The build process can be quite long and tedious. The **[F.A.Q.](build_faq.md)** section contains the most common issues and solutions that appear during the installation. However, the CARLA forum is open for anybody to post unexpected issues, doubts or suggestions. There is a specific section for installation issues on Linux. Feel free to login and become part of the community.
* __Ubuntu 18.04.__ CARLA provides support for previous Ubuntu versions up to 16.04. **However** proper compilers are needed for UE to work properly. The required dependencies for both Ubuntu 18.04 and previous versions are listed below. Make sure to install the ones corresponding to the system.
* __30GB disk space.__ Installing all the software needed and CARLA itself will require quite a lot of space, especially Unreal Engine. Make sure to have around 30/50GB of free disk space.
* __An adequate GPU.__ CARLA aims for realistic simulations, so the server needs at least a 4GB GPU. A dedicated GPU is highly recommended for machine learning.
* __Two TCP ports and good internet connection.__ 2000 and 2001 by default. Be sure neither the firewall nor any other application block these.
CARLA needs many dependencies to run. Some of them are built automatically during this process, such as *Boost.Python*. Others are binaries that should be installed before starting the build (*cmake*, *clang*, different versions of *Python* and much more). In order to do so, run the commands below in a terminal window.
The following commands differ depending on the Ubuntu version. While the only change is `libpng16-dev` becoming `libpng-dev`, the full set of commands is here twice to ease the copy.
To avoid compatibility issues between Unreal Engine and the CARLA dependencies, it is recommended to use the same compiler version and C++ runtime library to compile everything. The CARLA team uses clang-8 and LLVM's libc++. Change the default clang version to compile Unreal Engine and the CARLA dependencies.
A [GitHub](https://github.com/) account will be needed, as CARLA content is organized in different repositories in there. Also, [git](https://git-scm.com/book/en/v2/Getting-Started-Installing-Git) will be used in this build guide when facilitating commands to be run in terminal.
In order to access the Unreal Engine repositories, which are set to private, create an [Unreal Engine](https://www.unrealengine.com/en-US/feed) account and connect it to a GitHub account. To do so, there is a section in Unreal Engine's profile settings under the name of __Connected accounts__. [Here](https://www.unrealengine.com/en-US/blog/updated-authentication-process-for-connecting-epic-github-accounts) is a brief explanation just in case.
New Unreal Engine accounts need activation. After creating the account, a verification mail will be sent. Check it out, or the UE repository will be shown as non-existent in the following steps.
The current version of CARLA runs on __Unreal Engine 4.24__ only. The path is irrelevant, but for the sake of this tutorial, installation will be done under `~/UnrealEngine_4.24`. If the path chosen differs, remember to change it accordingly when running the commands on terminal.
Alternatively, there is this [guide](https://docs.unrealengine.com/en-US/Platforms/Linux/BeginnerLinuxDeveloper/SettingUpAnUnrealWorkflow/index.html) to build UE on Linux. When consulting it, remember that CARLA will need the __4.24 release__, not the latest.
Get a patch for Unreal Engine. The patch fixes some Vulkan visualization issues that may occur when changing the map. Download and install it with the following commands.
In case something went wrong, it is related with Unreal Engine There is not much CARLA can do about it. However, the [build documentation](https://github.com/EpicGames/UnrealEngine/blob/release/Engine/Build/BatchFiles/Linux/README.md) provided by Unreal Engine may be helpful.
The `master` branch contains the latest fixes and features. Stable code is inside the `stable` and previous CARLA versions have their own branch. Always remember to check the current branch in git with the command `git branch`.
Only the assets package is yet to be donwloaded. These are stored separately to make the repository a bit lighter. CARLA cannot be built without the assets. There is a script that downloads and extracts the latest content version. The package is >3GB, so downloading it may take some time.
The variable should be added to `~/.bashrc` or `~/.profile` to be set persistently session-wide. Otherwise, it will only be accessible from the current shell.
* __make launch__ compiles the server simulator and launches Unreal Engine. Press **Play** to start the spectator view and close the editor window to exit. Camera can be moved with `WASD` keys and rotated by clicking the scene while moving the mouse around.
The project may ask to build other instances such as `UE4Editor-Carla.dll` the first time. Agree in order to open the project. During the first launch, the editor may show warnings regarding shaders and mesh distance fields. These take some time to be loaded and the city will not show properly until then.
* __make PythonAPI__ compiles the API client, necessary to grant control over the simulation. It is only needed the first time. Remember to run it again when updating CARLA. Scripts will be able to run after this command is executed. The following example will spawn some life into the town.
If the simulation is running at very low FPS rates, go to `Edit/Editor preferences/Performance` in the UE editor and disable __Use less CPU when in background__.
