Spend a week reading Interlude server ads or lurking on the L2J boards and one name keeps coming back around: aCis. People talk about it like everyone already knows what it is — "it's aCis-based", "we run the latest aCis", "just start from aCis". If you're new to the server side of Lineage 2, that can be frustrating. So this is the article I wish someone had handed me: what aCis is, why so many Interlude projects are built on it, and how to actually get one running on your own machine.
No fluff, no filler. Just the project and the setup.
What aCis actually is
aCis is a Lineage 2 Interlude server project — a Java codebase, descended from L2J, that has been reworked over many years into something cleaner and closer to how Interlude is supposed to behave. It targets Interlude (C6) and only Interlude. That narrow focus is the whole point.
L2J is the big open-source Lineage 2 server family, spanning many chronicles and touched by countless hands. It's powerful but sprawling. aCis took the Interlude branch of that world and went in the opposite direction from "add more": it refactored, simplified, and rebuilt systems so they behave properly and so a developer can actually read the code without going cross-eyed.
The project has been maintained for over a decade, led by the developer the community knows as Tryskell, with contributions from others along the way. If you read the aCis forum for a while, the philosophy is impossible to miss — it shows up in how bugs get discussed and how features get rejected. The guiding idea is quality over quantity: retail-like behaviour, consistent structure, and as little junk as possible in the base. aCis is deliberately not a "pack" stuffed with custom zones and gimmicks. It's a clean foundation you're expected to build on top of.
That's exactly why serious Interlude projects gravitate to it. When you plan to customise the server yourself — new features, your own systems, real development — starting from a tidy, well-organised codebase saves you months of pain compared to wrestling a messy one.
What you actually get, and the free-vs-paid part
aCis is distributed as source code plus a datapack. The source is the Java for two programs: the login server and the game server. The datapack is everything that describes the world — the XML data, the scripts, and the SQL files that build your database. You compile the source yourself and point it at the datapack; there's no one-click installer that hides all of this from you, and honestly that's part of the learning.
On the money question, here's the straight version. There's a free, public revision — an older snapshot of the source that anyone can download and use. It's completely functional and it's the right place to learn. The latest revisions, with the newest fixes and improvements, live behind a subscription in the members area. That subscription is what keeps a decade-old project funded and maintained, which is fair. For your first server, and for learning, the free revision is more than enough — don't let the paid tier stop you from starting.
One more thing worth saying plainly: the aCis forum is the project's real home. The install guide, the changelog, the FAQ, the bug tracker, the community help — it's all there, and it's kept current in a way no third-party tutorial (including this one) can match. Use this article to understand the shape of things; use the forum for the exact version numbers and file names of whatever revision you download.
How to set up an aCis server
We'll build it locally, on your own PC first. That's how everyone should start — it's safe, it's free, and every step transfers directly to a real public server later. The plan is simple in outline: install the tools, grab the source, compile it, wire it to a database, run it, and connect.
A note before you start: exact JDK versions and some file names differ between aCis revisions. Where I say "check the forum," I mean it — matching the JDK the revision expects is the single most common thing beginners get wrong.
What you'll need
- A JDK (Java Development Kit) — the development kit, because you're compiling source, not just running it. Install the version the aCis download specifies.
- MariaDB or MySQL — the database that stores accounts, characters, and everything else.
- An IDE — Eclipse or IntelliJ IDEA. This is where you open, build, and launch the source. Both are free.
- The aCis source and datapack — the free public revision is fine to learn on.
- A Lineage 2 Interlude client — the game files you'll connect with. It has to be an Interlude client; aCis is an Interlude server.
1. Get the source and datapack
Download the aCis package and extract it to a short, plain path with no spaces or accents — C:\aCis is a good habit. Long or fancy paths cause avoidable errors down the line. You'll end up with the source (login + game server) and the datapack (data, scripts, and SQL).
2. Install the JDK
Install the JDK and let it register with your system. If your IDE later says it can't find a JDK, this is what to revisit. Use the version aCis asks for — both too old and too new will throw compile errors, and chasing those errors is a miserable way to spend an evening when the fix is just the right Java.
3. Set up the database
Install MariaDB (or MySQL) and start it. Create an empty database — most guides name it acis — and a user with a password that has full rights on it. Note the database name, user, and password; you'll type them into the config in step 5. Don't load any tables yet; that's step 6.
4. Open the project and build it
Import the aCis source into Eclipse or IntelliJ. Let it finish indexing, then build it. aCis ships with an Ant build script (build.xml); running it compiles everything and drops a ready-to-run output folder containing the login server, the game server, and their config folders.
If the build fails, it's nearly always the wrong JDK or a project that imported without its libraries. Fix the Java first — that's the usual answer.
5. Configure the server
In the compiled output there's a config folder with the settings files for the login and game server (names vary by revision). Open them and set two things:
- The database connection — the name, user, and password from step 3.
- The network / IP settings — for a local test, the localhost/internal defaults are correct. This is also where your real public IP goes later, when you take the server live.
Slow down here. A large share of "it won't start" posts on the forum come down to a mistyped database password or an IP field that doesn't match the setup.
6. Install the database tables
Now load the datapack's SQL into your acis database. Depending on the revision, that's either an install script or a set of .sql files you run with a tool like HeidiSQL or the MySQL command line. This creates every table — accounts, characters, items, NPCs, and so on. Running the full install again wipes and rebuilds those tables, so only do it on a fresh setup or a deliberate reset.
7. Start the servers — login first, then game
aCis runs as two programs, and the order matters:
- Start the login server and wait until it reports it's up and listening.
- Then start the game server. On first launch it does some setup and, when it's ready, tells you the world is loaded.
If the game server can't reach the database or the login server, the console will say so — read that error, it points straight at the value you got wrong in step 5.
8. Connect and make yourself a GM
Point your Interlude client at 127.0.0.1 (your own machine) instead of its default server — usually by editing the client's server list or host configuration. Launch it, enter a username and password at the login screen, and connect; L2J-based servers auto-create the account on first login.
To get Game Master powers, set your character or account access level in the database (in aCis that's an accesslevel field). Relog, and you'll have the admin command menu — your tool for spawning NPCs, testing, and running the server.
That's a working aCis Interlude server on your own PC.
When something breaks
- Build errors → wrong JDK, or libraries missing on import. Match the JDK.
- A server window closes instantly → the database: wrong name/user/password, or the SQL wasn't installed.
- Client stuck at login → it isn't pointed at
127.0.0.1, or the login server isn't running. - Kicked right after login → usually a client that isn't proper Interlude, or the game server didn't finish loading.
- No GM commands → access level not set in the database.
Taking it from your PC to a real server
Once it runs locally, going public is the same steps with a few additions: host it on an always-on box (a VPS or dedicated server, not your home PC), put your real public IP in the network config and open the required ports, keep the database credentials private, take backups, and think about DDoS protection before you advertise — a popular Interlude server attracts attention you didn't ask for. Then comes the fun part: your rates, your features, your community. That's the moment it stops being "an aCis install" and becomes your server.
Where to go from here
If you get stuck — and everyone does at first — the aCis forum is the answer. Because the project is so old, almost every build error and config trap has already been posted and solved. Search the exact error text before you ask; nine times out of ten someone hit it before you and the fix is right there.
And if reading this made you realise you'd rather play on a great Interlude server than build one just yet, that's a perfectly good outcome too. Browse the Interlude servers on the list, filter by the rates and features you want, and go see how a well-run aCis server feels from the inside — it's honestly the best homework you can do before building your own.
