Fine-tune Gemma 4 on a multi-host A4 GKE cluster

This tutorial shows you how to fine-tune a Gemma 4 31B large language model (google/gemma-4-31b-it) on a multi-host, multi-GPU Google Kubernetes Engine (GKE) Autopilot cluster on Google Cloud. This cluster uses two A4 (a4-highgpu-8g) virtual machine (VM) instances with a total of 16 NVIDIA B200 GPUs.

The three main processes described in this tutorial are as follows:

  1. Deploy a multi-host GKE cluster in Autopilot mode.
  2. Build a custom container image with the required fine-tuning dependencies by using Cloud Build.
  3. Orchestrate a distributed multi-host fine-tuning workload across all 16 GPUs by using Kubernetes JobSet and the Hugging Face Accelerate library with Fully Sharded Data Parallel v2 (FSDP v2), pushing checkpoints to Hugging Face Hub.

This tutorial is intended for machine learning (ML) engineers, researchers, platform administrators and operators, and data and AI specialists who deploy GKE clusters on Google Cloud to fine-tune LLMs across multiple hosts.

Objectives

  • Access the Gemma 4 model by using Hugging Face.

  • Prepare your environment.

  • Create and deploy a multi-host A4 GKE cluster.

  • Fine-tune the Gemma 4 31B model across 16 GPUs by using Kubernetes JobSet and Hugging Face Accelerate with FSDP v2.

  • Monitor your job.

  • View the fine-tuned adapter weights on Hugging Face Hub.

  • Clean up.

Costs

In this document, you use the following billable components of Google Cloud:

To generate a cost estimate based on your projected usage, use the pricing calculator.

New Google Cloud users might be eligible for a free trial.

Before you begin

To get the permissions that you need to complete this tutorial, ask your administrator to grant you the following IAM roles on your project:

For more information about granting roles, see Manage access to projects, folders, and organizations.

You might also be able to get the required permissions through custom roles or other predefined roles.

  1. Enable the required APIs, if any aren't already enabled:

    Roles required to enable APIs

    To enable APIs, you need the serviceusage.services.enable permission. If you created the project, then you likely already have this permission through the Owner role (roles/owner). Otherwise, you can get this permission through the Service Usage Admin role (roles/serviceusage.serviceUsageAdmin). Learn how to grant roles.

    gcloud services enable compute.googleapis.com container.googleapis.com artifactregistry.googleapis.com cloudbuild.googleapis.com logging.googleapis.com cloudresourcemanager.googleapis.com servicenetworking.googleapis.com
  2. Enable the default Compute Engine service account for your Google Cloud project:

    export PROJECT_NUMBER="$(gcloud projects describe "YOUR_PROJECT_ID" --format "value(project_number)")"
    gcloud iam service-accounts enable "${PROJECT_NUMBER}-compute@developer.gserviceaccount.com" \
        --project=YOUR_PROJECT_ID
  3. Grant the least-privilege IAM roles that the default Compute Engine service account needs to build the container image and run the fine-tuning workload:

    ROLES=(
      "roles/artifactregistry.writer"
      "roles/cloudbuild.builds.builder"
      "roles/logging.logWriter"
      "roles/monitoring.metricWriter"
      "roles/monitoring.viewer"
      "roles/stackdriver.resourceMetadata.writer"
      "roles/storage.objectViewer"
    )
    for role in "${ROLES[@]}"; do
      gcloud projects add-iam-policy-binding YOUR_PROJECT_ID \
          --member="serviceAccount:${PROJECT_NUMBER}-compute@developer.gserviceaccount.com" \
          --role="${role}" 1>/dev/null
    done
    unset ROLES
  4. Verify that the roles were granted to the default Compute Engine service account:

    echo "Displaying roles for ${PROJECT_NUMBER}-compute@developer.gserviceaccount.com:"
    gcloud projects get-iam-policy YOUR_PROJECT_ID \
        --flatten="bindings[].members" \
        --filter="bindings.members:serviceAccount:${PROJECT_NUMBER}-compute@developer.gserviceaccount.com" \
        --format="table(bindings.role)"
  5. Create local authentication credentials for your user account:

    gcloud auth application-default login
  6. Enable OS Login for your project:

    gcloud compute project-info add-metadata \
        --metadata=enable-oslogin=TRUE \
        --project=YOUR_PROJECT_ID

Access Gemma 4 by using Hugging Face

To use Hugging Face to access Gemma 4, complete the following steps:

  1. Sign in to Hugging Face and accept the Gemma 4 license agreement.
  2. Create a Hugging Face write access token.
    Click Your Profile > Settings > Access tokens > +Create new token.
  3. Copy and save the write access token value. You use this token to download the base model and push fine-tuned adapter checkpoints to Hugging Face Hub before GKE scales down the GPU nodes.

Prepare your environment

To prepare your environment, set the following environment variables:

export PROJECT_ID="YOUR_PROJECT_ID"
export CLUSTER_NAME="YOUR_CLUSTER_NAME"
export CLUSTER_REGION="YOUR_REGION"
export RESERVATION="YOUR_RESERVATION_NAME"
export HF_TOKEN="YOUR_HF_TOKEN"
export ARTIFACT_REPO_LOCATION="YOUR_ARTIFACT_REGISTRY_LOCATION"
export NUM_NODES="YOUR_NUMBER_OF_NODES"

gcloud config set project "${PROJECT_ID}"
gcloud config set billing/quota_project "${PROJECT_ID}"

Replace the following:

  • YOUR_PROJECT_ID: the ID of the Google Cloud project where you want to create the GKE cluster.

  • YOUR_CLUSTER_NAME: the name of the GKE cluster to create.

  • YOUR_REGION: the region where you want to create your GKE cluster. You can only create the cluster in the region where your reservation exists.

  • YOUR_RESERVATION_NAME: the identifier for your reserved capacity.

  • YOUR_HF_TOKEN: the Hugging Face write access token that you created in the previous section.

  • YOUR_ARTIFACT_REGISTRY_LOCATION: the Google Cloud region (for example, us-central1) where you want to create your Artifact Registry repository. To minimize image pull latency, use the same region that you specified for YOUR_REGION.

  • YOUR_NUMBER_OF_NODES: the number of A4 VM nodes in your fine-tuning job. For this multi-host tutorial with 16 NVIDIA B200 GPUs across two a4-highgpu-8g instances, set this value to 2.

Create a multi-host GKE cluster in Autopilot mode

Create a multi-host GKE cluster in Autopilot mode:

gcloud container clusters create-auto "${CLUSTER_NAME}" \
    --project="${PROJECT_ID}" \
    --location="${CLUSTER_REGION}"

Creating the GKE cluster might take several minutes to complete. To verify that Google Cloud has finished creating your cluster, go to Kubernetes clusters on the Google Cloud console.

Configure kubectl to communicate with your GKE cluster

Configure kubectl to communicate with your GKE cluster:

gcloud container clusters get-credentials "${CLUSTER_NAME}" \
    --location="${CLUSTER_REGION}"

Create a Kubernetes secret for Hugging Face credentials

Create a Kubernetes secret to store your Hugging Face token:

kubectl create secret generic hf-secret \
    --from-literal=hf_api_token="${HF_TOKEN}" \
    --dry-run=client -o yaml | kubectl apply -f -

Prepare your workload

To prepare your workload, you do the following:

  1. Create workload scripts.

  2. Use Docker and Cloud Build to create a fine-tuning container.

Create workload scripts

To create the configuration files and scripts that your fine-tuning workload uses, complete the following steps:

  1. Create a directory for the workload scripts. Use this directory as your working directory.

    mkdir llm-finetuning-gemma
    cd llm-finetuning-gemma
  2. Create the cloudbuild.yaml file to build your workload container image with Cloud Build and push it to Artifact Registry:

    steps:
    - name: 'gcr.io/cloud-builders/docker'
      args:
      - 'build'
      - '-t'
      - '$_ARTIFACT_REPO_LOCATION-docker.pkg.dev/$PROJECT_ID/gemma/finetune-gemma-multihost-gpu:2.0.0'
      - '.'
    images:
    - '$_ARTIFACT_REPO_LOCATION-docker.pkg.dev/$PROJECT_ID/gemma/finetune-gemma-multihost-gpu:2.0.0'
    options:
      logging: CLOUD_LOGGING_ONLY
  3. Create a Dockerfile file to define the environment and install the dependencies required to complete the fine-tuning job:

    FROM nvidia/cuda:12.8.1-cudnn-devel-ubuntu24.04
    RUN apt-get update && \
        apt-get -y install python3 python3-dev gcc python3-pip \
            python3-venv git curl vim && \
        rm -rf /var/lib/apt/lists/*
    RUN python3 -m venv /opt/venv
    ENV PATH="/opt/venv/bin:/usr/local/nvidia/bin:$PATH"
    ENV LD_LIBRARY_PATH="/usr/local/nvidia/lib64:$LD_LIBRARY_PATH"
    RUN pip3 install setuptools wheel packaging ninja
    RUN pip3 install torch torchvision torchaudio \
        --index-url https://download.pytorch.org/whl/cu128
    RUN pip3 install \
        "transformers>=5.5.0" \
        trl==0.29.1 \
        peft==0.18.1 \
        accelerate==1.13.0 \
        bitsandbytes==0.49.2 \
        datasets==4.8.4 \
        evaluate==0.4.5 \
        tensorboard==2.20.0 \
        protobuf==6.31.1 \
        sentencepiece==0.2.0
    WORKDIR /workspace
    COPY finetune.py /workspace/finetune.py
    COPY accel_fsdp_gemma4_config.yaml /workspace/accel_fsdp_gemma4_config.yaml
    CMD ["accelerate", "launch", "--config_file", "/workspace/accel_fsdp_gemma4_config.yaml", "/workspace/finetune.py"]
  4. Create the accel_fsdp_gemma4_config.yaml file. This configuration directs Hugging Face Accelerate to shard Gemma4TextDecoderLayer across 16 GPUs on two hosts by using FSDP v2:

    compute_environment: LOCAL_MACHINE
    debug: false
    distributed_type: FSDP
    downcast_bf16: 'no'
    enable_cpu_affinity: false
    fsdp_config:
      fsdp_activation_checkpointing: false
      fsdp_auto_wrap_policy: TRANSFORMER_BASED_WRAP
      fsdp_cpu_ram_efficient_loading: false
      fsdp_offload_params: true
      fsdp_reshard_after_forward: true
      fsdp_state_dict_type: FULL_STATE_DICT
      fsdp_transformer_layer_cls_to_wrap: Gemma4TextDecoderLayer
      fsdp_version: 2
    machine_rank: 0
    main_training_function: main
    mixed_precision: bf16
    num_machines: 2
    num_processes: 16
    rdzv_backend: static
    same_network: true
    tpu_env: []
    tpu_use_cluster: false
    tpu_use_sudo: false
    use_cpu: false
  5. Create the finetune.yaml Kubernetes JobSet manifest:

    apiVersion: resource.k8s.io/v1
    kind: ResourceClaimTemplate
    metadata:
      name: mrdma
    spec:
      spec:
        devices:
          requests:
          - name: mrdma
            exactly:
              deviceClassName: mrdma.google.com
    ---
    apiVersion: jobset.x-k8s.io/v1alpha2
    kind: JobSet
    metadata:
      name: finetune-jobset
      namespace: default
    spec:
      failurePolicy:
        maxRestarts: 2
      replicatedJobs:
      - name: workers
        replicas: 1
        template:
          spec:
            parallelism: ${NUM_NODES}
            completions: ${NUM_NODES}
            backoffLimit: 0
            template:
              metadata:
                annotations:
                  kubectl.kubernetes.io/default-container: finetuner
              spec:
                terminationGracePeriodSeconds: 600
                restartPolicy: OnFailure
                nodeSelector:
                  cloud.google.com/compute-class: "Accelerator"
                  cloud.google.com/gke-accelerator: "nvidia-b200"
                  cloud.google.com/reservation-name: ${RESERVATION}
                  cloud.google.com/reservation-affinity: "specific"
                  cloud.google.com/gke-gpu-driver-version: latest
                containers:
                - name: finetuner
                  image: $IMAGE_URL
                  command: ["bash", "-c"]
                  args:
                  - |
                    NUM_PROCESSES=$(( ${NUM_NODES} * 8 ))
                    accelerate launch \
                      --config_file /workspace/accel_fsdp_gemma4_config.yaml \
                      --num_machines ${NUM_NODES} \
                      --num_processes ${NUM_PROCESSES} \
                      --machine_rank ${JOB_COMPLETION_INDEX} \
                      --main_process_ip finetune-jobset-workers-0-0.finetune-jobset.default.svc.cluster.local \
                      --main_process_port 29500 \
                      /workspace/finetune.py \
                      --base_model google/gemma-4-31b-it \
                      --new_model gemma-31b-text-to-sql \
                      --per_device_train_batch_size 4 \
                      --gradient_accumulation_steps 4 \
                      --num_train_epochs 3 \
                      --learning_rate 1e-5 \
                      --save_strategy steps \
                      --save_steps 15 \
                      --push_to_hub
                  resources:
                    limits:
                      nvidia.com/gpu: "8"
                      memory: "1000Gi"
                      ephemeral-storage: "350Gi"
                    requests:
                      nvidia.com/gpu: "8"
                      memory: "1000Gi"
                      ephemeral-storage: "350Gi"
                  env:
                  - name: HF_TOKEN
                    valueFrom:
                      secretKeyRef:
                        name: hf-secret
                        key: hf_api_token
                  - name: NUM_NODES
                    value: "${NUM_NODES}"
                  volumeMounts:
                  - mountPath: /dev/shm
                    name: dshm
                volumes:
                - name: dshm
                  emptyDir:
                    medium: Memory
                    sizeLimit: 64Gi
  6. Create the finetune.py supervised fine-tuning script:

    import argparse
    import torch
    from datasets import load_dataset
    from huggingface_hub import login
    from peft import LoraConfig
    from transformers import AutoConfig, AutoModelForCausalLM, AutoTokenizer
    from trl import SFTConfig, SFTTrainer
    
    
    def get_args():
        def str2bool(v):
            if isinstance(v, bool):
                return v
            return v.lower() in ("yes", "true", "t", "1")
    
        parser = argparse.ArgumentParser()
        parser.add_argument(
            "--base_model",
            "--model_id",
            dest="base_model",
            type=str,
            default="google/gemma-4-31b-it",
            help="Hugging Face model ID",
        )
        parser.add_argument(
            "--hf_token",
            type=str,
            default=None,
            help="Hugging Face token for gated models and Hub uploads",
        )
        parser.add_argument(
            "--trust_remote",
            type=str2bool,
            default=False,
            help="Trust remote code when loading tokenizer",
        )
        parser.add_argument(
            "--use_fast",
            type=str2bool,
            default=True,
            help="Determines if a fast Rust-based tokenizer should be used",
        )
        parser.add_argument(
            "--dataset_name",
            type=str,
            default="philschmid/gretel-synthetic-text-to-sql",
            help="Hugging Face dataset name",
        )
        parser.add_argument(
            "--new_model",
            "--output_dir",
            dest="new_model",
            type=str,
            default="gemma-31b-text-to-sql",
            help="Directory and repository name to save model checkpoints",
        )
    
        # LoRA arguments
        parser.add_argument(
            "--lora_r", type=int, default=16, help="LoRA attention dimension"
        )
        parser.add_argument(
            "--lora_alpha", type=int, default=32, help="LoRA alpha scaling factor"
        )
        parser.add_argument(
            "--lora_dropout",
            type=float,
            default=0.05,
            help="LoRA dropout probability",
        )
        # SFTConfig arguments
        parser.add_argument(
            "--max_length",
            type=int,
            default=1024,
            help="Maximum sequence length",
        )
        parser.add_argument(
            "--num_train_epochs",
            type=int,
            default=3,
            help="Number of training epochs",
        )
        parser.add_argument(
            "--per_device_train_batch_size",
            type=int,
            default=4,
            help="Batch size per device during training",
        )
        parser.add_argument(
            "--gradient_accumulation_steps",
            type=int,
            default=4,
            help="Gradient accumulation steps",
        )
        parser.add_argument(
            "--learning_rate", type=float, default=1e-5, help="Learning rate"
        )
        parser.add_argument(
            "--logging_steps", type=int, default=10, help="Log every X steps"
        )
        parser.add_argument(
            "--save_strategy",
            type=str,
            default="steps",
            help="Checkpoint save strategy",
        )
        parser.add_argument(
            "--save_steps",
            type=int,
            default=15,
            help="Save checkpoint every X steps",
        )
        parser.add_argument(
            "--push_to_hub",
            action="store_true",
            help="Push model back up to Hugging Face Hub",
        )
        parser.add_argument(
            "--hub_private_repo",
            type=str2bool,
            default=True,
            help="Push to a private repository on Hugging Face Hub",
        )
        return parser.parse_args()
    
    
    def main():
        args = get_args()
        # --- 1. Setup and Login ---
        if args.hf_token:
            login(args.hf_token)
        # --- 2. Create and prepare the fine-tuning dataset ---
        dataset = load_dataset(args.dataset_name, split="train")
        dataset = dataset.shuffle().select(range(12500))
        dataset = dataset.train_test_split(test_size=2500 / 12500)
        # --- 3. Configure Model and Tokenizer ---
        if torch.cuda.is_available() and torch.cuda.get_device_capability()[0] >= 8:
            torch_dtype_obj = torch.bfloat16
        else:
            torch_dtype_obj = torch.float16
        tokenizer = AutoTokenizer.from_pretrained(
            args.base_model,
            trust_remote_code=args.trust_remote,
            use_fast=args.use_fast,
        )
        if tokenizer.pad_token is None:
            tokenizer.pad_token = tokenizer.eos_token
    
        # --- 4. Define the Formatting Function ---
        def formatting_func(example):
            system_message = (
                "You are a text to SQL query translator. Users will ask you "
                "questions in English and you will generate a SQL query based "
                "on the provided SCHEMA."
            )
            user_prompt = (
                "Given the <USER_QUERY> and the <SCHEMA>, generate the "
                "corresponding SQL command to retrieve the desired data, "
                "considering the query's syntax, semantics, and schema "
                "constraints.\n\n<SCHEMA>\n{context}\n</SCHEMA>\n\n"
                "<USER_QUERY>\n{question}\n</USER_QUERY>\n"
            )
    
            messages = [
                {"role": "system", "content": system_message},
                {
                    "role": "user",
                    "content": user_prompt.format(
                        question=example["sql_prompt"],
                        context=example["sql_context"],
                    ),
                },
                {"role": "assistant", "content": example["sql"]},
            ]
            return tokenizer.apply_chat_template(messages, tokenize=False)
    
        # --- 5. Load Model and Configure LoRA ---
        config = AutoConfig.from_pretrained(args.base_model)
        config.use_cache = False
        print("Loading base model...")
        model = AutoModelForCausalLM.from_pretrained(
            args.base_model,
            config=config,
            attn_implementation="sdpa",
            torch_dtype=torch_dtype_obj,
        )
    
        peft_config = LoraConfig(
            lora_alpha=args.lora_alpha,
            lora_dropout=args.lora_dropout,
            r=args.lora_r,
            bias="none",
            target_modules=[
                "q_proj",
                "k_proj",
                "v_proj",
                "o_proj",
                "gate_proj",
                "up_proj",
                "down_proj",
            ],
            exclude_modules=r".*(vision_tower|embed_vision|audio_tower|embed_audio).*",
            task_type="CAUSAL_LM",
        )
        # --- 6. Configure Training Arguments ---
        training_args = SFTConfig(
            output_dir=args.new_model,
            max_length=args.max_length,
            num_train_epochs=args.num_train_epochs,
            per_device_train_batch_size=args.per_device_train_batch_size,
            gradient_accumulation_steps=args.gradient_accumulation_steps,
            learning_rate=args.learning_rate,
            logging_steps=args.logging_steps,
            save_strategy=args.save_strategy,
            save_steps=args.save_steps,
            packing=False,
            label_names=["domain"],
            gradient_checkpointing=True,
            gradient_checkpointing_kwargs={"use_reentrant": False},
            optim="adamw_torch",
            fp16=torch_dtype_obj == torch.float16,
            bf16=torch_dtype_obj == torch.bfloat16,
            max_grad_norm=0.3,
            warmup_steps=0.03,
            lr_scheduler_type="constant",
            push_to_hub=args.push_to_hub,
            hub_private_repo=args.hub_private_repo,
            report_to="tensorboard",
        )
        # --- 7. Create Trainer and Start Training ---
        trainer = SFTTrainer(
            model=model,
            args=training_args,
            peft_config=peft_config,
            train_dataset=dataset["train"],
            eval_dataset=dataset["test"],
            processing_class=tokenizer,
            formatting_func=formatting_func,
        )
        print("Starting training...")
        trainer.train()
        print("Training finished.")
        # --- 8. Save the final model ---
        print(f"Saving final model to {args.new_model}")
        if trainer.is_fsdp_enabled:
            trainer.accelerator.state.fsdp_plugin.set_state_dict_type(
                "FULL_STATE_DICT"
            )
        trainer.save_model(args.new_model)
        if torch.distributed.is_initialized():
            torch.distributed.destroy_process_group()
    
    
    if __name__ == "__main__":
        main()

Use Docker and Cloud Build to create a fine-tuning container

  1. Create an Artifact Registry Docker repository:

    gcloud artifacts repositories create gemma \
        --repository-format=docker \
        --location="${ARTIFACT_REPO_LOCATION}" \
        --description="Repository for Gemma fine tuning workload containers" || true
  2. Install the JobSet custom resource definitions (CRDs) required for orchestrating multi-host workloads:

    kubectl apply --server-side \
        -f https://github.com/kubernetes-sigs/jobset/releases/download/v0.12.0/manifests.yaml
  3. In the llm-finetuning-gemma directory that you created in an earlier step, submit the container build to Cloud Build:

    gcloud builds submit . \
        --substitutions=_ARTIFACT_REPO_LOCATION="${ARTIFACT_REPO_LOCATION}"
  4. Export the multi-host container image URL. You use it at a later step in this tutorial, when you deploy the JobSet manifest:

    IMAGE_REGISTRY="${ARTIFACT_REPO_LOCATION}-docker.pkg.dev/${PROJECT_ID}"
    export IMAGE_URL="${IMAGE_REGISTRY}/gemma/finetune-gemma-multihost-gpu:2.0.0"

Start your fine-tuning workload

To deploy and monitor your distributed fine-tuning workload, complete the following steps:

  1. Substitute environment variables into the fine-tuning manifest to create the fine-tuning job:

    envsubst '${RESERVATION} ${IMAGE_URL} ${NUM_NODES}' < finetune.yaml \
        | kubectl apply -f -

    Because your cluster runs in GKE Autopilot mode, it might take a few minutes to provision the two GPU-enabled A4 nodes and pull the container image.

  2. Watch the worker pods until both pods transition to the Running status:

    watch kubectl get pods
  3. After the worker pods transition to Running, stream the training logs:

    kubectl logs -l "job-name=finetune-jobset-workers-0" -f

Monitor your workload

You can monitor GPU utilization across your GKE cluster to verify that all 16 GPUs across both A4 hosts are actively processing training steps. Generate and open the observability link in your browser:

echo "https://console.cloud.google.com/kubernetes/clusters/details/${CLUSTER_REGION}/${CLUSTER_NAME}/observability?mods=monitoring_api_prod&project=${PROJECT_ID}&pageState=(\"timeRange\":(\"duration\":\"PT1H\"),\"nav\":(\"section\":\"gpu\"),\"groupBy\":(\"groupByType\":\"namespacesTop5\"))"

When you monitor your workload, expect the following behavior:

  • GPU utilization: For a healthy distributed fine-tuning job, you can expect to see GPU utilization across all 16 NVIDIA B200 GPUs rise and stabilize near 95%–100% during training steps.
  • Job duration: Across two a4-highgpu-8g nodes (16 B200 GPUs), the 3-epoch fine-tuning job takes approximately 2 and a half hours to complete.

View your fine-tuned adapter weights

When training finishes, view your fine-tuned LoRA adapter weights and checkpoints on Hugging Face Hub at https://huggingface.co/YOUR_HF_USERNAME/gemma-31b-text-to-sql.

Clean up

To avoid incurring additional charges, delete the resources created during this tutorial.

Delete your resources

  1. Delete the fine-tuning JobSet:

    kubectl delete jobset finetune-jobset
  2. Delete your GKE cluster:

    gcloud container clusters delete "${CLUSTER_NAME}" \
        --region="${CLUSTER_REGION}"
  3. Delete your Artifact Registry repository:

    gcloud artifacts repositories delete gemma \
        --location="${ARTIFACT_REPO_LOCATION}" \
        --quiet

What's next