A new implementation of the LambdaMOO server

View the Project on GitHub verement/etamoo


This is experimental software. While it is now mostly functional, it is not yet fully complete.

Until such time as the EtaMOO database format is well tested and considered stable, please make and keep LambdaMOO-format backup copies of your EtaMOO databases.


EtaMOO is a new implementation of the LambdaMOO server written in Haskell.

LambdaMOO is a network-accessible, multi-user, programmable, interactive system well-suited to the construction of text-based adventure games, conferencing systems, and other collaborative software.

EtaMOO differs from LambdaMOO in a few significant ways:

The implementation of EtaMOO otherwise closely follows the specifications of the LambdaMOO Programmer's Manual, and should be compatible with most LambdaMOO databases as of about version 1.8.3 of the LambdaMOO server code.


EtaMOO is built with Cabal, the Haskell package manager. In the simplest case, running:

cabal install EtaMOO

should automatically download, build, and install the etamoo executable after doing the same for all of its Haskell dependencies.

Cabal itself is part of the Haskell Platform which is available for many distributions and platforms.

There are a few options you can give to cabal install to customize your build:

Option Feature
-j Build in parallel using multiple processors
-f llvm Use GHC's LLVM backend to compile the code
-f 64bit Enable 64-bit MOO integers

EtaMOO has non-Haskell dependencies on three external libraries: liblmdb for database persistence, libpcre (with UTF-8 support enabled) for regular expression matching, and, possibly, libcrypt (often part of the standard libraries) for the MOO crypt() built-in function. You should ensure you have these available before installing EtaMOO (e.g. on Debian-derived systems, sudo apt-get install liblmdb-dev libpcre3-dev).


etamoo is nearly a drop-in replacement for the LambdaMOO moo executable; the main difference is that etamoo takes a single database path, rather than both input and output paths. You can run etamoo --help for a command-line synopsis.

EtaMOO uses a native binary database format that allows quick loading and checkpointing, and instantaneous crash recovery. You can create a native database from a LambdaMOO-format database by using etamoo --import. You can also go the other way and convert an EtaMOO database back to a LambdaMOO-format database with etamoo --export.

If you don't already have a database, you can find LambdaMOO-format cores for various MOOs online -- for example there is the venerable LambdaCore, or you can request a character on Waterpoint and then perform a live JHCore extraction. (Note that Waterpoint's core extraction process requires running an actual LambdaMOO server executable on the precore database to obtain the final core database; EtaMOO cannot yet do this itself.)

By default, EtaMOO will make use of all available CPUs for maximum parallelism. If you'd rather limit the number of processors EtaMOO uses, you can use the command-line option +RTS -Nn-RTS where n is the number of processors to use.

If you want to enable statistics from the memory_usage() built-in function, you will need to add +RTS -T -RTS to the command line options.


The following LambdaMOO features are currently unsupported:

See also the file for other differences between EtaMOO and LambdaMOO.


Documentation is available for the various types, data structures, and functions used internally by EtaMOO.