description": "The version of Minecraft to download.",
        "env_variable": "MINECRAFT_VERSION",
        "default_value": "latest",
        "server_value": "1.20.4",
        "is_editable": true,
        "rules": "required|string|max:20"
      }
    }
  ],
  "meta": {
    "startup_command": "java -Xms128M -Xmx{{SERVER_MEMORY}}M -jar {{SERVER_JARFILE}}",
    "docker_images": {
      "Java 17": "ghcr.io/pterodactyl/yolks:java_17",
      "Java 11": "ghcr.io/pterodactyl/yolks:java_11"
    },
    "raw_startup_command": "java -Xms128M -Xmx{{SERVER_MEMORY}}M -jar {{SERVER_JARFILE}}"
  }
}

Variable Properties

name - Human-readable variable name
description - What the variable does
env_variable - Environment variable name
default_value - Default if not customized
server_value - Current value for this server
is_editable - Whether users can modify it
rules - Validation rules

Only variables with is_editable: true can be modified by users. Admin-only variables are hidden or read-only.

Updating Variables

Modify a startup variable:

Update Variable

PUT /api/client/servers/{server}/startup/variable
Content-Type: application/json

{
  "key": "MINECRAFT_VERSION",
  "value": "1.20.4"
}

Response

{
  "object": "egg_variable",
  "attributes": {
    "name": "Server Version",
    "env_variable": "MINECRAFT_VERSION",
    "server_value": "1.20.4"
  },
  "meta": {
    "startup_command": "java -Xms128M -Xmx2048M -jar server.jar",
    "raw_startup_command": "java -Xms128M -Xmx{{SERVER_MEMORY}}M -jar {{SERVER_JARFILE}}"
  }
}

Navigate to Startup

Go to the Startup tab in your server panel.

Modify Variables

Edit the variables you want to change. The interface shows current and default values.

Save Changes

Click Save. The new values are validated against the rules.

Restart Server

Restart your server for changes to take effect. Variables are only applied at startup.

Common Variables

Minecraft Variables

Server Jar File

SERVER_JARFILE=server.jar

The jar file to execute. Common values:

server.jar - Vanilla Minecraft
paper.jar - Paper server
spigot.jar - Spigot server
forge.jar - Forge modded server

Minecraft Version

MINECRAFT_VERSION=1.20.4

Which version to download/run:

latest - Latest release
1.20.4 - Specific version
1.19.2 - Older version

Build Number

BUILD_NUMBER=latest

For Paper/Spigot:

latest - Latest build
450 - Specific build number

Forge Version

FORGE_VERSION=47.2.0

Forge version for modded servers.

Source Engine Variables

Game ID

SRCDS_APPID=730

Steam App ID:

730 - CS:GO
232330 - CS2
4020 - Garry’s Mod
232250 - Team Fortress 2

Map

SRCDS_MAP=de_dust2

Starting map for the server.

Game Mode

GAME_MODE=competitive

Game mode configuration.

Generic Variables

Server Memory

SERVER_MEMORY=2048

Memory allocation in megabytes. Usually auto-set based on server limits.

Server Port

SERVER_PORT=25565

Primary allocation port. Auto-set from network allocations.

Server IP

SERVER_IP=0.0.0.0

IP address to bind to. Usually 0.0.0.0 for all interfaces.

Variable Validation

Variables have validation rules:

{
  "env_variable": "MINECRAFT_VERSION",
  "rules": "required|string|max:20"
}

Common Rules

required - Must have a value
string - Must be text
integer - Must be a number
boolean - Must be true/false
max:20 - Maximum length
in:value1,value2 - Must be one of listed values
regex:/^[a-z]+$/ - Must match pattern

If validation fails:

Error Response

HTTP/1.1 422 Unprocessable Entity

{
  "errors": [
    {
      "code": "ValidationException",
      "detail": "The value field must be a string.",
      "meta": {
        "rule": "string"
      }
    }
  ]
}

Docker Images

Servers run in Docker containers with specific images:

Available Images

{
  "docker_images": {
    "Java 17": "ghcr.io/pterodactyl/yolks:java_17",
    "Java 11": "ghcr.io/pterodactyl/yolks:java_11",
    "Java 8": "ghcr.io/pterodactyl/yolks:java_8"
  }
}

Some eggs allow users to select the Docker image. This is useful when different game versions require different Java versions.

Changing Docker Image

If allowed by the egg configuration:

Update Docker Image

POST /api/client/servers/{server}/settings/docker-image
Content-Type: application/json

{
  "docker_image": "ghcr.io/pterodactyl/yolks:java_17"
}

Success

HTTP/1.1 204 No Content

Changing the Docker image requires a server restart. Ensure the new image is compatible with your server software.

Read-Only Variables

Some variables cannot be modified by users:

Read-Only Variable

{
  "name": "Server Memory",
  "env_variable": "SERVER_MEMORY",
  "server_value": "2048",
  "is_editable": false
}

These are typically:

Resource limits (memory, CPU)
Network configuration (IP, port)
Security settings
License keys

Only administrators can modify read-only variables.

Environment Variables

All variables are passed as environment variables to the container:

Inside Container

echo $SERVER_MEMORY
2048

echo $MINECRAFT_VERSION  
1.20.4

echo $SERVER_JARFILE
paper.jar

Startup scripts can access these in any language:

Bash

#!/bin/bash
java -Xmx${SERVER_MEMORY}M -jar ${SERVER_JARFILE}

Python

import os
memory = os.environ.get('SERVER_MEMORY')
jarfile = os.environ.get('SERVER_JARFILE')

Startup Command Preview

The panel shows the final startup command with variables replaced:

Raw Command

java -Xms128M -Xmx{{SERVER_MEMORY}}M -jar {{SERVER_JARFILE}}

Processed Command

java -Xms128M -Xmx2048M -jar paper.jar

This helps verify your variables are set correctly.

Activity Logging

Variable changes are logged:

Example Log

{
  "event": "server:startup.edit",
  "properties": {
    "variable": "MINECRAFT_VERSION",
    "old": "1.20.1",
    "new": "1.20.4"
  }
}

Common Configurations

Minecraft Paper Server

SERVER_JARFILE=paper.jar
MINECRAFT_VERSION=1.20.4
BUILD_NUMBER=latest

Paper automatically downloads the specified version on first start.

Minecraft Forge Modded

SERVER_JARFILE=forge.jar
MINECRAFT_VERSION=1.20.1
FORGE_VERSION=47.2.0

Forge version must match Minecraft version.

CS:GO Server

SRCDS_APPID=730
SRCDS_MAP=de_dust2
SRCDS_GAMETYPE=0
SRCDS_GAMEMODE=1
SRCDS_MAXPLAYERS=32

ARK: Survival Evolved

SERVER_MAP=TheIsland
SESSION_NAME=My ARK Server
MAX_PLAYERS=70
SERVER_PASSWORD=
ADMIN_PASSWORD=SecureAdminPass123

Best Practices

Test After Changes

Always test your server after changing variables. Check logs for errors related to invalid configurations.

Use Latest Versions

For production servers, use specific version numbers instead of “latest” to prevent unexpected updates:

MINECRAFT_VERSION=1.20.4  # Good
MINECRAFT_VERSION=latest  # May break unexpectedly

Document Custom Variables

If you modify variables from defaults, document why:

Take screenshots of working configurations
Note dependencies between variables
Keep a changelog of what you changed

Verify Compatibility

When changing versions, verify compatibility:

Plugin versions match server version
World format is compatible
Forge/mod versions align

Troubleshooting

Server Won't Start After Variable Change

Check server logs for error messages
Verify variable value is valid (check rules)
Revert to previous working value
Ensure Docker image supports the configuration

Cannot Edit Variable

Check if is_editable is false
Verify you have startup.update permission
Some variables are admin-only
Contact server owner/admin

Validation Error

Read the validation rule carefully
Check for typos in your value
Ensure correct data type (string vs integer)
Stay within length limits

Variables Not Taking Effect

Restart the server after changing variables
Variables only apply at startup, not runtime
Check if game-specific config file overrides them
Verify variable name matches exactly

Getting Started

Panel Administration

Server Management

User Guide

Configuration

Advanced

Understanding Startup Variables

Viewing Startup Configuration

Variable Properties

Updating Variables

Common Variables

Minecraft Variables

Source Engine Variables

Generic Variables

Variable Validation

Common Rules

Docker Images

Changing Docker Image

Read-Only Variables

Environment Variables

Startup Command Preview

Activity Logging

Common Configurations

Best Practices

Troubleshooting

Build docs developers (and LLMs) love

Getting Started

Panel Administration

Server Management

User Guide

Configuration

Advanced

​Understanding Startup Variables

​Viewing Startup Configuration

​Variable Properties

​Updating Variables

​Common Variables

​Minecraft Variables

​Source Engine Variables

​Generic Variables

​Variable Validation

​Common Rules

​Docker Images

​Changing Docker Image

​Read-Only Variables

​Environment Variables

​Startup Command Preview

​Activity Logging

​Common Configurations

​Best Practices

​Troubleshooting

Build docs developers (and LLMs) love

Understanding Startup Variables

Viewing Startup Configuration

Variable Properties

Updating Variables

Common Variables

Minecraft Variables

Source Engine Variables

Generic Variables

Variable Validation

Common Rules

Docker Images

Changing Docker Image

Read-Only Variables

Environment Variables

Startup Command Preview

Activity Logging

Common Configurations

Best Practices

Troubleshooting