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Setting LD_LIBRARY_PATH for CUDA on Ubuntu

Ubuntu 19

In this article, we will guide you through the process of setting the LD_LIBRARY_PATH for CUDA on Ubuntu. This is an essential step when installing CUDA, as it allows the system to find the CUDA libraries during runtime.

Quick Answer

To set the LD_LIBRARY_PATH for CUDA on Ubuntu, you can either create a .conf file in the /etc/ld.so.conf.d/ directory and add the paths to the CUDA libraries, or modify the .bashrc file by adding the paths to the LD_LIBRARY_PATH environment variable. Both methods ensure that your system can find the CUDA libraries during runtime.

What is LD_LIBRARY_PATH?

LD_LIBRARY_PATH is an environment variable that specifies a list of directories where shared libraries are searched for first. If you are developing programs using CUDA, you need to ensure that the system knows where to find the CUDA library files.

Why Set LD_LIBRARY_PATH for CUDA?

When you install CUDA on your system, it’s not enough to just have the software installed. Your system needs to know where to find the CUDA libraries when running CUDA-based applications. By setting the LD_LIBRARY_PATH, you are telling your system where to look for these libraries.

How to Set LD_LIBRARY_PATH for CUDA on Ubuntu

There are two main methods to set the LD_LIBRARY_PATH for CUDA on Ubuntu:

  1. Creating a .conf file
  2. Modifying the .bashrc file

Method 1: Creating a .conf file

This method involves creating a new configuration file in the /etc/ld.so.conf.d/ directory.

Step 1: Create a new .conf file in the /etc/ld.so.conf.d/ directory. For example, you can create a file named nvidia.conf using the command:

sudo nano /etc/ld.so.conf.d/nvidia.conf

Step 2: Open the file and add the paths to the CUDA libraries. For instance:

/usr/local/cuda-5.0/lib64
/usr/local/cuda-5.0/lib

These paths tell the system where to find the 64-bit and 32-bit CUDA libraries respectively.

Step 3: Set the permissions and ownership of the file to match the other files in the directory. You can use the following commands:

sudo chown root:root /etc/ld.so.conf.d/nvidia.conf
sudo chmod 644 /etc/ld.so.conf.d/nvidia.conf

The chown command changes the ownership of the file to the root user and group, while the chmod command sets the file permissions to 644 (read and write for the owner, and read for the group and others).

Step 4: Run sudo ldconfig to update the library cache. This command reads the configuration files and updates the links and cache to the most recent shared libraries found in the directories specified in the configuration files.

Method 2: Modifying the .bashrc file

This method involves adding the paths to the CUDA libraries to the LD_LIBRARY_PATH environment variable in the .bashrc file.

Step 1: Open the .bashrc file located in your home directory with a text editor. For example:

nano ~/.bashrc

Step 2: Add the following code at the end of the file:

if [ -z "$LD_LIBRARY_PATH" ]; then
 LD_LIBRARY_PATH=/usr/local/cuda-5.0/lib64:/usr/local/cuda-5.0/lib
else
 LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/cuda-5.0/lib64:/usr/local/cuda-5.0/lib
fi
export LD_LIBRARY_PATH

This code checks if LD_LIBRARY_PATH is empty. If it is, it sets LD_LIBRARY_PATH to the paths of the CUDA libraries. If it’s not empty, it appends the paths of the CUDA libraries to the existing LD_LIBRARY_PATH.

Step 3: Save the file and exit.

Step 4: Run source ~/.bashrc to apply the changes to your current session. The source command reads and executes commands from the file specified as its argument in the current shell environment.

After following either of these methods, you can check if the LD_LIBRARY_PATH is set correctly by running echo $LD_LIBRARY_PATH. It should display the paths to the CUDA libraries.

Please note: Make sure to replace /usr/local/cuda-5.0 with the actual path to your CUDA installation if it’s different.

Conclusion

Setting the LD_LIBRARY_PATH for CUDA on Ubuntu is a crucial step in setting up your CUDA development environment. It allows your system to find the CUDA libraries during runtime, enabling you to run CUDA-based applications. By following the steps outlined in this article, you should now be able to set the LD_LIBRARY_PATH for CUDA on Ubuntu.

What is the purpose of setting LD_LIBRARY_PATH for CUDA on Ubuntu?

The purpose of setting LD_LIBRARY_PATH for CUDA on Ubuntu is to specify the directories where shared libraries are searched for first. This allows the system to find the CUDA libraries during runtime when running CUDA-based applications.

How does LD_LIBRARY_PATH work?

LD_LIBRARY_PATH is an environment variable that contains a list of directories where shared libraries are searched for first. When a program is executed, the system looks for the required shared libraries in the directories specified in LD_LIBRARY_PATH before searching the default system library paths.

Why do we need to set LD_LIBRARY_PATH specifically for CUDA?

Setting LD_LIBRARY_PATH specifically for CUDA is necessary because when you install CUDA on your system, the system needs to know where to find the CUDA libraries when running CUDA-based applications. By setting LD_LIBRARY_PATH, you are informing the system about the locations of these libraries.

How does Method 1 (creating a .conf file) work?

Method 1 involves creating a new .conf file in the /etc/ld.so.conf.d/ directory and adding the paths to the CUDA libraries in that file. The ldconfig command is then run to update the library cache based on the configuration files in the /etc/ld.so.conf.d/ directory.

How does Method 2 (modifying the .bashrc file) work?

Method 2 involves adding the paths to the CUDA libraries to the LD_LIBRARY_PATH environment variable in the .bashrc file located in the home directory. This ensures that the LD_LIBRARY_PATH is set correctly every time a new terminal session is started.

How can I check if LD_LIBRARY_PATH is set correctly?

To check if LD_LIBRARY_PATH is set correctly, you can run the command echo $LD_LIBRARY_PATH in the terminal. It should display the paths to the CUDA libraries that you have set.

What should I do if my CUDA installation path is different?

If your CUDA installation path is different from the one mentioned in the instructions, you should replace "/usr/local/cuda-5.0" with the actual path to your CUDA installation in the .conf file or .bashrc file, depending on the method you chose.

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