> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cudocompute.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Build a custom image for OpenMPI and CUDA Toolkit

> In this tutorial we with build a custom disk image that can be used on CUDO Compute virtual machines. The disk image will have OpenMPI with CUDA support.

OpenMPI is an open-source message passing interface (MPI) library used for parallel computing on distributed systems. It enables developers to create high-performance computing applications by allowing multiple processes to communicate and coordinate with each other across a network.

## Quick start guide

1. Prerequisites
2. Starting a virtual machine with cudoctl
3. Installing NVIDIA CUDA Toolkit and OpenMPI via SSH
4. Creating a custom disk image

## Prerequisites

* Create a project and [add an SSH key](/docs/tutorials/how-to-generate-ssh-keys)
* Download the [CLI tool](/cli-tool)

## Starting a virtual machine with cudoctl

Start a virtual machine with the base image you require, here we will start with an image that already has NVIDIA drivers.

You can use the CUDO Compute console to start a virtual machine using the **Ubuntu 22.04 + NVIDIA drivers + Docker** image or alternatively use the command line tool `cudoctl`

First we search to find a virtual machine type to start

```shell theme={null}
cudoctl search --vcpus 4 --mem 8 --gpus 1
```

After deciding on a machine type of `epyc-milan-rtx-a4000` in the `se-smedjebacken-1` data center we can start a virtual machine:

```shell theme={null}
cudoctl vm create --id mpi-cuda --image ubuntu-nvidia-docker --machine-type epyc-milan-rtx-a4000 --memory 8 --vcpus 4  --gpus 1 --boot-disk-size 100 -boot-disk-class network --data-center se-smedjebacken-1
```

## Installing NVIDIA CUDA Toolkit and OpenMPI via SSH

Get the IP address of the virtual machine

```shell theme={null}
cudoctl vm get mpi-cuda | grep IP
```

Insert the IP address into this snippet and run it to install CUDA and OpenMPI

```shell theme={null}
ssh root@<YOUR_IP> << EOF
wget https://developer.download.nvidia.com/compute/cuda/repos/ubuntu2204/x86_64/cuda-ubuntu2204.pin
mv cuda-ubuntu2204.pin /etc/apt/preferences.d/cuda-repository-pin-600
wget https://developer.download.nvidia.com/compute/cuda/12.3.2/local_installers/cuda-repo-ubuntu2204-12-3-local_12.3.2-545.23.08-1_amd64.deb
dpkg -i cuda-repo-ubuntu2204-12-3-local_12.3.2-545.23.08-1_amd64.deb
cp /var/cuda-repo-ubuntu2204-12-3-local/cuda-*-keyring.gpg /usr/share/keyrings/
apt-get update
apt-get -y install cuda-toolkit-12-3

wget https://download.open-mpi.org/release/open-mpi/v5.0/openmpi-5.0.2.tar.gz
tar xf openmpi-5.0.2.tar.gz
cd openmpi-5.0.2
./configure  --with-cuda=/usr/local/cuda
make -j8 all
make install
echo >> export LD_LIBRARY_PATH=/usr/local/lib:$LD_LIBRARY_PATH >> ~/.bashrc
EOF
```

Wait for the installation to finish

## Creating a custom disk image

Create a new disk called `mpi-cuda-image`

```shell theme={null}
cudoctl vm save-image --vm mpi-cuda mpi-cuda-image
```

Now we can create an MPI worker with it

```shell theme={null}
cudoctl vm create --id mpi-cuda-worker --image mpi-cuda-image --machine-type epyc-milan-rtx-a4000 --memory 8 --vcpus 4 --gpus 1 --boot-disk-size 100 -boot-disk-class network --data-center se-smedjebacken-1
```