# Adding SLURM and MPI to the Compute Node After getting our nodes to boot using our compute images, let's try running a test MPI job. We need to install and configure both SLURM and MPI to do so. We can do this at least two ways here: - Create a new `compute-mpi` image similar to the `compute-debug` image using the `compute-base` image as a base. You do not have to rebuild the parent images unless you want to make changes to them, but keep in mind that you will also have to rebuild any derivative images. ### Building Into the Image We can use the `image-builder` tool to include the SLURM and OpenMPI packages directly in the image. Since we're building a new image for our compute node, we'll base our new image on the compute image definition from the tutorial. You should already have a directory at `/opt/workdir/images`. Make sure you already have a base compute image with `s3cmd ls`. ```bash # TODO: put the output of `s3cmd ls` here with the compute-base image ``` If you do not have the image, go back to [this step](https://github.com/OpenCHAMI/tutorial-2025/blob/main/Phase%202/Readme.md#243-configure-the-base-compute-image) in the tutorial, build the image, and push it to S3. Once you have done that, proceed to the next step. Now, edit a new file at path `/opt/workdir/images/compute-slurm-rocky9.yaml` and copy the contents below. ```bash options: layer_type: 'base' name: 'compute-slurm' publish_tags: - 'rocky9' pkg_manager: 'dnf' parent: 'demo.openchami.cluster:5000/demo/rocky-base:9' registry_opts_pull: - '--tls-verify=false' # Publish SquashFS image to local S3 publish_s3: 'http://demo.openchami.cluster:9000' s3_prefix: 'compute/base/' s3_bucket: 'boot-images' # Publish OCI image to container registry # # This is the only way to be able to re-use this image as # a parent for another image layer. publish_registry: 'demo.openchami.cluster:5000/demo' registry_opts_push: - '--tls-verify=false' repos: - alias: 'Epel9' url: 'https://dl.fedoraproject.org/pub/epel/9/Everything/x86_64/' gpg: 'https://dl.fedoraproject.org/pub/epel/RPM-GPG-KEY-EPEL-9' packages: - slurm - openmpi ``` Notice that the only changes to the new image definition were to the `options.name` and `packages`. Since we're basing this image on another image, we only need the packages we want to add to the new image. We can build the image and push it to S3 now. ```bash podman run --rm --device /dev/fuse --network host -e S3_ACCESS=admin -e S3_SECRET=admin123 -v /opt/workdir/images/compute-slurm-rocky9.yaml:/home/builder/config.yaml ghcr.io/openchami/image-build:latest image-build --config config.yaml --log-level DEBUG ``` Wait until the build finishes and check the S3 bucket to confirm that it is there with `s3cmd ls` again. Add a new boot script to `/opt/workdir/boot/boot-compute-slurm.yaml` which we will use to boot our compute nodes. ```bash kernel: 'http://172.16.0.254:9000/boot-images/efi-images/compute/debug/vmlinuz-5.14.0-570.21.1.el9_6.x86_64' initrd: 'http://172.16.0.254:9000/boot-images/efi-images/compute/debug/initramfs-5.14.0-570.21.1.el9_6.x86_64.img' params: 'nomodeset ro root=live:http://172.16.0.254:9000/boot-images/compute/debug/rocky9.6-compute-slurm-rocky9 ip=dhcp overlayroot=tmpfs overlayroot_cfgdisk=disabled apparmor=0 selinux=0 console=ttyS0,115200 ip6=off cloud-init=enabled ds=nocloud-net;s=http://172.16.0.254:8081/cloud-init' macs: - 52:54:00:be:ef:01 - 52:54:00:be:ef:02 - 52:54:00:be:ef:03 - 52:54:00:be:ef:04 - 52:54:00:be:ef:05 ``` Set and confirm that the boot parameters have been set correctly. ```bash ochami bss boot params set -f yaml -d @/opt/workdir/boot/boot-compute-slurm.yaml ochami bss boot params get -F yaml ``` Finally, boot the compute node. ```bash sudo virt-install \ --name compute1 \ --memory 4096 \ --vcpus 1 \ --disk none \ --pxe \ --os-variant centos-stream9 \ --network network=openchami-net,model=virtio,mac=52:54:00:be:ef:01 \ --graphics none \ --console pty,target_type=serial \ --boot network,hd \ --boot loader=/usr/share/OVMF/OVMF_CODE.secboot.fd,loader.readonly=yes,loader.type=pflash,nvram.template=/usr/share/OVMF/OVMF_VARS.fd,loader_secure=no \ --virt-type kvm ``` Your compute node should start up with iPXE output. If your node does not boot, check the [troubleshooting](Troubleshooting.md) sections for common issues. ### Installing via Cloud-Init Alternatively, we can install the necessary SLURM and MPI packages after booting by adding packages to our cloud-init config and use the `cmds` section for configuration. Let's start by making changes to the cloud-init config file in `/opt/workdir/cloud-init/computes.yaml` that we used previously. Note that we are using a pre-built RPMs to install SLURM and OpenMPI from the Rocky 9 repos. ```bash - name: compute description: "compute config" file: encoding: plain content: | ## template: jinja #cloud-config merge_how: - name: list settings: [append] - name: dict settings: [no_replace, recurse_list] users: - name: root ssh_authorized_keys: {{ ds.meta_data.instance_data.v1.public_keys }} disable_root: false packages: - slurm - openmpi cmds: - systemctl enable slurmctld - systemctl enable slurmdbd ``` We added the `packages` section to tell cloud-init to install the `slurm` and `openmpi` packages after booting the compute ### Prepare SLURM on Head Node ### Run a Sample MPI job across two VMs After we have installed both SLURM and OpenMPI on the compute node, let's try and launch a "hello world" MPI job. To do so, we will need three things: 1. Source code for MPI program 2. Compiled MPI executable binary 3. SLURM job script We create the MPI program in C. First, create a new directory to store our source code. Then, edit the `/opt/workdir/apps/hello.c` file. ```bash mkdir -p /opt/workdir/apps/mpi/hello # edit /opt/workdir/apps/mpi/hello/hello.c ``` Now copy the contents below into the `hello.c` file. ```c /*The Parallel Hello World Program*/ #include #include main(int argc, char **argv) { int node; MPI_Init(&argc, &argv); MPI_Comm_rank(MPI_COMM_WORLD, &node); printf("Hello World from Node %d\n",node); MPI_Finalize(); } ``` Compile the program. ```bash cd /opt/workdir/apps/mpi/hello mpicc hello.c -o hello ``` You should have an `hello` executable in the `/opt/workdir/apps/mpi/hello` directory now. We can use this binary executable with SLURM to launch process in parallel. Let's create a job script to launch the executable we just created. Create a new directory to hold our SLURM job script. Then, edit a new file called `launch-hello.sh` in the new `/opt/workdir/jobscripts` directory. ```bash mkdir -p /opt/workdir/jobscripts cd /opt/workdir/jobscripts # edit launch.sh ``` Copy the contents below into the `launch-hello.sh` job script. > [!NOTE] > The contents of your job script may vary significantly depending on your cluster. Refer to the documentation for your institution and adjust the script accordingly to your needs. ```bash #!/bin/bash #SBATCH --job-name=hello #SBATCH --account=account_name #SBATCH --partition=partition_name #SBATCH --nodes=1 #SBATCH --ntasks-per-node=1 #SBATCH --cpus-per-task=4 #SBATCH --time=00:00:30 export OMP_NUM_THREADS=$SLURM_CPUS_PER_TASK /opt/workdir/apps/mpi/hello/hello ``` We should now have everything we need to test our MPI job with our compute node(s). Launch the job with the `sbatch` command. ```bash sbatch /opt/workdir/jobscripts/launch-hello.sh ``` We can confirm the job is running with the `squeue` command. ```bash squeue ``` You should see a list with a job named `hello` that was given in the `launch-hello.sh` job script. ```bash # TODO: add output of squeue above ``` If you saw the output above, you should now be able to inspect the output of the job when it completes. ```bash # TODO: add output of MPI job (should be something like hello.o and/or hello.e) ``` And that's it! You have successfully launched an MPI job with SLURM from an OpenCHAMI deployed system.