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In addition to the OpenSimulator code itself, certain other packages need to be installed on different platforms in order to get OpenSimulator binaries to run.

As well as the information on this page (which should be expanded), you may find more information on dependencies in Build Instructions though this will also contain dependencies required only for building. This are also more hints in Troubleshooting.

After solving dependencies, you may need to configure the firewall installed in your system by default so that the viewers outside can access to OpenSimulator inside it. See Firewall Settings for more informations.

NAT Loopback Routers Router and Nat Loopback Information to help you configure your Router / Modem.



OpenSimulator 0.7.6 requires .NET Framework 3.5 when running under Windows. If you run OpenSimulator on Windows 7 or Windows Server 2008 R2, it is already bundled so you can run OpenSimulator 0.7.1 out-of-the-box. On Windows Vista, Windows Server 2008, Windows Server 2003 or Windows XP, you'll need to upgrade it to 3.5, downloading from Microsoft .NET Framework Download Page@.NET Framework Developer Center. Note that prior versions of Windows(ex. NT or 2000) are NOT supported.

If you run on Windows XP ensure it is updated to at least Service Pack 2 (SP2).

Current OpenSimulator development code requires .NET Framework 4.0, as will the next OpenSimulator release.

Double-click or execute on command prompt:

  • 32-bit version of Windows: OpenSim.exe
  • 64-bit version of Windows: OpenSim.32BitLaunch.exe

Depending on your installation, you may have to run the program as administrator(right click -> 'Run as administrator'). It will pop up a window asking permission, select "Allow".

Linux and Mac OSX

OpenSimulator 0.7.6 requires Mono 2.4.3 or later. WARNING: OpenSimulator is known to have significant performance and scalability problems with Mono versions 2.8.x, 2.10.0 and 2.10.1. As of Mono 2.10.2, the scalability problems appear to have been resolved. Mono 2.6.x also appears to be fine, though the mono VM does seem to have some issues (crashing with a native stacktrace) on simulators running many regions or lots of users/prims. Therefore you should either use Mono 2.6.x or Mono 2.10.2 or later. You can also use Mono 2.4.3, but it is fairly old now.

There are also reports that anything between Mono 2.10.9 and 3.0.3 has major issues; 3.0.7 is supposedly OK.

OpenSimulator development code requires Mono 2.8 or later, with at least Mono 2.10.8 recommended.

To run OpenSimulator with mono, execute

mono --debug OpenSim.exe

This is the same for 32 bit and 64 bit systems. The --debug switch isn't strictly necessary, but it will insert line numbers for stack traces if you ever need to make a bug report, and the overhead of using it is very small.


sudo apt-get install mono-complete

RHEL, Fedora, CentOS or Any Other RedHat-based Distributions

First, run "yum info mono-core" to see the version of the mono packages in the core repository for your distribution. If it shows 2.4.3 or later, proceed to #Installing from Core Repository. If not, skip to #Installing from Mono Repository. Note that the current version you can get from yum repository for some distributions is lower than requirement (ex. 1.2.4 on CentOS). Unlike Ubuntu, RedHat-based distributions should be always conservative, therefore it is natural that they don't so often update their repository. What you can do to manage this problem is to add an extra repository for mono.

Installing from Core Repository

Just type:

sudo yum install  mono-core mono-data-sqlite mono-extras libgdiplus

It will also install dependent modules. After that you can launch OpenSim.exe with mono out-of-the-box.

Installing from Mono Repository

This procedure is tested on CentOS 5.5 & 5.6 box with OpenSimulator 0.7.1.

Go to yum config file folder and create new one for mono.

cd /etc/yum.repos.d
sudo vi mono.repo

And then in mono.repo :

name = novell-mono

Now, you can yum install the later version of mono from this repository. Additional note that make sure all of mono packages are i386(not IA64 build). If your box is 32bit, don't care and you can even install properly without ".i386" suffix.

sudo yum install mono-addon-core.i386 mono-addon-data.i386 mono-addon-data-sqlite.i386  \
      mono-addon-extras.i386 mono-addon-web.i386 mono-addon-winforms.i386 mono-addon-libgdiplus0.i386

Yum will install mono into /opt/novell/mono, so you can create a symbolic link to /usr/bin :

sudo ln -s /opt/novell/mono/bin/mono /usr/bin/mono

After that, you should be able to launch OpenSim.exe without any errors.


Debian 4 (Etch) is no longer supported by Update at least to 5 (Lenny) before running OpenSimulator. See Upgrades from previous for detail.

For Debian 5 (Lenny) or later, just Type:

sudo aptitude install mono-gmcs libmono-microsoft8.0-cil \
    libmono-system-runtime2.0-cil libmono-i18n2.0-cil

You can even use apt-get instead of aptitude. They both will also install dependent packages.

Tested on Debian 5(Lenny), Debian 6(Squeeze) and Debian 7(Wheezy) unstable.


Just type:

sudo zypper install  mono-core mono-data-sqlite mono-extras libgdiplus

It will also install dependent modules. After that you can launch OpenSim.exe with mono out-of-the-box.

Mac OS X

All you have to do is to fetch Mono Runtime package from Mono Download Page and install it. Alternatively, you can install mono with homebrew with:

brew install mono

If you are using OS X 10.4, you should also install X11 from the OS X install CDs. In OS X 10.5, this is not required.

Locales and Regional Settings

OpenSimulator will only work properly when you run it with an English locale or regional setting. With other settings than English, you are likely to see a variety of issues, ranging from misbehaving scripts to crashes.


In Linux, you can easily use the standard "C" locale just for running OpenSim.exe, as explained in Troubleshooting#ScriptEngine Issues:

env LANG=C mono OpenSim.exe

For information about changing your locale in a more general way, see Troubleshooting#Locales Issues


If you are not using an English regional setting in Windows by default, then there is not a solution as easy as for Linux, unfortunately. I did it with an additional user account that I created just for OpenSimulator in which I set the regional setting to "English (US)". I run OpenSim.exe from my normal user account with "Run as..." (or check "Run with different credentials" in a shortcut's advanced properties) and specify the OpenSimulator account as the one to be used.

Additional Resources

OSGrid Technical Support Forum with many installation tutorials:

MONO Project:

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