Installer

Double-click/execute it for a window. Run it with arguments for command-line interaction.

java -jar installer.jar                      # Graphical installer
java -jar installer.jar client               # Add a profile to the Minecraft launcher
java -jar installer.jar server -d ./server   # Set up a dedicated server
java -jar installer.jar server --starter-jar # Also write server.jar, for hosts that only take a jar path
java -jar installer.jar mmc                  # Create a Prism/PolyMC/MultiMC instance
java -jar installer.jar --help

Usage

Modes

Mode	Does
client	Writes the Cleanroom version into .minecraft and adds a launcher profile
server	Sets up a dedicated server in a directory
mmc	Creates a MultiMC based (PolyMC/PrismLauncher etc) instance, or updates an existing one
list-versions	Prints the installable Cleanroom versions, newest first
uninstall	Removes a Cleanroom version installed by client
version	Prints the installer's own version

Every mode installs the newest Cleanroom version unless --version <id> names one. --dir overrides the detected install directory.

Client

• Writes versions/<id>/<id>.json and the Cleanroom universal jar.
• Leaves the other libraries for the launcher to download. --full downloads them all now, for an offline-ready install.
• Adds or updates one profile in launcher_profiles.json. Every other profile and key is kept, and a timestamped backup is taken first.
• Re-running a complete install changes nothing. --force reinstalls anyway.
• uninstall removes one installed version. Pass --version when more than one is installed.

Option	Effect
--profile-name <s>	Launcher profile name
--no-profile	Leaves launcher_profiles.json alone
--launcher-profiles <path>	Profile file to write, when it is not in --dir
--jvm-args "<args>"	JVM arguments for the launcher profile
--full	Downloads every library now

Server

• Downloads the libraries and the vanilla server jar.
• Writes unix_args.txt and win_args.txt, and the launch script this machine can run (run.sh or run.bat).
• Writes user_jvm_args.txt once. A reinstall keeps the existing file and ignores --memory.

Option	Effect
--memory <size>	Heap size written to a new user_jvm_args.txt, e.g. 6G
--no-scripts	Skips the launch script
--no-server-jar	Skips the vanilla server jar
--starter-jar	Writes server.jar, for hosts that only take a jar path
--pin-java	Writes the Java path into the scripts, always done for a provisioned Java

MMC

--dir decides what happens.

--dir points at	Result
A launcher or its instances directory	Creates a new instance
An existing Cleanroom instance	Repairs it, or moves it to the requested version
An existing Forge instance	Replaces Forge with Cleanroom, after a prompt unless --yes
An existing vanilla instance	Installs Cleanroom into it

An update keeps the instance's instance.cfg settings, except the keys the installer sets.

Option	Effect
--instance-name <s>	Name for a new instance
--launcher <name>	prism, polymc or multimc
--replace-java-path	Points the instance at the Java the installer found

Java

The installer looks for a Java that matches the version's install profile.

Option	Effect
--java <path>	Uses this Java installation
--java-version <n>	Java feature version to use
--java-vendor <name>	Preferred vendor, e.g. zulu, temurin
--provision-java	Downloads a Java runtime when none is found
--no-provision-java	Never downloads one

General

Option	Effect
--gui / --no-gui	Forces the window or the command line
--offline	Uses only what is already downloaded
--dry-run	Prints the plan, writes nothing but the installer cache
--force	Reinstalls even when everything is in place
-y, --yes	Skips the safety checks on the install directory
--json	Machine-readable output, see JSON Output
--quiet / --verbose	Less or more logging
--log-file <path>	Where to write the log

The installer does not update itself, update mods, or check for newer Cleanroom versions on its own.

Exit Codes

Code	Meaning
0	Success
1	Internal error
2	Usage error
3	Network failure
4	A download failed its size or SHA-1 check
5	The install directory is unusable
6	No suitable Java was found or could be fetched
7	Cancelled

JSON Output

--json prints one JSON object per line on standard output. Log lines go to standard error.

Event	Fields	Printed
stage	name	When a phase starts
progress	stage, detail, done, total	During a phase, total -1 if unknown
versions	versions	By list-versions, newest first
plan	target, version, root, actions, notes	By --dry-run, in place of result
result	ok true, root, files, notes	After a successful run
result	ok false, code, message	After a failed run, code is the exit code

Cache

Everything the installer keeps lives in ~/.cleanroom. Set -Dcleanroom.homeDir=<path> to move it.

Path	Contains
installer/installers/	Downloaded Cleanroom installer jars
installer/packs/	Downloaded MultiMC packs
installer/versions.txt	The version list, refreshed after an hour
installer/logs/	Run logs
java/	Java runtimes fetched by --provision-java

--dry-run still downloads the installer jar into the cache, because the plan is read from it.

Install Profile

An installer jar carries install_profile.json. Spec 1 keeps every spec 0 key and adds the ones below. A profile without them gets the defaults.

Key	Type	Meaning
spec	number	1
cleanroomVersion	string	Cleanroom version, derived from path when absent
java.minimum	number	Lowest Java feature version accepted, default 25
java.maximum	number	Highest Java feature version accepted, default 25
java.recommended	number	Version to look for first and to provision, default 25
java.distro	string	Preferred vendor when provisioning, default zulu
jvmArgs	string[]	Default JVM arguments for the launcher profile
serverMainClass	string	Server main class, default is the one in version.json
serverTweakers	string[]	Server tweak classes, default is the built-in list

The installer does not read mainClass, tweakers, serverJarPath and repositories yet.

Layout

Module	Contains
core	Profiles, downloads, targets, Java resolution, directory detection
ui	The installer's window and its Swing look and feel
app	Entry point, the command line, and the shaded jar.

Adding a Mode

• Implement a new InstallTarget and add to core/src/main/resources/META-INF/services/com.cleanroommc.installer.target.InstallTarget.

Compatibility

• Two paths inside the installer jar are set in stone: /version.json and /maven/com/cleanroommc/cleanroom/<version>/cleanroom-<version>-universal.jar.
  • CleanroomRelauncher reads both directly out of published installer jars.
• version.json is written self-contained, with no inheritsFrom.
• Inheriting from 1.12.2 would cause the launcher to merge parent libraries which ends up adding LWJGL 2 onto the classpath. (Previous installer/zip did this.)